GEOLOGY OF THE FOX HILLS FORMATION
(LATE CRETACEOUS) IN THE WILLISTON BASIN OF NORTH
DAKOTA, WITH REFERENCE TO URANIUM POTENTIAL
by
A. M. CVANCARA
UNNERSITY OF NORTIl DAKOTA DEPARTMENT OF GEOLOGY GRAND FORKS, NORTII DAKOTA 58202
REPORT OF INVESTIGATION NO. 5S
NORTH DAKOTA GEOLOGICAL SURVEY
E. A. Noble, State Geologist
1976
PREPARED FOR mE U.S. ENERGY RESEARCH AND DEVELOPMENT ADMINISTRATION GRAND JUNCTION OFFICE UNDER CONTRACT NO. AT(05-1)-1633 G1O-1633-1
CONTENTS
ABSTRACT ~ag~
INTRODUCTION . 1
ACKNOWLEDGMENTS .... 1
MATERIALS AND METHODS 2
STRATIGRAPHY ...... 2 Definition and relationship to other rock units .. . . 2 Distribution ...... 3 Lithology and sedimentary structures .. 3 Persistence of lithologic units ...... 7 Contacts ...... , 7 Thickness ...... 8
STRUcrURE ... 8
PALEONTOLOGY . 9 Fossil groups . 9 Occurrence of fossils · ..... , 9
AGE AND CORRELATION 10
DEPOSITIONAL ENVIRONMENTS ...... 10
URANIUM POTENTIAL . · 12 General ...... , 12 Fox Hills Formation . 13
REFERENCES . · 14 ILLUSTRATIONS
Figure Page 1. Fox Hills and adjacent Formations in North Dakota (modified from Carlson, 1973) . . . 4
2. Schematic stratigraphic column of Fox Hills Formation in North Dakota (modified slightly from Erickson, 1974, p. 144). The Linton Member was named by Klett and Erickson (1976)...... 5
Plate 1. Northwest-southeast cross section (Dunn to Sioux Counties) of Fox Hills Formation in southwestern North Dakota ...... (in pocket)
2. Southwest-northeast cross section (Bowman to Pierce Counties) of Fox Hills Formation in western North Dakota (in pocket)
3. Southwest-northeast cross section (Adams to Burleigh Counties) of Fox Hills Formation in southwestern North Dakota (in pocket)
4. Isopach map of Fox Hills Formation in North Dakota (in pocket) ABSTRACT model is followed for the deposition of Fox Hills sediments. The lower Fox Hills, The Fox Hills Formation is a marine of the Trail City and Timber Lake and brackish sequence ofprimarily medium Members, is believed to represent the lower and fine clastics within the Late Cretaceous to upper shoreface of a barrier bar Montana Group. In the Williston basin of environment. The upper Fox Hills, of the North Dakota, four members (in ascending Iron Lightning and Linton Members, order) are recognized: Trail City, Timber suggests deposition within a deltaic Lake, Iron Lightning (with Bullhead and complex as does the overlying Hell Creek Colgate lithofacies), and Linton. The Fox Formation. Specific environments may Hills conformably overlies the Pierre Shale have included tidal channel, bay, estuary, and conformably and disconformably prodelta, and various environments underlies and interfingers with the Hell associated with a delta-plain and the Creek Formation; it occurs in about the seaward part of a distributary system. western two-thirds of the state. Principal Water depths may have been a few hundred lithology includes poorly consolidated fee t and less. sandy shale and siltstone (Trail City); fine Since the Hell Creek, Fox Hills, and to medium-grained, poorly consolidated Pierre Formations are at least in part and well-indurated sandstone (Timber penecontemporaneous, a variety of Lake); interbedded, poorly consolidated depositional environments were in areal sandstone and shale or siltstone (Bullhead jUx tap osition during Late Cretaceous time. lithofacies); medium-grained, poorly Streams originating or passing through consolidated, muddy sandstone (Colgate coastal plain bogs (of the Hell Creek) could lithofacies); and very fine- to fine-grained, have carried uranium ions (derived from indurated, siliceous sandstone (Linton), A volcanic materials) into bays, lagoons, or conspicuous volcanic ash occurs in the the open sea where they were deposited formation and rises in the section from syngenetically. Epigenetic uranium may central Emmons County to southeastern occur in finer clastics in the Fox Hills that Morton County. Lignite beds occur in the directly underlie a volcanic ash bed. subsurface in part of southwestern North Dakota. Considerable lithologic variation INTRODUCTION occurs in the subsurface away from the main outcrop area in the south-central part The 1Fox- Hills Formation is a marine of the state, and the members are difficult d brac£'ish unit of mostlr,. medi1!-!!WUl. to trace. The thickest recognized sequence 'f1!tLf1asticrdeposited primarily in the is 391 feet in northwestern Hettinger northern Great Plains during.....1a!e County; sequences thicker than 300 feet Q.etaJ:e_ous_ time. It conformably oyerlie_ also occur in two other areas-Dunn and 'tk Pierre S~e and_b.,pth c.Qn(orm3blx ai!ci Mercer, and Burke and Ward Counties. unconformaoly ~derlies the HelrCree Nearly 300 feet of Fox Hills has also been Formation. reported as far east as western Pierce This report summarizes the geology of County. Fox Hills rocks generally dip the Fox Hills Formation in North Dakota, about 10-20 feet per mile toward the the stratigraphy of which is based on center of the Williston basin; regionally, dip previous surface information and recent values may be considerably greater (few to subsurface data, and evaluates its potential many degrees on the flanks of the Cedar for uranium. Creek an tieline) or less. Principal macrofossils are bivalve and gastropod ACKNOWLEDGMENTS mollusks that occur primarily in limestone and sandstone concretions and indurated This study was supported by part of sandstone. A barrier bar (or island)-deltaic grant AT (05-1)-1633 from the u.s. 2
Atomic Energy Commission. The North may not always be present at the top of the Dakota State Water Commission provided Fox Hills (e.g., as indicated in pI. 2, section unpublished subsurface stratigraphic data 13) and the thicknesses gained from logs in for Dunn, Grant, Morton, and Sioux places may be less than they are in reality. Counties. The North Dakota Geological Thicknesses of the unit from logs was also Survey provided the use of mechanical logs partly gauged by a continuous plot of of oil and gas wells. C. G. Carlson, North values on a working map as the study Dakota Geological Survey, provided useful progressed. Depths to the top of the Fox aid and advice during the course of this Hills and other similar data are on We in study. F. D. Holland, Jr., Department of the Department of Geology, University of Geology, University of North Dakota, North Dakota. The letter designation in the reviewed the manuscript. legal description of well or outcrop localities is that of the North Dakota State MATERIALS AND METHODS Water Commission.
The cross sections prepared for this STRATIGRAPHY report (pIs. 1-3) are, with One exception, based exclusively on recent unpublished Definition and Relationship and published subsurface data of the North to Other Rock Units Dakota State Water Commission because outcrop sections are rarely complete. These The Fox Hills Formation, originally subsurface data, although based on "Formation No.5" (Meek and Hayden, samples, are, in certain cases, difficult to 1856, p. 63), was named by Meek and use because of inconsistent or incomplete Hay den ( 1 8 6 1 , P . 4 1 9 , 4 2 7) for the descriptions. Contacts of the Fox Hills youngest marine sandy deposits in the were changed in several instances from western interior. The name is from Fox those placed by previous worurs. The Hills (or Fox Ridge), an ill-defined part of datum for the cross sections is the top of the divide between the Cheyenne and the Pierre Shale. The isopach map (pI. 4) is Moreau Rivers in Ziebach and Dewey based on the same type of Water Counties, north-central South Dakota. Commission data as well as on mechanical Waage (1968, f1£;. 1) has outlined the logs; about 200 control points were used approximate "historical type locality," and for this map. About 90 electric logs proposed a larger type or reference area (resistivity, spontaneous potential, and (ftg. 2) that includes the Fox Hills outcrop laterolog) from oil and gas wells were used in most of Ziebach and Dewel Counties to supplement the Water Commission and in Corson County south 0 the valley subsurface data. On these logs, the of Oak Creek. Pierre-Fox Hills contact was picked where Good stratigraphic discussions of the the curves gradually but notably began to formation are by Waage (1968) in the type depart from the shale line as they are area and by Feldmann (1972) and Erickson traced from the Pierre Shale into the (1971, 1974) in North Dakota. overly ing Fox Hills. In the Water Waage (1968, p. 18-48) has Commission wells, this contact was picked comprehensively discussed the history of so as to include shale and silty shale in the study of the formation in the type area, Pierre and siltstone and sandstone in the including the development of the Fox Hills. The upper contact was more classification and nomenclature of the unit difficult to pick consistently on the logs; it (his fIg. 4). His proposed revision of was generally taken where the spontaneous subdivision includes three members (in potential and resistivity decreased abruptly ascending order): Trail City, Timber Lake, at the top of what was interpreted to be a and Iron Lightning. Feldmann (1972, p. sandstone bed about 20 feet or more in 5-15) has traced the history of study of the thickness. A pronounced sandstone bed Fox Hills in North Dakota. His subdivision 3 of the formation recognized three members sandy shale or siltstone that passes upward (in ascending order), the Timber Lake, to brown- and greenish-gray-weathering, Bullhead, and Colgate. Erickson (1974, fIg. poorly consolidated sandstone (Fisher, 3) recognized a subdivision essentially that 1952, p. 10) with abundantly fossiliferous, of Waage (1968, fig. 5) with the addition of medium to dark gray, limestone another member, the Linton (Klett and concretions that weather light tan to light Erickson, 1976), at the top of the sequence gray. These concretions are as large as more (fig. 2). I rrefer to follow the subdivision than three feet in diameter. Erickson scheme 0 Erickson (1974) in North (1974, p. 145) recognized this member in a Dakota. few outcrops in Emmons, Logan, and The Fox Hills Formation overlies the sou theastern Sioux Counties, but Pierre Shale with gradational contact. It Feldmann (1972) did not 'recognize it in conformably (Waage, 1968, p. 119) and the state. In the type area of South Dakota, unconformably (Frye, 1969, p. 20-24) the Trail City consists of two lithofa.cies, underlies the Hell Creek Formation. The the Little Eagle and Irish Creek. The Little Fox Hills and Pierre Formations constitute Eagle lithofacies is of gray-weathering the Montana Group, which might include "clayey silt and clayey sand" containing the Hell Creek Formation as well (Gill and abundantly fossiliferous concretions and Cobban, 1973, p. 12). generally lacking well defined bedding; this lithofacies occurs generally in the eastern Distribution part of the type area. The Irish Creek lithofacies is of gray-weathering "clay and The Fox Hills FormatiO'n occurs in silt with some fine-grained sand" in which .w~r!:Nor~andSouth "1?ak~1 eastern fossiliferous concretions are lacking or rare yoming, eastern Montana, and eastern and thin interbedding is well defined; this Colorado south to the Colorado Springs lithofacies generally occurs in the western area (Cobban and Reeside, 1952; Gill and part of the type area (Waage, 1968, p. Cobban, 1973). In North Dakota this unit 61-73). occurs in about the western two-thirds of Overlying the Trail City with the state (pI. 4), occurring primarily in the gradational contact is the Timber Lake subsubsmface. The outcrop area (fig. 1) is Member, which consists primarily of buff primarily in a slightly arcuate band to yellowish, Hne- to medium-grained, extending north-south across the state at poorly consolidated sandstone that about mid-length, with a smaller area in the weathers yellowish or reddish brown. southwesternmost part of the state. Most Lenticular ledges of reddish-brown of the northern two-thirds of the primary weathering, well-indurated sandstone occur outcrop band, however, is covered by throughout but are more numerous toward glacial drift. The best outcrops are in the the top of the member. Well-indurated, south-central part of the state in Sioux, a bun dan t 1y fossiliferous, sandstone Morton, and Emmons Counties in the concretions are common. Lenticular beds drainage of the Missouri River (Feldmann, (up to several inches thick) of 1972, fig. 1). well-indurated, red- or orange-weathering claystone and the trace fossil Ophiomorpha Lithology and Sedimentary Structures are also conspicuous, and are particularly abundant near the top of the member, The following summary of the where trough and tabl.llar crossbedding is lithology and sedimentary structures of the also characteristic. The sandstone is lithic Fox Hills Formation is largely after graywacke and subgraywacke. Sand grains Erickson (1974), Feldmann (1972), and consist mostly of about 25-30% quartz, Waage (1968). 35-40% rock fragments, 10-15% feldspar, The lower Fox Hills in North Dakota 0-5% biotite, and a minor amount of consists of the Trail City and Timber Lake glauconite; the remainder of the sandstone Members (fig. 2). The Trail City, the basal is of interstitial limonite or calcite member, is of brown- to gray-weathering (Feldmann, 1972, p. 25-26). Lindberg -.-.:;'-I-~' ~9:' ~q~'- ~ 49,104'r, -•..0 '03' . " ,-'""'r~'.".;<",-<·<:'l',--, -,,..- - , ---'., ~. Crosby """·I:.,<,['~'~r>v.v • o~F 0 I V ~ 0 E I 1-' ,~~'ijl<-><~c'Z~, ~~/,,1r·.~/,'->e-'~~ ~ ;'v';,,~v,*1.-t,rr(,~ , ,I ~ C~",~,,(' ~ • I ->,"r" ~(.,_.& R' ( 4 L ' '\;', r v. (, • ,I. >" l A "- I p £. M 8 I N A
t1f._-- ' • .A '4"<"'- '\-t",',2 A<,,-«." ",':' .: . --.""._.-; " ~>'<)~r:f€?_.',~,',-.
1:.·.~J Hell Creek Formation ~ Fox Hills Formation lij.¥,;'} Pierre Formation
Figure 1. Fox Hills and adjacent Formations in North Dakota (modified from CaIlson, 1973). RECl eRE
I~:' -.~ ~ LM - LL I NTON BR.7~~~:?-;-;Q?fS;.,;-:-';)?ffi; (f) ..J ..J (!) I z x z ~ rr. ~ a:: C) CD cr I"... •• ~-- _ w ..J ~ ,". ------ Cl.. let Cl.. Z ~.; :-:-==-=---_-:: :::> o .-:'~ ------ ~ a:: ~ --~------'0:: .. .. " '0 LL en ...J ~ ...J cr V) al ::I: ..J ~ ..J w I- ~ x ~ o X ....J lL. {Z a:: w a:: CD w :!: ~ I- 0 ....J
Figure 2. Schematic stratigraphic column of Fox Hills Formation in North Dakota (modified slightly from Ertckson, 1974, p. 144). The Linton Member was named by Klett and Erickson (1976). . 6
(1944) identified 16 heavy minerals associated laterally. The Bullhead is of presumably from this member from 10 "thinly interbedded clay, silt and very samples at two sections in southern Morton fine-grained sand that weathers to a County; green amphibole was the markedly banded, light-brownish-gray characteristic heavy mineral. The TimbdT outcrop"; the Colgate is of "very fme- to Lake Member has been recognized in all the medium-grained, clayey, subgraywacke major areas of outcrops to as far west as, sand that usually weathers to fluted Bowman County. light-gray or grayish-white The upper Fox Hills consists of the outcrops..."(Waage, 1968, p. 116). Iron Lightning and Linton Members (fig. Sandy beds in the Bullhead are commonly 2). Within the Iron Lightning are two crossbedded, and trough crossbedding so-called lithofacies, the Bullhead and (mostly) and tabular crossbedding is Colgate (Waage, 1968). Feldmann (1972) common in the Colgate. The sand fraction treated these lithofacies as members. The of the Colgate is generally 30-50%, of Bullhead, conformably overlying the mostly quartz with the remainder rock Timber Lake Member, is of interbedded, fragments, chiefly quartzite, foliated rock poorly consolidated sandstone and siltstone fragments, and chert (Waage, 1968, p. or shale. The sandstone interbeds, about 121-123). Lindberg (1944) identified 15 1-11 inches thick, are buff, thinly heavy minerals presumably from the laminated, and weather buff or reddish Colgate from 21 samples at four sections in buff; the sandstone is fine-grained and a Morton and Sioux Counties, North Dakota; subgraywacke. The siltstone or shale green amphibole and epidote were the interbeds, about 1-7 inches thick, are dominant heavy minerals. chocolate brown and weather light gTay or The uppermost member of the Fox buff. Lignite laminae or very thin beds Hills is the Linton (fig. 2). It consists of occur throughout this lithofacies light olive gray to grayish brown, very fine (Feldmann, 1972, p. 28-30). Lindberg to fine-grained, subangular, moderately to (1944) identified 16 heavy minerals poorly sorted, indurated, siliceous presumably from this lithofacies from eight sandstone that weathers light gray to samples at three sections in Morton and brown. The unit is generally massive but Sioux Counties; epidote and green flat bedding and large-scale trough(?) or amphibole were the dominant heavy planar crossbedding are present locally. minerals. Ripple marks and mud cracks are rare. The The Colgate lithofacies overlies the sandstone is compositionally a Bullhead or completely or partially replaces subgraywacke to a feldspathic arenite, it laterally as in southern Morton County contains generally about 28% matrix and a along the lower Cannonball River (Laird substantial percentage of volcanic shards. and Mitchell, 1942, p. 6). In places, the The Linton Member is known to cap buttes Colgate overlies the Bullhead in Emmons and eastern Sioux Counties, disconformably, as in northern Sioux North Dakota, and extends southward well County (134-81-33b; Feldmann, 1972, p. into the type area of the Fox Hills in South 30) and may form channels within it Dakota (Klett and Erickson, 1976). (Erickson, 1972, pI. 1). The Colgate is A volcanic ash occurs within the Fox characteristically of medium-grained, Hills Fonnation in central and southern white, muddy graywacke with uncommon, Emmons, northeastern Sioux, and thin laminae or beds of lignitic shale. southeastern Morton Counties (Artzner, Weathered surfaces are characteristically 1974, fIg. 2). The ash is about 80% volcanic fluted (Feldmann, 1972, p. 31). The glass, 10% quartz, 7% feldspar, 1% Colgate is recognized in outcrop in hornblende, and 2% minor constituents. Bowman County and at least as far east as This ash apparently rises up section as it is north-central Sioux County (134-81-33; traced from east to west (Feldmann, 1972, Feldmann, 1972, p. 31). In the type area of fIg. 11). It occurs from very near the base the Fox Hills in South Dakota, the of the Fox Hills in central Emmons County Bullhead and Colgate are intimately (Fisher, 1952, p. 15) to about 48 feet 7
above the Fox Hills-Hell Creek contact in sequence of about 10 feet; gray-weathering southeastern Morton County (Artzner, shale of the Pierre gives way to buff- or 1974, p. 7). yellow-weathering fine-grained sandstone I have not attempted to portray the with b~Jwnish shale or siltstone of the Fox members in subsurface sections (pIs. 1-3) Hills (Feldmann, 1972, p. 23-25). In the because of the difficulty in recognizing type area in South Dakota, the contact is them. In well 9 (pI. 1) perhaps the Trail drawn at the lithologic change from silty City, Timber Lake, and Lightning shale of the upper Pierre to clayey siltstone (Bullhead lithofacies) Members are of the lower Fox Hills. This corresponds to represented. In wen 22 (pI. 3), perhaps the a marked concentration of jarosite ("lower Trail City, Timber Lake, Iron Lightning (? jarositic zone"), which should not be Bullhead lithofacies), and Linton Members confused with other occurrences ofjarosite are represented. In general, away from the in the lower Fox Hills and upper Pierre main outcrop area in the south-central part (Waage, 1968, p. 57-58, fig. 7). In the of the state, considerable lithologic subsurface of North Dakota, I have variation exists, and the various members included reported siltstones in the lowest seem to be difficult to recognize. The Fox Hills and shales or silty shales in the relatively thick lignites reported in certain uppermost Pierre. On electric logs, the sections (e.g., pI. 1, sections 5 and 6) are Pierre-Fox Hills contact was drawn where particularly conspicuous. the curves gradually but notably began to depart from the shale line as they are Persistence of Lithologic Units traced from the Pierre into the overlying Fox Hills. In the main outcrop area in the =-eFOx Hills-Hell Creek contact i south-central part of the state, the various North Dakota in outcrop is generally, members of the Fox Hills have been traced picked at the base of a l!gnite or lignitic a few to several tens of miles as implied in shaleJ(Fel~--;um,19-n--: p~32), Jf:Hanitic "- ...... -..-o~ the previous section. The volcanic ash bed s_~d~ton~(Frye, 1969,.p. 20-2~; fIg-so 3-4). is distributed over an area of about 600 Euher poorly consohdated mterbedded square miles (Artzner, 1974, p. 7) in sandstone and shale (Bullhead lithofacies); Emmons, Morton, and Sioux Counties. In poorly consolidated white sandstone the subsurface, away from the main area of (Colgate lithofacies); indurated, light gray exposure, there seems to be decreasing to brown sandstone (Linton Member); or persistence of recognizable members as well volcanic ash (Frye, 1969, p. 20) may be at as individual beds. the top of the Fox Hills. The contact is both gradational and erosional. Along the Contacts valley of the Missouri River and its tributaries south of Bismarck, North In North Dakota, the Pierre-Fox Hills Dakota, the contact is gradational, and the contact is gradational. It is poorly exposed Fox Hills and Hell Creek interfmger in in the state and is best seen near Linton in places as in southern Morton County Emmons County (132-76-17d) and on the (134-80-21d). In the Little Missouri Valley east flank of the Cedar Creek anticline in in Slope and Bowman Counties, the Bowman County (131-106-4bb). At the contact is gradational or erosional (Frye, Emmons County locality, the contact, in 1969, fig. 4, also p. 20-22). In the type area going up section, is marked by the first of the Fox Hills in South Dakota, the appearance of layers of jarosite. At this upper contact is placed "at the base of the general level, sandy or silty shale of the first appreciably thick lignite or lignitic Pierre changes gradually to fine- to clay or shale" (Waage, 1968, p. 118). The medium-grained sandstone of the Fox Hills. contact is considered to be gradational; The contact is also about 10-12 feet below locally, in the type area, interfmgering of the lowest concretions of the lower Fox the Hell Creek and Fox Hills occurs within Hills. At the Bowman County locality, the an interval of a few tens of feet and at a gradational contact occurs through a much larger scale to the west (Waage, 1968, 8 p. 119, pI. 11). County; Laird and Mitchell, 1942, p. 6) In the subsurface cross sections (pIs. and the Colgate lithofacies is at least 40 1-3), I have generally not been able to place feet thick (Bowman County; Feldmann, the upper contact at the base of lignitic 1972, p. 31). The Linton Member is up to lithology. This lithology generally did not about 23 feet thick but averages about 6.5 exist (or was not reported) at about the feet; it is known to thin westward in Sioux level where the top of the Fox Hills might County (Klett and Erickson, 1976). The be expected based on projected thicknesses volcanic ash is up to more than 40 feet of this formation and younger formations thick in central Emmons County (Artzner, in adjacent wells. On electric logs, the 1974, fig. 4) and thinner elsewhere. upper contact was generally taken where the spontaneous potential and resistivity STRUCTURE decreased abruptly at the top of what was interpreted to be a sandstone bed about 20 An overview of structure affecting the feet or more in thickness. Because a Fox Hills Formation in North Dakota is pronounced sandstone bed may not always provided by Anderson (1969) and occur at the top of the formation, this Osterwald and Dean (1957). The major procedure may have resulted in erroneous structural feature is the thicknesses in places. north-nonhwest-trending Williston basin. Two main structural lows within the basin Thickness occur in the vicinity of williston in McKenzie and Williams Counties and in a The area of greatest thickness of the region centered along the common Fox Hills Formation in North Dakota boundary of Dunn and Mercer Counties appears to be in Bowman, Slope, Hettinger, (Anderson, 1969). The two main structural and possibly Grant Counties (pI. 4). I have highs within the basin are the interpreted a maximum thickness of 391 northwest-trending Cedar Creek anticline in feet in northwestern Hettinger County (pI. the southwesternmost part of the state and 2, well 12). Two other thick areas, with the north-trending Nesson anticline in the thicknesses greater than 300 feet, occur northwestern part (Sandberg, 1962, p. 10). primarily in Mercer and Dunn Counties and The regional dip toward the center of in Burke and Ward Counties (pI. 4). The the Williston basin is generally about 10-20 formation thins markedly southwestward feet per mile but may be less or along the flanks of the Cedar Creek considerably higher in the vicinity of local anticline in western Bowman and Slope or regional structures. Dips on the Fox Counties. In western Pierce County the Hills on the Cedar Creek anticline are 5-200 reported Fox Hills is nearly 300 feet thick on the west limb and 30 or less on the east (pI. 2, well 16). This locality is not too limb (Hares, 1928, p. 44). Along the east distant from the eastern limit of the Fox and west flanks of the Nesson anticline the Hills (pI. 4), implying that the formation regional dip is about 71 feet per mile probably once extended considerably (Anderson, 1969). In southern Morton farther eastward. County, using the base of the Ludlow as In outcrop, the thickness of the Trail datum, the regional dip is about 15 feet per City Member is poorly known but seems to mile to the north or northwest, and small be at least 75 feet thick (Fisher, 1952, p. domes and noses are superimposed on this 10); it thins northward from the type area structure (Laird and Mitchell, 1942,p. 38). (Waage, 1968, p. 58). The Timber Lake In Emmons County, using the base of the Member is at least 128 feet thick (Sioux Linton Member of the Fox Hills as datum, County; Feldmann, 1972, p. 25); it the regional dip is generally 10-20 feet per thickens northeastward from the type area mile to the northwest but dips up to 50 (South Dakota) at the expense of the Trail feet per mile are common (Fisher, 1952, p. City Member (Waage, 1968, p. 91). The 29). In Burleigh County the Fox Hills has a Bullhead lithofacies of the Iron Lightning regional dip of about 14-15 feet per mile to Member is at least 112 feet thick (Morton the west and northwest (Kume and Hansen, 9
1965, p. 42-43). In the Souris River area of to be comprehensive.) Mollusks, chiefly north-central North Dakota, Upper bivalves and gastropods, are the most Cretaceous and Tertiary strata are believed frequently found macro-organisms. to lie within a broad, northwest-trending syncline whose axis is approximately in the Occurrence of Fossils position of the eastern part of the Souris River loop. Within the syncline are minor In the type area of South Dakota, in folds and undulations. Steepest dips occur the Trail City and lower part of the Timber near the Coteau du Missouri (may mark the Lake Member, most macrofossils occur in edge of the southwestern limb) and limestone concretions. In the upper part of decrease northeastward, so that 10 miles the Timber Lake Member and the Iron from the escarpment the strata are nearly Lightning Member, macrofossils occur horizontal (Lemke, 1960, p. 108). primarily in shellbeds or are scattered Besides the large scale and small scale through the matrix (Speden, 1970, p.1S). structures mentioned above, numerous In the Trail City and lower Timber Lake, other small scale structures, particularly several fossil zones restricted to concretions folds, faults and joints, are known to affect have been recognized. From oldest to Upper Cretaceous and Tertiary strata youngest, they are: Lower nicolleti (many summarized, for example, by Assemblage Zone, Limopsis-Pseudoptera Osterwald and Dean, 1957). Assemblage Zone, Upper nicolleti Assemblage Zone, Protocardia-Oxytoma PALEONTOLOGY Assemblage Zone, Nucula layer, Abyssinus concretions, Sphenodiscus layer, Cucullaea Fossil Groups Assemblage Zone, and Cymbophora-Tellinimera Assemblage Zone. The Fox Hills biota consists of Most of the zones or assemblages are foraminiferids (Lemke, 1960, p. 27; Mello, interpreted to be essentially isochronous. A 1969), a sponge (borings; Palubniak, 1972), notable exception is the overlying bryozoans (Palubniak, 1972), linguloid Tancredia-Ophiomorpha biofacies of the brachiopods (Meek, 1876, p. 10; Mello, upper Timber Lake (Waage, 1968, p. 54-56, 1969, p. 38), mollusks (Cvancara, 1956; 153; Speden, 1970, p. 10-12, 16). Erickson, 1974; Feldmann, 1967; Meek, In North Dakota, macrofossils occur 1876; Palubniak, 1972; Speden, 1970; principally in limestone and sandstone Waage, 1965), annelid worms (shell blisters, concretions and well indurated, lenticular burrows; Palubniak, 1972), a limulid sandstone. Most fossiliferous exposures are arthropod (Holland, Erickson, and O'Brien, in south-central North Dakota; those in 1975), barnacles (borings; Palubniak, Bowman County in the southwestern part 1972), ostracodes (Lemke, 1960, p. 27), of the state are essentially unfossiliferous the crustacean burrow Ophiomorpha (Erickson, 1971, p. 12). (Land, 1972, p. 38, 49; Waage, 1968, pI. The fossil zonation in North Dakota is 8), an echinoid (Holland and Feldmann, not as well known as in the type area of 1967), vertebrates (sharks, other fishes, South Dakota, but at least five assemblages crocodiles and turtles and other have been recognized (Feldmann, 1972, p. vertebrates; Palubniak, 1972; Waage, 1968, 41-43). In the lower "thirty to forty feet of p. 127, pI. 12), various trace fossils the Timber Lake Member" (p. 41) (= Trail (A renicolites, Cylindrichnus?, City Member as used here) is an assemblage Rhizocorallium; Land, 1972, p. 41,39, and of Scaphites (Hoploscaphites) nicoletti, 32), dinoflagellates and hystrichospaerids Limopsis, "Gervillia" and other mollusks (Artzner, 1974), and various lower and similar to the lowest two assemblage zones higher plants (Artzner, 1974; Brown, 1939; of Waage (1968). In the middle Timber Klett and Erickson, 1976; Knowlton, Lake (up to about 50 feet below the top) is 1916). (The references given above to an assemblage of Nucula, Sphenodiscus, documen t the existence of various Cucullaea, and other mollusks organisms in the Fox Hills are not intended corresponding to perhaps several zones in 10 the type area of South Dakota. The upper Boissevain Formation (southern Manitoba; part of the Timber Lake is less fossiliferous Williams and Burk, 1961, p. 169,174-175). than it is below; it is characterized by an Selected approximate correlatives in the assemblage of Ophiomorpha, Tancredia, Atlantic Coastal Province are the Red Bank Crassostrea, and other mollusks depending Sandstone (New Jersey) and Pedee on locality. This assemblage presumably Formation (North and South Carolina) corresponds to the Tancredia-Ophiomorpha (summarized by Murray, 1961, p. 360). biofacies of Waage (1968). The Bullhead Selected probable correlatives in the Gulf lithofacies of the Iron Lightning Member is Coastal Province are the Corsicana Marl and the least fossiliferous unit of the Fox Hills Kemp Clay (both in Texas; Stephenson, in North Dakota; it contains an assemblage 1941, p. 26, 29) and the Arkadelphia Marl of such fossils as vertebrate remains and (Arkansas, Louisiana, and Texas; oyster fragments. The Colgate lithofacies is Stephenson, 1941, p. 29). generally unfossiliferous but may contain an assemblage of abundant oysters DEPOSITIONAL ENVIRONMENTS (Crassostrea), Corbicula, and other mollusks in places. In addition to these During much of the Late Cretaceous, assemblages is that of the Linton Member. the western interior was covered by an Faunal remains are rare in the member; but epicontinental sea that extended from the common Equisetum, mangrove-like root Gulf of Mexico to the Arctic Ocean and systems, and other plant remains are from the present Rocky Mountains to characteristic (Klett and Erickson, 1976). about eastern Minnesota (Gill and Cobban, 1973, fIg. 1). A cordilleran highland AGE AND CORRELATION flanked the epicontinental sea on the west and served as a source of sediments The age and correlation of the Fox deposited to the east. During this time, Hills Formation has been discussed by variations in the rate of epeirogenic Erickson (1974, p. 146-149) and Waage subsidence, amount of orogenic activity, (1968, p. 139-146). Although the and eustatic change of sea level resulted in formation generally has been considered four major transgressive-regressive cycles Maestrichtian (latest Cretaceous) (e.g., (McGookey et al., 1972; Weimer, 1960). Cobban and Reeside, 1952), it is unclear The Fox Hills is the record of a regressive what part of the Maestrichtian is phase of the last major cycle. Regression represented (Waage, 1968, p. 143). was generally to the east but regionally to Jeletzky (1962, p. 1006) said the lower the north, south, and west as well. The Fox part of the Fox Hills was Early Hills regression from Montana is believed to Maestrichtian in age and showed (figs. 1-2) have begun about 72 millionyears ago and that part of the Fox Hills was also Late to have taken about 2.5 million years. It Maestrichtian. Recendy, Gill and Cobban was slow at fIrst, averaging about 35 miles (1973, fig. 12) have given the age of the per million years, but near the end the Fox Hills as generally Early Maestrichtian. strand line moved more than 250 miles in Several correlatives or possible less than 0.5 million years (Gill and correlatives of the Fox Hills occur in North Cobban, 1973, p. 28, 33-34, fIgs. 18-19). America. In the western interior, selected As the Fox Hills was being deposited, correlative units are the Horsethief and deeper-water marine sediments of the Lennep Formations (central and western Pierre Formation were being laid down Montana; Gill and Cobban, 1973, fig. 9), generally to the east and largely continental Dad Sandstone Member of the Lewis shale sediments of the Hell Creek Formation (south-central Wyoming; Gill and Cobban, were being deposited generally to the west 1973, p. 20), Trinidad Sandstone (McGookey et al., 1972, fig. 50). (southeastern Colorado and northeastern The continental climate in North New Mexico), Lion Canyon Sandstone America during the Late Cretaceous was Member of the Williams Fork Formation possibly largely sub tropical (data (McGookey et al., 1972, fig. SO), and the summarized by Dott and Batten, 1971, p. 11
384-385 and fig. 13.43; Sloan, 1970, p. commonly tabular, and trough 428-429). A sharp climatic zonation may crossbedded, Ophiomorpha-bearing not have existed, although seasonal we:ather sandstone of the upper Timber Lake is changes may have occurred. Ocean suggestive of the middle and upper temperatures may have been on the order shoreface environment. Concentrations of of 60-75 0 F in present middle latitudes worn and oriented mollusks in the (Dott and Batten, 1971, p. 384-385). In well-indurated sandstones of the upper North Dakota, the Fox Hills Formation Timber Lake imply periodic storms was possibly deposited adjacent to (Erickson, 1971, p. 44-48). Paleocurrent lowlands supporting vegetation growing analysis of cross-strata in the upper Timber within a humid, subtropical to tropical Lake indicate primary marine currents climate (Artzner, 1974, p. 41, 43). coming from the northeast (Chayes and Prevailing winds may have been from the Erickson, 1973) and moving sandy west (Dott and Batten, 1971, fig. 13.43). If sediment well into the type area (Waage, so, the source of the volcanic ash in the 1968, figs. 19-23). Fox Hills of North Dakota may have been Waage (1968) interpreted the upper the Elkhorn Mountains and Deer Creek Fox Hills as a deltaic sequence that volcanic centers in western and southern overstepped the barrier bar sequence upon Montana (Gill and Cobban, 1973, fig. 19). regression. Hubert, Butera, and Rice (1972) A barrier bar (or island)-deltaic have proposed a deltaic model for the model has been proposed for the Fox Hills somewhat older Parkman Sandstone in the Formation in the type area of South Powder River basin of Wyoming. The upper Dakota (Waage, 1968). This model has Fox Hills seems to reflect a similar been accepted, with modification, by depositional setting. Evidence in South Erickson (1971), Feldmann (1972), and Dakota for a deltaic sequence includes Speden (1970). I, too, accept this general correlative units to the southwest of the model with little modification and type area bearing lignite and Ophiomorpha, elaboration. a sequence similar to present-day deltaic In the outcrop area of the Fox Hills in successions including thin and regular southern North Dakota, the Trail City and bedding and contorted bedding, abundant Timber Lake Members of the lower Fox plant remains, and marine and brackish Hills suggest a barrier bar or barrier island animal fossils that are generally sparse and sequence (characteristics summarized by of low species diversity. In addition, the Spearing, 1974). A barrier island sequence upper Fox Hills sequence passes upward has also been recognized for part of the and interfmgers with the Hell Creek Fox Hills in Wyoming (e.g., Land, 1972). sequence. In south-central North Dakota Evidence in North Dakota includes a the Hell Creek consists of marine, brackish, sequence that generally and gradually freshwater, and terrestrial sediments that becomes coarser grained upward (in going indicate deposition within a deltaic upward from the Trail City to the Timber complex on a coastal plain (Frye, 1967). Lake and in going upward within the This deltaic complex is apparently that Timber Lake), mostly horizontal bedding labelled the "Sheridan delta" by Gill and in the lower part of the sequence and Cobban (1973, fIg. 19). This is one of three common crossbedding near or at the upper or possibly four deltaic complexes that part, and common to abundant fossils of affected sedimentation in the Rocky near normal salinity (Feldmann, 1972, p. Mountain region during Late Cretaceous 50). The interbedded shale, siltstone, and time (Weimer, 1970). Waage (1968) did not sandstone of the Trail City Member and the recognize a strict lagoonal facies because lower Timber Lake Member suggests (p. 154-155) the Timber Lake was not deposition in the lower shoreface or recognizable in places where the Iron "transition zone"; the sandstone interbeds Lightning Member persists, the contact were probably deposited during storms between the Iron Lightning and Timber (Reineck and Singh, 1973, p. 285, Lake Members was not observed to be 307-308). The moderately- to well-sorted, gradational, and the Colgate lithofacies 12 appears to directly overlie the Timber Lake water depth by using the Pierre-Fox Hills at several places. contact as the base of the I generally agree with Waage's (1968) coarsening-upward sequence and assuming deltaic complex but suggest that at least the top of the Timber Lake Member to part of the interbedded sandstone and shale represent the approximate position of sea or siltstone of the Bullhead lithofacies level. This approach gives a water depth of represents a lagoonal facies, at least in parts at least 240 feet (upper part of section of south-central North Dakota and possibly incomplete) for a composite section of the within the northern part of the type area. lower Fox Hills (sections 38, 30, 196,199) In the outcrop area of North Dakota, the in western Dewey County, South Dakota Timber Lake-Bullhead contact is (Waage, 1968, figs. 25, 15). This same gradational (Feldmann, 1972, p. 28). It is section suggests a wave base of more than also possible, in places at least, that a 140 feet (thickness of Timber Lake) at this barrier island, lagoon, and delta-complex locality. were all in existence concurrently as where In the subsurface, to the north and the Guadalupe River enters the Texas Gulf northwest of the main outcrop area in (Donaldson, Martin, and Kanes, 1970). The south-central North Dakota, the Fox Hills Bullhead lithofacies, therefore, may have sequence appears to become more variable. been deposited within the delta front, This implies a greater compleXity of prodelta, bay, or lagoon environments. The depositional environments. The presence of commonly crossbedded, muddy sandstone lignite in the sequence at wells 4, 5, 6, 12, of the Colgate lithofacies, occurring and 18 (pIs. 1-3) suggests the influence of a commonly as channel mls as well as beds com plex of delta-plain environments and containing brackish and marine fossils, similar to what produced the lignite-bearing suggests deposition within a tidal channel Fox Hills in west-central South Dakota or distributary (Reineck and Singh, 1973, (Pettyjohn, 1967). p. 268) system. The generally massive sandstone of the Linton Member, URANIUM POTENTIAL containing common Equisetum and mangrove-like root systems but rare faunal General remains, suggests deposition within an estuarine, tidal channel, or deltaic Denson and Gill (1965) summarized distributary system (Klett and Erickson, the uranium occurrences in the Williston 1976). basin except those in the Cave Hills of Water depths for the Fox Hills South Dakota, which have been described sequence can be inferred from different by Pipiringos, Chisholm, and Kepferle approaches. On the basis of comparing (1965). Noble (1973) discussed uranium depth preferences of Fox Hills bivalve production in North Dakota. Estimated genera with living analogues, the maximum reserves in the basin of rock containing 0.1 depth for the deposition of Fox Hills percent uranium are greater than 1 million sediments has been approximated at 80 tons (Denson and Gill, 1965, p. 64). fathoms or 480 feet (Feldmann, 1972, p. Uranium in the basin occurs primarily 44). The presence of Ophiomorpha in in impure lignite and lignitic shale (Vine, well-sorted sandstone (as in the upper 1962) but has been found also in Timber Lake) indicates intertidal or carbonaceous siltstone, phosphatic shallow subtidal depths, but somewhat claystone, and sandstone. Generally, a greater depths in poorly sorted sandstone thick sandstone directly overlies or (Weimer and Hoyt, 1964, p. 766). underlies the uranium-bearing host rock. Assuming minimal compaction and The richer deposits are aligned about subsidence, the thickness of the sediments north-south along the axis of the Williston may be used to estimate water depth for basin. The more significant deposits, presumed barrier island sequences (Klein, containing 0.1 percent or more uranium, 1974). If the lower Fox Hills is a barrier occur in the Cave Hills (northern Harding island sequence, one might extrapolate a County, South Dakota; Ludlow and 13
Tongue River Formations), Slim Buttes into ~s or lagoons or out into the 0Een (southeastern Harding County, South sea. (J'he source of the uraniumIons m~ Dakota; Ludlow Formation), and along the ave been the volcanic materials, now i Little Missouri River escarpment in the the form of bentonite and bentonid vicinity of Saddle Butte and Rocky Ridge d~e!1J~,~ln...the ~_eJ1.creek FormatioJ) (eastern Billings and northwestern Stark The uranyl humates may have ~n Counties, North Dakota; Sentinel Butte concentrated as a flocculant precipitated Formation). All significant uranium by the action of sea water (Vine, 1962, p. deposits are less than 300 feet 161), or plant debris and other organic stratigraphically below the base of the matter may have extracted uranyl ions out pre-Oligocene unconformity or its of solution. Following this model, one projected base (Vine, 1962, p. 141-142). might search for syngenetic uranium Overlying this unconformity are middle primarily in the interbedded mudstone and and late Tertiary rocks containing volcanic sandstone sequence of the Bullhead materials. A common belief (e.g., Denson lithofacies that contains laminae of lignite and Gill, 1956) is that these volcanic and other organic material. Secondarily, materials were the source of the uranium. uranium could be present in the sandy Groundwater leached the uranium from the shale or siltstone of the Trail City Member volcanic materials and carried it downward or perhaps the shale of the uppermost and laterally. Lignite and carbonaceous Pierre Formation. rocks served as receptors that may have Epigenetic uranium might be searched extracted uranium by ion exchange or by for in the Fox Hills below the volcanic ash the formation of organometallic that is known to occur in central and compounds. Uranium mineralization may southern Emmons, northeastern Sioux, and have occurred since Oligocene (Pipiringos, southeastern Morton County (Artzner, Chisholm, and Kepferle, 1965, p. A50) or 1974, fig. 2). Specific areas to search might late Miocene (Denson and Gill, 1965, p. be in central Emmons County where the 67) time. ash is generally thickest and is in the lower part of the Fox Hills; in eastern Sioux Fox Hills Formation County where it is at the top of the Bullhead lithofacies; and in southeastern Although u.ranmm -iii"tli'e willisto Morton County where it is about 48 feet l1--asmhaSbeen found almost entirely above the Fox Hills-Hell Creek contact arly Tertiary lignite ...,and.-nomnarine (Artzner, 1974, p. 7). Groundwater could 'carbonaceQus .-rocks,ra good possibility leach possible uranium from the volcanic exists for its occurrence in the Late ash and redeposit it in the finer clastics Cretaceous marine and brackish strata of containing organic materials in the Fox the Fox Hills. Uranium is known from Hills and Hell Creek Formations. It is also marine sandstone (e.g., Clinton and possible that uranium might be deposited Carithers, 1956) and marine black shales in permeable sandstone (as of the Timber (e.g., Swanson, 1956). A model for the Lake Member) because of a reducing syngenetic origin of possible uranium in the environment provided by localized Fox Hills is as follows. carbonaceous material or hydrogen sulfide. It is clear that the Hell Creek, Fox To provide a sound basis for further Hills, and Pierre Formations are at least in exploration in the Fox Hills Formation, part ~en~~~p.8.raneou~ these considerable additional stratigraphic study formations, therefore, represent a variety is warranted. This study might be of depositional environments that were concentrated in a fringe area surrounding areally in j~t~p~itk>n~Streams originating the known occurrence of the volcanic ash or passingtlirougl1 coastal plain bogs (sites in the south-eentral part of the state and of later lignite formation within Hell Creek also farther west where lignite and environments) could have carried uranium carbonaceous shale occurs in the Fox Hills ions, fixed by organic matter in solution section. (Vine, 1962, p. 161), that would be carried 14 REFERENCES Survey Prof. Paper 463, 75 p. Donaldson, A. c., Martin, R. H., and Anderson, S. B., 1969, Structure map on Kanes, W. H., 1970, Holocene top of Cretaceous Pierre Formation: Guadalupe delta of Texas Gulf Coast, N. Dak. Geo!. Survey, unpublished. in Morgan, J. P., ed., Deltaic Artzner, D. G., 1974, Palynology of a sedimentation, modern and ancient: volcanic ash in the Fox Hills Soc. Econ. Paleont. Mineral. Spec. Formation (Maestrichtian) of Pub. No. 15, p. 107-137. Emmons, Morton, and Sioux Dott, R. H., Jr., and Batten, R. L., 1971, Counties, North Dakota: M.S. thesis, Evolution of the earth: New York, Kent State Univ., 122 p. McGraw-Hill Book Co., 649 p. Brown, R. W., 1939, Fossil plants from the Erickson, J. M., 1971, Gastropoda of the Colgate member of the Fox Hills Fox Hills Formation (Maestrichtian) sandstone and adjacent strata: U.S. of North Dakota: ph.D. dissertation, GeoI. Survey Prof. Paper 189-1, p. Univ. of N. Dak., 247 p. 239-275. Erickson, J. M., 1974, Revision of the Carlson, C. G., 1973, Generalized bedrock Gastropoda of the Fox Hills geologic map of North Dakota: N. 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A., and Reeside, J. B., Jr., Dak. Geo!. Survey Bull. 26,47 p. 1952, Correlation of the Cretaceous Frye, C. I., 1967, The Hell Creek formations of the western interior of Formation in North Dakota: ph.D. the United States: Geo!. Soc. America dissertation, Univ. N. Dak., 411 p. Bull., v. 63, p. 1011-1044. Frye, C. I., 1969, Stratigraphy of the Hell Cvancara, A. M., 1956, Gastropoda from Creek Formation in North Dakota: N. the Pierre Shale (Upper Cretaceous) of Dak. Geol. Survey Bull. 54,65 p. Emmons County, south-eentral North Gill, J. R., and Cobban, W. A., 1973, Dakota: M.S. thesis, Univ. of N. Dak., Stratigraphy and geologic history of 62 p. the Montana Group and equivalent Denson, N. M., and Gill, J. R., 1956, rocks, Montana, Wyoming, and North Uranium-bearing lignite and its and South Dakota: U.S. Geol. Survey relation to volcanic tuffs in eastern Prof. Paper 776, 37 p. Montana and North and South Hares, C. J., 1928, Geology and lignite Dakota: U.S. Geo!. 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J 16
Palubniak, D. S., 1972, Paleoecology of invertebrate fossils of the Navarro Upper Cretaceous oysters in the Fox group of Texas: Univ. Tex. Pub. No. Hills Formation, North Dakota and 4101,641 p. comparisons with recent oyster Swanson, V. E., 1956, Uranium in marine ecology: M.S. thesis, Kent State Univ., black shales of the United States: U.S. 119 p. Geol. Surv. Prof. Paper 300, p. Pettyjohn, W. A, 1967, New member of 451-456. Upper Cretaceous Fox Hills Vine, J. D., 1962, Geology of uranium in Formation in South Dakota, coaly carbonaceous rocks: U.S. Geol. representing delta deposits: Am. Survey Prof. Paper 356-D, p. 113-170. Assoc. Petroleum Geologists Bull., v. Waage, K. M., 1965, The Late Cretaceous 51, no. 7, p. 1361-1367. coleoid cephalopod Actinosepia Pipiringos, G. N., Chisholm, w. A, and canadensis Whiteaves: Peabody Mus. Kepferle, R. c., 1965, Geology and Nat. Hist. (Vale Univ.) Postilla, no. uranium deposits in the Cave Hills 94,33 p. area, Harding County, South Dakota: Waage, K. M., 1968, The type Fox Hills U.S. Geo!. Survey Prof. Paper 476-A, Formation, Cretaceous (Maestrichtian), 64 p. South Dakota. Part I. Stratigraphy Reineck, H. E., and Singh, I. B., 1973, and paleoenvironments: Peabody Mus. Depositional sedimentary Nat. Hist. (Vale Univ.) Bull. 27,175 environments: New York, p. Springer-Verlag, 439 p. Weimer, R. J., 1960, Upper Cretaceous Sandberg, C. A., 1962, Geology of the stratigraphy, Rocky Mountain area: williston basin, North Dakota, Am. Assoc. Petroleum Geologists Montana, and South Dakota, with Bull., v. 44, no. 1, p. 1-20. reference to subsurface disposal of Weimer, R. J., 1970, Rates of deltaic radioactive wastes: U.S. Geo!. Survey sedimentation and intrabasin Rept. TEI-809, 148 p. deformation, Upper Cretaceous of Sloan, R. E., 1970, Cretaceous and Rocky Mountain region, in Morgan, J. Paleocene terrestrial communities of P., ed., Deltaic sedimentation, modern western North America: North and ancient: Soc. Ecan. Paleont. American Paleont. Convention, Mineral Spec. Pub. 15, p. 270-292. Chicago, 1969, Proc., E., p. 427-4-53. Weimer, R. J., and Hoyt, J. H., 1964, Spearing, D. R., 1974, Summary sheets of Burrows of Callianassa major Say, sedimentary deposits with geologic indicators of littoral and bibliographies: Geol. Soc. America shallow neritic environments: Jour. MC-8. Paleont., v. 38, no. 4, p. 761-767. Speden, I. G., 1970, The type Fox Hills Williams, G. D., and Burk, C. F., Jr., 1966, Formation, Cretaceous Chapter 12, Upper Cretaceous, in (Maestrichtian), Part 2. Systematics of McCrossan, R. G., and Glaister, R. P., the Bivalvia: Peabody Mus. Nat. Hist. eds., Geolopical history of western (Vale Univ.) Bull. 33, 222 p. Canada: Calgary, Alta., Alberta Soc. Stephenson, L. W., 1941, The larger Petroleum Geologists, p. 169-189.
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