BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA VOL. 68. PP. 413-420. 1 PL. APRIL 1957

FRENCHMAN FORMATION OF EASTERN , ,

BY W. O. KTJPSCH

ABSTRACT In the eastern Cypress Hills the (Upper ), a correla- tive of the Hell Creek in , consists of a clay lithosome and a lithesome. Study of sections shows that either lithological unit may form the lowest unit of the Frenchman and that they may alternate vertically. Equivalence of the two lithologies is suggested also by their similar content. The Frenchman is distributed over a larger area than previously assumed. Certain formerly interpreted as belonging to the Formation (the Fox Hills of Montana) are assigned to the Frenchman because of their fossil content. Differences in grain size, color, accessory minerals, stratification, and other characteristics can be used to distinguish Eastend sands from the sand lithosome of the Frenchman. The Frenchman rests on a surface of erosion; the upper contact is abrupt but conforma- able.

CONTENTS TEXT ILLUSTRATIONS Page Plate Facing page 1. Distribution of Frenchman Formation in the Introduction and acknowledgments 413 eastern Cypress Hills, Saskatchewan, General 413 Canada 418 Definition of the Frenchman Formation 414 Distribution and thickness 415 TABLES Lithology 415 Table Page Description of two Frenchman lithostrati- 1. Development of stratigraphic nomenclature graphic units 415 in the Cypress Hills 414 Relationship of the two lithostratigraphic 2. Lithological characteristics of Eastend and units 417 Frenchman sands 416 Paleontology 419 3. from Frenchman Formation, eastern References cited 419 Cypress Hills 418

INTRODUCTION AND ACKNOWLEDGMENTS and Mr. N. L. Mclver who assisted in measur- ing stratigraphic sections in the field, and Mr. The Frenchman Formation of southwestern B. K. Smith who conducted heavy-mineral and Saskatchewan presents three problems: (1) mechanical analyses. Mr. R. Rudichuk of the sands belonging to the Frenchman Formation University of Saskatchewan prepared the map are not everywhere easily distinguishable from for publication. Thanks are also due the Sas- sands belonging to the stratigraphically lower katchewan Research Council for financial aid. ; (2) the relationship of The author is indebted to Dr. F. H. McLearn, two different lithostratigraphical units of the Dr. L. S. Russell, and Mr. William E. Benson Frenchman has been differently interpreted for offering valuable criticism of the manuscript. by various workers; (3) some geologists de- scribed the upper boundary of the Frenchman GENERAL STRATIGRAPHY as conformable with the overlying Ravenscrag, others suggested a disconformable relationship. Rocks of and early Tertiary The writer wishes to thank Mr. S. P. Jordan age are well exposed in the eastern part of the 413

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Cypress Hills, especially in the valley of the ous day and impure lignite, and the upper of (formerly called White Mud refractory white, gray, and mauve clays, sandy River) between Ravenscrag and Eastend, in places. In addition McLearn recognized Saskatchewan. The stratigraphic section in this an uppermost or fourth member consisting of valley attracted geologists as early as 1883, dark, bentonitic, nonrefractory shales. Lithol-

TABLE 1.—DEVELOPMENT or STRATIGRAPHIC NOMENCLATURE IN THE CYPRESS HILLS Correlatives in adjacent McConnell, 1885 McLearn (in Eraser et al., 1935) Furnival, 1946 areas of the U.S.A.

Upper Ravenscrag Fort Union Ravenscrag Lower Frenchman Hell Creek

No. 4 zone Battle Laramie No. 3 zone Colgate \ Whitemud member / No. 2 zone Whitemud

No. 1 zone / Fox Hills Fox Hill Eastend Eastend

Pierre Bearpaw Bearpaw Bearpaw

and a lithologic description was published ogy and stratigraphic position indicate that the (McConnell, 1885, p. 27c). White sands and Whitemud Formation is the Canadian equiva- clays, now referred to as the Whitemud Forma- lent of the Colgate member of the Fox Hills tion, constitute the most conspicuous unit of Formation in Montana and . the section. These and all overlying strata were Furnival (1946) adopted McLearn's divi- assigned to the Laramie by McConnell, whereas sions for the lower part of the section but he designated the underlying sands as Fox Hill. removed the uppermost dark-shale member The Pierre shales are at the base of McConnell's from the Whitemud and called it the Battle section, the division of which has undergone Formation. Through his work the Lower many changes introduced by various workers Ravenscrag became known as the Frenchman (Table 1). Formation, whereas the Upper Ravenscrag Detailed work was done by McLearn in the became simply . Eastend area, and the results were summarized in Fraser et al. (1935). McLearn used the name DEFINITION or THE FRENCHMAN FORMATION for the Upper Cretaceous marine shales, which were referred to as Pierre Furnival (1946, p. 94) defines the Frenchman by McConnell. The overlying very fine sands Formation as the strata lying above the Battle and silts, representing the youngest marine Formation and underlying the restricted deposits of the plains, were no longer called Ravenscrag Formation. The type area of the Fox Hill but Eastend. The name Whitemud Frenchman is along the Frenchman River was used for the conspicuous white sediments between Ravenscrag and Eastend, but no type which were treated as a separate formation. section was designated by Furnival. McLearn divided the Whitemud Formation of The upper boundary of the Frenchman is the Cypress Hills into three members, or zones the lowest commerical and mappable as he called them. The lowest consists of gray seam, which is placed in the Ravenscrag For- kaolinitic sand, the middle of brown carbonace- mation. In the Eastend area this lignite seam

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is called the No. 1 or Ferris seam. It is several These banks are mapped as Eastend on the feet thick and has a break of carbonaceous Regina sheet (Fraser et al., 1935, map) and no shale of about 6 inches separating a lower Ravenscrag (which would include the French- thicker bed from an upper. In Montana, where man) is shown east of the creek. From these the Hell Creek is the correlative of the French- key outcrops the Frenchman sand can be man and the Fort Union of the Ravenscrag, followed north where other fossil localities the lowest mappable lignite is also taken as the verify in places the lithologic correlations. base of the Fort Union (Colton, 1955). Plate 1 does not show the distribution of the The lower boundary of the Frenchman is Eastend, but it can be seen from the abbrevi- marked by a surface of erosion as McLearn ated sections that no Eastend beds are present had already recognized (in Fraser et al., 1935, north of T. 8, where the Frenchman everywhere p. 37). Where the pre-Frenchman erosion is lies directly on Bearpaw. nil or very slight, the Frenchman Formation The thickness of the Frenchman varies with rests on the Battle. In other places the French- the depth of erosion that took place before the man rests on one of the three members of the formation was deposited. It ranges from a Whitemud, the Eastend, or the Bearpaw. The minimum of 28 feet to more than 222 feet greatest amount of erosion took place in the where the Frenchman rests on some horizon northern and eastern parts of the area on the in the Bearpaw. The Frenchman increases in flanks of the Cypress Hills, where as much as thickness from the town of Eastend to the 200 feet of older formations was removed before north and to the east. deposition of the Frenchman. Less material was removed from the center of the hills in the LITHOLOGY Ravenscrag-Eastend area. Here the Frenchman commonly rests on Battle or on some stratum Description of Two Frenchman Lithostratigraphic of the Whitemud Formation and has some Units local channelling down to the Eastend sands. Two lithostratigraphic units make up the To the east the Frenchman lies on progressively Frenchman Formation. One is here referred lower strata down to some part of the Bearpaw to as the sand lithosome, the other as the clay shale at the eastern boundary of the map area. lithosome. These units were previously referred On the northern slope of the Cypress Hills also, to as zones (McLearn, in Fraser et al., 1935, the Frenchman overlies the Bearpaw. p. 41), phases (Russell, 1948, p. 32), and facies (Kupsch, 1956, p. 20). The increased knowledge DISTRIBUTION AND THICKNESS of the stratigraphical relationships between the Plate 1 shows the distribution of the French- two lithological units of the Frenchman and man Formation in the eastern Cypress Hills. the recent redefinition and clarification of many On older geological maps covering this general lithostratigraphical terms seem to justify the region (Fraser et al., 1935, Regina sheet) the adoption of the term lithosome. Wheeler and Frenchman was included in the Ravenscrag. Mallory (1956, p. 2718-2719) define a lithosome In general the Frenchman on Plate 1 coincides as a lithostratigraphic body which is mutually with the outer, lower border of the Ravenscrag intertongued with one or more bodies of differ- as mapped on the Regina sheet. Important ing lithic constitution. They point out that differences are noticeable in the northeastern several writers previously referred to such sector of Plate 1 where large areas previously vertico-laterally delineated units as "facies," mapped as Eastend are now shown as French- but that the restricted definition of lithofacies man. These are all outside the area examined as laterally segregated, statistical, lithic vari- by McLearn, as he did not map north of T. 8 ants of a stratigraphic interval necessitates the (Fraser et al., 1935, p. 2). Key outcrops for this introduction of the term lithosome. reinterpretation occur along the eastern bank The sand unit of the Frenchman Formation of Swift Current Creek in NW H sec. 13, T. 9, consists of medium- to fine-grained "salt-and- R. 20, W3., where the writer found typical pepper" sand or loosely cemented , Frenchman fossils in the sand unit (Table 3). which locally may be well cemented into large

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TABLE 2.—LITHOLOGICAL CHARACTERISTICS OF EASTEND AND FRENCHMAN SANDS

Sediments Sand from Lithological characteristics Sand lithesome of Frenchman Formation Eastend Formation Color Somber Pale Light olive gray to dark greenish gray Grayish yellow to light dusky yellow In places yellow to brown Some orange siltstone Grain size Medium- to fine-grained Very fine-grained Low silt and clay content High silt and clay content Sorting Poorly sorted Well sorted Presence of Common Present Visible Microscopic "Salt and pepper" sand Presence of carbonates Unindurated sand generally noncalca- Commonly calcareous reous Indurated masses calcareous Presence of mica Mica absent or subordinate Commonly micaceous Presence of carbona- Fragments common Comminuted plant material scattered ceous material Some thin lignite seams through sediment Large pieces of lignitic fossil wood in conglomerates Carbonaceous shales in places Heavy minerals Unstable heavy minerals predominate Stable heavy minerals predominate Green hornblende prominent (40%) Green hornblende present (3%) Stratification Very thick-bedded Thin-bedded Cross-stratification Common Present in places Medium to large scale Small scale Induration Indurated parts common Few indurated strata Large blocks of indurated calcareous sand ("loglike concretions") com monly lying on outcrop Splitting property Indurated parts massive Indurated strata flaggy Fossils Fairly common Rare Nonmarine; bone fragments, Marine (in eastern Cypress Hills); etc. pelecypods, etc. Associated sediments Some clay lenses in places Clay lenses and beds common Locally clay pellets In places interbedding of sands and clays Lower contact of East- Conglomerates of clay with few No conglomerates observed in Eastend end and Frenchman pebbles common at or near Contact between Bearpaw and Eastend formations lower contact of Frenchman where gradational erosional disconformity developed

hard sandstone masses. The sand is light-olive small macerated plant fragments, is common gray to dark-greenish gray, in places yellowish in the sand. Locally thin beds of carbonaceous orange to brown. Medium-scale cross-stratifi- shale, blocks of lignitic fossil wood, and thin cation is a common feature. Large indurated stringers of lignite are found. The sediment masses, well cemented by calcium carbonate, can best be described as a subgraywacke of the are rounded and elongated parallel to the "salt-and-pepper" variety. bedding. They are commonly referred to as In some outcrops it is not easy to distinguish "loglike concretions." In places lenses or thin the sand unit of the Frenchman from the sands beds of gray silt and clay occur in the coarser of the underlying Eastend Formation. It is sandstone. Carbonaceous material, such as important to discriminate between them where

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the Frenchman lies on the Eastend or on the Relationship of the Two Lithostratigraphic Units Bearpaw. Lithological characteristics helpful The relationship between the sand and the in distinguishing Frenchman sand from Eastend clay units of the Frenchman has been variously sand are listed in Table 2. Singly, any of the interpreted by previous workers. McLearn criteria in Table 2 may not be diagnostic, but (in Fraser et al., 1935, p. 41) considered the in combination they are sign posts for the sand as the basal unit of the Lower Ravenscrag presence of either formation in areas where the ( = Frenchman) and indicative of some erosion stratigraphic position of the questionable sand preceding the deposition of the clay unit. He is obscure because of the erosional removal of believed the sands to be absent where the entire the characteristic Whitemud beds separating Whitemud (including Battle) is present, which Eastend from Frenchman. McLearn (in Fraser indicates little or no erosion before Frenchman et al., 1935, p. 25) was aware of this problem time. In addition to this basal sand he men- when he wrote: "Owing to difficulty of identifi- tioned the presence of massive sands, in the cation of the Eastend in areas where the middle and near the top of the Frenchman near Whitemud is absent a sand at the base of the Climax road bridge, with clays between the Ravenscrag (= Frenchman) may be mistaken three sand units. for Eastend and vice versa. This may be true Furnival (1946, p. 95) regarded the sands even of the most painstaking work if the specific as the typical Frenchman and described the criteria are obscure." Therefore an extended clay unit as intercalated with the thick sand- list of lithologic characteristics (Table 2) may stone lenses and commonly occurring at the be helpful. Some of these characteristics, such top of the formation. Furnival followed Mc- as grain size, lignitic material, and nature of Learn in regarding the sand as the basal unit contact were used by McLearn; others were of the Frenchman Formation. He drew the discovered by petrological investigations of base of the Frenchman at the base of the lowest samples conducted by Fraser; others represent sand and referred any clays under this sand field and laboratory observations by the writer. and overlying the Whitemud to the Battle Although the Frenchman fossils do not neces- Formation. sarily require a time interval younger than Russell (1951, p. 34) indicated that the clay Eastend, they are helpful in distinguishing unit represents the typical Frenchman and that Frenchman sands from Eastend sands: fossils the sand occurs at the top of the formation. He are scarce in the Eastend, and all those in that regarded the sand as local channel filling at the formation, within the map area, are marine beginning of Ravenscrag deposition. He pointed (Russell, 1951, p. 26-27), whereas a continental out that equivalence of the sand and clay units origin is indicated for the Frenchman by both was not proved and that a local animal and plant fossils. might be present between the Frenchman and The clay unit of the Frenchman, different the Ravenscrag. Russell suggested removal of from the sand unit in its gross aspects, is com- the sand unit from the Frenchman and re- posed of grayish, grayish-green, and bluish to garded it as the lowest unit of the Ravenscrag. purplish bentonitic clays. Its physiographic In an attempt to solve the relationships be- expression is in sharp contrast to that of the tween the two lithostratigraphic units of the cliff-forming, or grass-covered, sand unit. The Frenchman the writer analyzed the lithological clay unit is characteristically exposed in characteristics of 49 sections in the eastern rounded badland outcrops with a cracked Cypress Hills. Plate 1 shows: (1) a complete surface and a sparse or absent vegetation cover. Frenchman section may be composed wholly of Some sand lenses are in places incorporated the sand unit, wholly of the clay unit, or of within the clay unit. They are very fine-grained both; (2) locally either the clay or the sand is and would not be easily distinguishable from the lowest unit, whether much erosion preceded the Eastend sand except that they are thin Frenchman deposition or not; (3) either clay or and are interbedded with clay strata charac- sand may be the upper unit; (4) the two units teristic of the clay unit of the Frenchman may alternate vertically; (5) the sand unit is Formation. not invariably present at the base of the French-

Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/68/4/413/3426947/i0016-7606-68-4-413.pdf by guest on 29 September 2021 TABLE 3.—FOSSILS FROM FRENCHMAN FORMATION, EASTERN CYPRESS HILLS Lithosome in whic Locality fossils found Fossils Number on Description (Ranges Plate 1 Name west of third m.) Sand Clay 1 Topham's NE Sec. 7, X Crest, horn, and vertebrae of Tricera- ranch T.7, R.22 tops; collected by H. Jones Two vertebral centra of Crocodilian scute Fragments of Aspideretes shells 2 Little French- SE Sec. 7, X Carpolithus (Cycadinocarpusf) ceratops; man Creek T.7, R.22 determined by C. A. Arnold. 3 Knollys SE Sec. 13, X? Skull of ; collected by C. M. T.6, R.23 Sternberg 4 Eastend SW Sec. 8, X Crocodilian tooth T.7, R.21 Costal plate of Aspideretes sp. mandible vertebrae S Chimney NE Sec. 17, X? Supraorbital horn core of Triceratops; Coulee T.7, R.21 collected by H. Jones 6 Anxiety SE Sec. 28, X Bone fragments, possibly dinosaurian; Butte T.7, R.21 determined by L. S. Russell Shell fragments of hard- and soft- shelled ; determined by L. S. Russell vertebrae; determined by L. S. Russell Scales of Lepidosteus; determined by L. S. Russell Mandibular tooth of a large ceratopsian 7 Swift Current NW Sec. 13, X Fragments of and Aspide- Creek T.9, R.20 retes shells Portions of an anterior caudal vertebra of a large carnivorous dinosaur, about the size of rex 8 Lookout Hill SE Sec. 25, X Claw from fore foot of a carnivorous T.ll, R.21 dinosaur Fragments of Aspideretes shell 9 Northwest of NE Sec. 17, X Crocodilian scute Busse's T.5, R.19 Fragments of turtle (f Aspideretes) shell ranch Dorsal vertebral centrum of Champso- saurus 10 Northeast of NE Sec. 16, X Skull of Triceratops; collected by H. Busse's T.5, R.19 Jones ranch Fragment of carnivorous dinosaur bone Dermal scute or cranial fragment of an armored dinosaur Fragment of right-angular bone (mandi- ble) of a small crocodilian Fragmentary crocodilian scutes and cranial elements Crocodilian tooth Large ceratopsian tooth Fragment of a large tooth, possibly crocodilian Small carnivorous dinosaur tooth of a form recognized in , but un- named If not indicated otherwise, all fossils collected by W. O. Kupsch; determinations by W. Langston in collaboration with L. S. Russell and C. M. Sternberg 418

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man Formation where pre-Frenchman erosion Cretaceous age is indicated by the fossils, has been considerable; (6) clay beds of the especially by the . Frenchman are locally in direct contact with An attempt was made to determine the Bearpaw strata; (7) there is no apparent lithostratigraphical unit of the Frenchman from relationship between the development of either which the fossils were collected; location and lithostratigraphic unit and the total thickness lithology are given in the literature (Fraser et of the Frenchman in an outcrop. al., 1935, p. 42) for some fossils collected by Because of these relationships the writer Sternberg and Jones in the eastern Cypress proposes that the sand and clay units are Hills area. Additional information was kindly lithosomes of equal importance in the French- given by Mr. H. Jones of Eastend. For all fos- man Formation. These mutually intertongued sils collected by the writer the lithology of the bodies are not to be regarded as members of the Frenchman in which they were found was noted. Frenchman because they do not produce any It is evident from Table 3 that similar faunules definite stratigraphic sequence over more than are present in both the clay and sand units. a restricted and therefore unmappable area. Previously Russell (1951, p. 33) had stated that Where the disconformity at the base of the no fossil bones, diagnostic or otherwise, have Frenchman is well defined, as in many outcrops been found in the sand unit and that correlation along the eastern and northern rim of the based upon fossils should therefore be applied Cypress Hills where the Frenchman lies on only to the clay unit. The finding of similar strata that are low in the stratigraphic section, fossils in the day and sand units supports the it is in several places characterized by a con- inference that the two units are equivalent glomeratic stratum. The consists mutually intertongued bodies. predominantly of rusty siltstone pebbles, with some fossil wood, dinosaur bones, and other REFERENCES CITED fragmentary fossils in places. A few quartzite Colton, R. B., 1955, Geology of the Wolf Point pebbles are commonly present; they closely quadrangle: U. S. Geol. Survey, Geol. Quad- resemble the quartzite pebbles of the later rangle Maps of the U. S. Fraser, F. J., et al., 1935, Geology of southern . This basal conglom- Saskatchewan: Geol. Survey Canada Mem erate is apparently of wide occurrence, al- 176, 137 p. though it is discontinuous. It has been reported Furnival, G. M., 1946, Cypress Lake map-area, Saskatchewan: Geol. Survey Canada Mem. from the Wolf Point area, Montana (Colton, 242, 161 p. 1955). Kupsch, W. O., 1956, Geology of the eastern Cy- No indications of a disconformity at the top press Hills: Saskatchewan Dept. Mineral Res., Rept. 20, 30 p. of the Frenchman exist anywhere in the eastern McConnell, R. G., 1885 [1886], Report on the Cy- Cypress Hills area. The lithological change press Hills, Wood Mountain, and adjacent country: Geol. Survey Canada Ann. Rept, from the Frenchman sediments to the bottom (new ser.), v. 1, pt. C, 78 p. coal bed of the Ravenscrag is abrupt but Russell, L. S., 1948 [1951], The geology of the conformable. A thin clay bed underlies the coal, southern part of the Cypress Hills, Southwest- ern Saskatchewan: Province of Saskatchewan even where the sand lithosome is the highest Dept, of Nat. Res., Petroleum Geology Ser. unit in the Frenchman. Rept. 1, 60 p. Wheeler, H. E., and Mallory, V. S., 1956, Factors in lithostratigraphy: Am. Assoc. Petroleum PALEONTOLOGY Geologists Bull., v. 40, p. 2711-2723 UNIVERSITY op SASKATCHEWAN, SASKATOON, SAS- The Frenchman beds in the eastern Cypress KATCHEWAN, CANADA Hills have yielded many dinosaurian bones in MANUSCRIPT RECEIVED BY THE SECRETARY or THE addition to remains of turtles, , crocodiles, SOCIETY, APRIL 13, 1956 PUBLISHED BY PERMISSION or THE DIRECTOR, and some fossil fruits (Table 3). An upper SASKATCHEWAN GEOLOGICAL SURVEY

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