ML20039D948

Geologic Map of Oak Ridge Reservation,Tn. Oversize Map Encl.Aperture Card Available in PDR

ML20039D948
Person / Time
Site:	Clinch River
Issue date:	11/23/1963
From:	Mcmaster W INTERIOR, DEPT. OF, GEOLOGICAL SURVEY, OAK RIDGE NATIONAL LABORATORY
To:
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ML20039D944	List: ML20039D943 ML20039D948 ML20039D949 ML20039D951 ML20039D952 ML20039D956 ML20039D961 ML20039D963 ML20039D969 ML20039D977
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7 EEALTH PHYSICS DIVISION

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GEOLOGIC MAP OF THE OAK RIDGE RESERVATION, TENNEESEE 2

William M. McMaster,-G5 ologist

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1 GE0I4GIC MAP OF THE CAK RIDGE RwatvATION, mTNESSEE

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By William M. McMaster*,

l Abstract TheOakRidgeareaisunderlain$ynineFaleozoicsedimentary formations or groups ranging in age from Early Cambrian to Early Mis-sissippian. These units consist mostly of dolomite, limestone', and

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shale. The Conasauga Group, the Knox Group, and the Chickanauga 11me-stone can be further subdivided, but on the map accompanying this report only the major contacts are shown.

The Oak Ridge reservation is crossed by two major thrust faults:

(1) the Copper Creek fault in the sauthe'aste'rn part of the area and

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(2) the Whiteoak Mountain fault in the n,orthwestern part. The strata and the fault zones dip primarily to the southeast.

The Whiteoak Moun-tain fault in the Oak Rid 6e area exhibits several subsidiary features,

' including branch faults, a syncline northwest of the fault, and two slices of dolomite of the Knox Group.

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• Geologist, U. SL Geological Survey, assigned to Oak Ridge National

.Inboratory.

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.y Introduction l

Location and Si::e of Area The Oak Ridge reservation is in the Tenness'ee Section of the' Val-ley and Ridge province and occupies parts of Anderson and Roane Cobuties.

It is bounded on the northeast, southeast, and southwest by the Clinch River. The area is approximately,14 miles long, has' an average width of 6 miles, and co= prises an area of about 86 square miles.

Purpose and Scope of Investigation The =apping project was undertaken by the U. S. Geological Survey in cooperation with the Radioactive Waste Disposal Section, Health Phys-ics Division, Oak Ridge National Laboratory; and the Division of Reactor Development of the U. S. Atc=ic Energy C-ission.

The purpose of the intestigation was to prepare a geologic map' of the Oak Ridge area on a recent topographic base map, showing locations of outezep of. major contacts and faults with as much accuracy as possi-ble within the available time.

ThegeologywasmappedonfiveTennesseeValleyAuthority71/2 min-ute quadrangles, each of which covers a part of the Oak Ridge reservation.

I These maps are: the Windrock quadrangle (129 'SE), the Clinton quadrangle (137 SW), the Iovell quadrangle (138 NW), the Bethel Valley quadrangle (130 NE), and the'Elverton quadrangle (130 NW). The geology was later iiransferred to a topographic =ap of ths Oak Ridge area having a scale of 1:31,680, prepared for the Oak Ridge Operations Office of the Atomic

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Energy C-4ssion by the Tennessee Valley Authcrity.

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Field work vas begun in December 1957 under the 4-ediate super-vision of R. M. Richardson. Most of the acco=panying map is the result,

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of field observations at rather videly spaced points.

Contacts have

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f aog for the most part, been valked out.

Only major faults and coh-tacts are indicated on the map. Three of the broad stratigraphic units shown - the Conasauga Group, the Knox Group, and the Chicka=auga Lime-stone - can be further subdivided.

'Ihe locations of faults and centacts are shown by solid lines where i

they have teen observed in the field, and by dashed lines where they IN El have been inferred on the basis of topography, or where they are covered.

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Previous Investigations Generalized geologic maps which include the Oak Ridge area are t

available (Keith, 1896; Rodgers, 1953); although these maps indicate the formations present and their approxi=aw occurrence, they are in-

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adequate to meet the needs for detailed infor=ation in the area.

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Detailed geologic studies have been made in s=all areas within the i

reservatien, such as that of the vicinity of the Oak Ridge National Laboratory site, cc=pleted in 1950 by stockdale,. De Buchananne, and j'

j Klepser (1951) and that of a part of Melton Valley by Barnett in 1954.

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. Topography and Drainage The topography of the Oak Ridge reservation is typical of the Val-1ey and Ridge province, being characterized by subparallel northeast g

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trending ridges and valleys. It reflects the geologic structure of the

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k area, which consists of generally southeast-dipping strata; the differ-ent lithologies of the for=ations result in different rates of weather.'

ing and erosion.

The ridge-producing for=ations of the Oak Ridge area are the Ro=e For=ation, the Knox Group, the Rockwood For=ation, and the Fort Payne Chert. Most of the valleys are underlain by the Conasauga Group and the Chickamauga Limes'.one.

Altitudes within the area range frain 741 feet in the southwestern part of the area to 1,356 feet at Melton Hill, which is also in the south-vestern part of the area, the maw"" relief being 615 feet.

The region is thought to have undergone two cycles of erosion and to be. presently in a third. The surfact resulting from the last ecx::plete cycle is repre-sente'd by the tops of the present ridges, which have a more or less uni-form altitude in the Oak Ridge area.

The drainage of the area is mostly of the' trellis type, although there are variations from this in some places. The = aster stream of the area is the Clinch River, an incised, meandering, superi= posed stream.

The largest tributary to the Clinch River in the reservation is the East Fork of Poplar' Creek, which flows southwestward through East Fork Val-ley to join Poplar Creek in the vestern part of the reservation. Poplar Creek enters the southwestern extre=ity of'the Oak Ridge area and flows about 2 miles within the area before entering the Clinch River.

Climate According to U. S. Weather Bureau records obtained at the Oak Ridge area station at X-lO from 1944 to 1%1, the average amm1 rainfall is 51.87 inches, the mean annual te=perature is 58.3 F, the average "Hmm L

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x te=perature is 69 2 F, and the average mini =um te=perature is k7 3 F.

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The coldest months are December, January, and February, and the hottest l months are June, July, and August.

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Rainfall is relatively well distributed throughout the year but I

varies seasonally, generally being greatest in December, January, Febru-ary, and March and least in September and October.

A secondary = vim m e.

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occurs in July due to thundershowers.

Snov forms only a s=all part of.

3 total precipitation and heavy snowfalls are infrequent.

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9 Acknowledgments l

The author ' expresses his appreciation to Stuart W. Maher, Tennessee Division of Geology, for his interest and very helpful suggestions con-

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ce'rning field problems, and to Dr. C. S. Shoup,. Chief, Biology Branch, ks 4.

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Research and Development Division, U. S. Atomic Energy Ccc=ission, Oak

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l iv Ridge, for his encouragement and assistance during the project.

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Stratigraphy g@-;w.l

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The Oak Ridge reservation is underlain by nine geologic for=a'tions

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M or groups ranging in age from Early Cambrian to Early Mississippian, b,

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':W The for=ations are of sedimentary origin, both chemical (limestone and P7..:

3 dolomite) and clastic (sandstone and shale) and from oldest to youngest 6

include the Rome For=ation, the Conasauga Group, the Knox Group, the N

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5 Chickamuga limestene, the Sequatchie For=ation, the Rockwood For=ation, the Chattanooga Shale, the Maury For=ation', and the Fort Fayne Chert.

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Of these, the =ost i=portant from the standpoint of occurrence in the 4.g N

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6 Oak Ridge airea are the Ro=e For=ation, the Conasauga Group, the Knox

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Group, and the Chicks =auga L1=estone. The others occupy relatively s=all parts of the area.

Three disconfor=1 ties are present in the colu=n:

one separating IcVer and Middle Ordovician rocks, one vithin the Middle Ordovician rocks, and one separating Iover Silurian and Devonian and Mississippian rocks. The total stratigraphic thickness of the sediments in the area is approxi=ately 9000 feet.

Cambrian and Ordovician Syste=s

' Pome For=ation.-- The Rome For=ation underlies Hav Ridge. (grid secticns G-1 to G-4 and F-5 to F-19), Pine Ridge (grid sections D-1 to D-19), and the southeastern side of the valley northwest of Pine Ridge.

The Ro=e Fo=ation is ce= posed of interbedded sandstone, siltstone, shale, and, locally, dolomite. Siltstone and shale fom the bulk of the'for=ation in the Oak Ridge area.

Sandstone beds in the Rome, which range in thickness from 3 to 14 inches, are = ore abundant in the upper half of the for=ation than in the lover.

The sandstone is co= posed of light-gray to light-brovri fine-to medium-grained quartz sand, ce=ented with silica or iron oxide. 'In places the sand is so well ce=ented as to be quartzitic.

Weathered surfaces of the sandstone generally are dark brow:i or red brown.

Siltstone in the Rome is generally li ht to dark brown and green 6

brown, thin bedded, and has irregular bedding surfaces along which small flakes of =ica are concentrated.

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A str'iking characteristic of the Rome is its banded. coloration, a 4; caused primarily by the shale beds, which are Green, maroon, red, vio,

BfM let, purple, yellow, tan, and brown.

Very small flakes of mica are pyp '

co= son alon6 the bedding surfaces.

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A belt of shale occurs northwest of Pine Ridge which heretofore I

has not been assi5ned a definite strati 6raphic position, as it is faulted above and belov, has no obvious lithologic similarity to other k-F for=atiens in the area, and lacks identifiable fossils. The shale is j

dm b mtly =aroon, red, and tan, fairly silt-free clay, interbeided i.

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with s= aller a=ounts of brown, purple, and green, more silty. clay. The

=aroon and red shale beds may be a potential source of brick clay, being very similar to the shale of the Pennington For=ation of Mississippian f

age which is used in several places in southwestern East Tennessee for Nii brick and pottery. The surface underlain by the shale is characteris-3.fg m

.tically strewn with 2-to 6-inch-diameter cobbles of dense blue-white

((j to blue chalcedony which is probably derived from weathering of cal-ON careous beds interbedded with the shale. Many of these cobbles exhibit

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cryptozoan-like structures on the exterior.

Wad (a hydrous manganese Q

f[4.h oxide mineral) occurs locally as nodules in the shale, and a few. fine-m to medium-grained, =aroon and brown thin-bedded' sandstone beds are y

3 present.

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'M The shale is thought to be an cider part of the Rose not exposed in the belts southeast of Pine Ridge, perhaps corresponding to the h.

Apison Shale member of the Rome, which crops out in southwestern East g..

t Tennessee. For the' purpose of differentistion from the Rome underlying h.

Eav Ridge the shale unit is designated by the symbol drs on the accom-

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8 The typical sandstenes and siltstones of the Rome are character-iced by abundant pri=ary features, such as ripple r. arks, rill marks, svash marks, mud cracks, and, locally, raindrop i= prints.

Theloverco.2tactoftheRo=eisnotexposehintheOakRidgearea, as it is everywhere in fault relationship with younger rocks which 11e j

underneath it.

The upper contact with shale of the Conasauga Group is gradational and va's chosen arbitrarily, based primarily on topography and the coloration of the shales, the shales of the Conasauga being less brightly colored than those of the Rome Formation.

The Rome For=ation underlies ridges which are typically narrow, steep sided, and broken by many closely spaced vind and water gaps which give the ridges a "comby" appearance.

The residual soil of the Rome is generally less than 15 feet thick, and is co= posed of sandy, silty, light-colored clay containing scat-

- tered siltstone ara sandstone fragments.

No fossils were found in the Ro=e of the Oak Ridge area, but those found elsewhere in the formation shov'that its age is youngest Early Cambrian. The total thickness of the for=ation is not present in the Oak Ridge area, but probably 800 to 1000' feet of the upper part o'f the Rome is represented. The thickness of the older part of the Rome has not been determined.

Conasauga Grcup.-- The Conasauga Group und.arlies the valley north-vest of Copper Ridge (grid sections D-1 te D-19), sear Creek Valley l

(grid sections E-1 to E-19), the valley northwest'of Black Oak Ridge 1

(grid sections A-1 to A-19), and a small area southwest of McKinney Ridge (grid sections C-A and C-S).

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The Conasauga is prf arily calc'areous shale interlayered with t

limestone and siltstone.

The group has been divided into four units-E F.

in Melton Valley (Barnett,1954), but is undifferentiated on the accom-

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panying geologic map.

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l The shale of the Conasauga ranges from pure clay shale to silty

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i shale and is brown, tan, buff, olive green, green, and dull purple'.

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Dark-grif, dense to crystalline, nodular, thin-bedded, silty limestone w'.

t is interbedded with the shale and siltstone in the lower two-thirds of 4

the group.

Siltstone, which is brown, red brown, buff, and tan, is y

present throughout the lover four-fifths of the group and is abundant

[.k in the layers underlying a line of knob-like hills on the northwestern 5

g sides of the.vaneys underlain by the Conasauga.

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Alternating beds of shale and light-gray, dense to crystalline, i'

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regularly bedded limestone are present about 500 feet below the top Le of the group., These beds are overlain by about 300 feet of =assive,

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light-to medium-gray, dense to coarselherystalline or oolitic lime-ll,i M

stone. The upper limestone beds of,the Conasauga are used in nany e

places in Fast Tennessee as a source of quarry stone for road ~ aggregate;'

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3 most of this limestone is fairly pure, and the oolitic beds are-composed w

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of nearly pure calcium carbonate.

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The contact between the limestone of the Conasauga Group and the Ly v

dolomite of the Knox Group is gradational from dolomitic limestone to dolomite cont ining stringers of limestone.

g The Conasauga Group underlies valleys between ridges formed by the Ec=e For=ation and the Knox Group.

The surfaces of these valleys are f.h Si characteristically irregular with many gullies and small hills. The p

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=ost prominent topographic feature is the line of knobs on the north-vestern sides of the valleys.

Residut:1 derived frcm shale in the Conasauga is generally thin.

Weathering has penetrated to a depth of about 20 feet in the layerc where shale predominates, but the weathered pari; retains the appearance of the original rock, except that most of the limestone has been removed.

The residut:m derived from the massive li=estone is characteristically i

orange red and contains little or no chert.

The thickness of the Conasauga Group is difficult to measure due to a number of minor folds and faults, but is estimated to be 1500 feet or more. The age of the Conasauga is Middle and late Cambrian.

Knox Group.-- The Knox Group is one of the most videly dist_ributed lithologic units in East Tennessee, and in the Oak Ridge reservation it.

occupies more surface area than any other unit.

The Knox underlies Copper Ridge (grid sections H-1 to H-19), Ciestnut Ridge (grid sections E and F,1-19), 31acioak Ridge (grid sections A and 3,1-19), McKinney Ridge (grid sections C-5 and 6), and'two areas along the Whiteoak Moan-tain fault.

The Knox is'co= posed pri=arily of r ssive, siliceous dolo =ite.

The group can be divided into five for=ations on the basis of lithologic variation, but on.the acco=panying =ap the group is undivided.

The general variation in lithology is from massive, dark gray, crystalme, very cherty dolomite at the base to generally less =as-s'ively bedded, lighter-gray, dense to finely crystalline, less cherty dolomite at the top. Thin beds of light-gray, dense limestone are present in the upper part, and thin beds of relatively pure sandstone e

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o 11 occur about 1000 feet above the base of the youp.

Outcrops of'the do16=1te are not abundant due to the rapid.reathering and deep soil,'

cover; however, on the northwestern sides of ridges underlain by the group, erosion has removed the soil cover to an extent that outcrops I

are fairly co mon.

The amount and type of chert left by veathering varies'from for-

=ation to for=ation within the group; and, because outcrops cf the-dolomite are not abundant, residual chert is used as a basis for dif-

' ferentiating the group.

Due to the varying amounts of chert retained

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in the residuus, the rate of erosion varies from for=ation to forma-tion, producing a distinctive topography which is an aiu.n =apping.

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The upper contact of the Knox Group is disconfor=able; that is, it is a surface once exposed to erosion, then covered by sediments, with no significant variation between the dip and strike of the layers beneath the eiosional surface and those above.

In scme places, the relief on this surface is rather high, as indicated by the irregular contact line on the nnp where it ii vall defined for so::,e distance.

(Seemap,B-10.} The Knox Group-Chicka=auga Limestone contact is usu-ally distinctj owing to the sharp cont *rast between the dolo =ite and the overlying basal beds of the Chicka auga; also, springs are co=on along or near the contact, especially in East Fork Vallef.

The Knox veathers to form a deep residual =antle held in place by the abundant chert on the surface. The surface of the bedrock beneath the soil mantle is very irregular; outcrops generally, represent the I

tops of pinnacles of bedrock projecting'through the soil.

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The Kncx Group underlies broad ridges generally having fairly gentle slopes on the southeastern side -and steeper slopes on the northwestern r

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a saddle shape in profile viewed parallel to strike.

Th'e dolonite of the Knox is very soluble and caverns are co==en, some of them of large size. Sinkholes are a persistent topographic, feature of the group.

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Fossils are not coc: mon in the Knox,,but s=all coiled gastropods vere found in a limestone bed in the upper part of the group on the northern side of McKinney Ridge. The age of the Knox is late Cambrian and Early Ordovician. The total thickness is about 3000 feet.

ChicV*-muna Limestone and Reedsv111e Shale.-- The Chickamauga limestone underlies Bethel Valley (grid sections F-1 to F-19), East Fork Valley (grid sections Band C,1-19), and a narrow belt northwest of Pine Ridge (grid sections D-8 to D-10).

lithologically, the Chickamauga is extremely variable, although the entire sequence is calcareous.

In the*tvo major valleys underlain-by the for=ation, East Fork Valley, where a ec=plete section is present, and Bethel Valley, where the upper 500 feet or more have been faulted out, the stratigraphic succession of beds within the for=ation is dissimil ar.

In East Fork Valley, the lovermost beds of the Chicka=auga are co= posed of discontinuous thin layers of bentonitic material, gray clay t,

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l' shale with obscure bedding, thin bedded, maroon, calcareous siltstone The

,i up to 50 feet thick, and gray, calcareous, micaceous siltstone.

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lateral continuity of these basal beds is irregular, and, in places, l

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i this sequence is absent.

Iccally, the basal layers contain frag =ents I-of chert derived from the underlying Knox Group. A sequence of li=estone i

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approximately 1500 feet thick lies above these layers. The limestone E.%

tC is dominantly light to medium gray and blue gray, dense to finely crys--

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talline, shaly, and thin bedded, and contains variable amounts of chert.

~ 5 These layers generally contain fra5nentary, s=all fossil brachiopods, f.g bryczoans, corals, and crinoid ste=s.

The character of these beds

• i changes along strike and similar lithologies recur in various zones,

.=aking division into units difficult.

Near the top of this limestone

. g sequence are two bentonit.e beds which lie about 50 feet apart, strati-graphically.

Above the upper bentonite is a 40-foot sequence of yellov i

and =aroon, calcareous siltstone beds, at the top of which is an appar-ently small disconformity. Blue-gray limestone, which is coarsely crys-l bS3 tall h e, extremely fossiliferous, relatively pure, and more massively i;G

?ena tedded than the underlying limestones, lies above the disconformity.

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! ds Unlike the layers of shaly limestone belov, this lithology is relatively lg d.; <

' ho=ogeneous alorig atrike.

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The coarsely crystalline limestone grades upward into the Reeds-g l.-

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ville Shale, a calca eous, an to orange-brovn, fissile, thin-bedded,

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. <7 fossilifero,:s shale, which is the uppermost unit of the Chickamauga

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[N Li=estone. This unit is 200 to 250 feet thick.

.b Lithologic differences within the for=ation are more distinct and j [,',3 i,M the stratigraphic sequence is more easily defined in Bethel Valley than li;$k in other parts of the area. The residuni mantle is generally thinner

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and outcrops of the beds are more co= mon than in East Fork Valley. Also, g

3 the beds t.re persistent in character along strike and each unit has more Pi-yb diagnostic features. The Chickamausa in ' Bethel Valley can be divided

[y Of into at least eight units (Stockdale, 1951). Three of these units iu M

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consist of redbeds: one about 120 feet above the base, another near the middle of the for=ation, and another at or near the top. These redbeds apparently are not represented in East Fork Vaney, although the thin, discontinuous redbeds at the base of the fomation in.this belt may correspond to the lover redbeds of Bethel Valley. No benton-ites have been observed in Bethe'l Vaney; apparently the Copper Creek fault displaced beds somewhat below the.bentonites.

In other respects, the beds of gray, shaly limestone in Bethel Valley are similar to those of East Fork Valley in color, bedding characteristics, and ch'ert and fossil content.

In East Fork Valley the Chicka=ausa Limestone-Sequatchie Fomation contact is placed below the lowest occurrence of maroon, calcareous siltstone. The contact generally is covered by residuum and has to be approximated in most areas.

The soil produced by veathering of thg Chicka=auga typically con-sists of yellev, light red-orange, or red clay cor.taining variable amounts of chert.

Chert is abundant enough in the lower layers to cause development of a line of lov hins on the northwestern sides of l

the valleys. This is more pronounced in. Bethel Valley, where the' basal caterial is co= posed of alternating siltstone beds and beds of blocky chert.

The surfaces of the vaneys underlain by the femation,are irregu-lar, the more silty and cherty layers underlying low ridges and hilla.

l Sinkholes are present, but these are not as nunerous or as large as those.in the Knox Group.

Fossils are co==on throughout the for=ation, and ' include b' achiopods, r

1 bryozoans, gastropods, cephalopods, crinoid ste=s, corals, and trilobites.

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The age of the Chicka=auga Limestone is Middle and Upper Ordovician.

M The boundary between Middle and Upper Ordovician rocks in this area is drawn at the base of the Reedsville Shale. The thickness of the Chicka-

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f, mauga in East Fork Valley is about 2kOO feet and in Bethel Valley about g

1750 feet.

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S Secuatchie Formation.-- The Sequatchie Fomation crops _out-on the N{

e flanks of East Fork Ridge (grid sections G-7 to G-13) and Filot Knob P

(grid sections G-17 and 18) and in a s=all isolated area near Gum Hol-3m lov southeast of East Fork Ridge (grid section C-10).

I 5 t.

The Sequatchie is predominantly maroon calcareous siltstone and y.

=aroon, silty and shaly limestone mottled with green.

The fer=ation

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contains a minor quantity of gray shaly 1 *estone. The beds are uniform 5

a and generally from 2 to 6 inches thick, although there are more massive p.y beds. There is a striking similarity betireen the maroon siltstones of l

i'B this for=ation'and those of the Chichmuga in Bethel Valley.

j h I g The fomation is best exposed in grid section C-18 where the upper fl conteet with the Rockvood For=atio1 is represented ~oy a 1-to 2-foot-thick h

dark-gray shale overlain by a massive bed of sandstone of the Rockwood i

. Fomation. This is the only place where the shale was observed,' and

e nothing is known of its lateral continuity. The contact generally is covered by residuum and has to be approxi=ated on the basis of the highest outcrcps of maroon siltstone.

9

'r, The residuum derived from the Sequatchie is typically dark =aroon, Q

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. fairly thin, silty clay. The Sequatchie is not topographically dis-a tinctive in the Oak Ridge area, although'it does underlie s=all knobs

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. i at the southwestern end of Pilot Knob and the northeastern end of East

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16 Fork Ridge, and in the srall outcrop area near the southeastern end of Gum Hollow it also for=s a small knob.

Fossils are not abundant in the Sequatchie except in the thin beds of gray 11=estone, which contain large brachiopods, colonial corals, and bryozoans. The Sequatchie represents the Rich =ond, or latest Ordovician j

stage. Its thickness is about 360 feet.

Silurian System Rockwood For=ation.-- The Rockwood For=ation caps Pilot Knob and j

the exterior ridges of East Fork Ridge.

The lithology of the Rockwood is variable. Alternatingthin(1to 3 inches) beds of sil, stone and shale form the bulk of the fornation.

3eds of =assive, medium-grained, iron-stained, vell-cemented sandstone are present near the base. The upper half of the for=ation contains

' thin ferruginc,us layers which are of two ganeral types: oolitic, shaly and silty iron oxide containing many crinoid stem fossils, up to 10 inches thick; and condwratic, pyrit'ic, sandy layers up to 3 fesT, thick. Both have been derived by veathering of ferruginous limestone which does not occur in outcrop in an unicathered condition. The fer-ruginous layers are interbedded with shale and siltstone which are yel-lov to' tan and light brovn. Weathering of the Rockwood produces a shallow sandy and silty soil containing many scattered chips of shale and siltstone.

IArge boulders of sandstone are scattered along the ridge tiops, and the slopes are covered with sandstone talus in places.

The Rockwood For=ation-Chattanooga Shale contact is disconf'or=able.

At Pilot Knob the upper =ost layers of the Rockwood have been re=oved by faulting.

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The Rockwood underlies ridges somewhat si=ilar to those of the

+4 t 1 gl Rome For=ation in that they are narrow and steepsided, but vind and n.2.

1 vater gaps are not as closely spaced.

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The age of the Rockwood is Early Silurian.

Its thickness in the l 1::c e.,

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7 Cak Ridge area is approxi=ately 690 feet.

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r Devonian and Mississ.'ippian Systens t

l Chattanooga Shale and Maury Formation.-- The Chattanooga Shale

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crops out in the central part of East Fork Ridge.

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f This for=ation is co= posed of black, bitt=tinous, fissile, pyri-i tiferous shale which in places is sandy.

Above the Chattanooga hle

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lies a 2-foot-thick layer of blue-green phosphatic shale known as the t

Maury For=ation.

1 The upper contact of the Maury is gradational over a short dis-iF tance into the siliceous limestone of the Fort Payne Chert and is rarely exposed in the Oak Ridge area owing to soil cover. The Chattanooga and i

the Maury vsather to produce a thin, dark. silty residuum containing scattered flakes of black shale. Topopaphically, these fomations are not distinctive, as their total thickness does not exceed 25 feet.

The Chattanooga Shale is generally considered to be both Devonian and Mississippian in age in this region. The Maury For=ation.is Early.

Mississippian in age."

Fort Payne Chert.-- The Fort Payne Chert crops out in the south-i vestern part of East Fork Ridge. In most of its exte'nsive area of out-crop in the southeast, the fo=ation is an extremely siliceous limestone or dolo::;ite which canly appears in outcrop as bedded chert which is

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18 white, porous, fractured, and contains many casts.of crinoid ste=s..

In the Oak Ridge area, however, the Fort Payne Chert is cc= posed pri-

=arily of very dense chalcedonic chert which is blue gray, massive, and contains few fossils.

'Ihin, irregular beds of sand and silt, '

interbedded with white chert, are fairly co==en southwest of Gus Hol-low; these layers contain the only fossils observed in the femation in the Oak Ridge area. Geodes are co=mo$1 throughout the fe mation.

The Fort Payne underlies narrow, steepsided, knobby ridges much like those underlain by the Rome Fomation. The residuum derived from the Fort Payne is very sandy, silty, light-colored clay, containing abundant chips and blocks of chert.

The femation is Early Mississippian in age and is correlated with the Osage series.

Ordinarily the fo=ation is about 150 feet thick in this region, but its topographic position in East Fork Ridge has resulted in the re= oval of much of the upper beds, leaving a maxi-mus thickness of about 90 feet.

Structure t

l The vestern part of the Tennessee section of the Valley and Ridge province is structurally characterized by =ajor subparallel thrust faults that trend northeast and dip southeast.' Along most of these faults, the Rome For=ation has been thrust over younger formations.

Defomation of the strata of the area resulted from co=pressional

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forces origins. ting.to the southeast of the Valley and Ridge province.

The strata reacted to the pressure bf developing faults and folds.

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19 ip ps EW Principal structural features of the Oak Ridge area are two =ajor W

thrust faults, a doubly plunging syncline, generally southeast-dipping strata, and *everal subsidiary faults.

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Copper Creek Fault D

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The trace of the Copper Creek fault appears along the nc7thwestern 4

flank of Hav Ridge. The fault extends northeastvard across the entire vidth of the State and brings the Ro=e For=ation to the surface through-M out its length. In the Oak Ridge area, the Rome is thrust over the middle units of the Chick m uga.

The fault'has an average strike of N. 55 E. in the Oak Ridge area.

The dip of the fault zone is not =easurable, but it is thought to be at Ti3 an angle of 45 or more to the southeast,.a considerably higher angle than that of the beds some distance stratigraphically above the fault.

i Near the fault, the beds of the Ro=e are defor=ed by s=all folds and 5*

faults and generally dip at a high angle to the sor.theaat. Above tne e

deformed zone, the re=aining beds of the fault block dip at an average I

The stratigraphic displacement caused by the Copper Q

angle of 20 SE K

Creek fault is approxi=ately 7200 feet.

40.

m.;

IM Ws Whiteoak Mountain Fault 4

I In the Oak Ridge area the Whiteoak Mountain fault is a co=plexly branching thrust fault along which lover shales of the Ro=e For=ation have been thrust over Middle Ca= brian and younger rocks,. The Whiteoak Mountain fault originates about 4 miles northeast of the Oak Ridge

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l 20 reservation near Clinton by the merging of the Hunter Valley and Wallen Valley faults. The fault extends southwestvard across che State, and throughout its length the Rone For=ation has been thrust over younger for=ations.

The shale beds of the lover Ro=e southeast of the fault are ver-l tical or dip steeply to the southeast and northwest. The excessive thickness of this for=ation in parts of the area suggests that a con-siderable a=ount of faulting has occurred within the shale, but suffi-cient work has not been done as yet to establish'a stratigraphic sequence in the shale. Thus, no faults have been indicated in this unit on the acco=panying geologic =ap.

Beds of typical Rone lithology lie above the shale. These beds have been thrust over the underlying shale and deformed by small folds and faults. Above the defor=ed zone the re=aining beds of the fault block dip at an ' average angle of 35 SE.

The structure of the area fro = Pine Ridge to the southeast is si=ple in ec=parison to the cc=plexity of the belt between Pine Ridge and East Fork Valley, where the strata have been disrupted by several faults of varyin's displacement, and folded into.a syncline.

East Fork Ridge-Pilot Knob syncline.-- A persistent feature of the khiteoak Mountain fault is the develep=ent' of synclinsi structures northwest of the fault., There.are several such structures southwest of the Oak Ridge strea and one within the area, vMeh vill be referred to as the East Fork Ridge-Pilot Knob syneline. Owing to the structure, rocks as young in age as Mississippian have been preserved.

A branch of the khitecak Mountain fault, along which rocks of the.

middle part of the Chicha=auga have been thrust up, truncates the I

2%

"7 7 -

e 21 southeastern limb of the syncline in the vicinity of Pilot Knob (Sec. A-A).

The brand f sult c=tends southwestward in a direction more or less paral-1el to the syncline to merge with the Whiteoak Mountain fault pear the northeastern end of East Fork Ridge.

In this vicinity, the stra,ta of the southeastern limb of the syncline have been complexly faulted and a part of the limb has been faulted out.

Another fault is exposed in the Mill ~

3 ranch gap (grid section C-12), where the Rockvood Fomation is thrust over the Chattanooga Shale.

The East Fork Ridge-Pilot Knob syncline is doubly plunging, fomin6 a structural feature known as a saddle, which is defined as an upfold along the axis of is syneline. The syneline plunges to the northeast and south -

vest, frem an area in the vicinity of grid section C-15 The upfolding along the axis of the syncline indirectly resulted in the 3-mile-long lowland which separates East Fork Ridge and Pilot Knob.

When the area' vas undergoing defor=ation, the rocks underlying the present lowland were raised to higher elevations than they were in other parts of i

the syneline.

During subsequent peneplanation the upper resistant rocks-in this area vere exposed to erosion and removed.

Later uplift was fol-loved by erosion which removed the relatively nonresistant Sequatchie.

Fomation and the uppe=est strata of the Chicka=auga Limestone down to the.present altitude.

Slices of Dolcmite of the Knox Groun Along the Whitecak Mountain

[

Fault.-- Another characteristic feature of the Whitecak Mountain fault is the occurrence of slices of dolomite of the Knox Group along the fault.

Two such slices are in the Oak Ridge area in grid sections C-14 to C-19 Structure at McKinney Ridge.-- Southwest of East Fork Ridge and within the East Fork Ridge-Pilot Knob syneline are exposures of the Knox Group 9

e 9

22 and the Conasauga Group. The area underlain by these groups is bounded on the' southeast by the Witeoak Mountain fault and on the southwest a$1d ncrthwest by a branch fault, but on the ncrtheastern side is in s,trati-graphic contact with the Chicka=auga Limestone.

Within this area the Knox underlies McKinney Ridge (grid sections C-5 and C-6). The ec=plexity of the structure of McKinney Ridge is indicated by exposures in the quarry '

on the southwestern end of the ridge, where there are a fault of unknown displacement and several folds.

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23 Selected Bibliography f

I Barnett, John,1954, Geologic investigation, vaste disposal area, Oak 5

Rid e National laboratory, Oak Rid e, Tennessee:

U. S. Army Corps

(

6 S

of Engineers.

i Bassler, R.

S., 1912, The Waverlyan period of Tennessee:

U. S. Nat. Mus.-

[

Proc., 1911, v. 41, no. 1851, p. 209-224.

Hayes, C. W.,1891, The overthrust faults of the southern Appalachians:-

Geol. Soc. Am. Bull., v. 2, p.'1kl-154.

[

Keith, Arthur, 1896, U. S. Geol. Survey Geol. Atlas, Ericev111e folio no. 33 Rodgers, John,1953, Geologic =ap of East Tennessee with explanatory I

text: Tennessee Div. Geol. Bull. 58, part 2.

f Safford, J. M.,1869, GeoloEy of Tennessee: Nashville.

(

Safford, J. P., and K111ebrev, J. B.,1900, The elements of the geology l

of Tennessee: Nashville. Revision of the edition of 1876.

[

C Stockdale, P.

B., de Buchananne, G. D., and Klepser, H.. J.,(1951, Geo-l

[

i logic conditions at the Oak Rid e National Laboratory X-10) area i

S relevant to the disposal of radioactive vaste: Technical Informa-tion Service, Oak Rid e, Tennesset.

, E E

Ulrich, E. O.,1914, The ordovician-Silurian boundary: 12th Internat.

t Cong.. Canada, 1913 Comte Rendu.

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