Stratigraphic Cross Sections and Subsurface Model of the Lance and Fort Union Formations, Great Divide Basin, Wyoming

Home , Fort Union Formation, Great Divide Basin, Lance Formation, Wasatch Formation, Wind River Basin

WYOMING STATE GEOLOGICAL SURVEY OPEN FILE REPORT 15-3 Thomas A. Drean, Director and State Geologist Laramie, Wyoming Interpreting the past, providing for the future

Introduction regressive and coarsening-up sandstone, visible on both gamma termed the Horse Butte coal bed. Approximately 250–350 ft (76–110 Cross Sections Study Area Location Map and SP geophysical logs, and below the first coal of the Lance m) above this coal is the main Cherokee coal zone consisting of the Cross Sections Uppermost Cretaceous and Paleocene strata characterize Laramide Formation. Sandstones of the Fox Hills interfinger with the under- Lower Cherokee, Cherokee, and Upper Cherokee coal beds. These basin development throughout much of Wyoming and the Rocky lying marine Lewis Shale and remain undifferentiated for this study. coals, while regionally correlative, contain many thick coals that are Tie Well Mountain region. These strata are of economic importance because Tie Well sometimes laterally discontinuous. Cherokee coals are of lower quality Lost Valley (F-F’) they can host thick and shallow coal deposits, as well as productive oil than China Butte coals and are lignitic to subbituminous C in rank. (C-C’) Tie Well Location map showing key features in the Great Divide Basin region, a sub-basin of the Lance Formation D Block-A 5 D’ Tie Well Stewart Creek and natural gas reservoirs. The Upper Cretaceous Lance and Paleocene Lost Valley 49-037-21923 (E-E’) Chain Lakes Sooner Greater Green River Basin. Inset map of Wyoming (left) highlights the Greater Green Bravo Federal 1 Unit 1 (D-D’) 11-5-23-93 Unit 2 Fort Union Formations in the Greater Green River Basin (GGRB) of The Maastrichtian Lance Formation contains thin sandstones, shales, South Unit 4 T26N R98W S30 North C Red Desert Reservoir 2 C’ River Basin (light green), the Precambrian outcrops or mountain ranges (purple), and the Wasatch and Battle Spring Formations, Undifferentiated 49-037-20064 49-037-21329 Encana Federal Molitor Seaver 49-037-25952 49-037-21025 southwestern Wyoming are no exception. The purpose of this study T24N R99W S22 MD Bravo Red Lake W-20355 1-5 49-037-21633 and coals that record the last of the Cretaceous Interior Seaway coast- 49-037-23513 T25N R98W S17 GR(ft) Res 21-31 Federal 1 Unit 1 T23N R93W S5 T23N R91W S5 Great Divide Basin study area (red box). Detailed map (below) shows outcrops of the Fort T23N R99W S4 West Unit 4 1-3 49-037-21186 T24N R92W S34 East WYOMING is to clarify the stratigraphy of the Lance and Fort Union Formations al- and delta-plain transitioning into terrestrial deposits (Flemings and The Wasatch and Battle Spring Formations represent the last phases MD GR(ft) Res MD 49-037-26691 49-037-25987 49-037-25498 MD Union Formation (brown), modified from the 1:500,000 scale geologic map of Wyoming Federal-I GR(ft) Res Wasatch & 49-037-23513 49-037-24914 T23N R94W S5 MD MD in the Great Divide Basin (GDB), a sub-basin of the northeastern MD 4.2 mi T23N R95W S9 GR(ft) Res SP (ft) Res. Nelson, 1991; Gillespie and Fox, 1991). Overall thickness of the Lance of basin filling in the Greater Green River Basin. The Battle Spring GR(ft) Res 3.8 mi 7.0 mi T24N R96W S31 T23N R96W S2 GR(ft) Res Ruddy 1 2500 Battle Spring T23N R99W S4 T23N R98W S1 MD (Love and Christiansen, 1985). Cross section locations are displayed as red lines, and MD GR Res F 1 GGRB, to help guide future hydrocarbon and coal exploration and aid Formation varies from 950–5,200 ft (290–1600 m). The lower boundary Formation is a thick succession of boulder conglomerate and sandstone Formations MD MD GR Res (ft) 5.6 mi 8.3 mi 4.1 mi 49-037-21011 MD MD GR(ft) Res GR(ft) Res (ft) wells used in the cross sections are named by their 10-digit API number and highlighted (part) GR(ft) Res GR(ft) Res 49-037-05934 in constraining the timing of local Laramide tectonic events. Formation is conformable and transitional with the underlying Fox Hills Sandstone, that records the uplift of the Granite Mountains (Pipiringos and Denson, T23N R99W S22 4.7 mi 1500 Tie Well Well Big Dune 8.5 mi 7.1 mi 4.2 mi 4.6 mi 9.9 mi T24N R90W S14 as large black dots. All other wells used in this study are denoted as small gray dots. 2.8 mi 1000 2000 tops, member tops, and coals were correlated throughout the GDB generally denoted below the first coal in the section. The Lance For- 1970). The distal part of the Battle Spring Formation interfingers with the MD 2500 SP(ft) Res 3000 3 Unit 2 1500 2000 MD Greater (B-B’) 1500 SP (ft) Res. from a Wyoming State Geological Survey database of 4,309 oil, gas, mation contains the upper Red Rim Member and the lower (unnamed) Wasatch Formation, the lateral and finer-grained equivalent. Coals are 49-037-05930 49-037-05918 5.9 mi 500 1500 Wasatch & Tie Well Black Rock Crk T23N R101W S1 T23N R100W S9 1500 and coal exploration wells (IHS, 2015; WOGCC, 2015). Stratigraphic member, which was further informally divided into an upper and lower present in the Wasatch Formation (Pipiringos, 1961; Masursky, 1962; 1000 2000 Green STUDY Upper Cherokee Battle Spring (A-A’) Unit 3 1500 500 3000 MD 2500 and coalbed nomenclature was derived from Madden (1989), Flores zone (Hettinger and others, 1991; Hettinger and Kirschbaum, 1991) Hettinger and others, 2008) but were not mapped as part of this study. Upper 500 MD Formations AREA 3500 SP(ft) Res SP(ft) Res 2000 2500 49-037-05868 2000 River 23-1 3.4 mi Lower Cherokee (part) and others (1999), Honey and Hettinger (2004), and Hettinger and and correlated through this study area. Coals are more prominent in the Arch Playa Unit T22N R99W S20 6.9 mi 1000 2000 Monell ? Cherokee Cow Butte Unit 81 3-1 49-037-20176 2000 500 others (2008). Results are presented in graphic format as a series of six lower zone of the lower member, but were neither denoted nor named in 15-22B 1500 2500 Unit 33-34 T21N R99W S23 MD Basin SP(ft) Res 2000 1000 49-037-05681 49-037-05785 3500 3000 1000 Horse Butte cross sections, three structure contour maps, and two isochore maps. this study. The lower zone of the lower member is generally comprised 49-037-26778 4000 500 2500 3000 T19N R99W S3 MD ? T20N R99W S22 2500 T19N R99W S34 SP(ft) Res 1500 2500 of thin and locally continuous sandstones interbedded with shale, coals, 500 The six cross sections of the Great Divide Basin depict Paleocene GRMD Res MD 2500 1000 MD 4.7 mi (ft) 3.7 mi SP(ft) Res 5.6 mi 6.3 mi 2000 3000 and carbonaceous shales. The upper zone of the lower member contains GR(ft) Res Fort Union Formation members and coal beds, as well as Cretaceous 2500 4000 1500 3500 References 1500 4500 1000 3000 3500 thicker sandstone beds and fewer beds of carbonaceous shale and coal. Lance Formation members. The datum for these stratigraphic cross 500 CB1200 3000 2000 103 102 101 100 99 98 97 96 95 94 93 92 91 90 89 88 85 1000 3000 28 sections is the top of the China Butte Member of the Fort Union The Red Rim Member is a prominent sandstone package named for Flemings, P.B., and Nelson, S.N., 1991, Paleogeographic evolution ? ? Member Overland 3000 1500 500 2500 3500 of the latest Cretaceous and Paleocene Wind River Basin: The basal sands Formation (described in more detail below) because it subdivides its color as it crops out south of Interstate 80 on the eastern rim of 3000 2000 4000 500 4500 CB1200 500 2000 5000 1500 3500 4000 Mountain Geologist, v. 28, p. 36–52. 500 CB700 the two members of the Fort Union Formation and highlights the two the Washakie Basin. Hettinger and others (1991) and Hettinger and 1000 3500 Nuttal? 2500 3500 27 CB700 1500 main coal zones. Cross sections A-A’, B-B’, and C-C’ are oriented Kirschbaum (1991) define the Cretaceous-Paleocene boundary at a CB700 3500 2000 Member Overland Flores, R.M., Ochs, A.M., Stricker, G.D., Ellis, M.S., Roberts, S.B., 1000 CB700 3000 4000 CB700 3500

CB700? 5000 Union Formation Fort 2500 4500 west to east. These cross sections cover the GDB from the east side conglomeratic horizon within but near the top of the Red Rim Mem- 1000 Keighin, C.W., Murphy, E.C., Cavaroc, V.V., Jr., Johnson, R.C., 1000 2500 5500 2000 CB700 4000 Middle Fort Union Lower 4500 ± Bairoil 1000 DATUM 4000 of the Rock Springs uplift (R101W) to the west side of the Rawlins ber. This boundary was defined through palynology at the outcrops 1500 ! ! and Wilde, E.M., 1999, Location, stratigraphy, and coal quality 3000 4000 Fort Union 15 2000 (!73 basal sands D' E'!(! 4903721309 26 Fort Union 14 ! uplift (R90W), a maximum distance of 84 mi (135 km). They show 2500 ! 0 6 12 18 Miles (Hettinger and others, 1991). No outcrops were examined for this Upper Deadman 1500 4000 !( ! ! for selected Tertiary coal in the northern Rocky Mountains and Fort Union 13 3500 4500 Fort Union 3 Lower Upper Big Red DATUM 4903721923 Upper Big Red 4000 Upper Deadman Deadman 5500 3000 5000 the variability in member thickness and coalbeds of the Fort Union study, and the conglomerate bed is not visible on geophysical logs. 1500 1500 ! Great Plains region: U.S. Geological Survey National Coal Fort Union 3 3000 Big Red ! ! Lower Deadman 6000 2500 4500 5000 1500 Lower Big Red 4500 Fort Union 4 2000 Muddy Creek Lower Big Red Formation and overall thickness of the Lance Formation from T20N For these reasons, the Cretaceous-Paleocene boundary was not deter- Resource Assessment Non-Proprietary Data, Open-File Report Fort Union 2 3500 Fillmore Ranch ! Fort Union 1 Fort Union 3 Muddy Creek Upper 4500 Fillmore Ranch ! 2500 Upper Big Red !( 4903721329 Separation Deadman Chicken Springs Lower Separation Creek Creek B Separation 4500 Fillmore Creek 3000 25 to T24N. Cross sections D-D’, E-E’, and F-F’ are oriented south to mined, and the unconformity associated with this boundary is assumed 2000 ! 5000 ! ! 4903721381! 99-376. 4000 !( ! Creek B Mbr. China Butte ! Lower Deadman Big Red ! ! Fort Union 3 4500 Red Rim 3500 5500 2000 Daley Ranch 6000 Muddy Creek ! north, and transect the GDB from the Wamsutter arch near Interstate to be at the top of the Red Rim Member. Age control established 2000 3500 ! Lower 6500 3000 Lower Big Red 5000 Muddy Creek 5500 2000 Gill, J.R., Merewether, E.A., and Cobban, W.A., 1970, Stratigraphy 2500 Separation Creek B 5000 4000 ! ! 80 (T19N) to the large reverse faults adjacent to the Wind River and from subsurface cores and cuttings would help refine this boundary. 5000 Separation Creek B ! 3000 poor log quality, ! !(! 4903721716 Muddy Creek Lower Separation ! 4903705934 and nomenclature of some Upper Cretaceous and lower Tertiary 5000 3500 Union Formation Fort ! ! ! ! 2500 correlations ! ! ! ! F' !( Lower Separation Creek 5500 !( ! Crooks Mountains in T26N, a maximum distance of 48 mi (77 km). Daley Ranch 4500 Creek 4903720064! ! ! ! ! !(! ! 24 5000 Riner ! C' rocks in south-central Wyoming: U.S. Geological Survey uncertain ! ! 6500 4000 6000 Great! ! Divide 4903721905 2500 4000 ! ! Well spacing in each cross section is approximately 3–10 mi (5–16 km). 2500 7000 5500 ! ! 3500 6000 ! ! ! 2500 4903726691!( ! 4903721633! 4903705930 ! ! upper zone ! ! ! !( Fort Union Formation 3000 ! Professional Paper 667, 53 p. 5500 !( ! Lower Riner C 4903723513 !(! ! 4500 !(! ! 4903725987 4903721186 5500 ! ! ! 3500 Red Rim ! ! !( !( !(! !(! ! ! ! Structure contour maps were created on the top of the Fort Union !(! 4903724914 ! ! !( 5500 4000 ! 4903725952 3000 6000 Red Rim ! ! 4903721025 The members of the Fort Union Formation were first noted by Gillespie, J.M., and Fox, J.W., 1991, Tectonically influenced 5000 Red Rim ! ! ! 4903725498! 287 ! ! ! £¤ 5500 4903705918 !( 4903721011! ! Formation, the middle of the Fort Union Formation (top of the Daley Ranch ! ! ! ! 7000 4500 6500 ! 23 3000 ! ! 3000 4500 7500 6000 6500 ! Hettinger and others (1991) and Hettinger and Kirschbaum (1991), sedimentation in the Lance Formation, eastern Wind River Basin, 4000 ! ! ! !(! 4903725975 3000 !(! ! ! ! ! China Butte Member), and the base of the Fort Union Formation 3500 6000 ! 4903721664 5000 ! ! Als Coal ! ! formally defined by Honey and Hettinger (2004), and further- ex Wyoming: The Mountain Geologist, v. 28, p. 53–66. 6000 ! 4000 Member China Butte ! ? ! ! (top of the Lance Formation), using sea level as datum. The struc- ! 6000 4500 ! 3500 6500 !(! ! ! !(! ! 789 5500 4903705879 ! panded by Hettinger and others (2008). The members, from oldest B ! 4903725727 ! !( ! 6000 ! ! Hansen, W.R., 1986, Neogene tectonics and geomorphology of the !( ! ture contour maps were then used to generate the two isochore 7500 5000 7000 ! ! ! ! B a s i n ! ! ! TD 4,520 ft 5000 4903705868 8000 Red Rim ! 22 TD 4,712 ft TD 4,290 ft 4500 6500 7000 !(! ! to youngest, include the China Butte Member, Blue Gap Member 4903705871 !(! ! ! 4903724769! ! ! ! ! R a wl i ns ! ! 4903726453! ! ! 4903725820 eastern Uinta Mountains in Utah, Colorado and Wyoming: U.S. 4000 6500 ! ! !( maps that show the calculated thickness of the upper Fort Union ! !( ! !( 5500 Member !( ! ! ! !( !( ! ! ! ! ! ! TD 4,303 ft 6500 ! 4903705865! ! ! ! (not present in the study area), and overlying Overland Member ? 4500 ! 4903720205 ! TD 5,500 ft ! 4903725769 4903725124 Geological Survey Professional Paper 1356, p. 1–78. ! ! Formation (Overland Member) and lower Fort Union Formation 5000 ! ! 6500 ! !( 4903721150 7000 ! ! 6000 ! ! ! !( U pl i f t ! ! (often mapped with a basal sandstone package). These members ! ! ! ! 4903725993 ! ! ! 6500 ! !( !B' 8000 5500 7500 (China Butte Member). The stratigraphy used on and interpretations ! ! ! 5500 ! ! 8500 7000 7500 ! ! 4903721308 Rawlins Heller, P.L., McMillan, M.E., and Humphrey, N., 2011, Cli- !(! were correlated, from the wells and outcrops presented in the afore- 4903720176! ! ! 21 lower zone TD 5,721 ft 7000 ! ! ! ! 4903721035! ! !( ! ! ! ! derived from these maps are described in the following sections. 6000 ! !( 4903725795 7000 mate-induced formation of a closed basin: Great Divide Basin, TD 5,998 ft Superior ! ! ! ! ! ! Cross Section D-D’ member lower ! ! mentioned studies, north and west into the Great Divide Basin. ! ! ! 7000 5500 ! Creston 7500 ! ! 6500 ! ! ! ! Wyoming: GSA Bulletin, v. 123, no. 1-2, p. 150–157. ! This study focuses on coal correlations and general Fort Union ! ! ! ! ! ! !

! Jct 7000 Formation Lance ! ! ! ! 371 ! ! ! ! ! 8500 ! ! ! ! ! This cross section shows variability of the Overland Member of the Fort Union Formation. Thinning onto the east flank 6000 8000 ! ! The China Butte Member is a coal-rich member, with at least 25 !( ! 6000 ! ! ! 4903724780 ! 4903727673 9000 7500 8000 ! 4903705785 !(! ! ! ! ! ! 80 Formation stratigraphy in an attempt to extend correlations from the ! ! ! !( !( ! ! ! ! ! !( ! R oc k !( ! ! ! ! 4903705781 § ! ¨¦ Hettinger, R.D., and Kirschbaum, M.A., 1991, Chart showing correla- 7500 ! !( ! ! ! ! ! !! ! ! !( !( 4903726285 of the Rock Springs uplift is accentuated by the erosional contact (unconformity) between the Fort Union Formation 6500 A !! ! named coals, interbedded with thin sandstones, siltstones, mud- ! ! ! ! ! TD 7,435 ft ! 20 7500 ! !( 4903724884 ! A' ! ! ! !( 4903705788 ! ! ! ! 71 known and well-described outcrops of the Atlantic Rim (east flank of upper zone ! ! ! 4903724713 !( ! ! !! ! ! ! ! ! ! A r c h !(! tions of some Upper Cretaceous and lower Tertiary rocks, from ! ! 4903705773 ! ! 4903720889 and the overlying Wasatch Formation. The Overland Member thickens significantly to the north, away from influence 7500 6000 ! ! stones, and carbonaceous shales. Coal seams from the China Butte ! TD 7,845 ft 8000 Wa m s u t te r !! 7000 ! ! !!! ! Wamsutter ! ! ! S p r i n gs ! ! ! ! the Washakie Basin) into the GDB. These correlations should guide ! ! 7500 ! ! ! ! 4903720810 9000 ! !( 4903705681! ! ! the east flank of the Washakie Basin to the east flank of the Rock 6500 8500 ! TD 6,006ft ! ! ! of the Rock Springs uplift, but no Cherokee coals are interpreted in this region. The basal sands of the Overland ! ! ! Member within the Great Divide Basin can be as thick as 96 ft (29 9500 8000 8500 ! ! £¤30 ! ! ! ! ! ! ! future coal availability assessments, in addition to conventional natural ! ! ! ! ! 8000 ! ! ! ! !( 4903721179 ! ! ! ! ! Springs uplift, Wyoming: U.S. Geological Survey Miscellaneous TD 7,845 ft ! ! ! !( 4900722364 ! ! Member only appear in one well. The Lance Formation thickens distinctly in the northern third of the cross section. 19 ! m) (Lower Deadman coal seam) but generally average less than 10 ") ! ! 8000 U pl i f t ! 19 ! ! ! gas and coalbed natural gas exploration in the Great Divide Basin. ! ! ! Investigations Series Map I-2152. 8000 ! 8500 ck Spr ! ! ft (3 m) thick. Interbedded sandstones are commonly less than 100 7500 ! ! ! ! !( ! ! !( 4900722860 4903726778 ! !(! 4903725676! 9500 9000 ! ! TD 9,167 ft ! ! ! 10000 ! ! ft (30 m) thick, although in rare instances can be much thicker. The 8500 9000 !(370 ! ! Hettinger, R.D., Honey, J.G., and Nichols, D.J., 1991, Chart showing 8500 8500 D E F Upper Cretaceous and Paleocene Geologic History China Butte Member ranges from 570–2,500 ft (170–760 m) thick. correlations of Upper Cretaceous Fox Hills Sandstone and Lance ")152 !(789 18 8500 8000 9000 The Overland Member overlies the China Butte Member. The base of Formation, and lower Tertiary Fort Union, Wasatch, and Green 9500 TD 14,410 ft 10500 Fox Hills Ss. 9000 9500 As the last of the Cretaceous Interior Seaway retreated toward the north River Formations, from the eastern flank of the Washakie Basin 9000 the Overland Member contains a sandstone package that is only present & Lewis Sh. 9000 and east, the marine shoreface deposits of the Fox Hills Sandstone tran- primarily in the south and southeast portions of the Great Divide Basin. to the southeastern part of the Great Divide Basin, Wyoming: (part) TD 11,450 ft 9000 9500 sitioned into the the overlying coastal plain of the Lance Formation. At U.S. Geological Survey Miscellaneous Investigations Series Map 10000 ? These sandstones thin to the north and west from a maximum thickness TD 11,490 ft 9500 10000 the same time, the Laramide orogeny began to form uplifts and basins I-2151, 1 sheet. 9500 of approximately 1,000 ft (300 m). There are, however, a few surpris- 9500 lower zone that resulted in more than 42,000 ft (13,000 m) of structural offset near 9500 member lower ingly persistent coals interbedded within these basal sands, including Hettinger, R.D., Honey, J.G., Ellis, M.S., Barclay, C.S.V., and East, TD 12,755 ft 10000 Generalized Coal Correlation Chart the adjacent Wind River Mountains. Pre-Fort Union erosion and uplift 10500 the CB700, Middle Fort Union, and Lower Middle Fort Union coals. Lance Formation Lance Generalized stratigraphic correlation chart for coal zones of the Fort Union Formation in the Great Divide Basin (GDB). Columns are divided into J.A., 2008, Geologic map of Upper Cretaceous and Tertiary strata Picket Lake Cross Section C-C’ 10000 10500 of the Cretaceous basin near Rock Springs commenced in the center Mud Springs sub-regions of the GDB, and coals are in general stratigraphic order from oldest at the bottom to youngest at the top. The main body of the Overland Member is a silty and shaly sequence and coal stratigraphy of the Paleocene Fort Union Formation, Tie Well W-14104A 1 TD 13,220 ft 10000 E W-21357 22-12 E’ of the GGRB as shown by tilted Lance and Fox Hills strata and an (C-C’) 49-037-21309 This northern GDB section shows a very thick Lance Formation throughout the GDB, with a maximum thickness toward 10500 Only the prominent coal beds are shown. WSGS coal bed nomenclature modified from Hettinger and others (2008). with the Cherokee coal zone exposed near the top. The Cherokee coals Rawlins–Little Snake River area, south-central Wyoming: U.S. 49-037-21381 angular unconformity between Upper Cretaceous and Paleocene rocks. Tie Well Unit T26N R97W S24 the east. There is only a very thin Red Rim Member in the center of the cross section. Coals from both the Cherokee and 11000 persist through much of the study area with a maximum coal bed thick- Geological Survey Scientific Investigations Map 3053, 3 sheets. South W-21716 5 T25N R96W S22 North TD 14,000 ft 10500 11000 Southwest Northwest Southcentral Northcentral Southeast Northeast This erosion and uplift was followed by early Paleocene deposition in (B-B’) Gale Unit Molitor MD China Butte coal zones do not continue to the eastern wells in this cross section. This absence of coals may be indicative of ness of 49 ft (15 m) (Cherokee coal seam) and average thickness of 8.2 49-037-21716 MD SP(ft) Res W-59143 2 Federal 1 GR(ft) Res Upper Scotty Lake poorly drained paratropical lowlands (Flores and others, 1999) before Honey, J.G., and Hettinger, R.D., 2004, Geologic map of the Peach Tie Well T24N R96W S9 Paleocene subsidence patterns. Isochore maps show the thickest parts of the GDB are in the northeast, suggesting a higher 11000 ft (2.5 m). The Overland Member is 400–3,000 ft (120–910 m) thick. McGinnity 49-037-21664 49-037-25987 Champlin 527 2000 Wasatch & TD 12,790 ft Scotty Lake Main 1 uplift of other potential sediment source areas including the Uinta Orchard Flat quadrangle, Carbon County, Wyoming, and descrip- (A-A’) T23N R96W S2 MD 3.9 mi 7.3 mi rate of relative subsidence that would have preferentially attracted and preserved fluvial deposition in this part of the basin. 11500 Federal 1 T23N R96W S25 GR & SP Res Battle Spring 11500 Mountains, the Park and Sierra Madre highlands, and re-activated The subsurface contact between the Fort Union Formation and the tions of new stratigraphic units in the Upper Cretaceous Lance Amoco A 1 (ft) Scotty Lake Main 2 49-037-26453 MD MD 3000 Formations Desert Flats Tipton II Wells Blu 49-037-21035 GR Res GR(ft) Res overlying and laterally equivalent Eocene Wasatch and Battle Spring Formation and Paleocene Fort Union Formation, eastern Greater T22N R96W S26 (ft) (part) movement on the Rock Springs uplift (Kirschbaum and others, 1994). 31-1 Unit 2 13-4 T21N R95W S19 TD 13,718 ft Formations is unconformable. Where the Battle Spring Formation 49-037-24884 MD 2000 2500 12000 Green River Basin, Wyoming-Colorado: U.S. Geological Survey 49-037-25676 49-037-21179 MD 5.7 mi GR(ft) Res 5.4 mi 4.2 mi 5.4 mi 12000 Upper Cherokee Upper Cherokee Upper Cherokee Upper Cherokee The Paleocene Fort Union Formation in the GGRB records this compli- GR Res is present in the northeastern Great Divide Basin, the contact is T19N R96W S13 T20N R96W S13 (ft) Upper Scotty Lake coal zone ee coal Scientific Investigations Map 2835, 2 sheets. T19N R95W S31 3500 cated history of early Cenozoic basin evolution. The Fort Union Forma- 500 Scotty Lake Main 1 Cherokee Cherokee Cherokee Cherokee discernible on geophysical logs by a change in gamma ray log MD MD MD GR Res GR(ft) Res 1000 1500 tion contains the deposits of southeast-flowing rivers that were initially IHS, 2015, Direct Connect database, IHS Petra software, used through GR(ft) Res (ft) 4.8 mi Scotty Lake Main 2 er ok Lower Cherokee Lower Cherokee Lower Cherokee Lower Cherokee character; due to the presence of uranium and granitic clasts Battle 2500 3000 12500 3.8 mi 5.5 mi 12500 ? derived from the Wind River Mountains to the north. Subsequent uplift a subscription service with IHS. 500

Fox Hills Ss. Ch 500 Lower Scotty Lake Cow Butte Cow Butte Spring gamma readings are very high and usually off scale. The 2500 4000 & Lewis Sh. of the Granite Mountains and Rawlins uplift on the north and eastern 1000 Cherokee contact between the Wasatch and Fort Union was consistently picked Kirschbaum, M.A., Andersen, D.W., Helm, R.L., and Baldwin, ? 1500 2000 TD 14,982 ft (part) Horse Butte Horse Butte Horse Butte Horse Butte Horse Butte Lower Lower Scotty Lake margins of the basin resulted in a Fort Union depocenter in the north- 1500 3500 TD 15,640 ft a few hundred feet above the Cherokee coal zone, at a sandier (Fort R.J., 1994, Paleocene drainage systems, Rock Springs uplift, Cherokee 3000 Horse Butte Ov er land Me mber Nuttal CB1200 east GDB, followed by late Paleocene uplift of the Uinta Mountains 1000 Wyoming: The Mountain Geologist, v. 31, no. 1, p. 19–28. 1000 ? ? Cow Butte Union) to shalier (Wasatch) transition defined on gamma ray logs. 3000 4500 ? 1500 Horse Butte

l Fort Union 15 CB700 CB700 CB700 on the southern margin of the GGRB, resulting in a topographic low Lillegraven, J.A., and Ostresh, L.M., 1988, Evolution of Wyoming’s Cherokee 2000 2500 2000 Lower Cherokee Horse Butte ? ? 4000 dd Middle Fort Union Middle Fort Union that forced the low-gradient Fort Union river systems further south. 3500 Tie Well Coal Bed Stratigraphy early Cenozoic topography and drainage patterns: National 1500 Mi Tie Well e 1500 3500 5000

coal zone coal Fort Union 14 Extensive peat swamps formed early in Fort Union time, and again (E-E’) Geographic Research, v. 4, p. 303–327. 2000 (F-F’) Federal Windy Hill Champlin 573 Lower Middle Fort Union Lower Middle Fort Union during later Fort Union deposition. These peat swamps became the Only the coal beds of the Fort Union Formation were identified and 2500 3000 2-12 2500 4000 4500 Member Overland B McGinnity Luman Siberia Ridge Fed Monument Monument Lake 5-1 Amoco A 1 B’ coal beds that are extensively mined at the Bridger and Black Butte correlated in these cross sections. Coal bed nomenclature from Het- Love, J.D., and Christiansen, A.C., comps., 1985, Geologic map Federal 1 49-037-25993 49-037-21308 Fort Union 13 2000 27-1 29-4 49-037-21150 of Wyoming: U.S. Geological Survey in cooperation with the 2000 Red Desert-Fed 28-1 25-1 coal mines on the eastern flank of the Rock Springs uplift. These are tinger and others (2008) and J. Haacke (personal communication, 4000 5500 West 49-037-26453 49-037-25769 49-037-25124 T21N R91W S5 T21N R91W S12 T21N R90W S3 East Fort Union 9 2500 G 1-28 49-037-24769 49-037-25820 Geological Survey of Wyoming [Wyoming State Geological 3500 T22N R96W S26 T22N R95W S27 T22N R93W S29 MD some of the largest coal mines in Wyoming outside of the Powder River 2014) from the Washakie Basin and GDB along the eastern flank 3000 T22N R94W S28 T22N R93W S25 MD MD 3000 5000 49-037-20205 GR(ft) Res GR(ft) Res GR(ft) Res Fort Union 8 Survey], 3 sheets. 4500 MD MD Basin. The lower Fort Union coal beds mark the China Butte Member of the Washakie Basin was used to correlate surface coal beds into basal sands T22N R97W S28 GR(ft) Res MD MD MD CB700 2500 CB700 GR(ft) Res GR(ft) Res 4.6 mi 500 3.5 mi 2500 GR(ft) Res GR(ft) Res 500 Fort Union 7 4500 Lower Middle 6000 Tie Well 7.9 mi 4.5 mi 8.3 mi Wasatch & in the eastern GGRB, while the upper Fort Union coals (Cherokee the subsurface and additional names were added where necessary. Madden, D.J., 1989, Geologic map and measured coal sections of the 3000 MD 500 5.0 mi 5.5 mi 3.5 mi Fort Union GR Res 4000 (ft) Battle Spring Chicken Springs Chicken Springs Chicken Springs Chicken Springs coal zone) mark the Overland Member (Hettinger and others, 2008). A generalized stratigraphic correlation chart is shown for the Fort 3500 DATUM (D-D’) Bitter Creek NW quadrangle, Sweetwater County, Wyoming: 3500 5000 5500 Govt 1000 500 Formations

8.0 mi Union Formation Fort GU Union Formation coals, grouped by member, coal zone, and general U.S. Geological Survey Coal Investigations Map C-121, 2 sheets. 3000 F-22-98-30-D1 1000 (part) 3000 1000 1000 6500 Black Rock Crk 1000 5000 Chicken Springs 49-037-05865 1000 ? location within the GDB. Many of the individual coal beds correlate Fillmore Ranch 3500 Unit 3 1000 ? Upper Deadman Upper Big Red Upper Big Red Masursky, H., 1962, Uranium-bearing coal in the eastern part of the Upper Big Red 4000 4500 T22N R98W S30 Structure regionally as multiple coal beds; thus, coal beds correlated on the Big Red 49-037-05868 ? 4000 5500 6000 Upper Cherokee 1500 1000 Deadman Big Red Big Red Fillmore Ranch Fillmore Ranch Fillmore Ranch Red Desert area, Wyoming: U.S. Geological Survey Bulletin Separation Creek B Muddy Creek 500 Cherokee State-Husky T22N R99W S20 MD ? cross sections may actually consist of more than one individual bed. 3500 Fillmore Creek SP(ft) Res 1500 3500 1500 Lower Cherokee 1500 7000 1500 Lower Deadman Lower Big Red Lower Big Red Fillmore Creek Fillmore Creek Fillmore Creek The GDB is the northeastern sub-basin of the Greater Green River 1099-B, 152 p. 5500 Fillmore Ranch 1 Cow Butte 1500 4000 Federal MD 1500 Riner SP(ft) Res The oldest coal zone in the Fort Union Formation is the China Butte Riner Riner 4500 5000 Muddy Creek 49-037-05871 Horse Butte Muddy Creek Muddy Creek Muddy Creek Muddy Creek Basin. Other sub-basins include the Washakie Basin, Sand Wash Basin, Fillmore Creek D1 Maywood, P.S., 1987, Stratigraphic model of the southern portion 4500 Riner 6500 T22N R100W S16 5.8 mi 5.0 mi 2000 1500 coal zone. The lowest coal bed identified within the China Butte coal Lower Riner Separation 6000 49-037-05879 1000 and Green River Basin; intervening uplifts include the Rock Springs Lower Riner Fort Union 4 of the Jim Bridger coal field, Sweetwater County, Wyoming: 4000 Creek B Lower 500 2000 4000 T22N R101W S12 MD 2000 2000 zone is the Daley Ranch coal bed, which is correlated intermittently 6000 7500 2000 uplift, Wamsutter arch, and Cherokee Ridge arch. The Great Divide Red Rim 4500 Separation Creek SP(ft) Res 2000 Portland, OR, Portland State University, M.S. thesis, 128 p. 2000 Upper Fort Union 3 Daley Ranch Riner MD 3.2 mi Basin is flanked on the north by an extension of the south-verging Wind across the GDB as the basal Fort Union Formation coal. The Red 5000 5500

SP(ft) Res 5000 6500 7000 Member China Butte 2500 2000 Fort Union 3 Lower Riner 500 1500 Rim coal bed intermittently correlates across the study area approx- McMillan, M.E., Heller, P.L., and Wing, S.L., 2006, History and Daley Ranch River thrust fault, on the east by the Rawlins uplift, on the south by the 4500 1000 2500 4500 2500 2500 causes of post-Laramide relief in the Rocky Mountain orogenic 6500 8000 2500 Me mber tt e Lower Fort Union 3

e coal zone coal tt e imately 80–100 ft (24–30 m) above the Daley Ranch. Similarly the 2500 Wamsutter arch, and on the west by the Rock Springs uplift. The deepest 5000 2500 5500 6000 basal sands Member Overland Separation Creek 1 parts of the basin in the north and east are more than 20,000 ft (6,100 Lower Riner and Riner coal beds, 40–120 ft (12–37 m) above the plateau: Geological Society of America Bulletin, v. 118, p. Red Rim 500 5500 7000 7500 3000 interval 2500 1000 2000 393–405. Member not m) below sea level, or more than 27,000 ft (8,200 m) deep. The deepest Red Rim coal, correlate throughout the GDB. The Lower Separation 5000 500 1500 Separation Creek 2 CB700 CB700 3000 5000 3000 3000 logged 7000 8500 Fort 3000 Creek and Separation Creek B are coals 500–600 ft (150–180 m) 5500 Lower Middle 3000 Lower Middle Fort Union coals in the GDB are 8,000 ft (2,400 m) deep (T26N R96W). Pipiringos, G.N., 1961, Uranium-bearing coal in the central part of

3000 China Bu Separation Creek B Separation Creek B Separation Creek B Separation Creek B Fort Union 14 Union 15 China Bu 6500 Fort Union Fort Union above the Riner coals, and also correlate for very long distances 6000 1000 the Great Divide Basin: U.S. Geological Survey Bulletin 1099-A, 6000 7500 8000 Fort Union 13 3500 3000 DATUM Structural subsidence was contemporaneous with paludal, lacustrine, 1500 2500 Lower Separation Creek Lower Separation Creek Lower Separation Creek Lower Separation Creek SP shift Fort Union 14 across the GDB. Above this are the intermittently observed Muddy 5500 Upper Deadman 1000 2000 3500 104 p. 5500 3500 3500 and fluvial deposition during Lance time. The GGRB was originally 7500 9000 3500 Fort Union 2 upper zone Lower Deadman GU Coal 3500 Creek coals 120–140 ft (37–43 m) above the Separation Creek coals. 6000 Chicken Springs 3500 Big Red part of a foreland basin bounded by the Sevier fold and thrust belt to 7000 Big Red Chicken Springs Pipiringos, G.N., and Denson, N.M., 1970, The Battle Spring Forma- 6500 1500 Fort Union 1 Fillmore Ranch 6500 8000 8500 Fillmore Creek 4000 3500 The thickest coal beds of the China Butte coal zone are the Fillmore 2000 Muddy Creek 3000 the west during the Late Cretaceous through early Eocene. Laramide tion in south-central Wyoming: Wyoming Geological Association Fillmore Creek Riner Riner Riner Riner Riner 6000 1500 2500 6000 4000 4000 4000 Ranch and Fillmore Creek coals, 150–220 ft (46–67 m) above the Mud- 9500 ? ? Lower Separation Creek 4000 Muddy Creek uplifts later partitioned the foreland region into individual basins Guidebook, twenty-second annual field conference, p. 161–168, 8000 GR Separation Creek B 4000 6500 Log change

interval not logged 4000 Muddy Creek 1 Union Formation Fort Lower Riner Lower Riner Lower Riner Lower Riner Lower Riner SP bounded by narrow basement-cored ranges (Snoke, 1993). These dy Creek coals. The Fillmore Ranch coals in the eastern GDB correlate 7000 7500 ? Riner Separation Creek B 2 sheets. 2000 7000 8500 9000 4500 4000 Olson Draw 2500 3500 Lower Separation Creek early Laramide uplifts influenced Lance drainage patterns; local directly to the Big Red coals of the central and northwestern GDB. Riner 6500 2000 3000 Pyles, D.R., and Slatt, R.M., 2008, Integrating outcrop and subsurface 6500 Lower Riner 4500 4500 4500 Consequently, the Big Red coals correlate directly to the Deadman and 8500 10000 4500 Lower Olson Draw depocenters and sediment sources mark the onset of Maastrichtian 7000 Lower Red Rim 4500 4500 Red Rim Lower Riner Lower Riner data to define regional and reservoir-scale patterns in the Lewis Hadsell Draw Laramide deformation (Lillegraven and Ostresh, 1988), followed Upper Deadman coals near the Bridger Mine area on the west side of 7500 8000 2500 Daley Ranch 7500 9000 9500 5000 Lower Red Rim Red Rim 4500 Shale and Fox Hills Sandstone of the Great Divide and Washakie 3000 4000 Riner by intermittent Paleocene deposition of clastics and coal formation the GDB. In outcrop at the Bridger Mine these coals split into the D31 TD 10,566 ft Red Rim Red Rim Red Rim Red Rim Red Rim 7000 3500 TD 9,649 ft 7000 5000 Daley Ranch 5000 Lower Red Rim 5000 Basins, Wyoming: AAPG Rocky Mountain Section Meeting, 10500 TD 3,678 ft 5000 and D54 coal beds (Maywood, 1987), but these names were not used 5000 in fluvial floodplain and lacustrine settings (Tyler and others, 1995). 7500 TD 6,900 ft 5000 Daley Ranch Daley Ranch Daley Ranch Daley Ranch abstracts. in this subsurface study. The Fillmore Creek coals of the eastern GDB 8000 8500 TD 9,145 ft member lower Daley Ranch TD 6,956 ft 9500 10000 5500 Continental Divide 5000 The Wamsutter arch separates the GDB from the Washakie Basin. 3500 4500 Al’s Coal Continental Divide lower zone

correlate directly to the Lower Big Red and Lower Deadman coals of Ritzma, H.R., 1963, Geology and occurrence of oil and gas, Formation Lance 4000 Continental Although often viewed as an east-west extension of the Rock Springs 5500 5500 5500 11000 5500 5500 Divide the western GDB. Most of these coals are too deep to mine in the GDB, Wamsutter arch, Wyoming, in Childs, O.E., and Beebe, B.W., 8000 5500 uplift, the Wamsutter arch was not active until the latest Cretaceous, with the exception of the Deadman coals in the western part of the eds., Backbone of the Americas: tectonic history from pole to TD 11,625 ft 8500 9000 10000 10500 6000 5500 and was minimally active during Fort Union deposition. Post-Fort 4000 5000 study area, but have coalbed natural gas potential. The Big Red coals pole: Tulsa, OK, American Association of Petroleum Geologists Cross Section E-E’ 4500 TD 5,500 ft 6000 6000 6000 Union episodic uplift that occurred until at least the Oligocene and 11500 6000 6000 have been the target for coalbed natural gas exploration in the north- Memoir 2, p. 188–195. 6000 Cross Section Explanation possibly as recent as Pleistocene (Ritzma, 1963, 1968), accounts This cross section is similar to B-B’ in that it highlights the deepest part of the Great Divide Basin. In E-E’ the coal beds of the China 9000 9500 west part of the GDB. The Chicken Springs coal is a thin discontinuous 10500 11000 6500 6000 Age for the majority of the uplift on the Wamsutter arch. Isochore maps Ritzma, H.R., 1968, Geology and occurrence of gas, Wamsutter Butte Member are relatively straightforward, and the overall thickness of the China Butte does not vary. The thick Cherokee coal zone of 5500 coal marker just above the Upper Big Red coal. In the western part of TD 10,731 ft 5000 6500 6500 6500 Red Rim Mbr. Member China Butte Member Formation (Series) arch, Sweetwater County, Wyoming, in Beebe, B.W., and Curtis, the Overland Member is more discontinuous than in other sections, but is still apparent. The Scotty Lake coals highlighted in the Picket 12000 6500 ? Correlation line—Dashed where probable; generated on the upper and lower members of the Fort Union Forma- TD 13,220 ft TD 13,747 ft 6500 the GDB, Flores and others (1999) named the correlative coals above TD 7,211 ft 6500 Wasatch & queried where uncertain tion do not suggest much, if any, thinning over the Wamsutter arch. B.F., eds., Natural gases of North America, volume one: Tulsa, Lake W-14104 A 1 well (T26N R97W) are here interpreted as part of the Cherokee coals and not Wasatch Formation coals (Eocene) Battle Spring the Deadman coals as Fort Union 7, 8, 9, and 13, which are considered 11500 7000 6500 Eocene 6000 Cretaceous-Paleocene unconformity— OK, American Association of Petroleum Geologists Memoir, p. as assumed by the operators of the wells in that region (WOGCC, 2015). This section shows the deepest Fort Union coals in the GDB. Formations The GDB became isolated and internally drained during middle the youngest coal beds in the China Butte coal zone. Most of the China 7000 7000 7000 Location approximate, may be lower in 12500 7000 817–827. 7000 Red Rim Sandstone; after Hettinger and 7000 to late Miocene time (Hansen, 1986; Lillegraven and Ostresh, Butte coals are subbituminous B and C in rank (Hettinger and others, TD 14,550 ft others (1991) and Hettinger and 1988), after deposition of the Wasatch and Green River Formations. Sanders, R.B., 1974, Geologic map and coal resources of the Riner Fox Hills Ss. 7500 upper zone 7000 Kirschbaum (1991) 2008), but bituminous coal has been reported deeper in the basin. 6500 Overland Regional tectonics affected the GDB margins, including late Ce- quadrangle, Carbon and Sweetwater Counties, Wyoming: U.S. & Lewis Sh. 7500 7500 7500 13000 TD 8,075 ft 7500 ? The middle coal zone of the Fort Union Formation separates the (part) 7500 basal Lower Lance subdivision—Interpreted 7500 nozoic extensional collapse of the Granite Mountains (11–7 Ma), Geological Survey Coal Investigations Map C-68, 1 sheet. sands division between the upper and lower China Butte coal zone from the overlying Cherokee coal zone, and TD 13,602 ft zones of the lower member of the Lance Rio Grande Rift tectonics east of the Sierra Madre Mountains (10–8 8000 7500 Formation; queried where uncertain is usually, but not always, part of the basal sandstone package of the Snoke, A.W., 1993, Geologic history of Wyoming within the tectonic 8000 Ma), and eruption of the Leucite Hills (3–0.8 Ma) (summarized in 8000 8000 Paleocene Cross Section B-B’ 8000 framework of the North America Cordillera, in Snoke, A.W., 8000 China ? Overland Member. This generally sandy interval is mostly barren of 8000 Coal correlation—Line thickness approxi- Heller and others, 2011). From 8 Ma to at least 4 Ma (and possibly Butte mately correlates to bed thickness; queried coal, with the exception of thick and continuous coals correlated as the Steidtmann, J.R., and Roberts, S.M., eds., Geology of Wyoming: Tie Well This cross section highlights a thickening Lance Formation to the east, that is approximately 400 TD 11,625 ft Union Formation Fort 8500 8000 where uncertain more recent; McMillan and others, 2006), regional doming was (C-C’) feet (122 m) thicker than on A-A’. The Red Rim Member only extends across the eastern half of this Lower Middle Fort Union and Middle Fort Union (J. Haacke, personal Geological Survey of Wyoming [Wyoming State Geological 8500 8500 8500 responsible for uplift of the GDB to its near-present elevation. 8500 8500 ? Geophysical logs Survey] Memoir No. 5, p. 3–56. Stratton Draw cross section. The China Butte Member thins to the west onto the flank of the Rock Springs uplift ? Formation Lance communication, 2015), CB700, and CB1200. These coals are some of Chain Lakes

lower member lower SP spontaneous potential 18422 1 where all but the Deadman coals are present. The absence of lower China Butte coals on the flank Red the most persistent coal markers throughout the entire GDB. CB700 Tyler, R., Kaiser, W.R., Scott, A.R., Hamilton, D.S., and Ambrose, F 11-5-23-93 F’ TD 10,663 ft 9000 lower zone 8500 GR gamma ray Tie Well 49-037-21905 Rim Res resistivity 49-037-25952 3.7 mi of the Rock Springs uplift suggests the uplift was structurally high during China Butte time and the Stratigraphy is informally named as the main coal 700 ft (210 m) above the Big W.A., 1995, Geologic and hydrologic assessment of natural Chain Lakes T24N R93W S21 TD 11,294 ft 9000 9000 9000 MD measured depth South (B-B’) T23N R93W S5 North 9000 Monument Lake 27-1 older coals that are present elsewhere in the GDB were not deposited near or on this structural high. TD total depth Red coal. In the far western part of the study area the Fort Union 14, gas from coal: Greater Green River, Piceance, Powder River, MD 11-1 49-037-25975 MD GR(ft) Res upper zone Fox Hills Sandstone and Lewis Shale, Undifferentiated 15, and Nuttal coal bed names were used following Madden (1989). and Raton Basins, Western United States: Bureau of Economic Tie Well Monument Lake 4.0 mi GR(ft) Res 9000 gas show 25-1 49-037-25727 T23N R93W S27 (A-A’) Wasatch & 9500 Geology and Gas Research Institute, Report of Investigations No. T22N R93W S11 2000 9500 9500 lower gas production The Fox Hills Sandstone contains marine and nearshore-marine The youngest Fort Union coals of the Overland Member are grouped Fivemile 49-037-25820 MD Echo Springs GR(ft) Res Battle Spring TD 11,656 ft oil production 228, 219 p. Champlin T22N R93W S25 3.2 mi MD 3.1 mi 1500 Lance Formation Lance sand and shale deposited by the last of the Cretaceous Interior as the Cherokee coal zone. These coals crop out near Riner on the east Echo N. State 23-1 GR Res Formations lower zone 222 G-8 5-16 49-037-25795 (ft) 9500 Seaway as it regressed toward the east (Gill and others, 1970; Pyles side of the GDB (Sanders, 1974), and are as deep as 3,700 ft (1,100 Well 16-2 MD (part) WOGCC, 2015, Wyoming Oil and Gas Conservation Commission 49-007-22860 49-007-22364 GR(ft) Res 1000 Upper Cretaceous Datum for stratigraphic cross sections is the top of the 49-037-24713 T21N R93W S23 ? 10000 10000 10000 and Slatt, 2008). The contact between the Fox Hills Sandstone m) in the northern part of the GDB. Where present, the Cherokee coal T19N R93W S33 2.6 mi T19N R93W S16 5.4 mi 5.0 mi 5.6 mi 2500 China Butte Member of the Fort Union Formation. website, at http://wogcc.state.wy.us/ T20N R93W S16 MD 1500 Fox Hills Ss. 2000 TD 12,371 ft Approximate distance between wells is in miles (mi), and and the overlying Lance Formation was marked above the highest zone of the Overland Member consists of a basal contiguous coal MD MD GR(ft) Res & Lewis Sh. GR(ft) Res GR(ft) Res MD ? 10000 depth is in feet (ft). Coal names are above corresponding GR(ft) Res 500 1000 ? TD 13,302 ft Fox Hills Ss. coal bed wherever possible. 1500 Upper Cherokee TD 12,800 ft ? 3000 & Lewis Sh. 2000 Cherokee 2500 TD 13,302 ft (part) Lower Cherokee ? 500 ? 500 1000 1500 ? 2000 Horse Butte 500 ? 3500 ? Upper Cherokee Cow Butte 2500 3000 Tie Well ? Horse Butte ? Cow Butte 1000 (E-E’) Tie Well 1000 1500 2000 Structure Contour Maps, Fort Union and Lance Formations ? 2500 Red Desert (F-F’) ? 1000 4000 Wells Blu 3000 14-1 3500

Mustang 103 102 101 100 99 98 97 96 95 94 92 91 90 103 102 101 100 99 98 97 96 95 94 92 91 90 103 102 101 100 99 98 97 96 95 94 93 92 91 90 89 5 Member Overland 13-4 Wamsutter 93 89 88 85 28 93 89 88 85 28 88 8 28 A 49-037-24780 Echo N. State A’ 1500 Unit 1 49-037-24884 32-13 1500 2000 2500 Well 16-2 3000 T20N R95W S14 Federal Depth Depth 1500 49-037-05773 T20N R96W S13 49-037-27673 Depth 4500 West 49-037-24713 East 27 27 27 MD 4-22-20-92 Subsea (ft) Subsea (ft) 3500 Middle T20N R97W S22 GR Res T20N R94W S13 Subsea (ft) 4000 CB700 MD (ft) T20N R93W S16 49-037-26285 basal sands Fort Union MD GR(ft) Res +7400 SP(ft) Res MD +7250 +7550 CB700 2000 Lower Middle 7.2 mi 6.9 mi 7.2 mi GR(ft) Res MD T20N R92W S22 2000 2500 3000 CB700 Middle GR Res 3500 Playa UT Almond 500 (ft) 2000 Fort Union Fort Union Tie Well 0 6 12 18 Miles 0 6 12 18 Miles -2000 0 6 12 18 Miles 5000 7.2 mi 500 3.2 mi MD A PA 4-21G 500 6.3 mi GR(ft) Res 26 26 26 4000 (D-D’) 4500 DATUM 49-037-05781 6.3 mi 0 3000 4000 2500 Playa Unit T20N R98W S21 500 ? 0 2500 3000 3500 500 Chicken 4000 1000 +4875 4000 3200 +3750 +2550 2500 Fillmore Ranch 5500 15-22B MD 1000 Champlin 252 25 25 25 Springs Big Red SP Res Cherokee 1000 3000 4500 Fillmore Creek (ft) Upper Cherokee 0 Fillmore Ranch 5000 approximate Union Formation Fort Cherokee 2000 -2000 49-037-05785 5.1 mi ? Amoco A 1 Red Rim Fillmore Creek Separation Cherokee contact at 5000 500 0 (S.L.) T20N R99W S22 Lower Cherokee 49-037-20810 1 2000 Muddy Creek 3000 Creek B 3.7 mi 1000 Cow Butte surface 4000 3000 3500 4000 1000 4500 1500 T20N R91W S27 7000 Separation Creek B MD 49-037-20889 3000 6000 Horse Butte 4 ? Lower Separation Creek Muddy SP(ft) Res ? 1500 Horse Butte 3.6 mi Wasatch & 24 24 2 Muddy Creek approximate 1500 T20N R90W S19 6000 2000 Riner Creek 1 5000 Lower Separation MD -2300 5500 Winegardner SP(ft) Res Battle Spring +2500 0 (S.L.) Creek contact at Lower Riner 500 1000 MD Formations 0 1 surface SP(ft) Res 2000 Olson 3500 1500 3500 4000 4500 1500 (part) 4000 0 Draw 5000 Riner 49-037-05788 2000 3500 ? 7000 23 23 23 6500 2000 Red Rim Lower Riner T20N R100W S24 2000 4000 5500 Red Rim 5000 4000 5000 2000 6000

4000 6000 6000 Daley Ranch 500 5400 Daley Ranch MD Nuttal? 1000 Lower SP(ft) Res 1500 7000 4000

6000 Red Rim

2000 4000 4500 5000 Member China Butte 500 5500 2000 7000 2 CB700 2500 CB700 ? 22 22 2 4000 7000 2500 500 7000 CB700 2500 6000 basal sands? 6500 2 1000 000 1500 2000 DATUM Mbr. Overland 4000 4500 5000 2500 1000 6000 6000 4500 5500 6000 2500 6000 21 21 21 Upper 3000 4500 7500 500 Chicken Springs 1000 7000 2000 Deadman 3000 3000 Fillmore 6500 Lower Deadman Upper Big Red Fillmore Ranch 7000 Fort Union 3 1500 Fillmore Ranch Ranch Fillmore 2000 ? Fort Union 2 2500 6000 Lower Big Red Fillmore Creek ? Creek 5000 3000 Muddy Creek Muddy Creek 2 1500 5000 5500 Red Rim 6000 7000 20 6500 3000 20 20 3500 6000 5000 8000 1000 Fort Union 3 1500 Muddy Creek Member 3500 Lower Separation Creek Separation Creek B 7000 3500 Separation 6000 7000 Fort Union 1 Riner Creek 1 Separation 7500 2000 Lower Separation Creek 2500 3000 Creek 2 6000 Riner 4000 5500 3500 5000 19 19 2000 19 5500 6000 6500 Lower Riner 2000 4000 7000 3500 4000 4000 6000 5500 8500 1500 Lower Riner 5000 4000 4000 2000 2000 4000 7500 Fort Union Formation Fort 8000 2500 Olson Draw 3000 3500 Red Rim Top of Fort Union Formation Top of China Butte Member Top of Lance Formation 6000 4000 Daly Ranch 18 18 18 6000 6500 7000 2500 Daley 7500 4000 A B C 4500 (200 ft contour interval) (400 ft contour interval) (400 ft contour interval) 6000 Ranch upper zone 9000 4500 2500 TD 3,220 ft 4500 8000 8500 3000 3500 4000 6500 4500 6500 7000 7500 3000 8000 4500 5000 6500 9500 5000 3000 5000 8500 ? TD 4,520 ft Isochore Maps, Fort Union Formation 9000 4000 4500 7000 5000 7000 7500 8000 3500 8500 ? 5000 5500 7000 103 102 101 100 99 98 97 96 95 94 93 92 91 90 89 88 85 103 102 101 100 99 98 97 96 95 94 93 92 91 90 89 88 85 10000 5500 3500 Structure contour maps of the (A) top of the Fort Union 28 28 TD 9,553 ft

5500 Red Rim Mbr. Member China Butte 9000 Formation, (B) top of the China Butte Member of the Fort 9500 Thickness (ft) Thickness (ft) member lower 5000 TD 9,820 ft 7500 TD 6,072 ft 5500 8000 lower zone 8500 4000 Union Formation, and (C) top of the Lance Formation. Con- 27 3000 27 9000 5500 3500 Formation Lance 6000 10500 6000 4000 6000 tours are relative to sea level (S.L.). Contours were generated 9500 ± 10000 ± Maps Explanation in ESRI’s ArcGIS using spline with barriers (faults), based ! 5500 ! ! ! 8000 6000 0 6 12 18 Miles 0 6 12 18 Miles 8500 9000 4500 ! ! 26 9500 on geophysical log correlations from wells (black dots) and 26 ! 6000 ! ! ! ! 6500 ! ! ! TD 10,330 ft 11000 6500 4500 Well—Used in this study TD 10,135 ft 10000 6500 outcrop interpolation at the outcrop. Sparse well data in the ! ! ! 1500 1750 ! ! ! ! 10500 upper zone ! Cross Section F-F’ ! Fault—Ball and bar on downthrown block north and northeast generated less certain contour information ! Cross Section A-A’ 6000 ! 25 TD 11,298 ft ! 25 ! 9500 5000 ! ! ! ! ! ! 10000 ! ! 6500 in these regions. The Wamsutter arch is visible on all three ! ! ! 7000 ! ! ! Thrust fault—Sawteeth on upper plate This is the easternmost cross section in the GDB. It shows, from south to north, a thickening 11500 5000 ! ! 7000 ! ! This cross section is sub-parallel to the Wamsutter arch and reflects the shallowest Fort Union Formation coal across 7000 10500 maps. On the eastern flank of the basin, progressive flattening 11000 ! ! ! ! ! of the Overland Member and a separation of the Cherokee coals. The basal sand package ! Lance Formation Lance ! ! ! ! the GDB. It highlights the two members of the Fort Union: the upper Fort Union is the Overland Member (with a ! ! Fort Union Formation outcrop—Includes ! from the steeply dipping Lance-Fort Union contact (C) to ! ! ! ! 0 ! ! ! ! ! 6500 0 !! ! ! ! TD 9,145 ft ! ! ! ! ! ! ! ! ! ! ! ! ! of the Overland maintains relative uniform thickness, but the China Butte Member thins ! ! Overland Member and China Butte ! 24 5500 ! ! 24 ! 10000 TD 12,850 ft basal sandstone package present in all but the western-most wells in the cross section), and the lower Fort Union ! ! ! ! ! ! ! ! 7000 ! ! ! ! the less-steeply dipping Fort Union-Wasatch contact (A) is ! 7500 ! ! ! ! Member ! ! ! ! ! ! ! 12000 lower member lower ! ! ! slightly toward the south. The China Butte coals are contiguous and thick, and become 5500 ! ! ! ! ! ! ! ! ! ! ! ! TD 12,371 ft ! ! ! ! ! is the China Butte Member. The Lance Formation is divided into a Red Rim Member at the top and the underlying ! ! ! 11000 7500 ! ! ! ! ! ! ! ! evident, suggesting that development of the eastern flank of ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! quite numerous in the northeast part of the GDB, a feature not observed in outcrop. The ! TD 13,718 ft ! ! ! ! Wells from WOGCC (2015). Faults and Fort Union (unnamed) lower member below. The cross section shows thicker units overall in the deeper part of the central ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 7000 the Great Divide Basin occurred during Fort Union deposition. ! ! ! ! ! ! ! ! ! ! ! 23 Formation outcrops modified from Love and Christiansen TD 13,438 ft ! ! 23 ! ! Red Rim Member of the Lance Formation is only present in the southern two thirds of lower zone ! ! ! 6000 ! ! ! ! ! ! ! ! basin, and a thinner China Butte Member and Lance Formation on the flank of the Rock Springs uplift. The Red ! ! ! TD 9,915 ft 7500 ! ! ! ! ! ! ! ! (1985). ! 12500 ! ! Fox Hills Ss. ! ! ! 6000 ! ! ! F-F’, as the Lance Formation thickens considerably into the northeast part of the basin. ! ! ! ! ! Rim Member of the Lance Formation does not reach the western third of the GDB, either due to non-deposition on 8000 ! ! ! ! ! ! & Lewis Sh. ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! (part) the structurally high Rock Springs uplift or erosion after deposition from later movement of the Rock Springs uplift. ! ! ! ! ! ! ! ! ! ! ! 7500 ! ! ! 22 ! ! 22 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! TD 14,871 ft Isochore (true vertical thickness) maps of the (D) Over- ! ! ! ! ! ! ! ! 6500 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 8000 ! TD 10,540 ft ! ! ! ! ! ! ! ! ! ! ! 6500 ! ! land Member and (E) China Butte Member. Maps were ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! TD 10,330 ft ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! generated in ESRI’s ArcGIS by subtracting the raster images ! ! ! ! ! ! Fox Hills Ss. ! ! ! ! ! ! ! ! ! ! ! ! 21 8000 ! ! ! ! 21 ! ! ! ! ! ! ! ! ! ! ! ! ! ! & Lewis Sh. ! ! ! ! ! 7000 generated from the creation of the structure contour maps. ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! (part) ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! Thinning on the east flank of the basin is partly an artifact ! ! ! ! ! ! ! ! ! ! ! ! ! TD 10,737 ft TD 12,030 ft ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! TD 11,682 ft ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! of sparse well control, but is also partly due to uplift of the ! ! ! ! ! ! !! ! ! ! ! ! ! ! !! ! ! ! ! ! !! ! ! ! ! ! !!! ! ! ! ! ! ! ! ! 20 ! ! ! 20 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! !! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! basin margin during Fort Union deposition. Thinning on the ! ! ! ! ! ! ! ! ! ! !! ! ! !!! ! !! ! ! !!! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! west side of the basin is the result of coeval movement and ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! Isopach Base! ! 19 uplift of the Rock Springs uplift, which was structurally high ! 19 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! during Fort Union time. The basin depocenter moved from ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! the east, along the flank of the Rawlins uplift during China ! ! ! ! ! ! ! ! ! ! ! ! ! China Butte Member! ! Overland Member ! ! ! ! 18 ! ! ! ! ! 18 ! ! ! ! Butte deposition, to the northeast during Overland deposition. D ! ! E ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !!! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

DISCLAIMERS ACKNOWLEDGMENTS STRATIGRAPHIC CROSS SECTIONS AND SUBSURFACE MODEL OF THE LANCE AND FORT UNION FORMATIONS, NOTICE TO USERS OF INFORMATION FROM THE NOTICE FOR OPEN FILE REPORTS PUBLISHED Users of these cross sections and maps are cautioned against using the data at scales different from those at which This work would not have been possible without significant collaboration. We sincerely appreci- WYOMING STATE GEOLOGICAL SURVEY BY THE WSGS the data were compiled. Using these data at a larger scale will not provide greater accuracy and is a misuse of the data. ate assistance from the following people: James Rodgers was instrumental in drafting, digitizing, and lay- The WSGS encourages the fair use of its material. We request that credit be expressly This WSGS Open File Report has not been technically reviewed or edited for out. Deirdre Ratigan aided in coal correlations and digitizing. Elizabeth Cola, Jeffrey Hannon, and James Staf- The Wyoming State Geological Survey (WSGS) and the State of Wyoming make no representation or war- given to the “Wyoming State Geological Survey” when citing information from conformity with WSGS standards or Federal Geographic Data Committee digital ford all helped with coal correlations. Jacob Carnes assisted with log digitization. Suzanne Luhr helped with editing. ranty, expressed or implied, regarding the use, accuracy, or completeness of the data presented herein, or this publication. Please contact the WSGS at 307-766-2286, ext. 224, or by email cartographic standards. Open File Reports are preliminary and usually require of a map printed from these data. The act of distribution shall not constitute such a warranty. The WSGS This study also significantly benefited from discussions with John Haacke, Robert Hettinger, and Mark Kirschbaum. Thanks to all. GREAT DIVIDE BASIN, WYOMING at [email protected] if you have questions about citing materials, preparing additional fieldwork and/or compilation and analysis; they are meant to be a first does not guarantee the digital data or any map printed from the data to be free of errors or inaccuracies. acknowledgments, or extensive use of this material. We appreciate your cooperation. release of information for public comment and review. The WSGS welcomes Partial support for this research was provided by the U.S. Geological Survey’s National Coal Resources Data System (NCRDS), any comments, suggestions, and contributions from users of the information. The WSGS and the State of Wyoming disclaim any responsibility or liability for interpretations made from under USGS award number G10AC00448. The views and conclusions contained in this document are those of the authors and by Individuals with disabilities who require an alternative form of this publica- these digital data or from any map printed from these digital data, and for any decisions based on the digi- should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government. tion should contact the WSGS. For the TTY relay operator call 800-877-9975. tal data or printed maps. The WSGS and the State of Wyoming retain and do not waive sovereign immunity. For more information about the WSGS or to order publications and maps, go to The use of or reference to trademarks, trade names, or other product or company names in this publication is for descriptive Ranie M. Lynds and Christopher J. Carroll www.wsgs. wyo.gov, call 307-766-2286, ext. 224, or email [email protected]. or informational purposes only, or is pursuant to licensing agreements between the WSGS or State of Wyoming and software Layout and design by James R. Rodgers or hardware developers/vendors, and does not imply endorsement of those products by the WSGS or the State of Wyoming. 2015