ML25346A261
| ML25346A261 | |
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|---|---|
| Site: | 05000614, 99902117 |
| Issue date: | 12/12/2025 |
| From: | Long Mott Energy |
| To: | Office of Nuclear Reactor Regulation |
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| 2025-PLM-NRC-016 | |
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Text
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.1-i December 2025 CHAPTER 2 SUBSECTION 2.5.1 BASIC GEOLOGIC AND SEISMIC INFORMATION LIST OF TABLES Number Title 2.5.1-1 Injection Well Data from the Site Vicinity (9 Sheets) 2.5.1-2 Description of Stratigraphic Units Between Subsections 2.5.1-3 Locations of Fracture Planes Recorded in Boring Lab Data
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-ii December 2025 LIST OF FIGURES Number Title 2.5.1-1 Physiographic Provinces and Surficial Geology of Texas 2.5.1-2 Physiographic Regions Surrounding and Beneath the Gulf of Mexico 2.5.1-3 Geology of the Site Region 2.5.1-4 Geology of the Gulf of Mexico 2.5.1-5 Main Tectonic Terrains of the United States and Mexico 2.5.1-6 Ouachita Structural Elements in the Site Region 2.5.1-7 Sequence of Mesozoic Rifting in the Gulf of Mexico 2.5.1-8 Map of Crustal Types and Depth to Basement in Kilometers in the Gulf of Mexico 2.5.1-9 Sediment Thickness Above Bedrock in the Site Region 2.5.1-10 Oligocene Depositional Environments in Coastal and Offshore Texas 2.5.1-11 Regional Cross Sections 2.5.1-12 Tectonic Map of the 200-Mile Site Region (2 Sheets) 2.5.1-13 Map of the Location of the Vicksburg and Frio Fault Zones and Salt Basin Locations 2.5.1-14 Fault Sources in in the Central and Eastern United States in the USGS 2023 National Seismic Hazard Map Project
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-iii December 2025 2.5.1-15 Locations of Injection Wells Permitted in the Site Vicinity 2.5.1-16 InSAR Vertical Deformation Data for the Gulf Coastal Region of Texas 2.5.1-17 Magnetic Anomaly Map for the Site Region 2.5.1-18 Bouguer Gravity Anomaly Data for the Site Region 2.5.1-19 Geology of the Site Vicinity 2.5.1-20 Surficial Geology of the Site Area 2.5.1-21 Generalized Cross Section at the LMGS Site 2.5.1-22 Generalized Stratigraphic Column at the LMGS Site 2.5.1-23 Locations of Data Collection Boreholes and SASW Arrays at Site 2.5.1-24 Fence Diagram of Interpreted Subsurface Stratigraphy - SASW Array 3 2.5.1-25 Fence Diagram of Interpreted Subsurface Stratigraphy - SASW Array 4 2.5.1-26 Fence Diagram of Interpreted Subsurface Stratigraphy - SASW Array 6 2.5.1-27 Fence Diagram of Interpreted Subsurface Stratigraphy - SASW Array 7 2.5.1-28 Eight-Shear Wave Velocity Profiles Modeled from SASW Data Arrays at the Site 2.5.1-29 Victoria County Station Growth Fault Projections 2.5.1-30 Statistical Analysis of Eight Shear Wave Velocity Profiles 2.5.1-31 Victoria County Station Assessment of Lineaments from LiDAR
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-iv December 2025 2.5.1-32 LiDAR and Mapped Potential Growth Faults in the Site Vicinity
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-v December 2025 Acronyms and Abbreviations Acronym/Abbreviation Definition CEUS SSC Central and Eastern United States Seismic Source Characterization for Nuclear Facilities cu. mi.
cubic mile EGM2008 Earth Gravitational Model 2008 ft.
foot in.
inch InSAR Interferometric Synthetic-Aperture Radar ka kilo annum (one thousand years ago) km kilometer km2 square kilometers km3 cubic kilometers LiDAR Light Detection and Ranging LMGS Long Mott Generating Station Ma mega annum (one million years ago)
MCU Mid-Cretaceous Unconformity mi.
mile mGal milligal mm millimeter Mw Moment Magnitude PSAR preliminary safety analysis report
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-vi December 2025 Acronyms and Abbreviations Acronym/Abbreviation Definition NMSZ New Madrid Seismic Zone NOAA National Oceanic and Atmospheric Administration NRC Nuclear Regulatory Commission UCSD University of California, San Diego RG Regulatory Guide SASW Spectral-Analysis-of-Surface-Waves USGS.
United States Geological Survey VCS Victoria County Station VS shear wave velocity WGM2012 World Gravity Map 2012
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-1 December 2025 2.5.1 BASIC GEOLOGIC AND SEISMIC INFORMATION The geologic and seismologic information presented in this section was developed through a review of published scientific literature, interpretation of available scientific figures, and a review of other peer-reviewed publications, and as well as analysis of geotechnical data collected at the site.. Additional site-specific field data and associated analysis will be provided by the end of 2025.
This subsection demonstrates compliance with the requirements of 10 Code of Federal Regulations 100.23(c).
Section 2.5.1 describes the geological and seismological characteristics of the Long Mott Generating Station (LMGGMS) (200 mi. [320 km]), sSite vVicinity (25 mi. [40 km]), and Site site A area (5 mi. [8 km]) radii. Subsection 2.5.1.1 describes the physiographic, geologic, and tectonic characteristics of the site region. Subsection 2.5.1.2 describes the physiographic, geologic, and tectonic characteristics of the LGMS LMGS site vicinity and site area. The geological and seismological information presented in this section was developed in accordance with Nuclear Regulatory Commission (NRC) Regulatory Guide (RG) 1.206 and NUREG-0800.
2.5.1.1 Regional Physiography and Geology This subsection provides information regarding the physiography, geologic history, stratigraphy, structures, and tectonic setting within the 200-mi. (320-km) radius of the LGMSLMGS site.
The Long MottLMGS site is located within the Coastal Prairies subprovince of the Gulf Coastal Plains physiographic province (BEG, 1996) (Figures 2.5.1-1 and 2.5.21-2). The Coastal Prairies subprovince extends from the Gulf of Mexico (Gulf) shoreline and is made up of flat grasslands that slope to the southeast. In the Coastal Prairies, the strata are subhorizontal. The ground surface elevation within the subprovince ranges from 0 ft. to 300 ft. (91 m), with a northward and westward elevation increase (BEG, 1996).
The regional geologic map (BEG, 1992) shows the regional geology surrounding the Long MottLMGS site, including stratigraphy, geological structures, tectonic setting, bedrock type, and present-day topographic relief within a 200-mi. (320-km) radius (Figures 2.5.1-3 and 2.5.1-4). To provide a framework for evaluation of the regions geologic and seismologic hazards, summaries of these aspects are presented in the following subsections.
2.5.1.1.1 Regional Physiography and Geomorphology The Long MottLMGS site is within the Coastal Prairies subprovince of the Gulf Coastal Plains physiographic province (BEG, 1996) (Figures 2.5.1-1 and 2.5.1-2).
The surrounding region (200-mi., 320-km radius) includes five physiographic provinces, ranging from the North American platform south into the Gulf of Mexico.
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-2 December 2025 These provinces include the Edwards Plateau, the Central Texas or Llano Uplift, the Gulf Coastal Plains (including the Blackland Prairies, Interior Coastal Plains, and Coastal Prairies subprovinces), the Texas-Louisiana Shelf, and the Texas-Louisiana Slope (BEG, 1996). The following subsections describe each physiographic province mapped within the region.
2.5.1.1.1.1 Gulf Plains Physiographic Province The Gulf Coastal Plains border the western Gulf of Mexico, in an arc 180 mi. (290 km) wide, ranging from the Sabine River to the Rio Grande Border, and encompass three subprovinces from north to south: the Blackland Prairies, the Interior Coastal Plains, and the Coastal Prairies. The elevation of this province ranges from 0 ft.
(sea level) to 1,000 ft. (305 m), with an average elevation of approximately 500 ft.
(152 m) in its northeastern and central areas (BEG, 1996; Swanson, 1995).
The northern and innermost subprovince of the Gulf Coastal Plains is the Blackland Prairies Edwards Plateau. The Blackland Prairies are underlain by limestone, chalk, and marl that, which have weathered to create the regions characteristically black soil (Swanson, 1995: BEG, 1996). The topography is characterized by low, rolling terrain with a gentle undulating surface, which has beenwas cleared of most natural vegetation before the cultivation of crops (Swanson, 1995; BEG, 1996).
Continuing south, the Interior Coastal Plains topography comprises of parallel alternating belts of resistant, uncemented sand among weaker shale that differentially erode to form long, sandy ridges. The stratigraphy of the subprovince is composed of unconsolidated sand and mud, gently tilted toward the Gulf of Mexico. At least two major-growth fault systems trend nearly parallel to the coastline, with clusters of additional faults concentrated over underlying salt domes in East Texas. The eastern region is characterized by numerous streams and pine and hardwood forests, which decline in density to the west and south (BEG, 1996).
The southernmost subprovince of the Gulf Coastal Plains is the Coastal Prairies, which consists of a nearly flat topography beginning at the Gulf of Mexico shoreline.
Sparse trees along streams and oak mottes grow on the coarser underlying sediments of ancient streams. The stratigraphy is composed of deltaic sand, silt, and clay that eroded to form a nearly flat region of grasslands, with some minor steeper slopes created by subsidence of deltaic sediments along growth faults (BEG, 1996).
2.5.1.1.1.2 Edwards Plateau Physiographic Province The Edwards Plateau ranges in elevation from 450 ft. (137 m) to 4,200 ft. (1,280 m),
with the underlying bedrock comprising limestone, dolomite, carbonate, and alluvial sediment, capped by hard Cretaceous-age limestone (BEG, 1996). Elevation decreases gradually eastward until it is abruptly separated from the Gulf Coastal Plain Coastal Plains by the Balcones Escarpment (Figure 2.5.1-1). The escarpment was created by movement along the Balcones fault zone during the Oligocene to early Miocene (Swanson, 1995; Collins and Hovorka, 1997). The escarpment extends for 300 mi. (482 km), bounding the Edwards Plateau to the east and south (Swanson, 1995). The escarpment is a dissected limestone wall trending southwest
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-3 December 2025 from Waco to San Antonio, then curving westward until losing definition near Del Rio at the Mexican border. The eastern part of the plateau consists of heavily forested areas with oak, cedar, and mesquite, with some valleys lined with large deciduous trees. As precipitation decreases westward, trees become increasingly sparse and stunted (Swanson, 1995). Alternating hard and soft marly limestone units form a stairstep topography in the central interior of the province (BEG, 1996).
2.5.1.1.1.3 Central Texas Uplift The Central Texas Uplift (also known as the Central Mineral Region) consists of a knobby plain surrounded by parallel ridges (questas). The subprovince is composed of billion-year-old Precambrian granite and metamorphic rock that is locally exposed through the overlying Paleozoic and Mesozoic cover rocks. Elevation in this subprovince ranges from 800 to 2,000 ft. (244 to 610 m). Due to the semi-arid central Texas climate, the granite is less resistant to erosion than the limestone, thus forming a basin floored by metamorphic rock and granite rimmed by Paleozoic and Cretaceous limestone formations of the North-Central Plains and Edwards Plateau subprovinces. The rolling topography of the floor of the basin is studded with rounded granite hills (BEG, 1996; Swanson, 1995).
2.5.1.1.1.4 Texas-Louisiana Shelf The Gulf of Mexico continental shelf forms an almost continuous terrace around the margin of the Gulf, with a width that varies from 60 to 120 mi. (100 to 200 km) along Texas and Louisiana (Garrison and Martin, 1973). Salt domes occur along the continental shelf and slope (Martin, 1973; Garrison and Martin, 1973; Hudec et al.,
2013).
2.5.1.1.1.5 Texas-Louisiana Slope The Texas-Louisiana Slope is a continental slope, located off the shores of Texas and Louisiana, that encompasses an area of over 46,000 sq. mi. (119,500 km2) and lies in water depths ranging from 656 to 9,840 ft. (200 to 3,000 m) along the base of the Sigsbee Escarpment. The continental slope is underlain by large masses of salt that can protrude upward into overlying sediments (Martin, 1973).
2.5.1.1.2 Regional Geologic History The geologic and tectonic region of the Long MottLMGS site has formed by multiple continental collision and rifting events, including the Grenville, Laramide, and Ouachita Orogenies (Ewing, 1991). Repeated sea level transgression and regression related to glacioeustatic sea-level changes punctuated stratigraphy during the Pleistocene (Galloway, 2008). The main geological elements of the Texas region are shown on Figures 2.5.1-3 and 2.5.1-4.
2.5.1.1.2.1 Grenville Orogeny In Texas, the Llano or Grenville tectonic cycle is represented by a poorly known early rift and the Grenville Orogeny that caused deformation and metamorphism in the crust in central Texas (Ewing, 1991).
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-4 December 2025 2.5.1.1.2.2 Late Proterozoic Laurentian Rifting Rifting in the Ouachita rift is dated with synrift volcanic rocks to 530539 mega annum (Ma) (Thomas, 2011). The rifting of Laurentia is interpreted to have occurred in two major pulses, one at approximately 700 Ma and one at 570 Ma. Rifting led to the development of basins which filled with volcanic rocks, clastic sediments and minor amounts of limestone (Neton, 1992).
2.5.1.1.2.3 Ouachita Orogeny Beginning in the Mississippian period, strike-slip faults and thin-skinned thrust structures began to develop as part of the Ouachita Orogeny (Ewing, 1991).
Deformation from the event extends from Alabama to northern Mexico (Harry and Mickus, 1998; Figures 2-5.1-5; 2.5.1-76). East of the Ouachita thrust belt, north-northeast of the Llano uplift, subsidence and increased sedimentation led to the formation of thick foredeep marine shales and sandstones (Ewing, 1991).
2.5.1.1.2.4 Mesozoic Rifting (Opening of the Gulf of Mexico and the Atlantic Ocean)
Beginning in the Late Triassic, extension and later rift faulting began to contribute to the opening of the present-day Atlantic Ocean and the Gulf of Mexico (Ewing, 1991). Two basins divided by the Brazos transform fault developed in the northern Gulf of Mexico as the result of sea-floor spreading (Hudec et al., 2013) and is shown in Figure 2.5.1-67. During early stages of rifting, salt is often deposited.
Widespread deposition of the Louanne Salt occurred between 176 and 156 Ma (Stern and Dickinson, 2010).
Two phases of rifting resulted in the formation of the Gulf of Mexico, beginning in the Late Triassic and ending in the Early Cretaceous. The first phase occurred from the Late Triassic to the Middle Jurassic and was related to the breakup of Pangea and the separation of North America from Africa. This rifting resulted in northeast-southwest trending rift basins, which were then filled with fluvio-lacustrine sediments (Vasileiou et al., 2023). Additional Jurassic age salt and sediment deposition occurred at the end of this rifting phase, contemporaneous with the opening of the Central Atlantic (García-Reyes and Dyment, 2021).
Counterclockwise rotation of the Yucatan block, which began during the end of the first rifting phase, initiated a second rifting phase in the Gulf from the Late Jurassic to Early Cretaceous. North America continued to separate from Africa, eventually leading to the oceanic separation of Yucatan and North America. Orthogonal structures formed during the extensional phases. Strike-slip structures also are believed to have been active during the rifting episode (Vasileiou et al., 2023).
Figure 2.5.1-8 shows the distribution of continental and oceanic crust as a result of this phase of rifting.
2.5.1.1.2.5 Laramide Orogeny The Laramide compression occurred during the Late Cretaceous to Paleogene in southern Texas (Ewing, 1991) and contributed to the creation of the Central and Southern Rocky Mountains (Bird, 1998). The Rocky Mountains formed when the
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-5 December 2025 oceanic Farallon plate subducted at a low angle, resulting in the wide zone of mountain building (Bird, 1998; Schwartz et al. 2023). Large-scale progradation driven by the Laramide orogeny induced a transition from carbonate to clastic sediment deposition within the Gulf, as suggested by heavy mineral studies indicating a Rocky Mountain sediment provenance (Mackey et al., 2012).
2.5.1.1.2.6 Cenozoic History The configuration of the Gulf Coast geosyncline and the Mississippi embayment began with the deformation of the Paleozoic surface, prior to Mesozoic deposition.
Folding caused by the Ouachita orogeny formed the deep geosyncline that served as a catch basin for sediment accumulation. Increased sediment accumulation led to downwarping and downfaulting of the Gulf Coast geosyncline and slight deepening of the Mississippi embayment (Hosman, 1996). Repeated sea level fluctuation throughout the Texas Gulf Coastal Plain Coastal Plains and basin subsidence from isostatic adjustments caused cyclic sedimentary deposits. These sediments are discontinuous sand, silt, clay, and gravel within the inland areas of the Gulf that grade into finer brackish and marine sediments offshore (Chowdhurdy and Turco, 2006). The glacial erosion, high sediment discharge, and expanded drainages caused by late Cenozoic cooling resulted in an influx of sediment from the north into the western Gulf following the mid-Pleistocene transition (Hessler et al., 2018).
2.5.1.1.3 Regional Stratigraphy This subsection describes the regional stratigraphy of the Gulf Coastal Plains physiographic province.
2.5.1.1.3.1 Basement Rock The thickness of the Mesozoic and Cenozoic sediments below the Gulf Coastal Plains province is over 16,400 ft. (5,000 m) (Boyd et al., 2024) (Figure 2.5.1-109).
Few wells have been drilled through the full Mesozoic section (Hudec et al., 2013);
therefore, the stratigraphy is typically established through indirect methods.
Although views on the origin and type of crustal rock beneath the marine and nonmarine sediment in the Gulf of Mexico basin vary, data suggest that the crust beneath the Jurassic sediments is continental (Hudec et al., 2013). A thick sedimentary package overlies the crystalline basement (Boyd et al., 2024; Figure 2.5.1-109).
2.5.1.1.3.2 Paleozoic Stratigraphy The Gulf Coast geosyncline and the Mississippi embayment began formation with the downwarping and downfaulting of the Paleozoic Era, prior to Mesozoic deposition. Due to the extreme depths of pre-Cretaceous geology in the Gulf Coastal Plains region, knowledge of theis strata is limited, as it is beyond the depths of interest to petroleum drillers. Cenozoic coastal deposits are flanked by Paleozoic and Mesozoic rocks at the surface adjacent to the Gulf Coastal Plains at its updip boundary (Hosman, 1996).
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-6 December 2025 2.5.1.1.3.3 Mesozoic Stratigraphy Rifting related to the breakup of Pangea during the Late Triassic led to the formation of the Gulf of Mexico basin, with rifting ending in the Early Cretaceous (Galloway, 2008).
2.5.1.1.3.4 Triassic Stratigraphy An extended period of Late Triassic through Early Jurassic rifting created a series of grabens and half grabens contemporaneously filled with terrestrial sediments and volcanic rocks (Galloway, 2008). Erosion and deposition during the Mesozoic produced vast accumulations of sediment in the Gulf Coast geosyncline, and substantial amounts in the Mississippi embayment. Triassic and Jurassic deposits later filled the geosyncline (Hosman, 1996).
2.5.1.1.3.5 Jurassic Stratigraphy Seafloor spreading in the Gulf began in the Middle Jurassic, continuing for approximately 25 million years (Galloway, 2008). Initial rifting created a shallow basin connected to the Pacific Ocean across Central Mexico. Widespread deposition of Louann salt and anhydrite blanketed the subsiding continental-oceanic transitional crust. Up to 2.48 mi. (4 km) of halite was deposited over 10 million years, burying the underlying topography and onlapping northward onto the Gulfs structural basin. Salt deposition was replaced in the Late Jurassic by the deposition, widespread siliciclastic-dominated sequence known as the Norphlet Formation. The Norphlet deposits onlap the unconformity from the breakup that formed the Atlantic, especially in the structural embayments of the northeast Gulf margin. In the embayments, many small alluvial fans, braidplain, and delta systems created local depocenters up to 984 ft. (300 m) thick. Due to continued aridity, eolian, sabkha, and playa deposits were also deposited. Basinward, siliciclastics grade into marine shale and limestone (Galloway, 2008).
Following the deposition of Louann salt and the Norphlet Formation, the region was covered by a Late Jurassic marine transgression. This transgression resulted in the first carbonate-dominated depositional episode in the Gulf region. The Smackover, Buckner, and Gilmer Formations record an approximately 5-million-year cycle bounded above and below by transgressive flooding surfaces. Initial fine-grained, dark, carbonate ramp deposits were succeeded by a heterogeneous assemblage of carbonates. The Haynesville Formation formed in deltaic and shore zone systems. Terminal flooding and deposition of the transgressive Gilmer Limestone mark the end of this episode (Galloway, 2008).
The transgressive Gilmer and Haynesville strata were overridden by sandstones during the Cotton Valley depositional episode. Deposition throughout the Gulf basin changed from carbonate-dominated to siliciclastic-dominated deposition, indicating that continental uplift or climate change rejuvenated adjacent North American sediment source areas.
Suspended sediment from large, sandy delta systems in the East Texas basin, Mississippi salt basin, and Apalachicola embayment spread basinward to form a broad, muddy, marine shelf platform that built basinward beyond older Jurassic formations. Deltaic sedimentation was followed by a brief phase of carbonate accumulation, which led to the deposition of the Knowles Limestone to mark the terminal transgression of a clastic-dominated episode (Galloway, 2008).
The Cotton Valley depositional episode ended with a record of transgression, separated from the strata of the overlying Lower Cretaceous Hosston episode by a single prominent
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-7 December 2025 unconformity throughout the northern Gulf divergent margin. This unconformity encompasses the entire Valanginian and indicates subaerial exposure and erosion, reflecting the progressive uplift and basinward tilting of the northern Gulf margin. The unconformity coincides with termination of seafloor spreading in the Gulf. The seafloor spreading medial location within a 25-million-year phase of coarse clastic sedimentary influx within the northern basin indicates that it is a direct consequence of intraplate stress regime changes that led to the deformation of the North American plate (Galloway, 2008).
2.5.1.1.3.6 Cretaceous Stratigraphy Six composite depositional episodes occurred after the termination of the Gulf rifting. These episodes record a diminishing continental source area relief and basin-margin stabilization.
The climate during the Early Cretaceous was tropical and arid, with a decrease in clastic input leading to an abundance of carbonate deposition in the northern Gulf (Galloway, 2008).
Lower Hosston strata were buried during the Late Valanginian from the resumption of subsidence of the basin margin and northward expansion of the Gulf basin. Lower Hosston clastic accumulation was dominated by four deltaic depocenters. Four sandy fluvial systems that prograded deltaic deposits into the Apalachicola embayment, Mississippi salt basin, East Texas basin, and Rio Grande embayment. The only non-clastic dominated interdeltaic shelf was located above the San Marcos arch, which was carbonate dominated (Galloway, 2008).
After Late Hauterivian transgression ended, a mixed depositional episode of carbonates and clastics began the reef-rimmed carbonate margin progradation. Carbonate platform growth and consolidation continued for 10 million years, ending with an abrupt Aptian deepening that terminated the Sligo depositional episode, which blanketed the northern Gulf shelf in a thin, widespread Pine Island Shale. Following this deposition, the James Limestone and Bexar Shale record a rejuvenation of carbonate deposition, followed by extensive shelf drowning. Together, the Pine Island-James-Bexar interval, all part of the Pearsall Group of the Texas Gulf margin, constitute a retrodegradational stratigraphic systems tract, which culminated with basin-wide flooding (Galloway, 2008).
Shelf drowning was followed by the creation of the Stuart City Reef, a carbonate platform and barrier reef system made up of rudists, corals, encrusting algae, and stromatoporoids.
The Albian rimmed platform continued to grow during three deepening events and one event of clastic sediment input. These created three depositional episodes named for the outcropping Glen Rose, Fredericksburg, and Washita Groups. Strata of the Glen Rose episode are made up of sandy to argillaceous, oolitic, and bioclastic lime mudstone, packstone, and grainstone. The Glen Rose is separated from the overlying Fredericksburg by an updip unconformity, shoaling, and resurgent clastic influx onto the inner shelf. The Fredericksburg genetic sequence consists of three principal lithostratigraphic components:
the Paluxy Formation, Danzler Formation, and Edwards Group. The Paluxy and Danzler record depositional progradation of deltaic systems onto the inner to middle shelf of the East Texas basin. The limestone and dolomite of the Edwards Group then accumulated throughout the episode on the outer shelf and transgressed landward over the Paluxy inner-shelf, deltaic, and shore-zone systems late in the episode (Galloway, 2008).
The Stuart City reef continued to thrive along the shelf margin throughout the Fredericksburg episode, with significant progradation and aggradation occurring across the
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-8 December 2025 central Gulf. The McKnight salina formed during this episode, and the diversion of the Stuart City reef axis around the Maverick Basin contributed to the development of the Devils River trough (Galloway, 2008).
The Washita depositional episode spanned the boundary between the Early and Late Cretaceous, characterized by the growth climax of the Stuart City reef, and the widespread accumulation of shallow shelf sediments. The Washita ended with the establishment of one of the major discontinuities in the Mesozoic record of the Gulf, the Mid-Cretaceous Unconformity (MCU). This event replaced the carbonate reef depositional environments, which had persisted for 14 million years, with clastic progradation (Galloway, 2008).
The MCU marks a distinct shift from Early Cretaceous basinal carbonates to Late Cretaceous and Cenozoic basinal mudstones. Changes to clastic influx, along with differential tectonic uplift, led to a permanent change in basin-wide depositional style across the MCU, illustrating a significant geologic transformation in the Gulf region and clearly marking the transition from the Early to Late Cretaceous (Galloway, 2008).
The Late Cretaceous, defined by the strata overlying the MCU, contains at least six depositional episodes, with additional transgressive events used to further subdivide the section within the Gulf region. These include the Tuscaloosa, Woodbine, Austin, Taylor, Navarro, and Cretaceous-Tertiary episodes.
The Tuscaloosa/Woodbine composite depositional episode consists of deltaic progradation deposits of the Lower and Upper Tuscaloosa episodes of the Louisiana margin and the Woodbine and Eagle Ford episodes of the Texas margin. The Tuscaloosa system formed a prograding shelf-margin wedge of delta and delta-fed slope apron sandstone and mudstone. The Woodbine fluvial/deltaic system was wave-dominated. This system prograded to the southwest into the East Texas basin to build a muddy shelf margin.
Through the later Cenomanian, thermal uplift began to collapse, decreasing sediment supply. The episode terminated with regional flooding and development of a Late Turonian flooding horizon across the Gulf shelf, which recorded waning sediment supply and renewed subsidence (Galloway, 2008).
Depositional style changed dramatically in the northern Gulf due to global eustatic sea-level highstand during the Coniacian through Santonian. This was reflected in the Austin depositional episode, characterized by the accumulation of chalk deposits across the northern Gulf, reflecting a deep, clastic-starved shelf environment. Following the Austin episode, Upper Taylor deposition provided a renewed influx of sandy terrigenous sediment originating from multiple deltaic systems, including the Rocky Mountain system, the San Miguel system, and numerous volcanic cones that rose across the Rio Grande embayment and San Marcos arch. Relative sea level remained high throughout most of the Taylor episode, submerging the basin margin, with deposition occurring dominantly in shallow-to deep-shelf systems (Galloway, 2008).
The Navarro Group records the terminal Maastrichtian depositional episode of the Cretaceous Gulf of Mexico. This episode created a succession of strata that record a phase of siliciclastic-dominated progradation and shoaling, bounded above and below by intervals of erosion, marine transgression, shelf starvation, and prominent flooding surfaces. Multiple unconformities within the Navarro Group are interpreted to be the result of continued
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-9 December 2025 influence of Laramide crustal stress, uplift, and subsidence across the northern Gulf basin (Galloway, 2008).
The Cretaceous-Tertiary boundary strata of the Gulf recorded widespread sediment starvation throughout the area, as well as the Chicxulub meteorite impact event. This impact triggered seismic shocks, submarine slides, mass flows, and an impact tsunami.
The impact formed an oval crater beneath the Yucatan Platform that is 90 by 120 mi. (140 by 190 km) in diameter (Galloway, 2008).
2.5.1.1.3.7 Cenozoic Stratigraphy Paleocene Stratigraphy:
Paleocene deposits in the Gulf Coastal Plain Coastal Plains region include sediment from the Midway and part of the Wilcox Group, separated from the underlying Upper Cretaceous strata by a major disconformity in much of the region. However, a break in deposition is not apparent in all areas. The change in faunal assemblages from Cretaceous to overlying Midway strata is drastic, marking the extinction of many Mesozoic forms. This drastic change marks the demise of the dinosaurs and the beginning of the rise of early mammalian species (Hosman, 1996).
The rocks of the Midway Group are characterized by the most uniform lithology in the region and comprise the Clayton Formation, Porters Creek Clay, and Naheola Formation.
The deposition of hundreds to thousands of feet of clay is marked by a transitional change in lithology at the top and bottom of the Midway Group, due to extensive marine encroachment. Quaternary alluvium overlies the Midway Group along the northwestern flank of the Mississippi embayment from the vicinity of Little Rock, Arkansas, to the southern tip of Illinois (Hosman, 1996). The deepest unit of the Midway Group is the Clayton Formation, composed of limestone, calcareous sand, and sandstone, grading into marl and calcareous silt and clay downdip. Thickness ranges from under 100 to 200 ft. (30 to 60 m). Overlying the Clayton Formation is the Porters Creek Clay, which is present throughout the area and makes up the bulk of the Midway Group. It is a mostly dark-gray to black, blocky, micaceous clay, with some interbedded or thinly laminated fine sand and gray clay found in the northern portion of the Mississippi embayment (Hosman, 1996). The Naheola Formation is the uppermost stratigraphic unit of the Midway Group recognized in Mississippi and Alabama. The Naheola Formation is lithologically very similar to the overlying Wilcox Group (Hosman, 1996).
Eocene Stratigraphy:
Eocene deposits in the Gulf Coastal Plains region are composed of sediments from the Wilcox, Clairborne, and Jackson Groups. The base of the Eocene Series is placed at the tops of the Paleocene Naheola Formation and Porters Creek Clay. The Wilcox Group has a maximum thickness of over 1,200 ft. (365 m) in the Mississippi embayment, becoming thousands of feet thick gulfward in the southern parts of the region. The Wilcox Group strata are heterogenous, consisting mostly of arenaceous-argillaceous-carbonaceous deposits, similar to the Naheola Formation, and with an abundance of lignite (Hosman, 1996). Much of the Wilcox is deltaic in origin, containing deltaic beds composed of thinly laminated, very fine sand, silt, and clay. The Wilcox Group can form a gradational contact
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-10 December 2025 with the underlying Midway Group differentiated by a lithology composed of coarser sandy materials of both deltaic and nonmarine origin (Hosman, 1996).
The Carrizo Sand, or Meridian Sand, is the basal unit of the Clairborne Group. It was deposited onto an uneven and eroded Wilcox surface, leading to a variation in thickness of 100 to 1,200 ft. (30 to 365 m). The Carrizo Sand is predominately fine to coarse grained sand, light to brownish gray, with some micaceous clay lenses (Hosman, 1996).
The Reklaw Formation conformably overlies the Carrizo Sand, with contacts ranging from distinct to gradational in some areas. The formation is composed of a sequence of shales and sands. The upper portions can be nonmarine lignitic clay, while lower portions are made up of fossiliferous glauconitic sand (Hosman, 1996).
The Queen City Sand is a light gray to grayish brown, very fine-to medium-grained quartz sand, typically cross-bedded and lenticular, with interbeds of carbonaceous shale, silt, and lignite (Hosman, 1996).
The Weches Formation overlies the Queen City Sand and is classified as a greensand because it is high in glauconite. The formation comprises highly fossiliferous, cross-bedded, lenticular sand interbedded with thin beds of dark gray to black glauconitic clay and shale.
Due to the leaching of the glauconite deposits, there are also concentrated deposits of iron ore (Hosman, 1996).
The Sparta Sand extends northward from the Coastal Plain coastal plains to the central part of the Mississippi embayment. It is composed of a commonly laminated or cross-bedded very fine to medium unconsolidated quartz sand with subordinate beds of light gray carbonaceous clay, ranging in thickness from 100 to over 1,000 ft. (30 to 304 m) (Hosman, 1996).
The Cook Mountain Formation consists of typically marine deposits present throughout the Gulf Coastal Plain Coastal Plains region. Its thickness ranges from less than 200 ft. to over 900 ft. (60 m to over 274 m). The western portion, located in Texas, is composed mostly of clay, shale, and sandy shale, with lesser amounts of sand, glauconite, limestone, and ferruginous concentrations. The southern portion in southern Texas contains a larger proportion of sand and sandy clay, thickening downdip as the clay facies becomes the lithology (Hosman, 1996).
The Yegua Formation occurs across the entire Gulf Coastal Plain Coastal Plains region, with a maximum thickness of over 1,800 ft. (548 m). It comprises massive, laminated, and cross-bedded deposits of fine to medium sand, with brown and gray sandy clays and clays (Hosman, 1996).
The last marine inundation of the Coastal Plain coastal plains to occupy the Mississippi embayment was the Jackson Sea. The sediment of the Jackson Group conformably overlies the Yegua Formation. The Jackson Group of sedimentary units is composed of mostly marine sediments but includes some nonmarine beds in the central and northern portions of the Mississippi embayment. In Southern Texas, the Jackson Group includes the Caddell Formation, the Wellborn Sandstone, the Manning Clay and the Whitsett Formation (Hosman, 1996).
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-11 December 2025 The lowermost unit of the Jackson Group in Texas is the Caddell Formation, which rests conformably on the Yegua Formation, with a thickness ranging from 30 to 300 ft. (9 to 91 m). The formation has a variable composition that is typically marine in the lower portion and nonmarine in the upper (Hosman, 1996).
The Wellborn Sandstone Formation overlies the Caddell Formation and ranges in thickness from less than 100 ft. (30 m) to over 300 ft. (91 m). The lower portion consists of massive, locally quartz-rich sandstone with some fossiliferous marine clay beds. The middle section is a marine facies composed of fossiliferous sandy clays. The upper section is a massive gray to white argillaceous sandstone (Hosman, 1996).
The Manning Clay Formation comprises nonmarine beds 250 to 350 ft. (76 to 106 m) thick that overlie the Wellborn Sandstone. It consists of carbonaceous brown lignitic clay, which alternates with two major beds of gray sandstone and contains interbeds of sand, sandy shale, diatomaceous shale, and fossiliferous marine shale beds (Hosman, 1996).
The Whitsett Formation is the uppermost unit in the Jackson Group in southern Texas, with a maximum thickness of about 135 ft. (41 m). It consists of mostly nonmarine cross-bedded sand and sandstone interbedded with tuffaceous shale and fine sandy tuff. The formation also contains opalized wood, and fossil leaves (Hosman, 1996).
Oligocene Stratigraphy:
The lower part of the Oligocene Series in the Gulf Coastal Plain Coastal Plains is made up of predominantly marine deposits that belong to the Vicksburg Group, with the sediments containing increasing amounts of volcanically derived material and becoming more arenaceous in the higher stratigraphic portions of the series (Hosman, 1996). Oligocene depositional environments are shown in Figure 2.5.1-910.
Sediments of the Vicksburg Group overlie the Jackson Group, with exceptions in some areas where they overlie older Oligocene deposits. The Vicksburg Group is composed of a variety of marine lithologies and is recognized by its distinct faunal assemblages. Lithology varies from argillaceous and arenaceous to marl and limestone, with calcareous content generally increasing downdip and southeastward (Hosman, 1996).
Originally described from exposures in central Louisiana, the Catahoula Sandstone (labelled Catahoula Tuff in southern Texas) was later recognized in Texas, Mississippi, and southern Louisiana based on subsurface correlations. The sandstone is primarily composed of interbedded tuffaceous clay, sand, and sandstone, with irregular interbedding and commonly discontinuous individual strata. Composition becomes more volcanic in origin (pyroclastic) westward and is categorized as a tuff in southern Texas (Hosman, 1996). The Frio Formation is the deltaic marine downdip equivalent of the Catahoula Formation (Swanson et al., 2013).
The Frio Formation is time-equivalent to the Catahoula fFormation. The Frio Formation is the production unit for a large portion of oil and gas extracted from the Texas Coastal Plains (Bebout et al., 1983). The Frio Formation is composed of coastal sediments, including deltaic and wave-dominated coastline deposits (Galloway and Morton, 1989). The Frio Formation is cemented with quartz-and, calcite-cemented, and with has high rates of
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-12 December 2025 secondary porosity (Galloway and Morton, 1989; Loucks, 2006). Near the site, the Frio Formation is 5000 to -6000 ft. (1524 to 1829 m) below sea level (Figure 2.5.1-2011).
Miocene Stratigraphy:
Deposition during the Miocene Epoch in the Gulf Coastal Plain Coastal Plains consists of mainly marine regression deposits, with many temporary reversals producing cycles within the overall depositional pattern. This process resulted in the interspersion of fossiliferous marine strata in otherwise nonmarine sediments. The majority of Miocene age deposits are a heterogeneous assemblage of deltaic, lagoonal, lacustrine, palustrine, eolian, and fluvial clastic facies, with local calcareous reef facies (Hosman, 1996).
The Oakville Sandstone, part of the Fleming Formation, is a sandy unit that directly overlies the Catahoula Tuff in southern Texas, distinguishable by its predominantly sandy lithology.
The sandstone is a nonmarine clastic deposit composed of coarse sand and sandstone, grit and gritstone, and silt with subordinate amounts of interbedded clay. The sand units are irregularly bedded. The thickness of the Oakville Sandstone ranges from 200 ft. to over 500 ft. (60 m to over 152 m) (Hosman, 1996). In the central Texas Coastal Plains, the Oakville Sandstone is described as partially consolidated (Solís, 1981).
The Fleming Formation overlies the Oakville Sandstone and was first identified from surface exposures in southeastern Texas, and later recognized as extending into western and central Louisiana. The formation is primarily clay in southern Texas, with sand content increasing eastward. The Fleming Formation thickness ranges from 200 ft. (60 m) to thousands of feet in the subsurface (Hosman, 1996).
Pliocene Stratigraphy:
Pliocene deposits are very similar to those of the Miocene Epoch with some minor lithologic differences. The units are primarily distinguished based on faunal criteria. Additionally, Pliocene deposits are generally more arenaceous and thinly interbedded than those of the Miocene, with less calcareous clay and more lignitic sand (Hosman, 1996).
The Goliad Sand overlies the Fleming Formation. The lower Goliad strata are coarse-grained sediments, including cobbles, gravel, clay balls, and wood fragments, with irregular bedding suggesting alluvial river-bottom sediments. The upper portion of the Goliad Sand is predominantly sand, some of which is cemented with calcium carbonate or has a matrix of caliche (Hosman, 1996). The Goliad Formation is generally mapped as unconsolidated (Solís, 1981).
Pleistocene Stratigraphy:
Pleistocene sea level changes related to glacioeustatic sea level changes drove the creation of broad shelves. Sea level drawdowns led to the formation of deep valleys in the shelf (Galloway, 2008).
Holocene Stratigraphy:
The Holocene Epoch is characterized by alluvial deposition in the flood plains of aggrading streams and coastal deposition. Alluvium underlies the flood plains of all major drainage
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-13 December 2025 systems in the Gulf Coastal Plains region, with the largest drainage system being the Mississippi River. Flat-lying floodplain deposits are typically comprised of sand and gravel in the lower portion and silt and clay in the upper portion. Along the Gulf, the river sediments are deposited as deltaic fans of silt and clay. Other deposition continues in coastal marshes and in the nearshore environment where alongshore transport deposits sediments (Hosman, 1996).
2.5.1.1.4 Regional Tectonic Setting This subsection describes the regional history of the Long MottLMGS site region (200 mi.
[320 km] in diameter).
The Long MottLMGS site lies within the Texas Gulf Coastal Plains physiographic province, extending from Mexico in the west to Florida in the east (BEG, 1996) (Figures 2.5.1-1 and 2.5.1-112 [(1 and 2])). Most tectonic models suggest that the Gulf basin was formed by the counterclockwise rotation of the Yucatan Peninsula block away from the North American Plate, involving an ocean-continent transform boundary during the Late Jurassic (Bird et al.,
2011). Evolution of the convergent margin is interpreted in the context of the opening and closing of the Iapetus Ocean, as indicated by the distribution of early Paleozoic carbonate-shelf and deep-water facies in the Ouachita orogenic belt that suggests the trace of a shelf edge around the Ouachita region. This depositional framework implies that a rifted margin of continental crust controlled the location of the shelf edge (Thomas, 1985).
Following Appalachian-Ouachita orogenesis, evidence for the opening of the Gulf in the early Mesozoic is from a system of northwest-trending faults that cut Paleozoic rocks. Post-rift subsidence of the Gulf Coastal Plain Coastal Plains toward the Gulf is reflected in the present structural configuration of the Coastal Plain coastal plains sedimentary sequence above the Paleozoic structures of the Appalachian-Ouachita orogen and the adjacent foreland basins (Thomas, 1985). The principal tectonic events are summarized in the following subsections.
2.5.1.1.4.1 Precambrian to Paleozoic Plate Tectonic History Geologic evidence recording the tectonic history of the Precambrian is limited in Texas, due to the sparsity of Precambrian age rock outcrops (Ewing, 1991). Mesoproterozoic age metamorphic rocks are subareially subaerially exposed in the eastern Llano Uplift. These rocks were involved in a Grenville-age (1150 - 1160 mega annum [Ma]) arc-continent and continent-continent orogenic event along the southern margin of Laurentiathe ancestral North American continent. This event is characterized by polyphase ductile deformation synchronous with upper amphibolite-facies dynamothermal metamorphism (Mosher, 2004).
The Late Paleozoic Appalachian-Ouachita-Marathon orogen rimmed the eastern and southern margins of the North American craton and was part of the continent-scale system that resulted from the closure of the oceans that rimmed the Laurentian continent and the Late Paleozoic assembly of supercontinent Pangea (Thomas et al., 2021).
The rifting of Laurentia occurred in two major phases. The first began about 700 Ma with rift initiation varying along its trend, and the second began about 570 Ma. The developing rift basins received thick and varied fills of volcanic rocks, clastic sediment, and minor amounts of limestone as rifting proceeded (Neton, 1992). During the breakup of Rodinia, Neoproterozoic to Cambrian isolation of Laurentia was associated with multiple, large
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-14 December 2025 igneous provinces, protracted multiphase rifting, and variable subsidence along different margin segments. Many of Laurentias Neoproterozoic margins experienced multiple rift phases, indicative of reactivation by external forcing. This forcing was caused by early separation of large continental blocks leading to a widening ocean basin. Subsequent initiation of subduction zones within the ocean basin and changes in mantle flow resulted in stronger extensional forces transmitted to the margin, renewed rifting of ribbon fragments, and final rifted transition (Macdonald et al., 2023).
The western margin of Laurentia formed through multiple episodes of extension and magmatism during the Neoproterozoic and Cambrian. These episodes included sedimentation in basins, regional rifting and associated volcanism, regional subsidence with deposition of fine-grained siliciclastic and carbonate strata, and final rifting with development of structural unconformities. Limited mafic activity from 600 to 520 Ma, development of unconformities, and deposition of coarser, variably feldspathic strata with a change in detrital zircon age spectra record the final rifting along the western Laurentian margin (Macdonald et al., 2023).
The southern Laurentian margin ranges from the Alabama promontory to Sonora, Mexico, and is separated into the Ouachita and Sonoran segments. Rift-related volcanism from Oklahoma to Mexico with a significant pulse of magmatism occurring 532 Ma, is recorded in the Wichita large igneous province (Macdonald et al., 2023).
Deep drill hole and geophysical data taken from the subsurface beneath the Gulf Coastal Plains, along with outcrops in Ouachita Mountains of Arkansas and Oklahoma, provide a profile of the Ouachita orogen. Inheritance of the trace of the pre-orogenic Iapetan rifted margin of Laurentia is reflected in the Ouachita salient, which forms a large-scale cratonward convex curve with a bend of about 90 degrees in strike. The intersection of the Alabama-Oklahoma transform fault with the Ouachita rift frames the Ouachita embayment in the Iapetan-rifted margin of southern Laurentia, reflecting the late stages of continental rifting and breakup of supercontinent Rodinia. Iapetan rifting cut across the Grenville Front and excised part of the Laurentian Granite-Rhyolite province in the Ouachita embayment, indicated by synrift boulders and detrital zircons in the Precordillera having similar ages to the Granite-Rhyolite province. Cambrian to Mississippian deposits on the passive-margin shelf of southern Laurentia are dominantly shallow-marine carbonate rocks, extending from the onlap limit of the Canadian Shield southward to the shelf margin around the Ouachita foreland. Cambrian to Mississippian strata in the Ouachita thrust belt are an off-shelf deep-water mud-dominated facies that is the counterpart of the passive-margin shelf carbonates.
The muddy succession includes carbonate mudstone, carbonate-clast conglomerate, and quartzose sandstone, all indicating detritus from the shelf (Thomas et al., 2021).
Along the northern arm of the Ouachita thrust belt, Cambrian - Mississippian off-shelf passive-margin succession and overlying Mississippian - Pennsylvanian synorogenic muddy to sandy turbidites are imbricated in the Ouachita allochthon and thrust over the Cambrian - Mississippian passive-margin carbonate-shelf facies, which remained in the Ouachita footwall. The Maumelle chaotic zone of broken Mississippian - Pennsylvanian sandstone and shale represents the leading edge of the accretionary prism that was thrust onto the pre-orogenic shelf. Fragments of the oceanic crust of the Laurentian plate that were eroded from the down-going slab include rare tectonically bounded slivers of ultramafic rocks within the deformed sedimentary rocks along the uplifts. Upper Cambrian to Lower Mississippian off-shelf deep-water passive-margin strata and Middle Mississippian
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-15 December 2025 to Middle Pennsylvanian synorogenic clastic facies in the Ouachita frontal thrust belt were thrust over the shelf edge onto the Cambrian - Mississippian passive-margin shelf-carbonate facies as interpreted from drilling data and interpretation of seismic-reflection profiles. The Ouachita interior metamorphic belt trails the Ouachita sedimentary thrust belt, consisting of low-grade metasedimentary rocks and extending along strike southwestward around the Texas recess to the Marathon salient. The trailing part of the Ouachita orogen east of the Fort Worth basin may have been impacted by accretion of the Sabine terrane (Thomas et al., 2021).
The timing of the end of Ouachita thrusting in the accretionary prism is well constrained in the subsurface, where an angular unconformity separates deformed Ouachita facies rocks as young as early Middle Pennsylvanian from overlying undeformed shallow-marine successor-basin strata of late Middle Pennsylvanian to Middle Permian age. In the foreland, rocks as young as middle Desmoinesian are involved in folds that parallel the Ouachita thrust front. Based on these observations, the end of the Ouachita deformation is approximately 310 Ma in the interior structures, and the end of contraction on the frontal faults is approximately 309 Ma in the foreland (Thomas et al., 2021).
2.5.1.1.4.2 Mesozoic and Cenozoic Tectonic History The evolution of North America and subsequent creation of the Gulf of Mexico involved several tectonic events, beginning with the breakup of Pangea (Figure 2.5.1-67). Early extension began approximately 230 Ma along the Appalachian-collapse rift system, extending from Greenland and the British Isles in the north to the Takatu Rift in the south.
North America - Gondwana rifting ended when seafloor spreading began in the central Atlantic region, approximately 180 Ma. During this time, the Central Atlantic Magmatic province mantle plume erupted, producing 14,395 cu. Mimi. (60,000 km3) of flood basalts and associated intrusions over North America, South America, Africa, and Europe. Between 160 and 140 Ma the rotation of the Yucatan Block away from North America involved a single ocean-continent transform forming the Gulf of Mexico (Bird et al., 2011).
The development of the Ouachita orogenic belt in Late Paleozoic time marked the end of a full Wilson cyclethe cycle of the opening and closing of an ocean basin through continental rifting and collision (Viele and Thomas, 1989). South of the intersection of the Ouachita thrust front with basement structures along the southern Oklahoma fault system, post-orogenic Mesozoic - Cenozoic strata of the Gulf Coastal Plain Coastal Plains cover the Ouachita orogen and the proximal part of the Fort Worth basin in the footwall of the orogen (Thomas et al., 2021).
The Gulf continental margin is like the U.S. Atlantic margin in that the axis of Mesozoic continental breakup trended subparallel to the buried middle Paleozoic Ouachita fold-and-thrust belt. However, the Ouachita orogen acted as a zone of strength during continental rifting, rather than a zone of weakness like the Appalachian orogen. The strength of the Ouachita orogen is responsible for the abrupt northward termination on the southern flank of the orogenic belt, the broadly distributed extension throughout the coastal plains, shelf, slope, and rise between Late Triassic and Callovian time, and the rapid deepening of the distal shelf and onset of seafloor spreading in the early Oxfordian time. Tectonic structures inherited from Precambrian rifting and the Paleozoic Ouachita orogeny are the dominant controls on the style of rifting on the North American Gulf of Mexico continental margin (Huerta and Harry, 2012).
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-16 December 2025 The origin of the basin is reflected in the distribution and nature of the basement crust that consists of two types of transitional continental crust stretched and attenuated by Middle to Late Jurassic rifting (Figure 2.5.1-8). Most of the structural basin is underlain by a broad zone of thick transitional crust, which displays some modest thinning and lies at crustal depths between 1 and 7 mi. (2 and 12 km). The thick crust consists of blocks of near-normal thickness continental crust separated by areas of stretched crust that have subsided deeper to form a chain of named arches and intervening embayments and salt basins around the northern periphery of the region. The majority of the present inner coastal plains, shelf, and slope is instead underlain by relatively homogenous thin transitional crust, which is generally less than half the typical 21-mi. (35-km) thickness of continental crust and lies at depths of 6 to 10 mi. (10 to 16 km) below sea level (Galloway, 2008).
As continents drift apart, the growth of the adjacent ocean basins is reflected in magnetic data. Bands of linear anomalies flanking spreading centers represent episodic reversals in the polarity of Earths geomagnetic field. Closing ocean basins along geomagnetic isochrons is an objective method to analyze reconstructed margins because extensional rifting in passive margins essentially ceases once new oceanic lithosphere is created. Early seafloor spreading in the central Atlantic Ocean, from about 180 Ma to 160 Ma, included two significant location shifts in the seafloor spreading center, or ridge jumps. These ridge jumps may have coincided with rifting of the Yucatan block away from North America, and seafloor spreading in the Gulf. This mechanism is further supported by the timing of the second ridge jump (160 Ma) correlating with the timing of the initial rifting and rotation of the Yucatan block away from North America and seafloor spreading in the Gulf. Based on the closest North American-Gondwanan fit, final closure required that the Yucatan block rotate over 40 degrees clockwise from its present position in order to close the Gulf (Bird et al.,
2011).
Throughout the Late Jurassic, the Yucatan block rotated about 22 degrees counterclockwise around a pole presently located at 24 degrees north, 81.5 degrees west.
For this rotation to occur, a north-south oriented transform fault most likely existed off the coast of eastern Mexico. The 160 Ma westward ridge jump observed in the central Atlantic is interpreted to be linked to the clearing by the Florida shelf to the Trinidad corner, located on the north coast of South America to create space for the Gulf to open. This event was coeval with the onset of the Yucatan block rotation. During this block rotation, salt was widely deposited on extended and attenuated continental crust around the time of the second central Atlantic ridge jump (Bird et al., 2011).
Salt in the Gulf can be separated into two large regions considered to have formed contemporaneously: the northern Gulf of Mexico basin and the Campeche salt basin. The landward morphology of the Campeche salt margin and the northern Gulf salt basin represent rift valley walls that formed as continental blocks separated. The Keathley Canyon and Yucatan Parallel structures likely formed seaward boundaries for autochthonous Campeche and Louann salt as seafloor spreading occurred, until about 140 Ma. This is supported by the lack of autochthonous salt identified beneath the Keathley Canyon anomaly (Bird et al., 2011).
By 140 Ma, another 20 degrees of counterclockwise rotation by seafloor spreading completed the formation of the Gulf. Typical passive margin continental thickness of over
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-17 December 2025 12 mi. (20 km) thinning to typical oceanic thickness of 2 to 5 mi. (4 to 8 km) toward the basin is indicated by interpretation of regional seismic refraction data (Bird et al., 2011).
2.5.1.1.4.3 Present-Day Tectonic Stress The Long MottLMGS site is located within the Gulf Coast stress province, which coincides with the belts of growth faults in the coastal regions of Texas, Louisiana, Mississippi, Alabama, and northwestern Florida (Zoback and Zoback, 1989). North of the Gulf Coastal Plains stress province, a northwest-trending boundary between two major crustal stress provinces is in central Texas. The central and eastern United States is characterized by approximately northeast-southwest horizontal compression (Zoback and Zoback, 1989).
The southern Great Plains stress province is interpreted to be a transition between active extension in the western Basin and Range, and compressive stress in the eastern relatively stable midcontinent. The location of the mid-plate and southern Great Plains stress provinces reflects the paucity of stress indicator data to precisely constrain the location of the boundary. The southern Great Plains province generally coincides with the major 140-mi. (225-km) topographic gradient separating the midcontinent area and the thermally elevated western Cordillera (Zoback and Zoback, 1989).
2.5.1.1.4.4 Principal Tectonic Structures Late Proterozoic Tectonic Structures:
No significant Late Proterozoic features are mapped within the 200-mi. (320-km) radius of the site. The only window of Proterozoic rocks in the site region is the core of a Mesoproterozoic orogenic belt that formed along the southern margin of Laurentia during Grenville time, and now exposed by the Llano Uplift of central Texas (Mosher, et al., 2008; Figure 2.5.1-112 [(1 and 2])). Rocks exposed in the Llano Uplift record the deepest levels of the collisional Laurentian orogen. The continental margin arc was produced by earlier subduction with a northward polarity, ceasing sometime after 1232 Ma as indicated by a lack of plutonism or volcanism in the Llano Uplift. A passive margin sequence formed along the Laurentian margin and was involved in the initial stages of collision. The collision of Laurentia and an exotic arc, emplacement of ophiolitic rocks, and telescoping of the intervening basinal sediments resulted from subduction with a southward polarity. This subduction was followed by overriding of the arc and margin of Laurentia by a southern continent with transport towards Laurentia. Continent-arc-continent collision is recorded in the eastern uplift, with continent-continent collision recorded in the western uplift. Both regions of the Llano Uplift also expose different crustal levels in the orogen. The emplacement of ophiolites and formation of high-pressure rocks is similar to Phanerozoic orogens, implying that plate tectonic processes were active prior to the Neoproterozoic (Mosher et al., 2004; Mosher et al., 2008).
Paleozoic Plate Tectonic Structures:
Major Paleozoic tectonic structures in the 200-mi. (320-km) radius of the site are associated with the Late Paleozoic Ouachita Orogeny. The Ouachita orogenic belt is made up of rocks that were thrust onto the southern margin of the North American craton during the final stages of ocean closing. Geologic structures related to the Ouachita orogeny extend into the interior craton, beyond the boundaries of the belt (Viele and Thomas, 1989).
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-18 December 2025 The Ouachita orogenic belt comprises several tectonic provinces and records the collision along the southern margin of the North American craton. Evidence for the Ouachita in Oklahoma and Texas is mostly buried and is characterized based on drilling and seismic reflection data (Viele and Thomas, 1989). In the subsurface of eastern Texas, wells have penetrated rocks of the Ouachita orogen arranged in north-south-trending belts. The westernmost of the belts includes a non-metamorphosed pre-orogenic sequence containing rocks as old as the Ordovician black shales that lie beneath the upper siliceous succession of the Ouachita Mountains. Further east, flanking the non-metamorphosed belt, is a belt of dark colored clastic rocks. These rocks lie in two metamorphic zones: a western zone of incipient metamorphism and an eastern zone of greater recrystallization. Further east in the Ouachita subsurface is the interior metamorphic belt of slate, marble, phyllite, meta-quartzite, and schist. This interior metamorphic belt is the most strongly metamorphosed unit in the Ouachitas (Viele and Thomas, 1989).
The abrupt change from non-or slightly metamorphosed Ouachita rocks to metamorphosed rocks forming the interior metamorphic belts is marked by the Luling thrust sequence, interpreted from drilling and seismic-reflection profiling as an overthrust fault. The Luling thrust sequence comprises, from top to bottom: slices of granitic basement overlain successively by a thin sandstone, a thick unit of marble, and the contorted beds of the interior metamorphic belt in thrust contact with the marble (Viele and Thomas, 1989).
The Fort Worth basin developed in front of the advancing Ouachita fold belt during the Early and Middle Pennsylvanian (Thomas, 2003). Tectonic loading from the basin bounding the Ouachita fold-thrust belt caused flexural subsidence of the lithosphere to form a foreland basin. Sediments predominantly derived from the fold-thrust belt and trailing orogen then filled the deepest depozone of the basin (Alsalem et al., 2017). Some studies suggest that the Ouachita fold-thrust belt was the main source of sediment to the Fort Worth basin during the Late Mississippian to Late Pennsylvanian. Fault styles and orientations within the basin vary greatly, reflecting a complex stress field that may not be explained by a single structural element. Using isopach maps to display the relationship between accommodation and sediment fill, it is possible to infer the tectonic process by which the Fort Worth basin was developed.
The Fort Worth basin "ll thickened toward its northeastern corner, suggesting that the Fort Worth basin was at its initial foreland basin stage as early as the Middle to Late Mississippian. The depocenter of the Fort Worth basin continued to shift eastward during the Middle Pennsylvanian as basin subsidence accelerated (Alsalem et al., 2017). This shift in depocenter and accelerated subsidence is interpreted as a response to the westward propagation of the Ouachita fold-thrust belt and southward suturing of Laurentia and Gondwana. By the Middle Pennsylvanian, the depocenter of the Fort Worth basin shifted to the eastern margin of the basin. Strata thickness decreases in the western and northwestern parts of the basin, indicating the potential locations of the forebulge and backbulge depozones. This pattern and high magnitude of basin subsidence suggest that "exural subsidence of the Fort Worth basin continued during the Late Pennsylvanian and possibly Early Permian (Alsalem et al., 2017).
Mesozoic Tectonic Structures:
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-19 December 2025 As detailed below, major Mesozoic structural features that lie within the Long MottLMGS site region include:
Faults that accommodated renewed crustal rifting within the Triassic structures associated with seafloor spreading early in the formation of the Gulf.
Jurassic basins that formed in the early stages of the opening of the Gulf of Mexico structures associated with the movement of Jurassic salt deposits.
Large basement-involved uplifts and arches considered to have developed coeval with the Late Cretaceous-Early Tertiary Laramide orogeny to the west.
The initial stages of rifting that created the Gulf of Mexico basin began with an episode of crustal extension and seafloor spreading during the Mesozoic breakup of Pangea. The Gulf of Mexico basin opened by the separation of the North and South American plates as rifting spread southward along the Atlantic spreading ridge. Late Triassic through Early Jurassic extension led to the formation of basement grabens and extensional features filled with terrestrial red beds and volcanics. This period presaged the main phase of Late Jurassic-Early Cretaceous Gulf rifting. These basins form a ring around the modern-day Gulf of Mexico, developing into the Rio Grande embayment, East Texas basin, north Louisiana basin, Mississippi interior basin, and Apalachicola embayment. Structurally positive elements separate the rift basins, and include the San Marcos arch, the Monroe arch, and the northeast extension of the Wiggins arch (Foote et al., 1988; Galloway, 2008).
During the Late Triassic and Early Jurassic, marine incursion from the Pacific entered west-central Mexico. By the Middle Jurassic, initial transgression of highly saline waters entered the East Texas basin, to deposit evaporite sequences. Marine waters continued to flow into the rift basin, leading to rapid evaporation of highly saline waters under arid conditions causing the precipitation of salt. Large amounts of Louann Salt were deposited in the basin, providing the source from which all salt domes in the East Texas basin developed.
Numerous salt domes and diapirs are present in the East Texas basin forming a core of intrusive salt surrounded by an aureole of domed sediments (Foote et al., 1988).
Diapiric salt structures in the East Texas basin can be divided into three groups based on the time when the salt pierced the overlying strata. The oldest diapiric group pierced Early Cretaceous horizons from differential loading by deltas of the Shuler and Hosston Formations. The second group became diapiric in the mid-Cretaceous during maximum sedimentation in the center of the basin. This youngest group pierced the overlying strata in the Late Cretaceous (Foote et al., 1988).
During the Middle to Late Jurassic, continental crust was stretched and attenuated through rifting into transitional crust. Basement structures strongly influence the overlying stratigraphy, most readily apparent around the periphery of the basin underlain by thick transitional crust. Basement structures include epicratonic basins that open to the central Gulf, intervening arches, and uplifts. The thin transitional and oceanic crustal domains of the Gulf contain deep crustal structures that are difficult to define. However, gravity and magnetic inferred changes in basement topography, rates of subsidence, and salt distribution all suggest a family of northwest-southeast-trending basement transfer faults formed during the Gulf of Mexico and Atlantic extension and spreading phases (Galloway, 2008).
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-20 December 2025 Based on geologic interpretation, Mesozoic fault systems of the Gulf region are related to bodies of Louann Salt at depth, and include the Mexia-Talco, Milano, Charlotte-Jourdanton, and Karnes/Sample fault systems. Slip on these grabens likely began in the Late Jurassic and continues to the present on some faults (Ewing, 1991).
The Mexia-Talco fault system, along with the Balcones fault zone, rims the Gulf basin, forming a divide between Upper Cretaceous and Eocene strata. The Mexia-Talco fault system is made up of three sections of symmetric grabens that are linked by deep en-echelon normal faults and extend from central Texas to the Arkansas border. Thick sediment piles in the grabens provide evidence of fault movement beginning in the Jurassic, with continued later movement supported by offsets of Paleocene beds (Chowdhurdy and Turco, 2006). The Mexia-Talco Fault Zone location may have been partially controlled by Triassic rift faults and partly by the updip limit of Louann Salt (Jackson, 1982).
The Mount Enterprise-Elkhart Graben fault system has two fault zones: the Mount Enterprise Fault Zone to the northeast and the Elkhart Graben to the west. The Elkhart Graben is the western end of the Mount Enterprise-Elkhart Graben fault system and consists of parallel, normal faults with multiple offsets to define a graben approximately 25 mi. (40 km) long. This graben forms the southern component of a fan of central-basin faults, which trend towards Oakwood Dome on the southwest margin of the basin. The graben overlies broad anticlinal salt pillow structures and parallels the trend of these underlying structures. The Mount Enterprise Fault Zone comprises a regular array of parallel and en-echelon normal faults, which generally dip to the north. The Mount Enterprise Fault forms the largest and southernmost component of the fault system. The eastern and western portions of the fault system were most active between 120 Ma and 40 Ma, with the central portions being most active since 40 Ma. Although the original cause of the Mount Enterprise Fault Zone is uncertain, available evidence indicates that faults formed by long-continued extension and differential subsidence in the Louann and post-Louann strata (Jackson, 1982).
Tertiary Tectonic Structures:
The basinward thick Cenozoic sedimentary prism overlies thin transitional crust depressed more than 9 to 12 mi. (16 to 20 km) due to slow sedimentary loading. The Cenozoic prism extends beneath the coastal plain coastal plains and shelf and reaches its thickest point near the present continental margin. Paleogene through Neogene sedimentary deposits form an off-stepping series of sedimentary wedges, with Paleocene through Miocene wedges expanded and deformed by a succession of growth-fault families included within the Wilcox and mixed Upper Eocene and top salt detachment provinces. The off-stepping deposition pushed salt basinward, forming three major salt canopies (Galloway, 2008).
Transects through the northeast and northwest Gulf margins illustrate features of additional Tertiary structural domains. The crustal boundary pins the location of the Mesozoic shelf margin, which was built further basinward by approximately 31 mi. (50 km) from Tertiary deposition and displays few growth faults. The basinal toe has compressional features of the east end of the Miocene compression domain. The northwest displays Middle Cenozoic compressional domains, including the Port Isabel fold belt, which is linked to the Miocene
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-21 December 2025 Clemente-Thomas, Corsair and Wanda fault zones of the Oligocene-Miocene detachment province (Galloway, 2008).
Tertiary Salt Structures:
Progradation over deforming, salt structures derived from underlying autochthonous Jurassic salt largely controlled the Cenozoic structural evolution of the northern Gulf (Figure 2.5.1-123). The wide variety of structural styles found in the Gulf basin is the response to a combination of original Jurassic and Mesozoic salt structures, different depositional slope environments during the Cenozoic, and varying degrees of salt withdrawal from allochthonous salt sheets (Diegel et al., 1995).
Principal salt structures within the Cenozoic sedimentary wedge of the northern Gulf basin include a broad zone of relatively shallow salt stocks and coalesced autochthonous canopies beneath the continental slope; a base slope salt nappe forming the Sigsbee escarpment; and several sub-slope and basin-floor compressional fold belts. Additional gravity tectonic structure domains of the northern Gulf basin include salt diapirs and related structures of the East Texas, North Louisiana, Mississippi, and DeSoto Canyon salt basins.
These domains are located around the northern periphery of the Gulf basin, and a series of peripheral grabens including the Luling-Mexia-Talco, State Line, and Pickins-Gilberton fault zones control the landward extent of autochthonous Louann salt.
Oligocene to Recent extension detached on allochthonous salt canopies or marine shales.
Off-stepping deposition pushed salt upward into three major salt canopies. The inboard canopy was loaded and evacuated by subsequent deposition to form the vast central Gulf shelf mini-basin domains. A shallow salt canopy forms the slope mini-basin and salt canopy domains beneath the continental slope that terminate in the Sigsbee scarp. At the east end of the slope mini-basin province, salt rose directly from the autochthonous level. The base of the canopy rises through flat-lying basinal Cretaceous and Cenozoic strata to the final sheet, which is intruded into Pleistocene strata (Galloway, 2008).
Salt-withdrawal mini-basins with flanking salt bodies occur both as isolated structural systems and components of salt-based detachment systems. Progressive salt withdrawal from tabular salt bodies on the slope formed salt-bounded mini-basins during sediment progradation. These evolved into mini-basins bounded by arcuate growth faults and remnant salt bodies on the continental shelf. Associated secondary salt bodies located above allochthonous salt evolved from pillows, ridges, and massifs to leaning domes and steep sided stocks (Diegel et al., 1995). Successive pulses of Paleogene deposition had prograded the continental margin over the Cretaceous slope by the end of the Oligocene.
This deflated the thick salt under-layer by intrusion of salt stock canopy complexes under the advancing continental slope and further inflation of the abyssal salt sheet. The prograding continental margin migrated the Oligocene Frio growth-fault zone basinward where decollement occurred within the Upper Eocene mud and deeper salt. This decollement resulted in the continental slope being a mix of sediment and near-surface salt bodies. Subsequent Miocene-Pliocene deposition then loaded the salt canopies to trigger passive diapirism and further gravity spreading. Pleistocene deposition filled updip mini-basins and built the continental slope onto the distal salt sheet Present-day slope topography is dominated by incompletely filled mini-basins (Galloway, 2008).
Tertiary Growth Faults:
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-22 December 2025 Syndepositional growth faults are clustered by age in distinct spatial groups and are generally parallel to the Gulf coastline. Major growth fault systems within the site region include the Wilcox fault zone, the Yegua fault zone, the Vicksburg fault zone, and the Frio fault zone (Ewing, 1991) (Figure 2.5.1-123).
The oldest major-growth fault systems in southern Texas downdip of the middle Cretaceous margin are found in the Paleocene-Eocene Wilcox growth-fault province. The geometries of these systems are variable along strike, with listric faults either soling directly on the autochthonous Louann salt or in the Upper Cretaceous section before stepping down to the Louann level (Diegel et al., 1995).
The Wilcox growth fault trend contains two major structural styles. In southeast and central Texas, the structural style consists of continuous, closely spaced faults. Despite moderate expansion of this section, these faults have little associated rollover, with the fault plane exhibiting low flattening with depth. At the locations where the Wilcox trend crosses the Houston Diapir province, growth faults are localized by pre-existing salt pillows. Salt-related movements deform the growth faults because the salt diapirs pierce the growth-faulted horizons following the main phase of faulting. In contrast, in South Texas a narrow band of growth faults exhibiting high expansion and moderate rollover lies above and downdip of a ridge of deformed, overpressured shale, but updip of a deep basin formed by withdrawal of overpressured shale. This narrow band of faults is associated with large antithetic faults (Ewing, 1986).
The base of the Wilcox province is relatively shallow, and well imaged in southern Texas.
The most prominent feature of the trend is the great expansion of Wilcox deltaic strata confined to narrow depo-troughs. These are characterized by the absence of the Cretaceous strata well imaged outside the troughs. The landward edge of the troughs is the locus of the complex Wilcox growth-fault system. The landward edge of the troughs expands the upper Wilcox section by a factor of approximately 10. The complex imbricate fan of down-to-the-basin growth faults merges downward into major fault planes. These fault planes sole at the Jurassic Louann salt level, apparently directly overlain by Paleogene strata. Counter-regional faults bound the basinward edge of the Eocene-filled depo-troughs that extend to the Louann salt level and contain Cretaceous strata on their footwalls (Diegel et al., 1995).
The Frio growth-fault system is located just landward of the current Texas Gulf Coast coastline and occupies a 40-mi. (60 km) wide belt. The faults within the system formed contemporaneously with the progradation of the Late Oligocene shelf margin caused by major deltaic and barrier/bar strandplain systems. Growth faults formed in an area of thick diapiric salt within the Houston delta system and the Buna system. In general, the Frio fault system generally displays wide spacing and greater rollover than those found in the Wilcox fault systems. However, the Frio trend displays distinctive features at different locations throughout the system. Most Frio growth faults share a similar geometry, displaying substantial rollover, expansion of section, and a moderate flattening of the fault zone with depth. This flattening is possibly related to a deep decollement surface. Faults can be associated with salt or shale. The local variability in growth fault style is attributed to the magnitude of Frio Formation sedimentation and progradation and to the presence of thick salt or shale (Ewing, 1986).
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-23 December 2025 The Oligocene Vicksburg detachment system is a large shale-based detachment system located onshore in southern Texas. The detachment surface is about 2,296 ft. (700 m) below the Eocene Jackson shale, which is often penetrated along the detachment.
Although similar to salt withdrawal systems, the detachment system is geometrically distinct. Superficial similarities to salt withdrawal systems include the presence of expanded deltaic sediments above listric normal faults that sole into a sub-horizontal detachment surface.
Reconstructed cross sections display the profound geometric differences between the two systems. The shale-based detachment system features expanded sequences younging landward, while salt-based examples are expanded sequences that prograde basinward.
Typically, growth faults located above salt-based detachment systems become younger basinward, but Vicksburg detachment system reconstructions indicate periodic landward backstepping of the active growth fault. Another difference from salt-withdrawal fault systems is the extreme extension evident in the Vicksburg system. The oldest units in the Vicksburg were translated horizontally more than almost 10 mi. (16 km), with all the extension accumulated across a fault zone 1.5 mi. (2.4 km) in restored horizontal width.
The detachment system contains sand-prone Vicksburg deltaic sediments. These sediments are greatly expanded by a listric down-to-the-basin fault system that soles in Eocene Jackson shales. (Diegel et al., 1995).
The Yegua Formation consists of 1,500 to 2,000 feet (450 to 600 meters) of sand and shale, with sand-percent maps indicating that the northern half of the area was dominated by a fluvial regime with dip-oriented sandstones that fed a strike-elongate fault system in the southern half of the area. The fault zone is associated with southward shelf progradation during the middle to late Eocene that is best expressed southwest of the Houston Embayment where it is dominated by a domino-style growth fault system (Ewing, 1986; Ewing, 1991).
The major structural features on the outer continental shelf are gravity faults, including growth faults and faults controlled by salt diapirs (Reznak et al., 1983). Figure 2.5.1-112 shows the continuation of progressively younger bands of growth faults continuing on the continental shelf. From including from nearshore to near slope areas, these include: the Lower Miocene fault zone, the Corsair or Brazos Ridge fault zone and the Upper Miocene fault zone. These faults trend subparallel to the shoreline; and therefore, they do not trend toward the site area. Growth faults are interpreted to be non-seismogenic (Wheeler, 1999) and, therefore, are not included in the seismic hazard analysis.
Farther seaward near the shelf break in the LMGS site region, some near-surface faults are related to salt tectonics. Salt structures in the site region include the Flower Gardens Banks, whichthatwhich are the largest calcareous banks in the northwestern Gulf of Mexico (Trippet, 1980). The East Flower Garden structure has normal, step-like faults typical of domal uplift over salt domes, including local grabens. West Flower Garden Bank is older and has a more mature crestal faulting pattern (Rezak et al., 1983). Faulting in the area is considered to to still be activebe ongoing and localized to regions with salt-bearing units (Trippet, 1980).
Tertiary Basement-Involved Faults:
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-24 December 2025 The Balcones and Luling fault zones mark a fault belt that stretches across central Texas from the Rio Grande to the Red River and shows broken and displaced strata. The Balcones and Luling fault zones lie along a major structural hinge that separates the Texas Craton from the embayments of the Gulf Coast province. The major tectonic features delimiting the hinge zone include the surface faults of the Balcones and Luling systems and the buried Ouachita structural belt. Other features that lie along this trend include the updip subcrop of Jurassic strata, Cretaceous igneous plugs, and the updip outcrop of Tertiary rocks (Woodruff and McBride, 1979).
Stratigraphic and structural analyses demonstrate abrupt thickening and rapid changes in the dips of strata, facies changes, and complex faulting. Structural deformation began in the Late Paleozoic during the Ouachita deformation and continued into the Miocene, when the major events of Balcones faulting occur, spanning a period of more than 200 million years.
The Balcones and Luling fault systems formed in response to tensional stresses, potentially related to rifting during the opening of the ancestral Gulf. The Balcones fault system mainly shows down-to-the-coast displacement, while the Luling fault system is displaced both up to the coast and down to the coast. Additionally, in many areas a graben is superjacent to the Ouachita belt between the Balcones and Luling fault zones (Woodruff and McBride, 1979).
Normal faults along the Balcones fault zone have greatly shaped the geology and physiography of central Texas and its environs. At the regional scale, faults have positioned the geologic units of the Edwards Group and Glen Rose Formation into a framework that juxtaposes contrasting rock, soil, and terrain to produce a major physiographic boundary.
The Balcones fault zone is a fault system consisting of numerous normal faults with hanging walls that generally drop down towards the Gulf. Individual displacements range from 98 to 853 ft. (30 to 260 m), with up to 1,200 ft. (365 m) of total displacement across the fault zone. In general, faults dip steeply (45 to 85 degrees), with dip varying with local rock properties and stress fields (Saribudak, 2016).
The Balcones fault zone is a series of normal faults which are mostly down to the southeast. It marks the boundary between the uplifting plateau and subsiding Gulf Coast Basin. Total displacement has been measured to more than 1,650 ft. (500 m). The Luling fault zone is 30 to 60 km (98 19 to 196 37 mift.) (30 to 60 km) southeast of the Balcones fault zone and is a system of down to the northwest normal faults. Fault movement is mostly Miocene, and no Recent activity has been documented (Ewing, 1991).
Quaternary Tectonic Structures:
The Long MottLMGS site region is part of a present-day tectonically stable continental margin. The East Texas area has been regarded as relatively tectonically and geologically stable, though low-intensity seismicity and sporadic minor earthquakes do indicate a low-risk potential for damage. Previous studies in the region have found no evidence of Quaternary reactivation of regional structures active during Mesozoic and Tertiary times (Exelon, 2010Exelon, 2012a). The U.S. Geological Survey (USGS), in the recent update of its National Seismic Hazard Map did not designate any active fault sources in East Texas as potential earthquake sources (Thompson Jobe et al., 2022) (Figure 2.5.1-134). The closest fault used as a source for the 2023 USGS National Seismic Hazard Map is the Saline River at more than 400 mi. (650 km) from the site. Most of the faults discussed in this section are located outside of the 200-mi. (320-km) site region.
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-25 December 2025 Quaternary Growth Faults:
Surface deformation indicates Quaternary activity on some growth faults in the Texas Gulf Coastal Plains and continental shelf. Some surface deformation has been linked to the pumping of oil, gas and water from underground reservoirs. However, the consensus of the scientific community is that this motion is incapable of producing damaging earthquakes (Crone and Wheeler, 2000).
The gulf-margin normal faults in Texas are assigned as Class B structures because their low seismicity and because they may be decoupled from underlying crust, making it unclear if they can generate significant seismic ruptures that could cause damaging ground motion (Wheeler, 1999).
Per USGS criteria, a Class B structure is defined as follows:
Class B: Geologic evidence demonstrates the existence of Quaternary deformation, but either (1) the fault might not extend deeply enough to be a potential source of significant earthquakes, or (2) the currently available geologic evidence is too strong to confidently assign the feature to Class C but not strong enough to assign it to Class A (Crone and Wheeler, 2000).
This definition contrasts with Class A faults, which are defined as tectonic faults with Quaternary slip, and Class C faults, which are defined as having insufficient evidence of being tectonic faults or having Quaternary slip. According to the USGS, much of the belt of Gulf margin normal faults from Florida through Texas displays only sparse, low-magnitude seismicity within the belt (Wheeler, 1999). Furthermore, global analogs suggest that some of the sparse seismicity in the belt may have been artificially induced by extraction of oil and gas or injection of fluids for secondary recovery. The natural seismicity rate in the normal-fault belt, therefore, might be even less than the recent historical records (Crone and Wheeler, 2000).
The low seismicity observed in the belt may be due to the post-rift sequence and its belt of Gulf margin normal faults being mechanically decoupled from the underlying crust. The presence of seaward-facing normal faults through Florida to southern Texas indicates that the sequence is sliding and extending seaward on detachments in weak salt and overpressured shales. Due to the low ductility of the salt and shales, tectonic stresses may be unable to be transmitted upward from the underlying crust into the post-rift sequence.
Additionally, the overlying post-rift sequence itself is young, only partly dewatered, and poorly lithified, especially the Cenozoic portion. These factors contribute to an inability to transmit tectonic stress due to low elastic strength. This model is consistent with the observation that low velocity near-surface materials tend to stifle the propagation of seismic ruptures (Crone and Wheeler, 2000)
Growth faults in the site vicinity as well as the surface expression of growth faults were mapped by the Victoria County Station (VCS) PSAR (Exelon, 2010b). Section 2.5.3 further discusses investigations related to growth faulting in the LMGS site vicinity and site area.
Based on analyses in subsection 2.5.3, nNo surface expression of growth faultsing was interpreted from light detection and ranging (LiDAR) data or aerial photographs within the site area.
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-26 December 2025 Eagle Ford Faults:
The Eagle Ford Shale play is approximately 55 mi. (90 km) from the site. It consists of northwest-trending, syndepositional Cretaceous normal faults (McKeighan et al., 2022).
More than 160 normal faults have been mapped in the area (McKeighan et al., 2022).
Earthquakes in the Eagle Ford region increased between 2014 and 2019, and the rate has remained higher than the historical rate since 2018 (Li et al., 2021; McKeighan et al., 2022).
The increased earthquake activity has been linked to hydraulic fracturing (McKeighan et al.,
2022). Focal mechanisms indicate most recent earthquakes in the Eagle Ford were normal events (Li et al., 2021).
Injection wWells in the Site Vicinity:
Figure 2.5.1-15NEW maps shows the locations of permitted injection wells within the site vicinity (25 mi. [40 km]). Well locations are from the Texas Railroad Commission. Three wells are within the site area (5 mi. [8km]). The majority ofMost permitted injection wells in the site vicinity are part of a northeast-southwest trending band of wells?. Based on the project earthquake catalog (E[M] 2.9 and above; Figure 2.5.3-1630), and reviews of the USGS and TexNet earthquake catalogs through 23 October 23, 2025 (Magnitude 0 and above [USGS, 2025; TexNet, 2025]), there have been no recorded earthquakes in the site vicinity. and, tTherefore, there have been no recorded earthquakes associated with the injection of fluids within the site vicinity.
The volumetric injection rates permitted for the wells in the site vicinity range from 220 barrels (bbls)/day (35 m3/day) to 30,000 barrelsbbls/day (4770 m3/day) (Table 2.5.1-21). In a review of induced earthquakes, Moein et al. (2023) plotted empirical data from a global data set of events of induced seismicity and the injected fluid volume in cubic meters.
Based on their analysis, the maximum permitted volumes for injection predict lower than magnitude 2 earthquakes for the site vicinity from induced earthquakes. Figure 2.5.1-15NEW does not show clear correlation between the injection well locations and surface deformation from Interferometric Synthetic-Aperture Radar (InSAR) data (either uplift or subsidence).
Balcones Fault Zone:
As described in Subsection 2.5.1.1.4.3, the Balcones fault and Luling fault zones delineate a belt that stretches across central Texas, from the Rio Grande to the Red River, and lie along a major structural hinge that separates the Texas Craton from the embayments of the Gulf Coast province (Woodruff and McBride, 1979). Fault movement is mostly Miocene, and no Recent activity has been documented (Ewing, 1991).
The Balcones fault zone rims the Gulf basin, forming a divide between Upper Cretaceous and Eocene strata. The Balcones fault zone is primarily dominated by normal-slip faults, which run parallel to the trend of the Ouachita orogenic belt. Sediments have been displaced along these faults up to 1,500 ft. (457 m) downward toward the Gulf. The Balcones Escarpment formed where the faults juxtapose resistant Lower Cretaceous with more resistant Upper Cretaceous sediments. Along with other structural features throughout the Gulf Coast aquifer, the Balcones fault zone controlled the accumulation and distribution of sediments based on the observation that bedding commonly thins towards and over arches, and thickens in embayments (Chowdhurdy and Turco, 2006).
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-27 December 2025 Saline River Fault:
In southern Arkansas, the Saline River fault zone is associated with paleoliquefaction features that indicate that it has a possible slip rate of 1.1 to 1.5 mm (0.04 to 0.06 in.) per year with strike-slip motion. Paleoliquefaction mapping indicates a potential paleo M 6.1 to 6.3 earthquake and a more recent smaller magnitude event (Cox et al., 2014). This fault was not developed as a source for the Central and Eastern United States Seismic Source Characterization for Nuclear Facilities (CEUS -SSC) model or any USGS National Seismic Hazard Map studies prior to 2023 (Thompson Jobe et al., 2022).
Meers Fault:
The Meers fault is the only known Holocene active fault in the Wichita Frontal fault system in Oklahoma (Hornsby et al., 2020). The fault system forms the boundary between the Wichita-Amarillo uplift to the southwest and the deep Anadarko sedimentary basin to the northeast (Streig and Chang, 2018). The fault is 400 mi. (644 km) from the Long MottLMGS site at its closest approach (Figure 2.5.1-134). The Precambrian to Early Cambrian Southern Oklahoma aulacogen, a failed rift zone trending west-northwest across southern Oklahoma and the Texas panhandle, coincides with the Wichita Uplift. The location and trend of the Frontal Wichita fault system provide evidence that modern crustal deformation is accommodated along preexisting zones of crustal weakness. The Meers fault is a reactivated fault within the failed Precambrian rift that trends north 60 degrees west and has left lateral-reverse sense of motion (Streig and Chang, 2018).
The Meers fault has not hosted a large historical earthquake, but the fault offsets Holocene deposits. Two geomorphic sections make up the fault: 1. a southeastern section of the fault, approximately 23 mi. (37 km) long, that has been the focus of multiple paleoseismic investigations and is well defined, and 2. a northwestern section, approximately 11 mi. (18 km) long, that is poorly constrained with uncertain length (Streig and Chang, 2018).
Updates to the USGS National Seismic Hazard Map for 2023 included lengthening of the Meers fault section to 43 km (27 mi.) based on LiDAR mapping and paleoseismic trenching (Thompson Jobe et al., 2022).
Rio Grande Rift:
The Rio Grande Rift is a well-defined series of asymmetrical grabens, extending from Leadville, Colorado, to Presidio, Texas, and Chihuahua, Mexico, over more than 621 mi.
(1,000 km). Much of the length of the rift is part of a broader region of rift-like late Cenozoic deformation, characterized by large crustal blocks separated by steeply dipping normal faults. This region is more than 124 mi. (200 km) in width in central New Mexico and extends southwestward across the physiographic Colorado Plateau and into Arizona.
A broadly linear array of northeast-trending Cenozoic volcanic fields, commonly referred to as the Jemez lineament, separates this transition zone along the southeastern margin of the plateau from the less defined northwestern core. The Jemez lineament most likely corresponds to a major boundary or zone of weakness in the lithosphere. However, it is not related to a single expression of a fault, fracture zone, or single structure in the upper crust.
The rift is not physiographically distinguishable from the Basin and Range province, which
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-28 December 2025 extends across southern Arizona and New Mexico. Although the timing and extensional deformation style of the entire extended region are similar to those of the main rift grabens, the magnitude of deformation is much less. In the Mogollon-Datil region of southwestern New Mexico, deep, narrow grabens exist near the Datil, Reserve, and Silver City. However, these are separated by a region approximately 62 mi. (100 km), in which extensional deformation formed only shallow grabens (Baldridge et al., 1984).
Documentation of the Cenozoic geologic history of the Rio Grande Rift in New Mexico reveals a complex sequence of tectonic events, with at least two phases of extension. The first and early phase of rifting began in the mid-Oligocene (about 30 Ma) and may have continued to the early Miocene (about 18 Ma). Local high-strain extension events, low-angle faulting, and the development of broad, relatively shallow basins characterized this phase of extension. These features indicate an approximately northwest-southeast extension direction, consistent with the regional stress field at that time. Extension events during early phase extension were not synchronous and were often temporally and spatially associated with major magmatism. The early phase extensional style and basin formation indicate a ductile lithosphere and occurred during the climax of Paleogene magmatic activity in this zone (Morgan et al., 1986).
Beginning in the late Miocene (10 to 5 Ma), a late phase of extension occurred, with minor extension continuing into the present day. This late phase was characterized by apparently synchronous, high-angle faulting giving large vertical strains with relatively minor lateral strain. This strain produced the modern Rio Grande region morphology. The extension direction was approximately east-west, consistent with the contemporary regional stress field. Late-phase extensional style and basin formation indicate a brittle lithosphere, with this phase of extension following a middle Miocene lull in regional volcanism. Regional uplift of approximately 0.62 mi. (1 km) appears to have accompanied late-phase extension, with relatively minor volcanism continuing to the present day (Morgan et al., 1986).
New Madrid Seismic Zone:
The New Madrid Seismic Zone (NMSZ) is one of the most seismically active areas in North America east of the Rocky Mountains (Thompson Jobe et al., 2020). The three earthquakes occurred on December 16, 1811; January 23, 1812; and February 7, 1812, referred to as NM1, NM2, and NM3, respectively. Using isoseismal data for the region (Hough et al.,
2000) concluded that the NM1, NM2, and NM3 earthquakes had moment magnitudes of Mw 7.2 - 7.3, Mw 7.0, and Mw 7.4 - 7.5, respectively. The earthquakes were associated with extensive sand and water fountaining, and the formation of sunken lakes and barriers forming on the Mississippi River (Johnston and Schweig, 1996). Paleoseismic studies indicate at least five M greater than 6.4 earthquakes in the New Madrid region since 4.5 kilo-annum (ka) (Thompson-Jobe et al., 2022).
2.5.1.1.4.5 Regional Gravity and Magnetic Data The primary sources of magnetic data reviewed for this application are those of Bankey et al. (2002) and Meyer et al. (2017). The data from Bankey et al. (2002)magnetic data within the Long MottLMGS site region are shown in Bankey et al. (2002) Figure 2.5.1-157. The primary sources of terrestrial gravity data reviewed for this application are those of Bankey (2006), the Earth Gravitational Model 2008 (EGM2008) described by Pavlis et al. (2008),
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-29 December 2025 and the World Gravity Map 2012 (WGM2012) available from Bonvalot et al. (2012), which is based on EGM2008. The primary source of marine gravity data reviewed for this application is that described by Sandwell et al. (2014) and made available by the University of California, San Diego (UCSD) (2015). The gravity data presented by Pavlis et al. (2008) and Sandwell et al. (2014) are shown on Figure 2.5.1-148.
Sections 2.5.1.1.4.5.1 and 2.5.1.1.4.5.2 (below) describe the overall patterns and specific features indicated in the gravity and magnetic anomaly data.
2.5.1.1.4.5.1 Gravity Data Gravity anomaly data encompassing the site region are shown on Figure 2.5.1-148. The data are a compilation of EGM2008 on-land Bouguer gravity anomalies (Pavlis et al., 2008) and offshore free-air gravity anomalies described by Sandwell et al. (2014) and published by UCSD (2015). Overall patterns shown by the data are listed below, and specific features are described with reference to the areas labelled on Figure 2.5.1-148.
Overall gravity patterns:
Offshore free-air gravity published by UCSD (2015) is correlated primarily with bathymetry, since the free-air gravity anomaly is not corrected for water depth.
For igneous rocks, density usually increases with decreasing silica content. For sedimentary rocks, age, depth of burial, and mineral composition are the most important factors for density (Hays, 1976).
Figure 2.5.1-148 identifies the location of specific key gravity features:
A. A circular gravitational high is approximately is 200 mi. (320 km) northwest of the LMGS site, located to the northwest of San Antonio and Austin. This feature is likely to be related to the presence of high-density, crystalline rocks that form the Llano Uplift (Mosher, 1998).
B. A gravitational low immediately south and east of gravity feature A, passing through San Antonio, Austin, and Waco. This feature includes negative gravity anomalies as large as -35 mGal. This feature is likely to be related to the presence of low-density sediments in foreland basins, such as the Fort Worth basin, that are part of the Ouachita system (Kruger and Keller, 1986). These foreland basins are bounded to the south and east by the Ouachita orogenic front (Miall, 2019).
C. A gravitational high that is parallel to and immediately south and east of gravity feature B. This feature is referred to as the Ouachita System Interior Zone Maximum by Kruger and Keller (1986), who suggest several possible interpretations for the feature. These include the presence of the Ouachita orogenic core, a major transition in the basement crustal structure, or mafic intrusions associated with Mesozoic rifting (Hays, 1976; Kruger and Keller, 1986).
D. A gravitational low that gradually increases moving southeast towards the coast.
This feature is shown in the gravity profile and model of Mickus et al. (2009) and is likely attributable to the crustal thinning at the margin between continental and oceanic crust.
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-30 December 2025 E. A prominent, arcuate gravitational high located offshore and sub-parallel to the coastline. This feature extends alongside the full length of the Texas coast and has positive gravity anomalies Figure 2.5.1-148. This feature has been interpreted as a buried complex of mafic volcanics, likely representing a volcanic rifted margin (Mickus et al., 2009).
F. A decrease in the gravity moving further offshore (southeast) of gravity feature E. Bouguer anomaly maps show an increase in gravity further into the Gulf, shown to correspond to continued crustal thinning (Jacques et al., 2004).
G. A gravitational high with positive anomalies is noted on Figure 2.5.1-148, located approximately 260 mi. (418 km) southeast of the Long MottLMGS site. This feature, referred to as the Keathley Canyon anomaly (Bird et al., 2005), is correlated with a bathymetric high that may be linked to mafic intrusions as the lithosphere passed over a Late Jurassic mantle plume.
2.5.1.1.4.5.2 Magnetic Data Magnetic anomaly data encompassing the site region is shown on Figure 2.5.1-157. The data are a compilation of aeromagnetic surveys published by Bankey et al. (2002). Overall patterns shown by the data are listed below, and specific features are described with reference to the areas labelled on Figure 2.5.1-157.
Specific magnetic features:
A. Short-wavelength magnetic highs and lows northwest of San Antonio and west of Austin. These variations coincide with the Llano Uplift. Various metavolcanic and metaplutonic rocks form the uplift (Mosher, 1998).
B. A magnetic low immediately south and southeast of the Llano Uplift. As with gravity feature B, above, this feature is likely to be related to the presence of thick sediments in the foreland basins of the Ouachita system (Kruger and Keller, 1986).
C. A subtle magnetic high immediately south and southeast of magnetic feature B, spatially correlated with gravity feature C. This feature is likely linked to the transition from continental crust to rifted crust with some potential local effects from mafic intrusions associated with Mesozoic rifting (Kruger and Keller, 1986; Mickus et al., 2009).
D. A prominent magnetic high immediately inland of and sub-parallel to the coastline.
This feature is referred to as the Houston magnetic anomaly (e.g., Eddy et al.,
2018) and is interpreted to mark the presence of an igneous complex in a buried volcanic rifted margin between the continental and oceanic crust (Mickus et al.,
2009).
E. An area of distinct, localized magnetic highs approximately 190 to 250 mi. (305 to 400 km) offshore. This feature is approximately coincident with gravity feature G and is likely also linked to rocks intruded into the lithosphere as it passed over a Late Jurassic mantle plume (Bird et al., 2005).
2.5.1.2 Site Area Geology The Long MottLMGS site is located in Calhoun County, Texas, approximately 7 mi. (11.2 km) north of San Antonio Bay. The Long MottLMGS site and surrounding region are situated inwithin the Coastal Prairies subprovince of the Gulf Coastal Plains physiographic province, which extends as a broad band parallel to the Texas Gulf Coast (BEG, 1996).
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-31 December 2025 In tThe site vicinity (25 mi. [40 km]), geologic map (Figure 2.5.1-16) sits on interbedded clay, silt, and sand deposits of the Quaternary Beaumont Formation are the dominant mapped surficial geologic unit (Paine and Collins, 2013). The Beaumont Formation is mapped by Paine and Collins (2013) between the Louisiana - -Texas border and the Rio Grande. This formation and is recognized as a series of multiple, cross-cutting and/or superimposed incised stream channel fills and over-bank deposits formed during glacio-eustatic cycles inthroughout the Pleistocene (Paine and Collins, 2013; Jacobs, 2022).). The older Lissie Formation crops out inas a band parallel to the coast, typically inland of the Beaumont Formation, and has a mapped width of is about 30 mi. (48 km) wide from the Sabine River to the Rio Grande. The closest Lissie Formation outcrop to the LMGS site is approximately 12 mi. (20 km) northwest (Figure 2.5.1-169). Lissie Formation sediments comprise reddish, orange, and gray fine-to coarse-grained and cross-bedded sands.
Caliche beds often mark the base of the Lissie Formation. The Beaumont and Lissie Formations are the two dominant subdivisions of the Pleistocene in the regionsystem (Chowdhury and Turco, 2006).
The site area (5 mi. [8 km]) geologic map is shown on Figure 2.5.1-2017. The majority of the near-surface Beaumont Formation in the site area is predominantly clay facies of the Beaumont. The site area contains several man-made ponds and intersects with Green Lake and Mission Lake, a branch of San Antonio Bay (Figure 2.5.1-2017). Surface geology in the site area consists of sands and clays of the Beaumont Formation and Quaternary fine-grained deposits associated with the Guadalupe delta that lies to the west of the LMGS site.
2.5.1.2.1 Site Area Geologic History The major tectonic events that affected the site region were the Grenville, Ouachita, and Laramide compressional orogenies and the extensional Proterozoic and Mesozoic rifting.
See Subseection 2.5.1.1.2 for details of the tectonic history. Due to the poor exposure, the basement rocks in the site area are poorly known (Ewing, 1991). Since the opening of the Gulf of Mexico about 160 to 140 Ma, a thick sediment package has been emplaceddeposited on the passive margin of Texas (Bird et al., 2011; Boyd et al., 2024; Galloway, 2008).
Pleistocene global glacial advance and retreat resulted incaused rising and falling sea levels along the Gulf of Mexico and the eustatic changes in sea level. AtIn the LMGS site vicinity, the Lissie and Beaumont Formations were deposited in response to eustatic high sea level stands. The Lissie Formation was deposited as facies of alluvial fan-delta systems (Exelon, 2012aChowdhury and Turco, 2006). The age of the Lissie Formation has been bracketed by seismic reflectors linked with faunal succession data to approximately between 1.4 Ma and 400 ka (Exelon, 2012a). Studies estimate the Beaumont Formation to comprise deposits aged between 150 ka to 100 ka based on an association of the unit with the last interglacial sea level highstand (Exelon, 2012a). The depositional time gap between the Beaumont Formation (150 ka to 100 ka) and the Lissie Formation (1.4 Ma to 400 ka) is explained by the presence of older paleosol deposits within the Beaumont Formation, some as old as 350 ka (Exelon, 2012a). The presence of paleosols his suggests some deposition occurred throughout the Late Pleistocene and not just during the 150 ka to 100 ka time span previously estimated (Exelon, 2012a). The most recent glacial advance, the Wisconsinan glacial stage in North America ofin the late Pleistocene (100 ka to 11 ka),
lowered global sea levels and resulted in the coalescing deltas of rivers draining the continental interior during the eustatic low sea level stand of the sea (Exelon, 2012a). At the
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-32 December 2025 site, there is generally less than 0.4 ft. (0.1 m) of topsoil that has developed on the top of the Beaumont Formation.. that has developed on the top of the Beaumont Formation..
2.5.1.2.2 Site Area Stratigraphy GDescriptions of geologic formations and their depositional environments are described in greater detail in Subsection 2.5.1.1.2. The simplified stratigraphy at the LMGS site is a thick package of post-rift sediments The thick (approximately 30,000 ft. ([10,000 m]; Boyd et al.,
2024) sedimentary package that overlies the continental crust in the site area is the result of an influx of sediments from the Rocky Mountains (Mackey et al., 2012).
The generalized recent stratigraphyic column underlying the Long MottLMGS site includes sands and clays of the Holocene Guadalupe River fluvial-deltaic system in the topographically low areas near the Victoria Barge Canal. Surface sediments east of the river highbank escarpment are the sands and clays of the Pleistocene Beaumont Formation. The escarpment, termed the Highbank on Figure 2.5.1-21218,1 is the erosional bank of Guadalupe River (Figures 2.5.1-1782121, and 2.5.1-1892212, and 2.5.1-192023).
Miocene and younger sediments form an approximately 5,200 ft. (1,600 m) package of sands and muds including the Oakville, Flemming, Goliad-Willis, Lissie and Beaumont Formations (Figure 2.5.1-2011). At the LMGS site, the surface exposure of the Beaumont Formation consists of distributary channel faciesas. Deposits and comprising are clay, silt, sand, and minor gravel infrom a fluvial-deltaic interdistributary and distributary setting (Moore et al., 1993; Paine and Collins, 2013; Jacobs, 2022). Distributary channel facies are yellow to brownish gray, very fine to fine quartz sand, silt, and minor fine gravel that are intermixed and interbedded. The Beaumont Formation also includes stream channel, point bar, crevasse splay, and natural levee ridge deposits (Moore et al., 1993). Channel fill is organic-rich, dark-brown to brownish-dark-gray, laminated clay, and silt. These deposits interfinger with interdistributary facies and rest disconformably on the Lissie Formation.
Interdistributary facies include light-to dark-gray and bluish-to greenish-gray clay and silt that are intermixed and interbedded (Moore et al., 1993). Some sediment is cemented by calcium carbonate occurring in a variety of forms (veins, laminar zones, burrows, root casts, nodules, and irregular masses) (Moore et al., 1993).
At the LMGS site, interbedded sand and clay layers of the Beaumont Formation are correlated across the site in the hydrogeologic investigation described in Subsection 2.4.12.1.4. The general naming convention of these units is shown in Figure 2.5.1-1822.
The thickness of the Beaumont Formation mapped on regional cross sections is approximately 400 ft. (122 m) (Soliís, 1981). On the cross section shown in Figure 2.5.1-20a11, the Beaumont Formation thickness is approximately 300 ft. (91 m) thick near the site (SolisSolís, 1981). with Lissie Fbelow ground surface The top of the Lissie Formation may have been penetrated by deeper borings at the LMGS site that penetrate deeper than 300 ft. (91 m). The contact between the Beaumont and the Lissie Formations is difficult to determine in boreholes because of their similar lithology of the units. natural vertical and horizontal.
One hundred borings and four test pits were evaluated as part of this study (Figure 2.5.1-223). Of the one hundred100 borings, eight reachedextended to a depth of approximately 660 ft. (201 m) below ground surface. Subsection 2.5.4. providesis a A more detailed
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-33 December 2025 description of the geotechnical investigations at the LMGS site is located in subsection 2.5.4.
The Beaumont Formation is described as a relict deltaic coastal plain comprising interbedded clay, silt, and sand deposits (Exelon, 2012a; Jacobs, 2022). The interbedded sand and clay units observed in the borings match the literature description of the Beaumont Formation. andObserved sediments are mostly high plasticity clay, alternating with poor-to well-graded sand and silt, with some low plasticity clay (Figure 2.5.1-234, Figure 2.5.1-245, Figure 2.5.1-256, Figure 2.5.1-267). Three sand layers (A, C, and E) and four clay layers identified and described in Subsection 2.4.12.1.4 were also observed in the borings included in this section (Figure 2.5.1-234, Figure 2.5.1-245, Figure 2.5.1-256, Figure 2.5.1-267). The letter nomenclature for the sand units in the site area is based on the stratigraphy from Jacobs (2022), who defined the stratigraphic relationships of A, C, and E sands used in sSubsection 2.4.12. Within this subsection and sSubsection 2.5.13, the sands are defined as a units containing a majority of sand or silt to indicate a more energetic depositional environment than majority clay deposits. Therefore, sands are defined as units containing 50 percent% or more of sand or silt. Within sSubsection 2.4.12, the sands are more broadly defined as hydrostratigraphic units capable of transmitting and storing water, which is possible at a lower percentage of sand than used to define sand layers in this subsection. The sand and clay units are also defined in sSubsection 2.5.4, which describes the units for static and dynamic engineering properties. In sSubsection 2.5.4, Stratum I correlates generally with the A sands, the C sands overlap with sandy portions of Stratums I, II, and III, and the E sands generally contain sandy portions of Stratum IV, V, VI, and VII. Table 2.5.1-2 provides aA summary of stratigraphic unit definitions is provided in Table 2.5.1-x2. unitsrelatively the,that,,The upper sand was not observed in all of the borings. In borings X30, X51, X55, and X56, an additional sand layer can bewas observed as a laterally non-continuous layer across the site, situated stratigraphically between upper sand and lower sand (Figure 2.5.1-1821 and Figure 2.5.1-19).22).
During laboratory analysis, the samples from five borings (six samples) split before testing along single -planes (Table 2.5.1-13; Figure 2.5.1-223). In the laboratory, these features were documented as slickensides; however, based on laboratory observations, there is not evidence for displacement across. the planes. The sediment above and below the plane has consistent properties. The planes are do not occurare not at similar depths or have deeper or shallower depth wertrends in a mapany direction. One interpretation for the development of these planes is that they represent syneresis cracks that formed within clay deposits in response to changes in pore-water salinity (McMahon et al., 2016). This interpretation is consistent with the Holocene deltaic-fluvial depositional setting of the sSite aArea (Paine and Collins and Paine, 2013a), an environment that experiences episodic salinity changes and subaqueous shrinkage of cohesive muds (Buatois et al., 2011; McMahon et al., 2016). Alternatively, the planar features could have formed by purely mechanical dewatering during sediment compaction in the delta (McMahon et al., 2016).
The sedimentary prerequisites and mechanisms for shrinkage crack formation in subaqueous environments remain controversial (Harazim, 201425). Nearby borings did not contain similar planes that failedapparent during laboratory testing. Based on the location of borings that were also sampled and tested in the laboratory between the locations of planes, planes cannot be correlated between borings.
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-34 December 2025 Boring data from the site was developed into approximately shore perpendicular (Figures 2.5.1-234 and 2.5.1-245) and shore parallel (Figures 2.5.1-256 and 2.5.1-267) cross sections. Figure 2.5.1-223 shows the location of cross sections and borings. These cross sections align with the profiles used for Spectral-Analysis-of Surface-Waves (SASW) data collection at the site (Figure 2.5.1-278). Individual layers and sequences are not well-correlated along the cross sections, but three generally sandier units (upper, middle, and lower sands) can be traced. In general, the top 50 ft. (15 m) of sediment at the site are clay-rich with a laterally discontinuous upper sand in some locations, and usually less than 10 ft.
(3 m) thick. In the top 150 ft. (46 m) of sediments, the stratigraphy trends sandier downward.
SASW seismic testing was used to interpret shear wave velocity (VS) along eight arraysprofiles. AllThe eight Vs profiles generatedinterpreted at the site arehave similar VS.
The northeast-to southwest-oriented arraysprofiles (arrays 5, 6, 7, and 8; Figure 2.5.1-2798) show more variability than the northwest-to southeast-oriented arraysprofiles (1, 2, 3, and 4). Analysis of the variability between VS profiles shows that overall total variability is low, with the greatest variability near transitions between stiffer layers (Figure 2.5.1-2828).
Cross sections of the boring stratigraphy data were built along SASW arrays 3, 4, 6, and 7 (Figures 2.5.1-234, 2.5.1-245, 2.5.1-256, and 2.5.1-267). The stratigraphic cross sections do not cover the full lateral extent of the mapped arrays due to borehole the SASW arrays extending beyond the area focused on byof the boring data. The first transition on the SASW profiles occurs at approximately the 100 ft. (30 m) depth, which is the approximate depth of the lower sands. Stratigraphic Ccross sections along arrays 6 and 7 show greater variability in thickness between adjacent sand layers and the interbedded muds than along arrays 3 and 4, This result indicates that ing stratigraphic variability may be contributing to the greater variability measured in the VS profiles in that orientation. Regional cross sections (SolisSolís, 1981) also show more variability in sediment type and thickness in the Lissie and Beaumont Formations in shore-parallel sections when compared tothan in shore-perpendicular sections..
2.5.1.2.3 Site Area Structural Geology The Tectonic Map of Texas maps Cenozoic growth faults in the coastal region of Texas (Ewing, 1990). The Long MottLMGS site is within the Frio fault zone of growth faults (Figure 2.5.1-123). The site is near the transition between the early Oligocene Vicksburg fault zone and the Frio fault zone, (Figure 2.5.1-112 [(1 and 2]) and Figure 2.5.1-123). In the Frio fault zone, most of the faulting occurred during the deposition of the Late Oligocene Frio deltaic deposits. The Frio faults are typically moderate dip angle, listric faults (Ewing, 1991). shelf From the Tectonic Map of Texas data, thetwo growth faults are mapped in the site area, Fault A and Fault B. Fault A is mapped for approximately 80 mi. (130 km) subparallel to the modern shoreline. Fault B is approximately 3.75 mi. (6 km) long (Figures 2.5.1-1916 and 2.5.1-1720). In the Texas Gulf Coastal Plains, wells are used to map the subsurface data (Hosman and Weiss, 1991). The Victoria County Station (VCS) submittal (Exelon, 2012a and 2012b) to the NRC mapped two growth faults in the site area at a depth of approximately 5,370 to 6,450 ft. (1,637 to 1,966 m) below the surface (Exelon, 2012a, and 2012b). The study projected the faults to the surface based on interpreted dip. The VCS submittal (Exelon, 2012a and 2012b) used proprietary data from the Geomap company as a basis of their fault interpretations (Exelon, 2012a, and 2012b). The Long MottLMGS site is closest to their fault GM-AE, which dips to the south and was mapped at a lithologic
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-35 December 2025 boundary at 5,370 to 6,450 ft. (1,637 to 1,966 m) below the surface, and fault GM-AD a north-dipping fault that was mapped at 5,540 to 6,200 ft. (1,689 to 1,890 m) below the surface (Figure 2.5.1-29292). Some faults could be correlated on two different stratigraphic horizons, and the fault dip was calculated based on the change in strata location and depth.
In addition to the faults from the Geomap data, the VCS submittal interpreted the surface projection of faults from regional cross sections. These projections are indicated as dots on Figure 2.5.1-3029. The mapped interpretations in the VCS submittal (Exelon, 2012a and 2012b) states that the uncertainty in the projection location of faults projected to sea level is on the order of several miles (Exelon, 2012a, and 2012b). The VCS report (Exelon, 2012a and 2012b) did not report find any evidence in from their LiDAR lineament analysis of the faults GM-AE or GM-AD or the projected faults from cross -sections deforming the ground surface (Exelon, 2012a, and 2012b; Figure 2.5.1-3121). Additional LiDAR analysis and discussion of growth faults is presented in Subsection 2.5.3.2.2.3.
LiDAR data covering the LMGS site vicinity was reviewed for evidence of potential growth faulting deforming the surface (Figure 2.5.1-3NEW 2). Growth faults mapped in previous studies (Exelon, 2012cd; Paine and Collins, 2014; Paine and Collins, 2017) were mapped onto the LiDAR, and the entire site vicinity was mapped for evidence of growth faulting. No growth faults were identified in the surface LiDAR data in the LMGS site vicinity, and no potential growth faults were identified in the site vicinity that trend toward the site area.
Figure 2.5.1-2011a shows a shallow regional cross section extending into the Miocene Oakville Formation (SolisSolís, 1981). Faults mapped onto the cross sections from Geomap data, extend only into the Upper Flemming and do not displace units in the Pliocene Goliad-Willis Formation. Therefore, these growth faults near the site are interpreted to have not beenas inactive in the Quaternary and possibly since the Miocene.
Groundwater pumping and hydrocarbon extraction have been linked to subsidence and movement of growth faults in the coastal plain Gulf Coastal Plains of Texas (Campbell et al., 2018; Qiao et al., 2023). Regional InSAR data do not show no evidence of current subsidence or differential offset in the site area (Qiao et al., 2023; Wang et al., 2024)
(Figure 2.5.1-1623093). A further, more detailed description of ground water conditions at the site is discussed in Subsection 2.4.12 (Hydrologic Description), and an additional description of surface deformation potential is included in Subsection 2.5.3.
As shown in Figure 2.5.1-1630, in general, the Gulf Coastal Plains are at presently subsiding at a rate of less than 5 mm/yr (0.02 in/yr). Several zones experiencingof higher subsidence rates exist are known. The most prominent zone of subsidence is in Nnorthwest Harris County, near Katy, Texasx, where the withdrawal of groundwater has resulted in subsidence rates of up to 53 mm/yr (2.1 in/yr). The region near Galveston is also experiencing higher rates of subsidence (up to 13 mm/yr [0.5 in/yr]) that are which is also linked to local groundwater withdrawal (Wang et al., 2024).
Subsidence in the Gulf Coastal Plains is driven by two main causes:, natural, long-term causes and anthropogenic causes (Zhou et al., 2021). Natural causes include geological compaction of sediments through time due toin response to loading from younger sediments, isostatic adjustments, and tectonic movements. The rate of natural subsidence for coastal Texas is calculated to range frombetween 0.6 to 0.8 mm/yr (0.02 to 0.03 in/yr) in the central coastal region (Zhou et al., 2021). Anthropogenic causes of subsidence include compaction related to water, oil, and gas extraction (Zhou et al., 2021). The square
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-36 December 2025 kilometer that contains the LMGS site is interpreted based on InSAR analysis to have a present-day subsidence rate of approximately 0.4 mm/yr (0.02 in/yr; Wang, 2024; Wang et al., 2024; Figure 2.5.1-1630). Based on the calculated rate of subsidence due tofrom natural causes in the coastal region including the site (0.6 to 0.8 mm/yr [0.02 to 0.03 in/yr];
Zhou et al., 2021), a subsidence rate of 0.4 mm/yr (0.02 in/yr) suggests that mainly natural causes are drivingare primarily drivinge subsidence at the site.
Work analyzing the contributing factors to subsidence in the 56 counties that contain the Gulf Coast Aaquifer system in Texas concluded that population growth, ground water withdrawal, prolonged drought, and hydrocarbon extraction are correlated with higher subsidence rates (Younas et al., 2023). Calhoun County, where the LMGS site is located lost population from 2000 to 2022. Younas et al. (2023) also calculated that the rates of water and hydrocarbon withdrawal in Calhoun County were lower than most other regions in Ccoastal Texas. T, and the rate of water withdrawal did had not increased from 2000 to 2021.
2.5.1.2.4 Site Area Geologic Hazard Evaluation INo identified geologic units at the site are not subject to dissolution. The upper 170 ft. (50 m) at the site are identified as sands and clays (Jacobs, 2022). The site area is not within the main salt basins in the region (Hudec et al., 20232013; Figure 2.5.1-123). Other detailed studies in the area found no evidence that for salt structures that are subject to dissolution are present in the site vicinity (Exelon, 2010Exelon, 2012a). Borings at the site identified some carbonate within the unconsolidated sediments but did not identify any fully cemented carbonate units prone to karst or voids.
Volcanic activity is associated with plate boundaries and hotspot activity. Neither geologic setting is present in the site region based on global maps of plate boundaries and hotspot locations (Bird, 2003; Marzocchi and Mulargia, 1993) and no volcanic events are anticipated in the region.
There are no Quaternary volcanoes in the sSite rRegion (200 mi. [320 km]) or mapped Quaternary volcanic deposits within sSite vVicinity (25 mi. [40 km]) (BEG, 1992; Global Volcanism Program, 2024). Therefore, based on RG 4.26, which specifies if no Quaternary active volcanoes are identified in the sSite rRegion (200 mi. [320 km]), or Quaternary pyroclastic deposits within the Site site Vicinity vicinity (25 mi. [40 km]), the volcanic hazard can be screened out of further analysis.
As shown in the cross sections (Figures 2.5.1-234, 2.5.1-245, 2.5.1-256, and 2.5.1-267),
tthere is little topographic relief across the site. As described in Subsection 2.4.12.1.1., iIn the site vicinity, the greatest slope is the 25 to 30 ft. (7.6 to 9.1 m) escarpment located alongmarking the edge of the Victoria Barge Canal (. The escarpment along the Guadalupe River is more than 1.2 mi. (2 km) from the LMGS site. Based on the gentle topography of the site, landsliding is not expected in the site arealocation.
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-37 December 2025 References 2.5.1-1: Alsalem, O. B., M. Fan, and X. Xie, 2017. Late Paleozoic subsidence and burial history of the Fort Worth basin,. AAPG Bulletin, 101(11), pp.1813-1833, 2017.
2.5.1-2: Baldridge, W.S., Olsen, K.H. and Callender, J.F., 1984. Rio Grande rift: problems and perspectives. In Rio Grande Rift: Northern New Mexico. New Mexico Geological Society 35th Field Conference Guidebook (pp. 1-12), 1984.
2.5.1-3: Bankey, V., A. Cuevas, D. Daniels, C.A. Finn, I. Hernandez, P. Hill, R. Kucks, W. Miles, et al.,
2002. Digital Data Grids for the Magnetic Anomaly Map of North America, Open-File Report 02-414, U.S. Geological Survey, 2002.
2.5.1-4: Bankey, 2006. Texas Magnetic and Gravity Maps and Data - A Website for Distribution of Data.
U.S. Geological Survey Data Series 232. Denver, Colorado, USA. U.S. Geological Survey, 2006.
Access. date 19 July 2024.
2.5.1-5: Bebout, D. G., R. G. Loucks, R.G. and A. R. Gregory, A.R., 1983. Frio sandstone reservoirs in the deep subsurface along the Texas Gulf Coast: their potential for production of geopressured geothermal energy (No. NP-4901171). Texas Univ., Austin (USA). Bureau of Economic Geology.
2.5.1-56: BEG (Bureau of Economic Geology), 1992. Geologic Map of Texas. 1:500,000 scale. 1992.
2.5.1-67: BEG (Bureau of Economic Geology), 1996. Physiographic Map of Texas. 1:500,000 scale, 1996.
2.5.1-78: Bird, P., 1998. Kinematic history of the Laramide orogeny in latitudes 35 - 49 N, western United States. Tectonics, 17(5), pp.780-801, 1998.
2.5.1-98: Bird, P., 2003. An updated digital model of plate boundaries. Geochemistry, Geophysics, Geosystems, 4(3), 2003.
2.5.1-109: Bird, D. E., K. Burke, S. A. Hall, J. F. and Casey, 2011. Tectonic evolution of the Gulf of Mexico Basin. Gulf of Mexico Origin, Waters, and Biota: Volume 3, Geology, p.1. 2011.
2.5.1-110: Bird, D. E., K. Burke, S. A. Hall, and J. F. Casey, 2005. Gulf of Mexico tectonic history:
Hotspot tracks, crustal boundaries, and early salt distribution. AAPG Bulletin, 89(3), 311-328.
doi:10.1306/10280404026, 2005.
2.5.1-121: Bonvalot, S., A. Briais, M. Kuhn, A. Peyrefitte, N. Vales, R. Biancale, G. Gabalda, G.
Moreaux, F. Reinquin, and M. Sarrailh, 2012. Global grids: World Gravity Map (WGM2012). Bureau Gravimetrique International, 2012.
2.5.1-123: Boyd, O. S., D. Churchwell, M. P. Moschetti, E. M. Thompson, M. C. Chapman, O. Ilhan, T. L. Pratt, S. K. Ahdi, and S. Rezaeian, 2024. Sediment thickness map of United States Atlantic and Gulf Coastal Plain Strata, and their influence on earthquake ground motions. Earthquake Spectra, 40(1), pp.89-112, 2024.
2.5.1-14: Boyd, O. S., 2023,. Atlantic and Gulf Coastal Plains Sediment Thickness (v220517):
U.S. Geological Survey data release, Website: https://doi.org/10.5066/P9EBOWU8.
2.5.1-15: Buatois, L. A., L. L. Saccavino, and C. Zavala, 2011,. Ichnologic signatures of hyperpycnal flow deposits in Cretaceous river-dominated deltas, Austral Basin, southern Argentina, in R. M. Slatt and C. Zavala, eds., Sediment transfer from shelf to deep waterRevisiting the delivery system:
AAPG Studies in Geology 61, p. 153-170, 2011.
2.5.1-136: Campbell, M. D., M. David Campbell, and H. M. Wise, 2018. Growth faulting and Subsidence in the Houston, Texas Area: Guide to the origins, relationships, hazards, potential impacts and methods of investigation: An update. J. Geol. Geosci, 2(1), pp.001-053, 2018.
2.5.1-147: Chowdhury, A. H., and M. J. Turco, 2006. Geology of the Gulf Coast Aquifer, Texas, in Mace et all, eds, Aquifers of the Gulf Coast of Texas, Water Development Board Report 365, p. 23-50, 2006.
2.5.1-158: Collins, E. W. and Hovorka, S. D., 1997. Structure Map of the San Antonio Segment of the Edwards Aquifer and Balcones Fault Zone, South-Central Texas: Structural Framework of a Major Limestone Aquifer: Kinney, Uvalde, Medina, Bexar, Comal, and Hays Counties. KIP Articles. 5312.
1997.
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-38 December 2025 2.5.1-169: Cox, R. T., C. Lowe, Y.C., Hao, Y. and S.A. Mahan, S.A., 2014. Use of small-scale liquefaction features to assess paleoseismicity: an example from the Saline River fault zone, Southeast Arkansas, USA. Frontiers in Earth Science, 2, p.31. 2014.
2.5.1-1720: Crone, A. J., and R. L. Wheeler, 2000. Data for Quaternary Faults, Liquefaction Features, and Possible Tectonic Features in the Central and Eastern United States, East of the Rocky Mountain Front, Open-File Report 00-260, U.S. Geological Survey, 2000.
2.5.1-1821: Diegel, F., J. Karlo, D. Schuster, R. Shoup, and P. Tauvers, 1995. Cenozoic Structural Evolution and Tectono-Stratigraphic Framework of the Northern Gulf Coast Continental Margin, Salt Tectonics: A Global Perspective, AAPG Memoir 65, p. 109-151, American Association of Petroleum Geologists, 1995.
2.5.1-1922: Dodge, M. M., and J. S. Posey, J.S. 1981. Structural cross sections, tertiary formations, Texas Gulf Coast (Vol. 1). Bureau of Economic Geology, University of Texas at Austin, 1981..
2.5.1-2023: Eddy, D. R., H. J. A. Van Avendonk, G. L. Christeson, and I. O. Norton, 2018. Structure and origin of the rifted margin of the northern Gulf of Mexico: Geosphere, v. 14, no. 4, p. 1-14, Website: https:// doi.org/10.1130/GES01662.1, 2018.
2.5.1-2124: Ewing, J., 1986. Structural Styles of the Wilcox and Frio Growth Fault Trends in Texas:
Constraints on Geopressured Reservoirs, Report of Investigations No. 154, Bureau of Economic Geology, University of Texas, 1986.
2.5.1-225: Ewing, 1990. Tectonic Map of Texas. Bureau of Economic Geology, 4 sheets. 1990.
2.5.1-236: Ewing, 1991. The Tectonic Framework of Texas. Text to accompany "The Tectonic Map of Texas". Bureau of Economic Geology. 1991.
2.5.1-247: EXELON, 2012a. Victoria County Station ESP Application, Part 2-- Site Safety Analysis Report, Section 2.5.1 Revision 1, 2009, ML12131A060, 2012.
2.5.1-258:, EXELON, 2012b. Victoria County Station ESP Application, Part 2-- Site Safety Analysis Report, Section 2.5.1 Revision 1, 2009, ML12131A064, 2012.
2.5.1-269: EXELON, 2012c. Victoria County Station ESP Application, Part 2-- Site Safety Analysis Report, Section 2.5.1 Revision 1, 2009, ML12131A063, 2012.
2.5.1-2730: Foote, R. Q., L. M. Massingill, and R. H. Wells, 1988. Petroleum geology and the distribution of conventional crude oil, natural gas, and natural gas liquids, East Texas Basin. US Geological Survey, 1988.
2.5.1-2831: Galloway, W. E., 2008. Depositional evolution of the Gulf of Mexico sedimentary basin.
Sedimentary basins of the world, 5, pp.505-549, 2008.
2.5.1-32: Galloway, W. E., and R. A. Morton, 1989,. Geometry, genesis, and reservoir characteristics of shelf sandstone facies, Frio Formation (Oligocene), Texas coastal plain. 1989.
2.5.1-2933: García-Reyes, A., and J. Dyment, 2021. Structure, age, and tectonic evolution of the Gulf of Mexico. Earth and Planetary Science Letters, 577, p.117259, 2022.
2.5.1-3034: Garrison, L. E., and R. G. Martin, R.G., 1973. Geologic structures in the Gulf of Mexico basin (Vol. 773). US Government Printing Office, 1973.
2.5.1-315: Global Volcanism Program, 2024. [Database] Volcanoes of the World (v. 5.2.7; 21 Feb 2025). Distributed by Smithsonian Institution, compiled by Venzke, E., Website:
https://doi.org/10.5479/si.GVP.VOTW5-2024.5.2 2.5.1-36: Harazim, D., 2014. High-Energy Seafloor Processes and Biological Reworking as First-Order Controls on Mudstone Composition and Geochemistry, PhD Thesis, Memorial University of Newfoundland, May 2014.
2.5.1-327: Harry and Mickus, 1998. Gravity constraints on lithosphere flexure and the structure of the late Paleozoic Ouachita orogen in Arkansas and Oklahoma, south central North America. Tectonics, 17, p. 187-202, 1998.
2.5.1-338: Hessler, A. M., J. A. Covault, D. F. Stockli, and A. Fildani, 2018. Late Cenozoic cooling favored glacial over tectonic controls on sediment supply to the western Gulf of Mexico. Geology, 46(11), pp.995-998, 2018.
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-39 December 2025 2.5.1-349: Hays, W. W., 1976. Interpretation of gravity data (No.76-479). US Geological Survey, 1976.
2.5.1-3540: Hornsby, K. T., A. R. Streig, S. E. Bennett, J. C. Chang, and S. Mahan, 2020. Neotectonic and paleoseismic analysis of the northwest extent of Holocene surface deformation along the Meers Fault, Oklahoma. Bulletin of the Seismological Society of America, 110(1), pp.49-66, 2020.
2.5.1-3641: Hosman, R. L., 1996. Regional Stratigraphy and Subsurface Geology of Cenozoic Deposits, Gulf Coastal Plain, South-Central United States, Professional Paper 1416-G, 34 p., U.S. Geological Survey, 1996.
2.5.1-3742: Hosman, R. L. and J. S. Weiss, 1991. Geohydrologic units of the Mississippi embayment and Texas coastal uplands aquifer systems, south-central United States (No. 1416-B). US Government Printing Office, 1991.
2.5.1-3843: Hough, S. E., J. G. Armbruster, L. Seeber, and J. F. Hough, 2000. On the Modified Mercalli Intensities and Magnitudes of the 1811-1812 New Madrid earthquakes, Journal of Geophysical Research, v. 105, no. B10, p. 23,839-23,864, 2000.
2.5.1-3944: Hudec M. R., I. O. Norton, M. P. Jackson, and F. J. Peel, 2013. Jurassic evolution of the Gulf of Mexico salt basin. AAPG bulletin, 97(10), pp.1683-1710, 2013.
2.5.1-4045: Huerta, A. D., and D. L. Harry., 2012. Wilson cycles, tectonic inheritance, and rifting of the North American Gulf of Mexico continental margin. Geosphere, 8(2), pp.374-385, 2012.
2.5.1-4146: Jackson, M. P., 1982. Fault tectonics of the East Texas basin. Bureau of Economic Geology, Geological Circular 82-4, 31 pp, 1982.
2.5.1-4247: Jacobs, 2022. North Landfill and North Landfill Expansion Cell, Seadrift, Texas, Annual 2021 Groundwater Detection Monitoring Report: Permit No. HW-50190. 6 pp, 2022.
2.5.1-4348: Jacques, J. M., A. D. Price, and J. E. Bain, 2004. Digital Integration of Potential Fields and Geological Data Sets for Plate Tectonic and Basin Dynamic Modeling - The First Step Towards Identifying New Play Concepts in the Gulf of Mexico Basin, Leading Edge, v. 23, p. 384-389, 2004.
2.5.1-4449: Johnson, A. C., and E. S. Schweig, 1996. The enigma of the New Madrid earthquakes of 1811-1812, Annual Review Earth and Planetary Sciences, v. 24, pp. 339-384, 1996.
2.5.1-4550: Kruger, J. M., and G. R. Keller, 1986. Interpretation of Crustal Structure from Regional Gravity Anomalies, Ouachita Mountains Area and Adjacent Gulf Coastal Plain, AAPG Bulletin, v. 70, p.
667-689, American Association of Petroleum Geologists, 1986.
2.5.1-5146: Li, P., G. C. D. Huang, A. Savvaidis, F. Kavoura, and R. W. Porritt, 2021. Characteristics of seismicity in the Eagle Ford shale play, southern Texas, constrained by earthquake relocation and centroid moment tensor inversion. Seismological Society of America, 92(6), pp.3504-3515, 2021.
2.5.1-52: Loucks, R. G., 2005. Revisiting the importance of secondary dissolution pores in Tertiary sandstones along the Texas Gulf Coast, Gulf Coast Association of Geological Societies Transactions, Volume 55, 2005.
2.5.1-4753: Macdonald, F.A., W. A. Yonkee, W.A., R. M. Flowers, R.M. and N. L. Swanson-Hysell, N.L., 2023. Neoproterozoic of Laurentia. Geological Society of America, Memoir 220, P. 331-380.
2023.
2.5.1-4854: Mackey, G. N., B. K. Horton, and K. L. Milliken, 2012. Provenance of the Paleocene-Eocene Wilcox Group, western Gulf of Mexico basin: Evidence for integrated drainage of the southern Laramide Rocky Mountains and Cordilleran arc. Bulletin, 124(5-6), pp.1007-1024, 2012.
2.5.1-4955: Marzocchi, W., and F. Mulargia, 1993. Patterns of hot spot volcanism. Journal of Geophysical Research: Solid Earth, 98(B8), pp.14029-14039, 1993.
2.5.1-5056: Martin Jr., Raymond G. 1973. Salt structure and sediment thickness, Texas-Louisiana continental slope, northwestern Gulf of Mexico., No.73-179., U.S. Geological Survey, 1973.
2.5.1-5157: McKeighan, C., P. Hennings, E. A. Horne, K., Smye, and A. Morris., 2022. Understanding Anthropogenic Fault Rupture in the Eagle Ford Region, South-Central Texas., Bulletin of the Seismological Society of America, 112(6), pp.2870-2889, 2022.
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-40 December 2025 2.5.1-58: McMahon, S., A. Van Smeerdijk Hood, and D. McIlroy, 2016. The origin and occurrence of subaqueous sedimentary cracks, Geological Society London Special Publications, 448(1): 285-3112016, November 2016.
2.5.1-5259: Meyer, B., R. Saltus, and A. Chulliat, 2017. E 3., NOAA National Ce MAG2v3: Earth Magnetic Anomaly Grid (2-arc-minute resolution)., Version 3., NOAA National Centers for Environmental Information, Website: https://doi.org/10.7289/V5H70CVX,. Date accessed: July 7, 2022.
2.5.1-5360: Miall, A D., 2019. The Southern Midcontinent, Permian Basin and Ouachitas. The Sedimentary Basins of the United States and Canada, 369-399, doi:10.1016/b978-0-444-63895-3.00008-5, 2019.
2.5.1-5461: Mickus, K., R. J. Stern, G. R. Keller, and E. Y. Anthony, 2009. Potential field evidence for a volcanic rifted margin along the Texas Gulf Coast., Geology, 37(5), pp.387-390, Website: doi:
https://doi.org/10.1130/G25465A.1, 2009.
2.5.1-62: Moein, M. J., C. Langenbruch, C., R. Schultz, R.,F. Grigoli, W. L.F., Ellsworth, R.W.L., Wang, R.,
A. P. Rinaldi, A.P. and S. Shapiro, S., 2023. The physical mechanisms of induced earthquakes., Nature Reviews Earth & Environment, 4(12), pp.847-863, 2023.
2.5.1-5563: 2.5.1-56: Morgan, P., W. R. Seager, W.R. and M. P. Golombek, M.P., 1986. Cenozoic thermal, mechanical and tectonic evolution of the Rio Grande rift., Journal of Geophysical Research:
Solid Earth, 91(B6), pp.6263-6276, 1986.
2.5.1-5764: Mosher, S., 1998. Tectonic evolution of the southern Laurentian Grenville orogenic belt, Geological Society of America Bulletin, v. 110, no. 11, p. 1357-1375, 1998.
2.5.1-5865: Mosher, S., A. M. Hoh, and J. F. Reese, 2004. Tectonic Evolution of the eastern Llano Uplift, central Texas: A record of Grenville orogenesis along the southern Laurentian margin, Austin Geological Society, 2004.
2.5.1-5966: Mosher, S., J. F. S. Levine, and W. D. Carlson, 2008. Mesoproterozoic plate tectonics: A collisional model for the Grenville-aged orogenic belt in the Llano Uplift, central Texas, Geology, v. 36,
- n. 1, p. 55-58, 2008.
2.5.1-6067: Neton, M. J., 1992. "Late Proterozoic Rifting of Laurentia: Source and Deposition of Conglomerate Units of the Grandfather Mountain Formation, North Carolina Blue Ridge. " Master's Thesis, University of Tennessee, 1992.
2.5.1-68: Paine, J. G., and E. W. Collins., 20142014.. Geologic Map of the Mission Bay Quadrangle Mission Delta and Copano Bay Area, Texas Gulf of Mexico Coast: The University of Texas at Austin, Bureau of Economic Geology, Open-File Map No. 215, scale 1:24,000. 2014.
2.5.1-69: Paine, J. G., and E. W. Collins, 2017, 2017. Geologic Map of the Seadrift NE Quadrangle, Texas Gulf of Mexico Coast., The University of Texas at Austin, Bureau of Economic Geology, Open-File Map No. 0232, scale 1:24,000., 2017.
2.5.1-6170: Paine, J. G., and E. W. Collins, 2013. Geologic Map of the Guadalupe delta, Texas Gulf of Mexico Coast: Sheet 3, Green Lake Quadrangle, 1 Sheet, 2013.
2.5.1-6271: Pavlis, N. K., S. A. Holmes, S. C. Kenyon, and J. K. Factor, 2008. An Earth Gravitational Model to Degree 2160: EGM2008, presented at the 2008 General Assembly of the European Geosciences Union, Vienna, Austria, April 13-18, 2008.
2.5.1-6372: Qiao, X., T. Chu, P. Tissot, and S. Holland, 2023. Sentinel-1 InSAR-derived land subsidence assessment along the Texas Gulf Coast., International Journal of Applied Earth Observation and Geoinformation, 125, p.103544, 2023.
2.5.1-73: Railroad Commission of Texas, 2025. Injection Wells, July 1, 2024, Website:
https://www.rrc.texas.gov/, Date accessed: October 21, 2025.
2.5.1-74: Rezak, R., T. J. Bright, T.J. and D. W. McGrail, D.W., 19835. Reefs and banks of the northwestern Gulf of Mexico: tTheir geological, biological, and physical dynamics, 1983.
2.5.1-6475: Sandwell, D. T., R. D. Müller, W. H. F. Smith, E. Garcia, and R. Francis, 2014. New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure, Science, Vol. 346, no. 6205, pp. 65-67, doi: 10.1126/science.1258213, 2014.
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-41 December 2025 2.5.1-6756: Saribudak, M., 2016. Geophysical mapping of Mount Bonnell fault of Balcones fault zone and its implications on Trinity-Edwards Aquifer interconnection, Central Texas, USA., The Leading Edge, 35(9), pp. 752-758, 2016.
2.5.1-7667: Schwartz, J. J., J. S. Lackey, J.S., E. A. Miranda, K. A.E.A., Klepeis, G. K.A., Mora-Klepeis, F.G., Robles, F. and J. D. Bixler, J.D., 2023. Magmatic surge requires two-stage model for the Laramide orogeny., Nature communications, 14(1), p. 3841, 2023.
2.5.1-6778: Solís I, R. F., 1981. Upper tertiary and quaternary depositional systems, central coastal plain, Texas: Regional geology of the coastal aquifer and potential liquid-waste repositories., Report of Investigations No. 108., Texas Bureau of Economic Geology., 89 pp., 1981.
2.5.1-6789: Stern, R., W. R. Dickinson, and T. Lawton, 2010.
Introduction:
Making the southern margin of Laurentia. Geosphere, 6(6), pp.737-738, 2010.
2.5.1-8069: Stern, R. J., and W. R. Dickinson, W.R., 2010. The Gulf of Mexico is a Jurassic backarc basin., Geosphere, 6(6), pp.739-754, 2010.
2.5.1-7081: Streig, A. R., and CJ. Chang, J., 2018. Paleoseismic & Geophysical Evaluations to Improve Seismogenic Source Characterization of the Meers Fault, OK: Collaborative Research between Geological Sciences, Portland State University and the Oklahoma Geological Survey., 2018.
2.5.1-7812: Swanson, E., 1995. 2 Physiographic Provinces. of Texas. Geo-Texas: A Guide to the Earth Sciences, 18 (1995): 23, 1995.
2.5.1-7823: Swanson, S. M., A. W. Karlsen, A.W. and B. J. Valentine, B.J., 2013. Geologic assessment of undiscovered oil and gas resources: Oligocene Frio and Anahuac Formations, United States Gulf of Mexico coastal plain and State waters (No. 2013-1257)., U.S. Geological Survey, 2013.
2.5.1-7834: Swanson and Karlsen, 2009. PS USGS Assessment of Undiscovered Oil and Gas Resources for the Oligocene Frio and Anahuac Formations, Onshore Gulf of Mexico Basin, USA, 2009.
2.5.1-7845: Snedden, J. W., and W. E. Galloway, W.E., 2019. The Gulf of Mexico sedimentary basin:
Depositional evolution and petroleum applications., Cambridge University Press, 2019.
2.5.1-86: TexNet, 2025. TexNet Earthquake Catalog. Date aAccessed: 24 October 24, 2025. Website:
https://catalog.texnet.beg.utexas.edu/, Date accessed: October 24, 2025.
2.5.1-7587: Thomas, J. D. 2003. "Integrating synsedimentary tectonics with sequence stratigraphy to understand the development of the Fort Worth basin." AAPG Southwest Section Meeting. 2003.
2.5.1-7688: Thomas, W. A., 1985. The Appalachian-Ouachita connection: Paleozoic orogenic belt at the southern margin of North America., Annual Review of Earth and Planetary Sciences, Vol. 13, p. 175, 13, p.175, 1985.
2.5.1-7789: Thomas, W. A., 2011. The Iapetan rifted margin of southern Laurentia., Geosphere, 7(1),
pp.97-120. 2011.
2.5.1-7890: Thomas, W. A., G. E. Gehrels, G.E.,K. E. Sundell, K.E. and M. C. Romero, M.C., 2021.
Detrital-zircon analyses, provenance, and late Paleozoic sediment dispersal in the context of tectonic evolution of the Ouachita orogen,. Geosphere, 17(4), pp.1214-1247, 2021.
2.5.1-7991: Thompson Jobe, J., A. Hatem, R. Gold, C. DuRoss, N,. Reitman, R. Briggs, and C.
Collett, 2022. Revised earthquake geology inputs for the central and eastern United States and southeast Canada for the 2023 National Seismic Hazard Model. Seismological Society of America, 93(6), pp.3100-3120, 2022.
2.5.1-8092: Thompson Jobe, J. A., R. D. Gold, R. D., R. W. Briggs, R. W., R. A. Williams, R. A., W. J.
Stephenson, W. J., J. E. Delano, J. E., et al. 2020. Evidence for late Quaternary deformation along Crowleys Ridge, New Madrid seismic zone., Tectonics, 39, 2020.
2.5.1-8193: Texas Natural Resources Information System, 2017. Website: https://tnris.org/ Last Modified, 2017.
2.5.1-94: Trippet, A. R., 1980.Maps showing geology of East and West Flower Garden Banks, northwest Gulf of Mexico(No. 1232)., US Geological Survey, 1980.
Long Mott Generating Station Preliminary Safety Analysis Report Section 2.5 Geology 2.5.2-42 December 2025 2.5.1-8295: University of California, San Diego, 2015. Exploring Ocean Tectonics from Space. Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, Univ. of California, San Diego. Website: https://topex.ucsd.edu/grav_outreach/index.html#grid. Updated March 30, 2015.
2.5.1-96:
USGS), Texas Geographic Information Office (TxGIO), and The University of Texas at Austin Bureau of Economic Geology (UTBEG), 2007. Geologic Database of Texas, Scale: 1:250,000, United States Geological Survey, https://webapps.usgs.gov/txgeology/.
2.5.1-97: USGS, 2025. USGS earthquake catalog, Website:accessed 24 October 2025.
https://earthquake.usgs.gov/earthquakes/search/, Date accessed: October 24, 2025.
2.5.1-8398: Vasileiou, A., M. Gouiza, M.,E. Mortimer, ED., Paton, AD., Nanfito, A. and D. Lewis, D.,
2023. New insights into the crustal architecture and tectonic evolution of the Eastern Gulf of Mexico.,
Basin Research, 36(1), p.e12812., 2023.
2.5.1-8499: Viele, G. W., and W. A. Thomas, 1989. Tectonic Synthesis of the Ouachita Orogenic Belt, The Geology of North America, v. F-2, The Appalachian-Ouachita Orogen in the United States, p. 695-728, Geological Society of America, 1989.
2.5.1-85100: Wang, K., 2024. InSAR-derived Average Vertical Surface Deformation Rate (January 2017-December 2020) Over Upper Texas and Louisiana Coasts," Website:
https://doi.org/10.18738/T8/3HFQVJ, Texas Data Repository, V1, 2024.
2.5.1-86101: Wang, K., J. Chen, J.,E. Valseth, G. Wells, S. Bettadpur, C. E. Jones, and C. Dawson, 2024. Subtle land subsidence elevates future storm surge risks along the gulf coast of the United States. Journal of Geophysical Research: Earth Surface, 129(9), p.e2024JF007858, 2024.
2.5.1-102: Wermund Jr., E. G., D. W. Moore, A. C. Christiansen, and C. A. Bush, 1993. Quaternary geologic map of the Austin 4°x6° quadrangle, United States (No. 1420 (NH-14)),. US Geological Survey, 1993.
2.5.1-87103: Wheeler, R. L., 1999. Fault number 924, Gulf-margin normal faults, Texas, in Quaternary fault and fold database of the United States: U.S. Geological Survey Website:
https://earthquakes.usgs.gov/hazards/qfaults,. Date accessed:: August 11, 2024.
2.5.1-88104: Woodruff Jr., C. M., and M. W. McBride, M.W., 1979. Regional assessment of geothermal potential along the Balcones and Luling-Mexia-Talco Fault Zones, Central Texas. Final report (No.
DOE/ET/28375-1)., Texas Univ., Austin (USA)., Bureau of Economic Geology, 1979.
2.5.1-89105: Younas, M., S. D. Khan, O. Tirmizi, and Y. Hamed, 2023. Geospatial analytics of driving mechanism of land subsidence in Gulf Coast of Texas, United States. Science of the Total Environment, 902, p.166102, 2023.
2.5.1-90106: Zhou, X., G. Wang, K. Wang, H. Liu, H., H. Lyu, and M.J. Turco, 2021. Rates of natural subsidence along the Texas coast derived from GPS and tide gauge measurements (1904-2020).
Journal of Surveying Engineering, 147(4), p.04021020, 2021.
2.5.1-91107: Zoback, M. L., and M. C. Zoback, 1989. Tectonic stress field of the continental United States, in Geophysical framework of the continental United States, Geological Society of America, Memoir 172, p. 523-539, 1989.
Long Mott Generating Station Preliminary Safety Analysis Report Table 2.5.1-1 Injection Well Data from the Site Vicinity (Sheet 1 of 10)
FID Surface ID API Longitude Latitude Well ID H-10 Status Reported Fluid Max Liquid Injection Volume (bbls/day)
Top Injection Zone depth (ft.)
Bottom Injection Zone Depth (ft.)
765 85366 23903145
-96.5454 28.73296 3145 Active Salt water 6000 6690 6750 799 90463 23932181
-96.6822 28.78043 32181 Active Salt water 7500 5600 6000 702 90650 23932275
-96.6505 28.77617 32275 Active Salt water 15,000 5227 5354 156 91088 23932930
-96.6819 28.82939 32930 Active Salt water 3000 5250 5500 864 1247681 23933580
-96.6067 28.79492 33580 Active Salt water, CO2 20,000 5100 6241 1158 1295339 23933627
-96.5961 28.78242 33627 Active Salt water 20,000 5050 6339 870 1318822 23933656
-96.6037 28.79387 33656 Active Salt water, CO2 20,000 5641 6300 1072 1310224 23933660
-96.6009 28.7929 33660 Active Salt water, CO2 20,000 5645 6300 1082 1310315 23933665
-96.6048 28.79194 33665 Active Salt water, CO2 15,000 5700 6248 778 1310442 23933666
-96.6124 28.79207 33666 Active Salt water, CO2 15,000 5700 6265 884 1310492 23933669
-96.602 28.79069 33669 Active Salt water, CO2 20,000 5653 6300 902 1310707 23933672
-96.6038 28.78905 33672 Active Salt water, CO2 12,000 5700 6300 891 1310859 23933673
-96.6061 28.79003 33673 Active Salt water, CO2 20,000 5693 6300 Section 2.5 Geology 2.5.1-43 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Table 2.5.1-1 Injection Well Data from the Site Vicinity (Sheet 2 of 10)
FID Surface ID API Longitude Latitude Well ID H-10 Status Reported Fluid Max Liquid Injection Volume (bbls/day)
Top Injection Zone depth (ft.)
Bottom Injection Zone Depth (ft.)
771 1311048 23933678
-96.6056 28.78692 33678 Active Salt water, CO2 20,000 5656 6300 777 1313427 23933694
-96.6183 28.78664 33694 Active Salt water, CO2 20,000 5640 6300 668 116516 39100025
-97.0568 28.53065 00025 Active Salt water 3000 3907 3911 71 116548 39100040
-97.0487 28.52654 00040 Active Salt water 0
4435 4780 513 104480 39100211
-97.056 28.4216 00211 Active Salt water 15,000 3000 4060 10 104461 39100212
-97.0525 28.42443 00212 Active Salt water 15,000 3030 3970 833 104231 39100242
-97.0438 28.47698 00242 Active Salt water 2500 4490 4700 517 104336 39100255
-97.0419 28.47125 00255 Active Salt water 4000 3848 4118 679 116546 39103767
-97.0515 28.51912 03767 Active Salt water 3000 3178 3402 515 116538 39103770
-97.0486 28.52132 03770 Active Salt water 5000 3430 3790 732 104509 39131713
-97.0547 28.41977 31713 Active Salt water 10,000 2985 4030 554 104482 39131780
-97.0576 28.4241 31780 Active Salt water 15,000 3000 4050 634 104218 39131972
-97.0357 28.48714 31972 Active Salt water 7500 4530 4742 824 104205 39132019
-97.0387 28.4849 32019 Active Salt water 7500 4530 4748 165 1192216 39132893
-97.0128 28.48966 32893 Active Salt water 10,000 3190 4080 601 1195726 39132901
-97.0133 28.48899 32901 Active Salt water 10,000 3180 4062 64 1196034 39132908
-97.0609 28.53667 32908 Active Salt water 6000 2600 2990 Section 2.5 Geology 2.5.1-44 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Table 2.5.1-1 Injection Well Data from the Site Vicinity (Sheet 3 of 10)
FID Surface ID API Longitude Latitude Well ID H-10 Status Reported Fluid Max Liquid Injection Volume (bbls/day)
Top Injection Zone depth (ft.)
Bottom Injection Zone Depth (ft.)
880 1211878 39132964
-97.0651 28.539 32964 Active Salt water 6000 2600 3020 268 90938 46900253
-96.7408 28.79783 00253 Active Salt water 2000 4732 4738 1959 116415 46901574
-97.0063 28.52514 01574 Active Salt water 12,000 4600 4650 1973 116300 46901577
-97.0026 28.51939 01577 Active Salt water 4300 4413 4702 545 86348 46902212
-96.9992 28.52049 02212 Active Salt water 10,000 3602 3995 2340 86349 46902214
-96.9963 28.52019 02214 Active Salt water 9000 3605 3997 575 86374 46902221
-96.9968 28.51816 02221 Active Salt water 8000 3600 4000 498 86163 46902301
-96.9271 28.54957 02301 Active Salt water 5000 4850 5045 2970 87779 46902498
-96.8677 28.63924 02498 Active Salt water 4000 5400 6118 2078 87829 46902538
-96.8648 28.62966 02538 Active Salt water 4000 4970 5067 55 87620 46902643
-96.8096 28.69511 02643 Active Salt water 3000 4930 4950 1993 86881 46931496
-96.8876 28.65536 31496 Active Salt water 10,000 3460 4260 1813 87506 46931606
-96.8141 28.67568 31606 Active Salt water 10,000 4760 6200 2859 88037 46931905
-96.75 28.79711 31905 Active Salt water 10,000 2500 4210 2907 86364 46932033
-96.9885 28.52274 32033 Active Salt water 12,000 3626 4704 2077 86313 46932164
-96.9842 28.52534 32164 Active Salt water 12,000 3672 4350 2904 86299 46932291
-96.9935 28.5236 32291 Active Salt water 10,000 4386 4500 221 91072 46932429
-96.7415 28.80268 32429 Active Salt water 10,000 3620 4114 Section 2.5 Geology 2.5.1-45 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Table 2.5.1-1 Injection Well Data from the Site Vicinity (Sheet 4 of 10)
FID Surface ID API Longitude Latitude Well ID H-10 Status Reported Fluid Max Liquid Injection Volume (bbls/day)
Top Injection Zone depth (ft.)
Bottom Injection Zone Depth (ft.)
261 90930 46932430
-96.738 28.79941 32430 Active Salt water 10,000 3818 5585 222 90958 46932442
-96.7354 28.80239 32442 Active Salt water 10,000 3650 4561 2335 86400 46932511
-96.9917 28.52217 32511 Active Salt water 10,000 3600 4000 2914 116276 46932512
-97.0025 28.52684 32512 Active Salt water 10,000 3618 4676 28 86635 46932840
-96.8882 28.63264 32840 Active Salt water 5000 5417 5490 3254 86616 46932844
-96.8766 28.63171 32844 Active Salt water 7500 5363 5410 2916 90942 46932880
-96.7416 28.7952 32880 Active Salt water 2500 4770 4810 2909 86426 46933286
-96.9966 28.52278 33286 Active Salt water 10,000 3600 4000 38 86427 46933302
-96.9912 28.52357 33302 Active Salt water 10,000 4400 4480 1786 87902 46933333
-96.7697 28.73696 33333 Active Salt water 10,000 4880 5000 216 1095007 46933735
-96.736 28.80317 33735 Active Salt water 10,000 3600 4250 2336 1168054 46934074
-96.9921 28.52057 34074 Active Salt water 10,000 3592 4696 2026 1171585 46934090
-96.9429 28.59377 34090 Active Salt water 10,000 4522 4900 2028 1183710 46934124
-96.8876 28.65598 34124 Active Salt water 10,000 3475 4733 2126 1197173 46934171
-96.7375 28.75198 34171 Active Salt water 10,000 5630 6470 10 1206980 46934191
-96.7562 28.67641 34191 Active Salt water, other 25,000 4500 5440 1166 1223548 46934229
-96.786 28.71678 34229 Active Salt water, other 25,000 3530 5000 Section 2.5 Geology 2.5.1-46 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Table 2.5.1-1 Injection Well Data from the Site Vicinity (Sheet 5 of 10)
FID Surface ID API Longitude Latitude Well ID H-10 Status Reported Fluid Max Liquid Injection Volume (bbls/day)
Top Injection Zone depth (ft.)
Bottom Injection Zone Depth (ft.)
2041 1283687 46934291
-96.8101 28.82456 34291 Active Salt water 25,000 3908 4560 1858 1284895 46934293
-96.9024 28.65871 34293 Active Salt water 10,000 5150 6800 2972 1291271 46934303
-96.8964 28.66369 34303 Active Salt water 30,000 4700 5000 1864 1333182 46934367
-96.9997 28.52904 34367 Active Salt water 30,000 3600 4000 3289 1374006 46934439
-96.8271 28.73855 34439 Active Salt water 15,000 4400 5350 2728 87565 46980644
-96.8287 28.68381 80644 Active Salt water 12,000 4915 4965 1476 87732 05700016
-96.862 28.62734 00016 Active Salt water 5500 4790 5080 1470 87717 05700025
-96.8578 28.63219 00025 Active Salt water 6000 4840 5100 1396 85828 05700140
-96.8528 28.60484 00140 Active Salt water, other 20,000 5005 5480 1940 84968 05700483
-96.7305 28.59077 00483 Active Salt water 2500 1878 1912 1870 92756 05700844
-96.4798 28.63239 00844 Active Salt water 1500 2000 3000 209 85935 05730951
-96.9061 28.57404 30951 Active Salt water 1000 5780 5790 1580 1090826 05731640
-96.6954 28.53145 31640 Active Salt water 220 7000 7006 484 1136805 05731720
-96.8576 28.55901 31720 Active Salt water 10,000 3500 4450 1504 1358043 05731810
-96.854 28.6118 31810 Active Salt water 20,000 4011 5273 2046 1401968 46934465
-96.7946 28.72283 34465 Authorized by RRC to inject but not yet drilled Salt water 20,000 4010 5010 Section 2.5 Geology 2.5.1-47 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Table 2.5.1-1 Injection Well Data from the Site Vicinity (Sheet 6 of 10)
FID Surface ID API Longitude Latitude Well ID H-10 Status Reported Fluid Max Liquid Injection Volume (bbls/day)
Top Injection Zone depth (ft.)
Bottom Injection Zone Depth (ft.)
790 1378357 23933652
-96.6119 28.79684 33652 Converted Back to Production Salt water, CO2 20,000 5700 6300 1073 1310223 23933659
-96.6152 28.79327 33659 Converted Back to Production Salt water, CO2 20,000 5654 6300 210 1295713 23933629
-96.6305 28.80233 33629 Drilled but not yet completed Salt water 20,000 5050 6339 240 1296563 23933631
-96.6343 28.79635 33631 Drilled but not yet completed Salt water 20,000 5050 6339 680 90331 23931683
-96.6002 28.78974 31683 Permit Canceled Salt water 566 104493 39100206
-97.0542 28.41855 00206 Permit Canceled 432 85816 05701384
-96.852 28.58874 01384 Permit Canceled 2043 90941 46932879
-96.7478 28.79097 32879 Permit Reinstated Salt water 20,000 4760 5000 15 104807 39132115
-97.0533 28.42498 32115 Permit Suspended 1157 89429 23902605
-96.5956 28.78273 02605 Plugged Salt water Section 2.5 Geology 2.5.1-48 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Table 2.5.1-1 Injection Well Data from the Site Vicinity (Sheet 7 of 10)
FID Surface ID API Longitude Latitude Well ID H-10 Status Reported Fluid Max Liquid Injection Volume (bbls/day)
Top Injection Zone depth (ft.)
Bottom Injection Zone Depth (ft.)
281 90756 23902675
-96.6391 28.78458 02675 Plugged Salt water 2193 88050 46900751
-96.7507 28.78965 00751 Plugged 1141 86657 46902441
-96.8787 28.62591 02441 Plugged 971 86660 46902470
-96.8783 28.63891 02470 Plugged 1321 87252 46902591
-96.7822 28.69955 02591 Plugged 1375 87625 46902633
-96.8066 28.69745 02633 Plugged 1377 87650 46902649
-96.813 28.69668 02649 Plugged 2253 88142 46903166
-96.7875 28.75796 03166 Plugged 932 90644 23932313
-96.654 28.77533 32313 Temporarily Abandoned Salt water 15,000 5228 5356 473 1260530 23933594
-96.5517 28.73463 33594 Temporarily Abandoned Salt water 8000 4000 6570 986 1296947 23933632
-96.6006 28.77602 33632 Temporarily Abandoned Salt water 20,000 5488 5530 1056 1297315 23933634
-96.638 28.78479 33634 Temporarily Abandoned Salt water, CO2 20,000 5700 6300 516 104491 39130016
-97.0501 28.42179 30016 Temporarily Abandoned Salt water 6000 3725 3910 503 1169519 39132816
-97.007 28.48986 32816 Temporarily Abandoned Salt water 10,000 3190 4080 Section 2.5 Geology 2.5.1-49 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Table 2.5.1-1 Injection Well Data from the Site Vicinity (Sheet 8 of 10)
FID Surface ID API Longitude Latitude Well ID H-10 Status Reported Fluid Max Liquid Injection Volume (bbls/day)
Top Injection Zone depth (ft.)
Bottom Injection Zone Depth (ft.)
504 1230726 39132994
-97.0152 28.49138 32994 Temporarily Abandoned Salt water 10,000 3180 4060 2818 87045 46901906
-96.8415 28.67513 01906 Temporarily Abandoned Salt water 1500 4050 5000 2908 86381 46902207
-96.9926 28.52281 02207 Temporarily Abandoned Salt water 10,000 3600 4000 543 86395 46902225
-96.996 28.52068 02225 Temporarily Abandoned Salt water 5000 4403 4795 516 86185 46902330
-96.9264 28.54224 02330 Temporarily Abandoned Salt water 4000 4800 5050 3245 86617 46902465
-96.8803 28.63722 02465 Temporarily Abandoned Salt water 6000 4000 4120 2079 86658 46902472
-96.8778 28.64236 02472 Temporarily Abandoned Salt water 0
4120 4227 1281 87806 46902521
-96.8731 28.6297 02521 Temporarily Abandoned Salt water 5000 3975 4315 2072 87622 46902640
-96.8087 28.69714 02640 Temporarily Abandoned Salt water 10,000 4700 4988 3148 87212 46902773
-96.7981 28.71562 02773 Temporarily Abandoned Salt water, other 3000 3200 4200 2903 86291 46930485
-96.997 28.52419 30485 Temporarily Abandoned Salt water 10,000 3592 4712 Section 2.5 Geology 2.5.1-50 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Table 2.5.1-1 Injection Well Data from the Site Vicinity (Sheet 9 of 10)
FID Surface ID API Longitude Latitude Well ID H-10 Status Reported Fluid Max Liquid Injection Volume (bbls/day)
Top Injection Zone depth (ft.)
Bottom Injection Zone Depth (ft.)
2980 86890 46932853
-96.8892 28.62589 32853 Temporarily Abandoned Salt water 7500 5450 5525 1923 87377 46932969
-96.7512 28.67953 32969 Temporarily Abandoned Salt water 15,000 4290 5440 2188 88221 46933036
-96.8465 28.78997 33036 Temporarily Abandoned Salt water 300 4380 4390 2894 86424 46933287
-96.9939 28.52629 33287 Temporarily Abandoned Salt water 10,000 4368 4450 2498 1051901 46933447
-96.994 28.62255 33447 Temporarily Abandoned Salt water, other 1500 4280 4550 2855 1104553 46933824
-96.7295 28.79989 33824 Temporarily Abandoned Salt water 10,000 3600 4200 2120 1108092 46933852
-96.7311 28.75852 33852 Temporarily Abandoned Salt water 10,000 3600 5641 1865 1180894 46934113
-96.7313 28.79726 34113 Temporarily Abandoned Salt water 10,000 4700 5000 3054 1281884 46934288
-96.7817 28.71594 34288 Temporarily Abandoned Salt water, other 25,000 4000 5200 1230 85790 05700045
-96.8662 28.62218 00045 Temporarily Abandoned Salt water 5000 2000 5660 252 85789 05700046
-96.865 28.62291 00046 Temporarily Abandoned Salt water 5000 2100 5200 Section 2.5 Geology 2.5.1-51 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Table 2.5.1-1 Injection Well Data from the Site Vicinity (Sheet 10 of 10)
FID Surface ID API Longitude Latitude Well ID H-10 Status Reported Fluid Max Liquid Injection Volume (bbls/day)
Top Injection Zone depth (ft.)
Bottom Injection Zone Depth (ft.)
1677 85783 05700053
-96.8666 28.61847 00053 Temporarily Abandoned Salt water 300 3915 4100 631 84995 05700488
-96.7278 28.58813 00488 Temporarily Abandoned Salt water 2000 1880 1988 982 85528 05730200
-96.5242 28.69654 30200 Temporarily Abandoned Salt water 8000 1850 5300 1214 87880 05731384
-96.795 28.62574 31384 Temporarily Abandoned Salt water 2500 3700 5450 Source: Texas Railroad Commission, 2025 Key: API = American Petroleum Institute ID; bbls/day = barrels per day; = FID = Feature ID Section 2.5 Geology 2.5.1-52 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Table 2.5.1-2 Description of Stratigraphic Units Between Subsections PSAR Subsection 2.4.12 2.5.1 and 2.5.3 2.5.4 Unit A sand Upper sand Interbedded sands in Stratum I C sand Middle sand Interbedded sands in Stratum II and some sand lenses in Stratum I and III E sand Lower sands, including sands below those defined as E sands Interbedded sands in Stratum IV and sand lenses within Stratum V, Stratum VI and Stratum VII Technical Aspect Guiding Interpretation Determine hydrostratigraphic units capable of storing and transmitting groundwater as well as aquitards that do not transmit groundwater Correlate geologic units in the subsurface as they relate to the geologic history of the site including deformation history and potential for deformation. Note:
sand units defined in this manner are approximately equivalent in stratigraphic position but typically thinner than those defined based on their hydrologic characteristics defined in Subsection 2.4.12 Determine the static and dynamic engineering properties of foundation soils and rocks in the site area Section 2.5 Geology 2.5.1-53 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Table 2.5.1-3 Locations of Fracture Planes Recorded in Boring Lab Data Boring Number Top Depth (ft.)
Bottom Depth (ft.)
Sample Material Change in Lithology Across Plane?
X5 127.9 129.9 UD-4 fat clay No X11 31.8 33.8 UD-1 fat clay No X15 129.9 131.9 UD-5 fat clay No X15 230.0 231.0 UD-8 fat clay No X21 216.7 218.1 UD-7 fat clay No X52 27.6 29.4 UD-1 fat clay No Section 2.5 Geology 2.5.1-54 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-1 Physiographic Provinces and Surficial Geology of Texas Source: Modified from BEG, 1996 Key: ft = feet; ft/mi = feet per mile Section 2.5 Geology 2.5.1-55 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-2 Physiographic Regions Surrounding and Beneath the Gulf of Mexico Source: Modified from Galloway, 2008 Key: km = kilometers Section 2.5 Geology 2.5.1-56 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-3 Geology of the Site Region Section 2.5 Geology 2.5.1-57 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Source: Modified from BEG, 1992 Section 2.5 Geology 2.5.1-58 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-4 Surface Geology of the Gulf of Mexico Section 2.5 Geology 2.5.1-59 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Source: Modified from Snedden and Galloway, 2019 Source: Davis, 2017 Section 2.5 Geology 2.5.1-60 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-5 Main Tectonic Terrains of the United States and Mexico Source: Modified from Stern and Dickinsonet al., 2010 NoteKey: Y-C = Yucatan-Campeche block; Can = Canada; Mex = Mexico; km = kilometers; TT =
Tehuantepec Transform; Can = Canada; Mex = Mexico; USA = United States of America; Y-C = Yucatan-Campeche block; Section 2.5 Geology 2.5.1-61 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-76 Ouachita Structural Elements in the Site Region Source: Modified from Harry and Mickus, 1998 Section 2.5 Geology 2.5.1-62 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-67 Sequence of Mesozoic Rifting in the Gulf of Mexico Source: Modified from: Hudec et al., 2013 Key: km = kilometers; mi = miles Section 2.5 Geology 2.5.1-63 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-8:
Map of Crustal Types and Depth to Basement in Kilometers in the Gulf of Mexico Section 2.5 Geology 2.5.1-64 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Source: Modified from: Galloway, ( 2008)
Note: Grey area denotes original distribution of pre-marine evaporite.
Key: AE = Apalachicola embayment; ETB = East Texas basin; km = kilometers; MGA = Middle Ground arch; MSB = Mississippi salt basin; MU = Monroe uplift; NLSB = North Louisiana salt basin; RGE = Rio Grande embayment; SA = Sabine arch; SMA = San Marcos arch; SrA =, Sarasota arch; TA = Tamaulipas arch; TE =, Tampa embayment; MGA, Middle Ground arch; AE, Apalachicola embayment; WA =, Wiggins arch; MSB, Mississippi salt basin; MU, Monroe uplift; NLSB, North Louisiana salt basin; SA, Sabine arch; ETB, East Texas basin; SMA, San Marcos arch; RGE, Rio Grande embayment; TA, Tamaulipas arch.
Section 2.5 Geology 2.5.1-65 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-109:
Sediment Thickness Aabove Bedrock in the Site Region Data sSource: Boyd, (20243)
Section 2.5 Geology 2.5.1-66 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-109 Oligocene Depositional Environments in Coastal and Offshore Texas Source: Modified from: Swanson et al., 2013 Section 2.5 Geology 2.5.1-67 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-1120:
Regional Cross Sections (Sheet 1 of 2)
Source: Baker, 1979 Section 2.5 Geology 2.5.1-68 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-1120:
Regional Cross Sections (Sheet 2 of 2)
(b)
Source: Modified from: (a) Solis, (1981); (b) Dodge and Posey, (1981)
Note: Mapped view of cross-section locations are on Figure 2.5.1-169.
Section 2.5 Geology 2.5.1-69 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-112 Tectonic Map of the 200-Mile Site Region (Map)
(Sheet 1 of 2)
Note: Most faults are not mapped at the surface; contour shading indicates the depth at which the faults are mapped.
Section 2.5 Geology 2.5.1-70 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-112 Tectonic Map of the 200-Mile Site Region (Legend)
(Sheet 2 of 2)
Source: Modified from Ewing, 1990 Section 2.5 Geology 2.5.1-71 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-132:
Map of the Location of the Vicksburg and Frio Fault Zones and Salt Basin Locations Source: Modified from Swanson and Karlseon, (2009)
Key: km = kilometer; mi = miles; USGS = United States Geological Survey Section 2.5 Geology 2.5.1-72 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-134 Fault Sources in the Central and Eastern United States in the USGS 2023 National Seismic Hazard Map Project Source: Thompson Jobe et al., 2022 Key: NSHM = National Seismic Hazard Map; USGS = United States Geological Survey Section 2.5 Geology 2.5.1-73 December 2025
Long Mo Generang Staon Preliminary Safety Analysis Report
Figure 2.5.1-15 Locations of Injection Wells Permitted in the Site Vicinity Source: Texas Railroad Commission, 2025; Wang, 2024 Note: Active, permitted, and temporarily abandoned wells included as colored dots, gray, not reported dots include abandoned and plugged wells.
Section 2.5 Geology 2.5.1-74 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-1616:
InSAR Vertical Deformation Data for the Gulf Coastal Region of Texas Section 2.5 Geology 2.5.1-75 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Data Source: Wang, 2024 Key: InSAR = Interferometric Synthetic-Aperture Radar Section 2.5 Geology 2.5.1-76 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-175 Magnetic Anomaly Map for the Site Region Section 2.5 Geology 2.5.1-77 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-184 Bouguer Gravity Anomaly Data for the Site Region Section 2.5 Geology 2.5.1-78 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-169 Geology of the Site Vicinity Source: Texas Natural Resource Information System, ( 2017); BEG, (1992)
Note: Cross sections are provided in Figure 2.5.1-2011.
Section 2.5 Geology 2.5.1-79 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-1720 Surficial Geology of the Site Area Source: Texas Natural Resource Information System, (2017); BEG, (1992)
Section 2.5 Geology 2.5.1-80 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-219 Generalized Cross Section at the Long MottLMGS Site Source: Jacobs, (2022)
Key: LMGS = Long Mott Generating StationLong Mott Section 2.5 Geology 2.5.1-81 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-1822 Generalized Stratigraphic Column at the Long MottLMGS Site Source: Jacobs, (2022)
Key: LMGS = Long Mott Generating Station Section 2.5 Geology 2.5.1-82 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-223 Locations of Data Collection Boreholes and SASW Arrays at Site Key: CPT = cone penetration test; SASW = spectral analysis of surface waters Section 2.5 Geology 2.5.1-83 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-234 Fence Diagram of Interpreted Subsurface Stratigraphy - SASW Array 3 Key: ft = feet; SASW = Spectral Analysis of Surface Waves; USCS = Unified Soil Classification System Section 2.5 Geology 2.5.1-84 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-245:
Fence Diagram of Interpreted Subsurface Stratigraphy - SASW Array 4 Key: ft = feet; SASW = Spectral Analysis of Surface Wavesters; USCS = Unified Soil Classification System Section 2.5 Geology 2.5.1-85 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-2654:
Fence Diagram of Interpreted Subsurface Stratigraphy SASWAlong Array 6 Key: ft = feet; SASW = Spectral Analysis of Surface Wavesters; USCS = Unified Soil Classification System Section 2.5 Geology 2.5.1-86 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-2765:
Fence Diagram of Interpreted Subsurface Stratigraphy -- - SASW Array 7 Key: SASW = Spectral Analysis of Surface Wavesters; USCS = Unified Soil Classification System Section 2.5 Geology 2.5.1-87 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-278 Eight-Shear Wave Velocity Profiles Modelled from SASW Data Arrays at the Site Note: Profile locations shown on Figure 2.5.1-263.
Key: ft = feeoot; ft/sec = feet per second; m = meter; m/sec = meters per second; SASW = Spectral Analysis of Surface Waves Section 2.5 Geology 2.5.1-88 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-2929 Victoria County Station Growth Fault Projections Source: Exelon, 2012c Key: km = kilometer; mi = mile; VCS = Victoria County Station Section 2.5 Geology 2.5.1-89 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-2830 Statistical Analysis of Eight Shear Wave Velocity Profiles Key: COV = coefficient of variation; ft = feet; ft/sec = feet per second; m = meters; m/sec = meters per second; SASW = Spectral Analysis of Surface Wavesters Section 2.5 Geology 2.5.1-90 December 2025
Long Mott Generating Station Preliminary Safety Analysis Report Figure 2.5.1-2311:
Victoria County Station Assessment of Lineaments from LiDAR Source: Exelon, (2012b)
Key: km = kilometers; LiDAR = Light Detection and Ranging; mi = mile; VCS = Victoria County Stations Section 2.5 Geology 2.5.1-91 December 2025
LongMottGeneratingStation PreliminarySafetyAnalysisReport Figure 2.5.1-32 LiDAR and Mapped Potential Growth Faults in the Site Vicinity Section 2.5 Geology 2.5.1-92 December 2025
LongMottGeneratingStation PreliminarySafetyAnalysisReport Key: LiDAR = Light Detection and Ranging; LMGS = Long Mott Generating Station; VCS = Victoria County Station Section 2.5 Geology 2.5.1-93 December 2025