THE SLOPE (pALEOCENE) AND BULLION CREEK (PALEOCENE) FORMATIONS OF NORTH DAKOTA
by
Lee Clayton, C. G. Carlson, Walter L. Moore, Gerald Groenewold, F. D. Holland, Jr., and Stephen R. Moran
REPORT OF INVESTIGATION NO. 59
NORTH DAKOTA GEOLOGICAL SURVEY
E. A. Noble, State Geologist
1977 THE SLOPE (PALEOCENE) AND BULLION CREEK (PALEOCENE)
FORMATIONS OF NORTH DAKOTA
by
Lee Clayton, C. G. Carlson, Walter L. Moore, Gerald Groenewold, F. D. Holland, Jr., and Stephen R. Moran
REPORT OF INVESTIGATION NO. 59
NORTH DAKOTA GEOLOGICAL SURVEY
E. A. Noble, State Geologist
1977
Printed by Kaye's Inc. CONTENTS
Page ABSTRACT . 1
INTRODUCTION ...... 1
THE LUDLOW PROBLEM .... 1
SLOPE FORMATION (NEW NAME) ...... 7 Source of name 7 Type area and section ...... 7 Description ...... 7 Contacts 7 Thickness and regional extent 7 Differentiation ...... 9
THE TONGUE RIVER PROBLEM . 9
BULLION CREEK FORMATION (NEW NAME) . . 10 Source of name ...... 10 Type area and section , .,. 10 Description 10 Contacts 10 Regional extent...... 10 Thickness ...... 10 Differentiation ...... 10
REFERENCES ...... 13 ILLUSTRATIONS
Figure Page 1. Stratigraphic column incorporating revisions of the Fort Union Group as proposed in this paper 2
2. Location map 3
3. Generalized stratigraphic section from the North Cave Hills, South Dakota . 5
4. Diagrammatic cross sections showing alternative solutions to the Ludlow problem 6
5. Type section of the Slope Formation ..... 8
6. Type section of the Bullion Creek Formation 11 ABSTRACT The Slope Formation is a drab-colored, lignite-bearing sequence that Stratigraphic problems in correlating overlies either the Cannonball Formation the Ludlow and Tongue River Formations or the Ludlow Formation. It is separated between North Dakota and adjacent areas from the similar-looking, underlying are best resolved by a revision of the Ludlow Formation strata by the T Cross nomenclature and the introduction of two bed, which occurs at the top of the new formation names, the $lope Formation Ludlow. The sequence that is included in and the Bullion Creek Formation. The the Slope Formation has, in the past, been newly defined Slope Formation considered to be equivalent to the upper (Paleocene) consists of strata that have part of the Ludlow Formation or to part of been considered to be the upper part of the the Tongue River Formation. Ludlow Formation or part of the Tongue The Bullion Creek Formation consists River Formation. The newly defined of a bright-colored, lignite-bearing sequence Bullion Creek Formation (Paleocene) that occurs beneath the drab-colored consists of strata that have been considered Sentinel Butte Formation and above the to be equivalent to either the entire Tongue white marker zone at the top of the Slope River Formation or to the lower, middle, Formation. The sequence has been or upper part of the Tongue River considered to be equivalent to either the Formation. en t ire Tongue River Formation or, variously, to the lower, middle, or upper INTRODUCTION parts of the Tongue River Formation.
Over the years, many attempts have been made to correlate the complex THE LUDLOW PROBLEM sequence of continental deposits that make up the Fort Union Group over areas in The Ludlow was introduced by Lloyd which surface exposures are scarce and and Hares (1915) as a lignitic member testhole data were lacking. Most of the between the "Cannonball and Hell Creek Upper Cretaceous and Tertiary formations members of the Lance Formation" in in western North Dakota were introduced northwestern South Dakota and without designating specific type sections, southwestern North Dakota. Hares states and these poorly defined fonnation terms that the type locality is near the Ludlow have commonly been extended great post office (1928, p. 24) and later states (p. distances to other areas from their original 47) that the Giannonatti bed of localities without the benefit of detailed northwestern South Dakota corresponds to correlation or specific criteria for the T Cross bed of southwestern North recognition of formational boundaries. This Dakota. Hares restricted the term "Ludlow has led to placing contacts at different member" to bed'S below the "Cannonball horizons in different areas. member" in South Dakota; he mapped the With the completion of detailed field top of the Ludlow at a higher horizon in studies of Fort Union Group strata in western North Dakota. He considered a southwestern North Dakota and nearby sandstone bed to be the base of his areas recently, numerous stratigraphic "Tongue River member of the Fort Union inconsistencies have become apparent. Formation" in the Marmarth area, Several stratigraphic problems have arisen considering it to be similar to a sandstone in correlating the Ludlow and Tongue bed overlying the "Cannonball member" in River Formations between North Dakota exposures along the Cannonball River. and adjacent South Dakota and Montana. Moore (1976, p. 35), in detailed These problems can be best resolved by studies of these strata in Slope County (fig. revising the nomenclature and by 2), recognized a "white siliceous bed," introducing two new formation names, the which he described as aphanitic to Slope Formation and the Bullion Creek fine-grained quartz, a few centimetres to a Formation (fig. 1). few metres thick, white on fresh fractures, 2
White River Group Oligocene
Golden Valley Formation Eocene
Sentinel Butte Fm. > a. ~ ::J c ...0 Bu II ion Creek Fm. . (!) ~ - CI) c t- o Slope Fm. Paleocene c :::> -... Cannonball Fm. u..0 Ludlow Fm.
Hell Creek Formation Cretaceous
Figure 1. Stratigraphic column incorporating revisions of the Fort Union Group as proposed in this paper. but buff or yellowish on weathered Creek in Slope Coonty. Also, the lower surfaces. The siliceous bed is commonly member of the Golden Valley Formation, overlain by lignite or Iignitic shale, and it where the whitish silty clay is capped by a overlies a variety of sedimen t types, which siliceous bed such as at Pretty Rock Butte are bleached white. The bleached zone (T131N, R89W), is similar in appearance, ranges from a few centimetres to as much but it is separated from the white marker as ten metres thick. Moore found this white zone by a stratigraphic interval sufficiently marker zone to be a useful marker for the thick to eliminate the possibility of top of the Ludlow in Slope County, confusion. Siliceous zones bearing petrified although he noted that Hares (p. 48) wood also occur at various horizons within considered this "quartzite" marker to be the lignite-bearing strata. These are not just below the H bed, about 60 feet above associated with white bleached zones, so the base of his Tongue River in the they are not likely to be confused with the Marmarth area. Carlson, in agreement with white marker zone. White siliceous beds Moore, found the white marker zone to be about 50 to 80 feet above typical a useful marker in mapping the contact Cannonball Formation sediment in areas of between the Ludlow and Tongue River poor bedrock exposures in Adams, Grant, Formations in Bowman, Adams, Grant, and and Morton Counties (fig. 2) are considered Morton Counties. to be equivalent to the white marker zone. The white marker zone is relatively Moore divided the Ludlow into lower persistent, but it is not unique within the and upper units, with the T Cross bed as lignite-bearing zone. Moore noted small the base of the upper unit. He noted surface exposures of a similar material well brackish-water units in Slope County. A 3 below the white marker zone along Horse to 6-foot-thick bed of clay directly overlies 3
EXPLANATION • TYPE SECTION BULLION CREEK FORMATION
& TYPE SECTION SLOPE FORMATION
x EXPOSURES OF WHITE MARKER ZONE @ TYPE AREA OF LUDLOW FORMATION ~""""" ~/ '-...... '- ~~ , 1------\ r ,;~-...Jr) ! Me KEN Z I E I , ----I ~ L_-, I Me LEAN I ,I'" 1"'''°""" "V£H :'",--,--( . --__ -1.. DUN N !.., MER C E R '- Wo.~llurn -' i! ! I ---~ '1 I I I I I I ...--' i ,BILLINGS, I 'OLIVER \7r-. I I I 1_ I II -J U\ i;AOLl~i~-! l--L--~D;k,n.on ',------\ \ lIt STARK I 1 !_8~'~ '" 'BULLIOJ I M 0 R T ~ N ~ ,..I-I\.. BUTTE I ~ " ----T:-~::GER-I------i )~ ! i -II (HOff E 'Ir S LOP E. I .~ G RAN T,l~ FR:EK ~_ ..K i I C'4NNON'~LL I_-)I/~~~l : i---~~RTH -~------Jr---II-.!'-----Ii~~~ ~---~::~~~-----J I CAVE -Ludlow HILLS ::i I HARDING I 1 I Figure 2. Map of southwest North Dakota and Harding County, South Dakota showing locations of type sections for the Bullion Creek and Slope Fonnations and type area for the Ludlow Fonnation. Exposures of the white marker zone are designa ted by crosses. 4 the T Cross bed and an "oyster clay brackish-water clay; this has been used to and lignite" bed occurs approximately 1SO divide the Ludlow into upper and lower feet above the T Cross bed. The white members. Alternative D represents current marker zone is well above the brackish beds practice in westem North Dakota, except in this area. In South Dakota, the Ludlow that Ludlow is restricted to the western has been limited to the nonmarine strata area; and new names are introduced for the between the Hell Creek and cannonball nonmarine strata above and below the strata. In the absence of cannonball strata, Cannonball Formation to the east. a sandstone bed near the horizon of the Alternative E would restrict Ludlow to the Giannonatti bed has been considered to be strata between the Hell Creek and the base of the Tongue River. The white Cannonball Formations. It would introduce marker zone is present in the North Cave a new name for the strata between the Hills of South Dakota (fig. 3) where it is Cannonball Formation and the white present well above the "basal Tongue River marker zone in the eastern area and a new sand" and also above "lignite F" of name for the strata between the Hell Creek Pipiringos and others (1965, p. A6). and the white marker zone in the western Some of the various criteria for area. Alternative F would extend Montana placing the Ludlow-Tongue River contact names into North Dakota for the strata are shown as alternatives in a series of between the Hell Creek and Tongue River diagrams (Hg. 4). Alternatives A to C Formations. Alternative G continues the represent current or past practice while use of Ludlow as it has been used in the alternatives D to G represent options eastern area and extends it westward; a new considered in this paper. Altemative A name is required for the strata between the shows the Tongue River on Ludlow in the T Cross bed and the white marker zone, western part of the area and on Cannonball and this new name is extended eastward in. the eastem part of the area. This between the Cannonball Formation and the alternative illustrates common practice in white marker zone. the past. A' shows the actual position of Al ternative A is inappropriate because the white marker zone and the stratigraphic recent mapping (Carlson, Clayton, relationship of the Cannonball Fonnation unpublished) has shown that the to the nonmarine strata; the base of the bright/drab contact and the white marker Tongue River has therefore been placed at zone can be traced eastward, well above the different stratigraphic horizons in the top of the Cannonball Formation; it does western and eastern areas as shown in A". not accurately depict the actual Altemative B corrects this nomenclature stratigraphic relationship. Alternatives B problem by extending the term Ludlow and 0 seem inappropriate because the above the Cannonball and subdividing the Ludlow Formation in South Dakota is Ludlow into upper and lower members typically restricted to beds below the where the Cannonball is present. Cannonball Formation or below beds Alternative C illustrates current practice in considered to be equivalent to the T Cross South Dakota, where Ludlow is used either bed in North Dakota (Lloyd and Hares, for the nonmarine strata between the Hell 1915; Stevenson, 1956; Pipiringos, Creek and Cannonball Formations or for Chisholm, and Kepferle, 1965). Alternative strata between the Hell Creek and either C follows South Dakota usage, but it is the Giannonatti lignite bed (Stevenson, inappropriate because (1) it places the base 1956) or the "Carbonate No.2 lignite bed" of the Tongue River Formation much (Pipiringos and others, 1965) where the lower than it has usually been placed in Cannonball is absent. southwestem North Dakota, and (2) it In North Dakota, we now recognize includes drab beds in the otherwise bright mappable nonmarine strata both above and Tongue River. below the Cannonball Formation in the Alternative E has the advantage of interval between the Hell Creek Fonnation restricting the long-established Ludlow to and the white marker zone. In the western the strata between the Hell Creek and area the T Cross bed is overlain by Cannonball Formations, but it has the 5 SECTION NEAR LUDLOW, SOUTH DAKOTA (Modified from Pipirinooi and others, 1965, A6) z o a: o I- 300 ~ a:: 0 ...J 0 0 ~ u.. ...J --100 THICKNESS ~ IN FEET UJ a::UJ u ...J ...J UJ :I: Figure 3. Generalized stratigraphic section from the North Cave Hills near Ludlow, South Dakota. 0' TONGUE RI VER FM. TONGUE RIVER FM. TONGUE RIVER LUDLOW LOWER MBR. LUDLOW HELL CREEK FM. HELL CREEK "F M. HELL CREEK FM. A B E TONGUE RIVER FM. TONGUE RIVER TONGUE "'illli"«I"'I'" I , I I I 1 I I It, I " I,, x RIVER FM. TYPE + LUDLOW + LUDLOW TULLOCK HELL CREEK FM. HELL CREEK FM. HELL CREEK FM. AI c F TONGUE TONGUE RIVER TONGUE RIVER RI VER I. iii iii iii Ii I I I I i III i I I FM. LUDLOW LUDLOW FM. LUDLOW HELL CREEK F M. HELL CREEK FM. HE-LL -CREEK FM. A" o G Figure 4. Diagrammatic cross sections shOWing altemative solutions to the Ludlow problem. Alternatives A through C represent past or current practice; D through G are options considered in this paper. 7 disadvantage of requiring two new names. sedimentary rock over burned lignite beds Alternative F has the disadvantage of is brick red, the unit is predominantly drab, dropping the term Ludlow, and it extends brownish gray. the Montana terms long distances from Contac ts. - The Slope Formation rests their type areas. The Lebo in Montana is on the Cannonball Formation in central generally described as a drab shale unit North Dakota and on the Ludlow between the light-colored Tullock and Formation in western North Dakota where Tongue River strata. The Lebo contains the Cannonball is generally absent. In its very little lignite. In North Dakota, the type area in South Dakota, the top of the interval between the Hell Creek and the T Ludlow Formation is considered to be Cross bed is generally drab, the interval approximately at the top of "Carbonate between the T Cross bed and the white No.2 coal bed" (Pipiringos, Chisholm, and marker zone is mostly drab with some Kepferle, 1965) or near the top of the bright beds, and the strata above the white Giannonatti bed (Stevenson, 1956). The marker zone is generally bright. Giannonatti bed has been considered We prefer to use Alternative G to equivalent to the T Cross bed in North solve the Ludlow problem. It restricts Dakota (Hares, 1928, p. 47). The top of Ludlow to strata between the Hell Creek the T Cross bed is here considered to be at and Cannonball in the eastern area and to the con tact between the Ludlow the interval between the Hell Creek and T Formation and the Slope Formation in Cross bed in the western area. This usage is areas where the Cannonball Formation is consistent with usage in the Ludlow type absent. Moore (1976. p. 23) placed the area in northwestern South Dakota. contact between his upper and lower Alternative G requires the introduction of a Ludlow slightly lower at the base of the T new name for the strata between the T Cross bed so that all of the thick lignite Cross bed and the white marker zone. This beds would be in his upper unit, which new unit is here named the Slope essentially corresponds to the Slope Formation. Formation. The Slope Formation is apparently unconformably overlain by the Bullion SLOPE FORMATION (NEW NAME) Creek Formation (Moore, 1976). The top of the Slope Formation is marked by a Source of name. -Slope County, widespread, white bleached zone, which is North Dakota, where the formation is best commonly associated with a siliceous bed exposed. (the white marker zone of the previous Type area and section. -The type area discussion ). is T105N, R135W, in Slope County. The Thickness and regional extent. -The type section (fIg. 5) is in the south-facing Slope Formation is about 90 metres thick exposure in the northwest comer of section in its type area. It is exposed along the 15 and the southwest comer of sec 10, western margin of the Williston basin into T105N, R135W. eastern Montana, apparently as far south as Description. -The Slope Formation, the Cedar Creek anticline. Outcrops are like the other nonmarine Paleocene poor around the southeastern margin of the formations of the Williston basin, consists basin, but the formation is known to of alternating beds of clay, silt, sand, and extend northward into Morton County, lignite (Moore, 1976). Most of the where it has thinned to about 20 metres. sediment is unlithiHed or only moderately The maximum northeastward extent of the lithified. The clay and silt is unbedded or Slope Form::tion is unknown, but the thinly laminated but nonfissile. The sand formation probably becomes unmappable has plane bedding or large-scale or near Washburn in McLean County. The small-scale crossbedding. Less than a tenth lower part of the Slope Formation is of the unit is lignite, which typically occurs present in northwestern South Dakota, in beds less than 4 metres thick. Although where it is included in the Tongue River light yellowish beds are present and the Formation. 8 RI 05 W Golden VolleL.Q..O...:.. _ '. ---S\opeco-.- , I , ' Type Section z 10 ~~ 200- -= --=- =--: Z ~ ~ :-:-:~:'.'.:.. : ", 0 =.. -=- -- Yule Bed t- 50 - _'._'. -=. .- - -- .. ~.-----:- 20 w .'. Cool . ~ . . , C O -1 en Figure 5. Type section of the Slope Formation. ... '" " ...... " . 0-+=--=-=.--,"""'1 ---- T Cr 055 Bed c ------o _._._.'-'--' -_._. ~ 0 10 o - E , " 'l:l '"' ' ..... \ " j 0 ...J lL. 9 Differen tia tion. -The Slope (Hansen, 1956). Later, Royse (1967) Formation is distinguished from the argued that the Sentinel Butte is mappable overlying Bullion Creek Formation by its and should be re-elevated to formation color; in outcrop the Slope Formation is rank. He recommended that the "Tongue largely drab, brownish gray, while the River Fonnation" in North Dakota be Bullion Creek is largely light yellow. In restricted (again) to the bright-colored beds areas of poor outcrop, the contact can under the Sentinel Butte Formation. This sometimes be identified (Moore, 1976, p. recommendation was followed by later 35-36) by the presence of the white marker North Dakota geologists (Carlson, 1969; zone at the top of the Slope Formation. Jacob, 1976). This bed could probably be confused only The base of the bright-colored unit with the lower member of the Golden (Royse's "Tongue River") was long ago Valley Formation. placed at the base of a sandstone bed in southwestern North Dakota (Hares, 1928, p. 24). Most geolop'sts mapping in the area THE TONGUE RIVER PROBLEM where Cannonbal is present have also recognized a sandstone bed at the base of The term Tongue River was the bright-colored beds. It now appears introduced by Taff (1909, p. 129) to refer that this sandstone bed is below the to a group of lignite beds in the Sheridan previously mentioned white marker zone coal field, Wyoming, In that area these beds and is either a shoreline facies of the were reported as about 850 feet thick. In receding Cannonball sea or a fluvial deposit the adjacent Moorhead coal field, Montana, of the Slope Formation. Bryson and Bass (1973) include 1,400 to In the North Cave Hills of South 1,600 feet of lignite-bearing strata in the Dakota the white marker zone is present "Tongue River member" of the "Fort above "coal zone F H (Pipiringos and others, Union Formation." In both areas the 1965, p. A6). Vertebrate remains have been Tongue River is overlain by the Wasatch collected from "D" bed and "E" bed Fonnation of Eocene age. sandstones indicating a brackish or marine The Slope Formation and the Sentinel environment (probably the Cannonball Butte Formation are both drab-eolored Formation). This suggests that the interval units that are separated from each other by between the white marker zone and a bright-eolored unit. Leonard (1908) and "Carbonate No. 2 coal bed," which is Leonard and Smith (1909) were perhaps included in the Tongue River Formation in the first to recognize this bright-colored South Dakota (fig. 3), is probably unit in North Dakota; they referred to this equivalent to the newly defined Slope unit as "middle Fort Union." Thorn and Formation of North Dakota. Dobbin (1924) correlated it with the In Montana, Baker (1929), Oliver "Tongue River member" of the "Fort (1957), and Bryson and Bass (1973) have Union Formation" in the Powder River noted that the upper part of the Tongue basin for the following reasons: both units River has some beds that are as drab are about the same age, both have a similar colored as the overlying Eocene beds; lithology, both are generally bright colore~, perhaps the Sentinel Butte Formation is both are underlain by drab-eolored units, equivalent to the upper part of type and both were thought to be overlain by Tongue River. In the measured section of Eocene beds. "Tongue River" was the Bryson and Bass (1973, p. 13) petrified generally acce pted name for the wood is noted through about the upper bright-colored unit in North Dakota until 475 feet of section down to just below the Brown (1948) showed that the Sentinel Dietz lignite. Below this horizon petrified Butte Formation is Paleocene, not Eocene. wood was not noted. In North Dakota, The Sentinel Butte was then reduced in petrified wood zones are common in the rank, and both it and the unnamed, Sentinel Butte strata, but they are rarely bright-colored unit were considered to be found in the bright-colored strata below members of the Tongue River Fonnation the Sentinel Butte. 10 Thus, the interval between the white Formation is conformably overlain by the marker zone and the color change along the Sentinel Butte Formation. The Bullion Little Missouri River appears to be only a Creek rests apparently unconformably on part of the strata mapped as Tongue River the white marker zone at the top of the Formation in South Dakota or Tongue Slope Formation. River member of the Fort Union Regional extent. - The Bullion Creek Formation in Montana. To avoid the Formation occurs throughout western confusion of using different criteria for North Dakota. A few small patches occur defining the Tongue River in different in northwestern South Dakota, and areas, the bright-colored beds between the equivalent sediment occurs in southeastern white marker zone and the drab Sentinel Saskatchewan where it is included in the Butte Formation are here named the Ravenscrag Formation. The Bullion Creek Bullion Creek Formation. Formation can be recognized westward into Montana at least as far as the Cedar Creek anticline. Southwest of the Cedar BULLION CREEK FORMATION Creek anticline a facies change may occur. (NEW NAME) Both the Bullion Creek and Sentinel Butte Formations are probably equivalent to at Source of name. -Bullion Creek, 5 least part of the Tongue River member of kilometres north of the type section. the Fort Union Formation of the Powder Type area and section. -The type area River basin. is within a radius of 15 kilometres of Thickness. -In the type area, the Bullion Butte. The type section (fig. 6) is Bullion Creek Formation is nearly 100 the Red Hills section of Crawford (1967) in metres thick. It is about 200 metres thick the southwest quarter of section 27, the near the middle of the Williston basin and southeast quarter of section 28, the thins to about 50 metres around the south northeast quarter of section 33, and the and east edges of the basin. northwest quarter of section 34, T137N, Differentiation. -The Bullion Creek R103W, Golden Valley County, North Formation is distinguished from the Dakota (Crawford called this unit the overlying Sentinel Butte Formation by "lower member of the Tongue River color; in outcrop the Bullion Creek is Formation"). generally light yellow, whereas the Sentinel Description. -The Bullion Creek Butte is generally drab, grayish brown. Two Formation consists of alternating beds of beds (the "Upper Yellow Bed" and the clay, silt, sand, and lignite. The clay and silt "Lower Yellow Bed") within the Sentinel beds are unbedded to sharply bedded but Butte Formation are similar in color to the are generally non fissile; laminations a Bullion Creek Formation, and a few beds millimetre or less in thickness are common. within the Bullion Creek Formation are About a ten th of the formation is sand; the nearly as dark as the Sentinel Butte bottom part is especially sandy. The sand Formation; even so, color is the most typically has both small-scale and distinctive characteristic for differentiation large-scale, commonly trough-shaped, of the two formations. In areas of poor crossbedding. A small proportion of the outcrop. and in the subsurface, where the sand is cemented, forming ledges or butte sediment is unoxidized and the color caprock. Less than a tenth of the formation distinction is less obvious (the Sentinel is lignite. Lignite beds are typically about a Butte is olive or bluish gray, whereas the metre thick, but beds at least 4 metres Bullion Creek is brownish gray in fresh. thick are present in many areas. Where moist, unoxidized samples). other lignite beds have burned, the overlying lithologic characteristics may be useful; sediment has been baked, producing bright they have been described in detail by red colors. Most of the Bullion Creek Royse (1967 and 1970) and Jacob (1973 Formation has a light yellowish hue in and 1975). outcrop. The Bullion Creek Formation is Contacts. -The Bullion Creek distinguished from the underlying Slope 11 Senrme I Butte Fm R 103 W z '-'-' o - Type 80 Section 250 - - - ---------- - --- -- 70 . _. ------- --------- ----- ---- lOO --_. o I MI. I 60 =- -= -:...-.= I - - - o KM. --- -- - Red baked sediment [illj over burned - out lign ite. en en -= -=- -=---.-: o ••'· CI> 50 -=- -=--:..-= ~ c D.. '. Sand oX 150 = o =-.:::.::: W F?J u.J E=J Si It ". _ '. :. J ~ ~ Clay -- - a::: o o ~ u ~ Lignite tOO _- _':--H,:":,,,:-. 30- =:-:-.--:--= __ --_. -- - --- _._-_._.. . z -- 20 =-= =.=-; o - Figure 6. 'TYpe section of the Bullion Creek Formation. _._.-_._-. . - 10 =.' .-=,'. =-. -- ....- -- . " . :.' . '. '.... O-l~::-::::-::~-i....,,..,.--- - - - Slope ------- Fm. 12 Formation by color (the Slope is generally Formation consists of Paleocene (Brown, darker) and by the presence of a white 1962) fluvial-plain deposits, including marker zone below the unconformity overbank, flood basin, and point-bar between the two units. sediment (Jacob. 1976). Age and origin. - The Bullion Creek 13 REFERENCES environments of Paleocene Tongue River Formation, western North Baker, A A., 1929, A northward extension Dakota: Am. Assoc. Petroleum Geol. of the Sheridan coal field, Big Horn Bull. v. 57, no. 6, p. 1038-1052. and Rosebud Counties, Montana: U.S. Jacob, A. F., 1975, Criteria for Geo!. Survey Bull. 806-B, p. 15-67. differentiating the Tongue River and Barclay, C. S. V., 1970, Preliminary Sentinel Butte Formations geologic map of the Glen Ullin (Paleocene), North Dakota: North quadrangle, Morton County, North Dakota Geol. Survey Rpt. of Inv. 53, Dakota: U.S. Geo!. Survey, open-me 55 p. report. Jacob, A. F., 1976, Geology of the upper Barclay, C. S. V., 1971, Preliminary part of the Fort Union Group geologic map of the Dengate (Paleocene), Williston basin, with quadrangle, Morton County, North reference to uranium: North Dakota Dakota: U.S. Geo!. Survey open-file Geo!. Survey Rpt. of Inv. 58, 49 p. report. Leonard, A G., 1908, The geology of Brown, R. W., 1948, Correlation of the southwestern North Dakota with Sentinel Butte shale in western North special reference to the coal: North Dakota: Am. Assoc. of Petroleum Dakota Geol. Survey 5th Biennial Geol. Bull., v. 32, p. 1265-1274. Report, p. 27-114. Brown, R. W., 1962, Paleocene flora of the Leonard, A G., and Smith, C. D., 1909, Rocky Mountains and Great plains: The Sentinel Butte lignite field, North U.S. Geol. Survey Prof. Paper 374, Dakota and Montana: U.S. Geo!. 119 p. Survey Bull. 341, p. 15-35. Bryson, R. P., and Bass, N. W., 1973, Lloyd, E. R., and Hares, C. J., 1915, The Geology of Moorhead coal field, Cannonball marine member of the Powder River, Big Hom, and Rosebud Lance Formation of North and South Counties, Montana: U.S. Geo!. Survey Dakota and its bearing on the Bull. 1338, 116 p. Lance-Laramie problem: Jour. of Carlson, C. G., 1969, Bedrock geologic mar Geol., v. 23, p. 523-547. of North Dakota: North Dakota Geo . Moore, W. L., 1976, The stratigraphy and Survey Misc. Map 10. environments of deposition of the Clayton, Lee, 1972, Roadlog: North Cretaceous Hell Creek Formation Dakota Geol. Survey Misc. Series 50, (reconnaissance) and the Paleocene p. 2-30. Ludlow Form ation (de tailed), Crawford, J. W., 1967, Stratigraphy and southwestern North Dakota: North sedimentology of the Tongue River Dakota Geol. Survey Rpt. of Inv. 56, Formation (Paleocene), southeast 40 p. Golden Valley County, North Dakota: Olive, W. W., 1957, The Spotted Horse University of North Dakota master's coalfield, Sheridan and Campbell thesis, 73 p. Counties, Wyoming: U.S. Geo!. Cvancara, A. M., 1976, Geology of the Survey Bull. 1050, 83 p. Cannonball Formation (Paleocene) in Pipiringos, G. N., Chisholm, w. A., and the williston basin, with reference to Kepferle, R. c., 1965, Geology and uranium potential: North Dakota uranium deposits in the Cave Hills Geol. Survey Rpt. ofInv. 57, 22 p. area, Harding County, South Dakota: Hansen, Miller, 1956, Geologic map of U.S. Geol. Survey Prof. Paper 476-A, North Dakota: North Dakota Geo!. 64 p. Survey Misc. Map 2. Royse, C. F., Jr., 1967, Tongue Hares, C. J., 1928, Geology and lignite River-Sentinel Butte contact: North resources of the Marmarth field, Dakota Geol. Survey Rpt. of Inv. 45, southwestern North Dakota: U.S. 53 p. Geo!. Survey Bull. 775, 110 p. Smith, Henry L., 1973, Geologic map and Jacob, A. F., 1973, Depositional lignite deposits of the New Salem 14 quadrangle, Morton County, North Morton and Grant Counties, North Dakota: U.S. GeoI. Survey Map C-62. Dakota: U.S. Geol. Survey Map C-53. Stephens, E. Vernon, 1970a, Geologic map Stevenson, R. E., 1956, Areal geology of of the Heart Butte NW quadrangle, the Ludlow quadrangle: South Dakota Morton and Grant Counties, North Geol. Survey. Dakota: U.S. Geol. Survey Map C-52. Taff, J. A., 1909, The Sheridan coal field Stephens, E. Vernon, 1970b, Geologic map Wyoming: U.S. Geol. Survey Bull. of the Heart Butte quadrangle, 341-B, p. 123-150.