Chapter 4 Geologic overview Andrea M. Loveland

4-39 he Northeast River Basins (NERB) study area covers tuations until the final retreat of the seaway in the Late Tapproximately 14.86 million acres in northeast- Cretaceous. ern Wyoming, southeastern Montana, western South Dakota, and western Nebraska. The geologic setting of The Laramide orogeny commenced in the Late the NERB includes Precambrian-cored uplifts formed Cretaceous and continued through the Early Eocene. during the Laramide orogeny and adjacent basins filled Crustal shortening was accommodated by displacement with Phanerozoic clastic and carbonate rocks. The fol- of Precambrian crystalline basement rocks and the over- lowing information regarding the NERB study area is lying sedimentary cover rocks (Brown, 1993). Basement- provided in this chapter: cored Laramide structures border the NERB on three sides: 1) the Bighorn Mountains to the west, 2) the • An overview of the geologic history Black Hills to the east, and 3) the Rattlesnake Hills and Hartville Uplift to the south (fig. 4-1). • A summary of the structural geology • An outline of significant mineral and energy The geologic setting of the NERB study area is illustrated resources on the bedrock geologic map in plate 1. This map also displays surface water, highways, political boundaries, • Geologic cross sections and state and county data. Inset maps on plate 1 show the distribution of lineaments and a structure-contour map of the top of the Precambrian basement. Nine cross sec- 4.1 GENERAL GEOLOGIC HISTORY tions show subsurface structure in the NERB (figs. 4-2 through 4-11). Descriptions of the Precambrian- through During the Paleozoic Era, the area that is now the Tertiary-aged stratigraphic units exposed in the study NERB was located on the western margin of the North area are included in appendix A, and are not addressed American craton in a shelfal environment. Although specifically in this chapter. there is some evidence of minor movement along zones of weakness within the cratonic basement (Slack, 1981; 4.2 STRUCTURAL GEOLOGY Maughan and Perry, 1986; Dolton and others, 1990), the region was tectonically stable and only underwent minor The NERB study area includes the Powder River Basin, deformation in the form of gentle upwarping and subtle the easternmost edge of the Wind River Basin, and depressions. the northernmost tip of the Denver-Julesburg Basin. Significant uplift structures that bound these basins are Sediments deposited during the Paleozoic Era indicate also a part of the study area. These include the Bighorn episodic sea level shifts along the edge of the craton. Mountains, Black Hills Uplift, Rattlesnake Hills, Casper Consequently, Paleozoic rocks in the NERB range from Arch, and the Hartville Uplift (fig. 4-1). These and other terrestrial and near-shore marine sandstones to marine significant structural features are discussed below. shales and carbonates. Episodic late Paleozoic uplift events associated with the formation of the Ancestral 4.2.1 Powder River Basin (PRB) Rocky Mountains to the south further influenced deposi- tion of sediments across Wyoming (Maughan, 1993). The Powder River Basin is an elongate, north-north- west-trending sedimentary and structural basin in north- In the early Mesozoic Era, sea level fluctuations contin- eastern Wyoming and southeastern Montana. The basin ued to be a major control on sediment deposition. During is bounded by Laramide Precambrian-cored uplifts on most of the Triassic Period, the NERB was a coastal plain three sides: 1) the Bighorn Mountains to the west, 2) the environment where deposition of red beds occurred and Black Hills Uplift to the east, and 3) the Casper Arch and are now observed, particularly in the Chugwater Group Hartville Uplift to the south (fig. 4-1). Reverse and thrust (Spearfish Formation Equivalent; Cavaroc and Flores, faults are present along the flanks of some of these uplifts, 1991). occasionally with a strike-slip offset component (Clarey, 2009). The geometry of the basin is asymmetric, with a steeply dipping to overturned western limb and a gently As the Sevier orogeny began uplifting sedimentary cover dipping eastern limb. The synclinal axis is positioned rocks to form the mountain ranges of present-day western adjacent to the Bighorn Mountains near the western Wyoming (Royse, 1993), the NERB area was submerged margin of the basin (Ver Ploeg and others, 2008). The in the Cretaceous Interior Seaway. A thick succession of maximum thickness of Phanerozoic rocks in the basin is shales with interbedded sandstone, siltstone, and lime- 18,000 ft (Beikman, 1962). stone were deposited, indicating numerous sea level fluc-

4-40 4.2.2 Wind River Basin (WRB) 4.2.6 Black Hills The Wind River Basin is a structural and sedimentary The Black Hills of Wyoming are the northwestern con- basin in central Wyoming. A portion of the eastern end tinuation of the Black Hills in South Dakota (fig. 4-1). It of the northwest–southeast-trending basin is included formed in the late stages of the Laramide orogeny by the in the NERB study area. Within the NERB, the WRB intrusion of an alkaline igneous complex. The exposed is bounded to the southwest by the Rattlesnake Hills basement consists of Precambrian igneous and metamor- and to the northeast by the Casper Arch and Bighorn phic rocks, and is overlain by Paleozoic and Mesozoic Mountains (fig. 4-1). The basin formed during Laramide clastic and carbonate rocks. deformation as the trough subsided and mountains adjacent to the basin were uplifted. As the uplift struc- 4.2.7 Casper Arch tures began to erode, sediments were shed into the basin, resulting in the deposition of an 18,000-ft-thick sequence The Casper Arch is bounded to the southwest by a of Phanerozoic sediments, including fluvial and lacus- west-southwest vergent, large-displacement foreland trine sediments (Keefer, 1970). thrust fault that in the subsurface offsets Precambrian rocks above younger sedimentary rocks in the adja- cent Wind River Basin (Skeen and Ray, 1983; fig. 4-1). 4.2.3 Denver-Julesburg Basin (DJB) Although it is an uplifted area, it is not uplifted signifi- The northernmost edge of the Denver-Julesburg Basin cantly enough to form a mountain range with an exposed is included in the southeastern corner of the NERB core of Precambrian rock. Upper Cretaceous marine study area (fig. 4-1). The DJB is a north-south-trending shales are exposed at the center of the arch, with rocks as asymmetrical Laramide-aged basin that covers more young as Paleocene exposed on its flanks. than 70,000 mi2 (180,000 km2) in parts of Colorado, Wyoming, Kansas, and Nebraska. In the NERB, the 4.2.8 Rattlesnake Hills DJB is bounded to the north by the Hartville Uplift. Most of the subterranean strata preserved in the DJB was The Rattlesnake Hills are a Laramide uplift structure deposited during the Laramide orogeny and is Cretaceous located along the southern margin of the Wind River aged (Drake and others, 2014), however, most surface Basin (fig. 4-1). They are a northwest-trending anticlinal exposures in the basin are Tertiary, which in the NERB structure in which the crystalline-cored fold is overlain consists of the Arikaree Formation. by Phanerozoic rocks. Alkaline intrusive rocks are also exposed in the southern Rattlesnake Hills, and were emplaced after Laramide folding (Hoch and Frost, 1993). 4.2.4 Bighorn Mountains These exposures are not a part of the NERB study area, The Bighorn Mountains formed during the Laramide but are similar in age and structural setting, and share orogeny in the Rocky Mountain foreland (fig. 4-1). They mineralogical and geochemical signatures with the alka- are cored by Precambrian plutonic and metamorphic line igneous complex exposed in the Black Hills region of rocks that extend in an arcuate fashion from southcen- the NERB (Hoch and Frost, 1993). tral Montana to the northern margin of the Wind River Basin in central Wyoming. The Bighorn Mountains 4.2.9 Pine Ridge were thrust to the east and are flanked in the NERB study area by steeply dipping to overturned Paleozoic and Pine Ridge is a northwest–southeast-trending topo- Mesozoic sedimentary rocks on the east. graphic high on the eastern margin of the Casper Arch (fig. 4-1). It serves as a hydrologic divide between the Powder River and Cheyenne River hydrologic basins. 4.2.5 Hartville Uplift This area is part of the Powder River Basin uranium The Hartville Uplift is a north–northeast-trending district. Laramide structural uplift along the southern margin of the NERB (fig. 4-1). It is superimposed upon and 4.2.10 Pumpkin Buttes predates the Hartville Arch, which is a northeast-south- west-trending structure between the Powder River and Pumpkin Buttes are a group of large, orange-colored Denver-Julesburg basins. Iron and copper are among the Wasatch sandstone mesas in the central Powder River minerals mined in the Hartville mining district. Basin that are overlain unconformably by a 30- to 50- ft-thick cap of White River Formation (Sharp and others, 1964; fig. 4-1). A significant uranium deposit was discov- ered here in 1951.

4-41 4.2.11 Red Hills Basin is dominated by clinker-controlled topography, The Red Hills are clinker deposits that formed due to which forms resistant reddish layers that cap hills and naturally burning coal beds (fig. 4-1). They have burned buttes. In the Red Hills, exposures of the Tongue River since at least the early Pliocene (Heffern and others, Member of the Fort Union Formation are capped by 2007). About 1,600 mi2 (4,100 km2) of the Powder River resistant layers of clinker (Heffern and others, 2007).

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C A R B O N W Bairoil ¤£85 25 ¨¦§ Fort Laramie N Explanation Index Map N Base Data Base Data (continued)

_ City or town State boundary M O N T A N A 0 50 100 200 State or U.S. highway Basin extent WSGS 2018 Projection: NAD 1983 Interstate highway Geologic Features UTM Zone 13N S O U T H River or creek Data Source: D A K O T A Precambrian Lake or reservoir Wyoming State Geological Structural Basins Survey, 2008 Township boundary W Y O M I N G County boundary N E B R A S K A

Figure 4-1. Geologic features in the NERB, Wyoming.

4-42 4.3 MINERAL AND ENERGY RESOURCES eastern Wyoming from the early 1900s until now. The WSGS digitized the original cross sections and added The NERB is rich with various mineral and energy colors to the geologic units generally consistent with the resources, including aggregate (clinker, limestone, and Geologic Map of Wyoming (Love and Christiansen, gravel), oil and gas (including coalbed methane), coal, 1985). Geographic extents within the NERB for individ- gypsum, bentonite, and uranium (Harris and others, ual cross sections are noted below: 1992). Iron and copper are mined in the Hartville mining district. Chapter 5 of this study identifies potential con- Sections A-A’, B-B’, and C-C’ (figs. 4-3 through 4-5) are tamination sources related to the development of mineral from Lynds (2013). Section A-A’ extends through the and energy resources. Tongue River and Powder River drainages. Section B-B’ passes from the eastern Powder River drainage through The most significant resources in the NERB are the the Little Powder River and Belle Fourche drainages. near-surface coals mined in the Powder River Basin, Section C-C’ goes through the central part of the Powder which account for nearly half of all coal produced in the River drainage. United States. Oil and gas, including coalbed natural gas, and uranium are also key resources in the NERB. Sections D-D’, E-E’, and F-F’ (figs. 4-6 through 4-8) are by Darton (1906). Section D-D’ goes from the crest of The following is a partial list of references that provide the Bighorn Mountains through the Little Bighorn River detailed information about the major mineral and energy drainage into the Tongue River drainage. Sections E-E’ resources in the NERB: and F-F’ extend from the crest of the Bighorn Mountains into the Powder River drainage. Stratigraphy in theses Powder River Basin sections does not match Love and others (1993). The • Summary of mineral and energy resources in the Parkman, Piney, DeSmet and Kinsbury (sic) combined Powder River Basin (Harris and others, 1992) unit (Kpd) occupy an interval currently comprised of the Wasatch, Fort Union and Lance formations, and Foxhills • Petroleum system assessment for the Powder River Sandstone (Love and others, 1993). The “Colorado Basin (USGS, 2004; Anna, 2010) Shales” unit (Kc) refers to a stratigraphic interval that stretches from the Fall River Formation through the • Uranium deposits in the Pumpkin Buttes area Niobrara Formation of Love and others (1993). The (Sharp and others, 1964) “Embar” Formation is an abandoned unit name, widely • Coal geology and assessment of coal resources and used in past oil exploration, that has been replaced by the reserves in the Powder River Basin (Luppens and Park City, Dinwoody, and parts of the Chugwater forma- others, 2015) tions, and their stratigraphic equivalents (USGS Geolex, 2018). Wind River Basin • Petroleum system assessment for the Wind River Section G-G’ (fig. 4-9), obtained from Keefer (1970), Basin (USGS, 2007) passes through a small part of the Wind River Structural Basin located in the Powder River drainage. • Mineral resources (Hausel and Holden, 1978) Denver-Julesburg Basin Section H-H’ (fig. 4-10), from DeWitt and others (1989), extends from the crest of the Black Hills through the • Oil and gas in Denver-Julesburg Basin (USGS, Belle Fourche drainage into the Little Missouri River 2007) drainage. Black Hills • Mineral resource potential (DeWitt and others, Section I-I’ (fig. 4-11), from McLaughlin and others 1986) (2011), passes through southern parts of the Niobrara River drainage. 4.4 GEOLOGIC CROSS SECTIONS The maps and studies that contain the original cross sec- Plate 1 and fig. 4-2 show the locations of the geologic tions are available on the USGS National Geologic Map cross sections (figs. 4-3 through 4-11) provided in fold- Database (https://ngmdb.usgs.gov/ngm-bin/ngm_comp- out figures at the end of this chapter. The cross sections, search.pl) and the USGS Publications Warehouse website adapted from USGS and WSGS studies, also illustrate (https://pubs.er.usgs.gov/). the progression of stratigraphic nomenclature in north-

4-43 R60E T16N T5S R35E R40E R45E R50E R55E R1E R30E R5E Lodge Grass ¬«59 ¬«323 R O S E B U D T15N r Fort Smith eek r r ¤£212 ve Cr ve ive P O W D E R R I V E R Ri Ri C A R T E R R r

ive r B U T T E Grass B I G H O R N Tongue River R Alzada T9S orn Reservoir Rive R30E ¨¦§90 D M O N T A N A Bigh e Owl Lodge gu ¤£85 T58N uri Belle

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e i r i a r Creek P ¤£14 Arvada D Story C Shell £14 H C R O O ¤ Creek M Goose

y ¨¦§90 le ¨¦§90 N e Spearfish Greybull ¤£14 Sundance E T5N Clear Creek Litt O A Pin D H C R ¤£16 Cree H Y Basin B I G H O R N T Lead

E W Gillette Pine Haven 116 Buffalo k ¬« £85 T50N ¤ A

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Lance ¤£20 outh S Lightning N I O B R A R A T35N F R E M O N T G ¤£26 T35N

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¬« North A

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C A R B O N W Bairoil Fort Laramie 25 ¨¦§ N Explanation Index Map N Base Data Base Data (continued) Surface Geology _ Quaternary City or town Township boundary M O N T A N A 0 50 100 200 Miles State or U.S. highway County boundary Tertiary Interstate highway Mesozoic State boundary S O U T H River or creek Paleozoic Cross section line D A K O T A Lake or reservoir Precambrian

W Y O M I N G WSGS 2018 Data Source: N E B R A S K A Projection: NAD 1983 Wyoming State UTM Zone 13N Geological Survey

Figure 4-2. Locations of cross sections A-A’ through I-I’.

4-44 Cross Section A-A’

SW NE A A

FEET FEET 10,000 10,000 $ $ 5,000 $ Tmc 5,000

$ Tfu Sea level Ksc Km Sea level p_u 9 9 9 9 9 9 9 9 9999 9 9 9 $ 9 9 9 99 9 Km Ksc 9 9 9 9 9 9 -5,000 Ku ^c ^Pg Pp 9 9 9 9 -5,000 9 Ju 9 9 9 9 9 9 9 -10,000 Mu Ob _u -10,000 p_u -15,000 & -15,000 Modified from Stone (1987)

Index Map and Line of Cross Section Explanation Symbols Explanation Formation contact – Dashed where inferred Base Data & Fault – Dashed where inferred; arrows indicate relative movement

r

e

_ City or town v r i Drill hole – Well logs used to construct cross section e R o State or U.S. highway iv R r e Interstate highway iv

¨¦§90 E' R i

River or creek r Geologic Units

u o s

Ranchester s Lake or reservoir S H E R I D A N A i CENOZOIC PALEOZOIC Dayton M Tertiary Permian Township boundary e Sheridan Moncrief and Kingsbury Conglomerate gu ek Tmc Pp Phosphoria Formation on re Members of Wasatch Formation

County boundary T C e

Arvada l Triassic and Permian Big Horn ¤£16 t Tfu Fort Union Formation State boundary ar t ¤£14 le i C Clearmont L ^Pg Goose Egg Formation Cross section line ¤£14 MESOZOIC Story r Cretaceous Mississippian

Surface Geology de C A M P B E L L Km Meeteetse Formation Mu Mississippian rocks, undifferentiated

A ow

Quaternary Buffalo P Gillette Ordovician Tertiary Ksc Skull Creek Shale Ob ¨¦§90 Bighorn Dolomite Mesozoic Ku Cretaceous rocks, undifferentiated Paleozoic Cambrian §25 ¤£16 ¨¦ Jurassic Precambrian _u Cambrian rocks, undifferentiated ¬«59 Ju Ten Sleep ¬«50 Jurassic rocks, undifferentiated N O H N S O N PRECAMBRIAN 0 10 20 Miles Triassic p_u ^c Chugwater Formation Precambrian rocks, undifferentiated

Adapted from:

Lynds, R.M., 2013, Geologic storage assessment of carbon dioxide (CO2) in the Laramide basins of Wyoming: Wyoming State Geological Survey Technical Memorandum 3, Figure 4-3. Geologic cross section A-A’. 200 p., 20 pls.

4-45 Cross Section B-B’ W E B B FEET FEET 10,000 10,000

5,000 5,000 Tfu

Km Ksc Sea level Sea level Ku Ju ^c ^Pg

-5,000 p_u -5,000 Pp Mu _u Ob Tqm -10,000 -10,000 Modified from Stone (1987) p_u

Modified from Stone (1987)

Index Map and Line of Cross Section Explanation Symbols Explanation Formation contact – Dashed where inferred Base Data & Fault – Dashed where inferred; arrows indicate relative movement _ City or town Drill hole – Well logs used to construct cross section o

r

State or U.S. highway e r

v e Interstate highway i iv R R ¤£212 River or creek Geologic Units

r

e CENOZOIC PALEOZOIC

Lake or reservoir d i ur Tertiary Permian w so Township boundary o is P M e B' Tqm Quartz monzanite intrusion Pp Phosphoria Formation B ¬«112 h County boundary c r

e e R ¤£212 Triassic and Permian l l u i Tfu Fort Union Formation t v t

t o e State boundary t r i i F ^Pg Goose Egg Formation

L Cross section line L Hulett ¬«24 MESOZOIC e Arvada l ¬«111 Cretaceous Mississippian ¤£14 l Surface Geology ¬«59 e C R O O ¨¦§90 ¤£16 B Km Meeteetse Formation Mu Mississippian rocks, undifferentiated Quaternary ¤£14 Sundance Ksc Skull Creek Shale Ordovician Tertiary C A M P B E L L Ob Bighorn Dolomite Mesozoic Gillette Pine Haven Ku ¬«585 Cretaceous rocks, undifferentiated Cambrian Paleozoic ¨¦§90 Moorcroft Jurassic ¤£16 ¬«116 Precambrian ¤£85 _u Cambrian rocks, undifferentiated Upton Ju Jurassic rocks, undifferentiated ¬«59 N ¬«50 PRECAMBRIAN 0 10 20 Miles W E S T O N Triassic p_u Precambrian rocks, undifferentiated ^c Chugwater Formation

Adapted from:

Lynds, R.M., 2013, Geologic storage assessment of carbon dioxide (CO2) in the Laramide basins of Wyoming: Wyoming State Geological Survey Technical Memorandum 3, Figure 4-4. Geologic cross section B-B’. 200 p., 20 pls.

4-46 Cross Section C-C’ SW NE

C C

FEET FEET 10,000 10,000

5,000 5,000 Tw

Sea level Pp Tfu Sea level Kl Kml

-5,000 Kmv Kmr Kmd Jm -5,000 ^c -10,000 -10,000

Pp Mm _u -15,000 p_u DOb Ob -15,000 Modified from Wendell and others (1976)

Index Map and Line of Cross Section Explanation Symbols S H E R I D A N Clearmont Arvada £ Formation contact – Dashed where inferred Explanation Story ¤14 Creek ey r n e Fault – Dashed where inferred; arrows indicate relative movement Base Data i ¤£16 & P v _ ek i City or town ¨¦§90 k re R e C Drill hole – Well logs used to construct cross section e C' o State or U.S. highway r Buffalo C Interstate highway Clear River or creek Geologic Units

§90 CENOZOIC PALEOZOIC Lake or reservoir r ¨¦ an e Tertiary Permian

Crazy d Township boundary om

¤£16 W w Tw Wasatch Formation Pp Phosphoria Formation o

County boundary P ¬«196 Mississippian Ten Sleep O H N S O N Tfu Fort Union Formation State boundary N or Mm Madison Limestone th Cross section line F MESOZOIC §25 ¬«50 or ¨¦ Cretaceous k Devonian and Ordovician Surface Geology Devonian rocks and Bighorn Dolomite, Kl Lance Formation DOb Quaternary undifferentiated Ordovician Tertiary Kml Lewis Shale Kaycee ¬«192 Ob Mesozoic Bighorn Dolomite Kmv Mesaverde Formation S Paleozoic k k Cambrian For al e or l t idd C 387 Kmd Muddy Sandstone Precambrian C M F ¬« _u Cambrian rocks, undifferentiated h r t e e k N ou Kmr Mowry Shale 0 5 10 Miles S PRECAMBRIAN Edgerton Jurassic p_u N A T R O N A Midwest Precambrian rocks, undifferentiated Jm Morrison Formation Triassic ^c Chugwater Formation

Adapted from:

Lynds, R.M., 2013, Geologic storage assessment of carbon dioxide (CO2) in the Laramide basins of Wyoming: Wyoming State Geological Survey Technical Memorandum 3, Figure 4-5. Geologic cross section C-C’. 200 p., 20 pls.

4-47 Cross Section D-D’

SW NE

D D

FEET FEET 20,0000 20,0000 Basin Basin 15,000 15,000 Bighorn River Northeast River

_ River _ Bald Mtn _ O Cm

10,000 Little Bighorn Ct O Ct _ O 10,000 ^ Cm Ct Cm Ct Kc Kcv Kcv 5,000 gr 5,000 ^ Kpd Cm Kc Kp 0 0 SCALES Horizontal Vertical 0 1 2 3 4 5 miles 0 5,000 10,000 20,000 feet

Horizontal scale 2/3 vertical scale Base of sections is at sea level

Index Map and Line of Cross Section Explanation Symbols k e Contact Explanation e r r C e Base Data iv R Geologic Units _ City or town ss ra State or U.S. highway G rn o e h ¨¦§90 D' CENOZOIC–MESOZOIC PALEOZOIC Interstate highway dg ig Lo B Tertiary–Cretaceous Permian–Cambrian River or creek Kpd Parkman, Piney, and De Smet Ct Tensleep, Embar, and Lake or reservoir formations and Kinsbury Conglomerate Amsden formations e MESOZOIC Cm Madison Limestone Township boundary tl it Ranchester Cretaceous L County boundary O Bighorn Dolomite er Kp Pierre Shale State boundary Riv Dayton _ Deadwood Formation Kc Colorado shales Cross section line ¤£14A e Cretaceous–Jurassic PRECAMBRIAN Surface Geology gu ¤£14 on Cloverly-Sundance formations gr Granite T ek Kcv Quaternary re C Tertiary D S H E R I D A N Triassic ¤£14 ^ Chugwater red beds Mesozoic se oo Paleozoic G Precambrian B I G H O R N

N

Cr g l e i 0 5 10 Miles el ek Sh B

Adapted from:

Darton, N.H., 1906, Geology of the Bighorn Mountains: U.S. Geological Survey Professional Figure 4-6. Geologic cross section D-D’. Stratigraphy does not match Love and others (1993) Paper 51, 129 p., 5 maps, scale 1:125,000.

4-48 Cross Section E-E’

SW NE

E E FEET FEET 20,0000 20,0000 Basin Basin Bighorn River 15,000 Northeast River 15,000

Cm O _ 10,000 Cm O 10,000 Ct _ O Cm ^ ^ Conglomerate 5,000 gr 5,000 gr Kpd Cm O _ Kp Kpd 0 0 SCALES Horizontal Vertical 0 1 2 3 4 5 miles 0 5,000 10,000 20,000 feet

Horizontal scale 2/3 vertical scale Base of sections is at sea level

Index Map and Line of Cross Section Explanation Symbols ¤£87 ¤£14 Contact Explanation ¤£14E Story Fault-dashed where approximately located S Base Data he ll k e _ City or town Cr e Geologic Units ee r k C State or U.S. highway ¨¦§90 y Interstate highway e CENOZOIC–MESOZOIC PALEOZOIC n i Tertiary–Cretaceous Permian–Cambrian River or creek P ¤£16 Lake or reservoir B I G H O R N Kpd Parkman, Piney, and De Smet Ct Tensleep, Embar, and E formations and Kinsbury Conglomerate Amsden formations Township boundary ¨¦§90 Buffalo MESOZOIC Cm Madison Limestone County boundary Cretaceous O Bighorn Dolomite State boundary Kp Pierre Shale ¤£16 _ Deadwood Formation Cross section line E Triassic Surface Geology ^ Chugwater red beds PRECAMBRIAN N o gr Granite Quaternary wo ¨¦§25 od W A S H A I E Tertiary O H N S O N ¬«196 Mesozoic £ Ten Sleep Paleozoic ¤16

Precambrian R i v N e r 0 5 10 Miles

Adapted from:

Darton, N.H., 1906, Geology of the Bighorn Mountains: U.S. Geological Survey Professional Figure 4-7. Geologic cross section E-E’. Paper 51, 129 p., 5 maps, scale 1:125,000.

4-49 Cross Section F-F’

NW SE

F F

FEET FEET 20,0000 20,0000

15,000 Basin Basin 15,000 Bighorn River Northeast River Cm Cm 10,000 Ct _ Cm 10,000

Kcv Nowood River O Ct Ct _ Kp Kc ^ _ ^ ^ Kcv Kc Kp 5,000 Kc gr 5,000 gr gr gr gr 0 0

SCALES Horizontal Vertical 0 1 2 3 4 5 miles 0 5,000 10,000 20,000 feet

Horizontal scale 2/3 vertical scale Base of sections is at sea level

Index Map and Line of Cross Section Explanation Symbols Contact Explanation N ¬«196 Fault Ten Sleep o ¤£16 rt Base Data h ¨¦§25 F _ City or town o rk Geologic Units P State or U.S. highway ¬«434 o w Interstate highway d e MESOZOIC PALEOZOIC W A S H A I E r River or creek R Cretaceous iv Permian–Cambrian er Tensleep, Embar, and Lake or reservoir 191 Kp Pierre Shale Ct r ¬« Amsden formations

e O H N S O N v

Township boundary i Kaycee Kc Colorado shales Cm Madison Limestone R ¬«192 County boundary F Cretaceous–Jurassic ¬«190 r O Bighorn Dolomite State boundary r ive de R r Kcv Cloverly-Sundance formations w e o v _ Deadwood Formation Cross section line od P i o le Triassic H O T w d rk R No d Fo Surface Geology S P R I N G S i F' PRECAMBRIAN M ^ Chugwater red beds

Quaternary r gr Granite

e

Tertiary d

w Mesozoic o

P Paleozoic F R E M O N T N A T R O N A Precambrian k or N F 0 5 10 Miles th u So

Adapted from:

Darton, N.H., 1906, Geology of the Bighorn Mountains: U.S. Geological Survey Professional Figure 4-8. Geologic cross section F-F’. Paper 51, 129 p., 5 maps, scale 1:125,000.

4-50 SW Cross Section G-G’ NE G G Basin Basin FEET FEET Bighorn River 15,000 Northeast River 15,000 RATTLESNAKE HILLS ANTICLINE 10,000 10,000 Teu Mzr Tle

Pzr Pzr 5,0000 Tle 5,0000 p_r Kmc Kmc 0 TKfl 0 Mzr

Mzr Pzr -5,0000 Kmc -5,0000

-10,000 -10,000 Mzr p_r Pzr -15,000 -15,000 p_r SOUTH OWL CREEK MOUNTIANS fAULT -20,000 -20,000

-25,000 -25,000

Index Map and Line of Cross Section Explanation

Symbols ¤£26 Explanation Contact Well locations—solid if in line Fault—arrows show sense of displacement of section, dashed if projected ¤£20 Base Data into line of section _ G' City or town der ow r State or U.S. highway P Rive Geologic Units Interstate highway NOTE: uaternary deposits not shown k River or creek r o CENOZOIC PALEOZOIC Lake or reservoir F th Tertiary Permian–Cambrian ou Township boundary S Lower Eocene and younger Pzr Paleozoic rocks Teu Tertiary rocks, undivided County boundary Tle Lower Eocene rocks PRECAMBRIAN State boundary p_r Precambrian rocks Cross section line CENOZOIC–MESOZOIC Tertiary–Cretaceous Surface Geology TKfl Fort Union and Lance formations Quaternary MESOZOIC Tertiary Cretaceous Mesozoic Meeteetse, Lewis, Mesaverde, N A T R O N A Kmc Paleozoic and Cody formations Precambrian G Mzr Pre-Cody Mesozoic rocks

N 0 2.5 5 Miles Adapted from:

Keefer, W.R., 1970, Structural geology of the Wind River Basin, Wyoming: U.S. Geological Figure 4-9. Geologic cross section G-G’. Survey Professional Paper 495, 35 p.

4-51 Cross Section H-H’

NW SE

H H WYOMING

FEET SOUTH DAKOTA FEET 7,000 7,000 Tfx Wgr Tt Tpx XWb Tw O_wd 6,000 Tp Tt 6,000 BEND IN KJim SECTION KJim Tp Tt Pmo

Tw BEND IN 5,000 Tp Tp SECTION Jsg Tp Jsg 5,000 Kb Kms Jsg Tt KJim River Fourche Belle ^Ps XWp 4,000 Jsg 4,000 P*m Pmo Tp ^Ps Tt Tp Tt MDpe Tpx 3,000 P*m Wgr Wgr XWp 3,000 Pmo 2,000 MDpe O_wd XWgw XWgw 2,000

1,000 O_wd 1,000 0 0 Wu? Xu and (or) Wu? -1,000 -1,000 Wu? -2,000 -2,000

-3,000 -3,000 1000 feet = 305 meters

Index Map and Line of Cross Section Explanation Symbols e Contact h Explanation r ¬«112 c ¤£212 Fault—arrows show sense of displacement e r Ri v u ve Base Data i o r R F _ City or town Geologic Units ¬«24 State or U.S. highway i CENOZOIC MESOZOIC–PALEOZOIC PRECAMBRIAN r Hulett ¬«34 e u Tertiary Triassic–Permian Proterozoic Interstate highway l t o t ¬«111 k s ree i C s i Tw White River Group ^Ps Spearfish Formation Xu Undifferentiated Proterozoic rocks River or creek L water M ed Lake or reservoir C R O O R ¬«24 ¨¦§90 Tp Phonolitic intrusive rocks Proterozoic–Archean k PALEOZOIC e Township boundary H e Permian XWp Pegmatite r Tt Trachytic intrusive rocks C

County boundary Pmo Minnekahta Limestone and Opeche Shale

e s XWb Metabasalt l Tfx Feldspathoidal breccia State boundary l g e n ¤£14 i Permian–Pennsylvanian B r XWgw Metagraywacke I p Tpx Pyroxenite Cross section line n Sundance y S P*m Minnelusa Formation a n H' Archean Surface Geology MESOZOIC Pine K d Mississippian–Devonian a ¬«585 l Cretaceous Wgr Granite Quaternary ¬«113 Haven r o a C MDpe Pahasapa Limestone and Englewood Formation Tertiary Kb Belle Fourche Shale ¨¦§90 Wu Undifferentiated Archean rocks Mesozoic Mowry Shale, Newcastle Sandstone, Ordovician–Cambrian Moorcroft Kms C and Skull Creek Shale Whitewood Dolomite, Winnipeg Formation, Paleozoic r O_wd ¬«116 e and Deadwood Formation e ¤£85 Precambrian k Cretaceous–Jurassic ¤£16 KJim Inyan Kara Group and Morrison N Formation and Unkpapa Sandstone 0 5 10 Miles Upton W E S T O N Jurassic Jsg Sundance and Gypsum Spring formations Adapted from:

DeWitt, Ed, Redden, J.A., Buscher, D.P., and Wilson, A.B., 1989, Geologic map of the Black Hills area, South Dakota and Wyoming: U.S. Geological Survey Miscellaneous Figure 4-10. Geologic cross section H-H’. Investigations Series Map I-1910, scale 1:250,000.

4-52 Cross Section I-I’ River River Basin Basin NW Platte SE Northeast Basin Basin SILVER RAWHIDE Basin Basin

Platte River HARTVILLE CASSA CREEK DOME

I Northeast River FAULT I ANTICLINE SYNCLINE ANTICLINE Platte River 49-009-22239 49-027-07025 P*h Northeast River 49-015-20031 49-015-05087 METERS projected projected Taw Taw projected METERS TD=388.8 m P*h projected TD=448.8 m Taw KJ TD=949.7 m TD=1292 m 1500 1500 M_ KJ Taw P*h ^P ^P Ww Kmt 1000 P*h KJ Kpn 1000 M_ Xhg 500 ^P Kcgb 500 M_ 0 p_u Wr P*h 0 Ww p_u Ws M_ -500 -500 Wmf Wmf p_u Vertical exaggeration~2x

Index Map and Line of Cross Section Explanation

Symbols k ¤£85 Explanation e e Contact r ¬«270 ¤£18 Fault—arrows show sense of displacement, Base Data C and dashed where inferred _ City or town N I O B R A R A e R-6 State or U.S. highway c Well locations n a Interstate highway L River or creek Manville Lusk ¤£18 Geologic Units Lake or reservoir NOTE: uaternary deposits not shown ¤£20 Nio Township boundary brara CENOZOIC PRECAMBRIAN Riv County boundary I er Tertiary Proterozoic State boundary Taw Arikaree and White River formations, undivided Xhg Gneissic phase of Haystack Range granite Cross section line MESOZOIC Archean ¬«270 ¤£85 I Surface Geology Cretaceous Wr Rawhide Buttes Granite Quaternary Kpn Pierre Shale and Niobrara Formation,undivided Ww Wildcat Hills Formation Tertiary Glendo P L A T T E Kcgb Carlile Shale, Greenhorn Formation, Mesozoic G O S H E N and Belle Fourche Shale, undivided Ws Silver Springs Formation Paleozoic Mowry Shale, Muddy Sandstone, Kmt and Thermopolis Shale, undivided Wmf Mother Featherlegs Metabasalt Precambrian Jurassic p_u Precambrian rocks, undifferentiated N KJ Cloverly, Morrison,and Sundance formations, 0 5 10 Miles undivided Triassic ^P Chugwater and Goose Egg formations, undivided

PALEOZOIC Permian–Pennsylvanian

P*h Hartville Formation, undivided

Mississippian, Devonian, M_ and Cambrian () rocks, undifferentiated

Adapted from:

McLaughlin, J.F., Stafford, J.E., and Harris, R.E., 2011, Geologic map of the Lusk 30’ x 60’ quadrangle, Niobrara, Goshen, Converse, and Platte counties, Wyoming, and Sioux Figure 4-11. Geologic cross section I-I’. County, Nebraska: Wyoming State Geological Survey Map Series 82, scale 1:100,000.

4-53