Palynology of the Shaunavon and Gravelbourg Formations of Southern Saskatchewan

L.K. Kreis

Kreis, L.K. (1989): Palynology of the Shaunavon and Gravelbourg Formations of southern Saskatchewan, in Summary of Inves tigations 1989, Saskatchewan Geological Survey; Saskatchewan Energy and Mines, Miscellaneous Report 89-4.

This paper reports preliminary examinations made in 2. Palynological Results 1989 of palynological data from Jurassic strata in southern Saskatchewan. Sample preparation and iden The focus of this investigation is on the palynology of tification were conducted by Dr. E.M.V. Nambudiri, with the Shaunavon and Gravelbourg Formations of south the Energy Research Unit, University of Regina. The western Saskatchewan, and the Red Jacket Formation author acknowledges Dr. Nambudiri's invaluable con of the southeast. Although most samples are from the tribution towards an interpretation of the palynomorphs Wapella- Moosomin area, the results have aided present. stratigraphic correlations in both areas. To supplement Pocock's (1970, 1972) work, 52 samples from the The investigation is part of an ongoing study by the Shaunavon and Gravelbourg Formations were taken author entitled, 'Stratigraphy of the Jurassic System in from 20 wells across southern Saskatchewan (Figures the Wapella - Moosomin area, southeastern Sas 1a and 1b , in pocket). Only 38 samples from 18 wells katchewan' ('Study Area' in Figure 1a, in pocket). The proved to have sufficiently preserved, identifiable major goals of the study are 1) to establish the palynomorph specimens. A summary of typical stratigraphic relationships between the Jurassic section palynomorph assemblages for the upper and lower in the Wapella-Moosomin area of southeastern Sas members of the Gravelbourg Formation, upper and katchewan and the type area for the Jurassic in south lower members of the Shaunavon Formation, Rocanville western Saskatchewan (Figures 1a and 1b, in pocket), Member, Moosomin Member (units A and B) and Bur and 2) to provide an interpretation of the depositional rows Member (units A and 8) is given in Table 1. history for the Jurassic System in the Wapella Moosomin area. A more detailed discussion of the a) Lower Gravelbourg Member stratigraphic and ecological implications of the palynological results will be published later. Only three of seven samples taken from the lower Gravelbourg member yielded specimens of sufficient preservation to warrant examination, two from unit A 1. Previous Work and one from the overlying unit B. Poor preservation of Previous palynological investigations of the Jurassic palynomorphs in the latter sample likely resulted from strata in Saskatchewan are limited to reports by Pocock slow deposition in a high pH environment; conditions (1970 and 1972). Pocock (1972) established a considered by Traverse (1988) to be corrosive to framework of palynomorph assemblages for the major palynomorphs. The presence of abundant organic stratigraphic units defined by Milner and Thomas (1954) walled microforaminifera in unit B supports Pocock's for the Jurassic section in southwestern Saskatchewan, (1972) interpretation of a marine depositional environ namely (oldest to youngest) the Watrous, Gravelbourg ment. Microforaminifera were not found in Unit A, but and Shaunavon Formations and the Vanguard Group. the presence of acritarchs like Leiosphaeridia staplinii and Leiosphaeridia tangentensis suggest a marine in Numerous depositional breaks and lithofacies changes fluence for this unit as well. This compliments the inter within the Shaunavon Formation and upper member of pretation that the dolomitic and locally algally-laminated the Gravelbourg Formation in southeastern Sas limestones of unit A were deposited in a restricted shal katchewan make correlation with strata in the type area low marine environment; whereas the calcareous of southwestern Saskatchewan very difficult when at mudstones and bioclastic limestones of unit Bare inter tempted on the basis of lithological and geophysical log preted to have been deposited in a more open marine characteristics (Kreis, 1988). Kreis invoked an arbitrary environment. lithofacies boundary to separate the Shaunavon Forma tion and upper member of the Gravelbourg Formation The palynomorph assemblage in the lower member of of southwestern Saskatchewan from the equivalent the Gravelbourg Formation in the present study is strata in southeastern Saskatchewan, which he named, similar to that found in the same member by Pocock the Red Jacket Formation (Figures 1a and 1b). He sub (1972). Leiosphaeridia staplinii, Leiosphaeridia tangen divided the Red Jacket Formation into three members tensis, Murospora minor, and species of Concavis (0-Y): Rocanville Member, Moosomin Member and Bur simisporites are index species from unit A in this study, rows Member. For a more detailed discussion of and Lycopodiumsporites pseudoannotinus and species nomenclature see Kreis (1988). of Leiosphaeridia are the index species from unit B. All of these palynomorphs are also index species for the

Saskatchewan Geological Survey 133 Table 1 - Typical Palynomorph Assemblages lower member of the Gravel- bourg Formation described by STR1''l'IGRAPlllC UNITS Pocock (1972). LGA LGB UG LSl us RM MMll MMD BMA BMB ------·-·------Classopollis spores, reported PALYNOMORPHS "in abundance" by Pocock Terrestr ial spec ies (1972) in the lower member of the Gravelbourg Formation Bacula t i sporites truncatus x Bennet t i teaepollenites canadens is x x are rarer in unit A, and absent sennet tite aepolleni tes l ucif er x x in unit B of this report. How- Bennetti teaepollenites shaunavonansis x x Calamospor a mesoz oic a x x x x ever, in only one well did unit Calli alasp0rites triloba tus x x Ceratosporit eP spinosus x B yield identifiable Cerebropolle nites macrovorrucocus x x palynomorphs, and these Cerebr opolleni tes mesozoicus x Cerebr opol lenites s p . x were poorly preserved. Classopollis clas s oides x x Classo pollis i tunensi s x x x Concavissimisporit es ~elcourtii x Since Pocock (1972) does not Concavissimispor i tes southeyensis x x x Concavis simisporites subgranulatus x indicate the well location or Concav i ssimi s porites sp . x depths of recovery for most of Corrugatis porites ampl ectlformis x Corrugatis porit e s wallii x x his samples, it is difficult to Cyathidite s mi nor x Cycadopi t es jansonii x determine the southwestern cycadopite s minimus x x stratigraphic equivalents of Deltoidosp0ra harr1sii x x x Deltoi dospora minor x x x units A and B. Unit A appears Dictyophyl lidites s p. x Dictyotrilete s c r aterin x to be more similar than unit B Dis tanulis porites verrucosus x to the lower member of the Eucommildite s troedsonii x exesipollenites s cabratus x Gravelbourg described by Exesipolleni t es t umulus x Cleicheniidltes del i c atus x Pocock, having a greater num- Gloichcniidites granu lat us x ber of the palynomorph index Gl eicheniidites minor x Gleicheniidltes nil s s onii x species. On the other hand, Gl aich eniidi t es r ouse ii Har ri sis pora cqui eKi nus x unit B was found to be In aperturopol l 6ni tes tur batus x x x marine, and Pocock ( 1972) Lycopodiumsporites ba cculatus x Ly copodiumspori tes dejer s eyi x does not recognize a marine Lycopodi.uJDSporite s pseudoannotinus x sequence in the upper Gravel- Manumia verrucata x Murospora bicolla tera lis x x bourg. Unit 8, therefore, is Murosp0ra minor x Muro spora sp. x taken to be the uppermost Ovalipolli s canadensi s x unit of the lower member of Pityos porite s div ulg~tus x x Pl acysac cus lopsi nens i s x the Gravelbourg. Podocarpidites l angii Podocarpi dites waptllaensis x x Protoc oni rerus micros accus x Unit B is not present in the Protopicea e xilioidcs x x x Re ticulatisporite s juras s i cus x type section of the Gravel- Reticul a tispor jtes sp. x Triangulopsi s discoidal i s x x bourg Formation (well number 1 in Figure 1b ), instead, the Marine Species upper Gravelbourg rests un- organ i c - wa lled for a•inifera x x conformably on what appears d i noflagellat es (indetermi nate) x Chyt roeisphaerjdia variabilis to be unit A of the lower Comasphaeridium s p. A x Cymatiosphttens sp. x Gravelbourg. East of this well, Gonyaulacysta j uras sica x unit B overlies unit A all the Conyaulacysta ornata x Gonyaulax canad~nsis x way to the Wapella-Moosomin Leiot usa deunrfii x Le.i osphacridia hyallna x area (Figure 1b). A well- Leiosphaer idia s t aplinii x x x defined unconformity which Le iosphaer idi a tangentansis x x x x Leiosphaeridia s p . x separates these units in both Rugidinium orna tum x the southeast and southwest, Rugi d i nium undula turn x Rugi d i nium sp. x exhibits weathered dolomite, Sol i sphaeridium deflandrei x Tasmani t es cla icmontensis )( with vugs filled by secondary Tasmanites s uevi cus x x quartz and bluish grey chal- Ta smanj t es y arboensis x cedonic chert (Kreis, 1988). Ahbrev lat1ons: LGA - Lowe r Gra velbour g, Unit ,. The contact between the LGB - Lower Gravel bourg, Uni t B UG - Upper Gravelbourg upper and lower member of LSl - LO.-er Shaunavon, Unit 1 US - Upper Shauna von the Gravelbourg Formation is RM - Rocanv i l le Me na.her sharp, but evidence of erosion MMA - MoosoJ1.i n Member, Uni t A MMB - Moosomin "efflber, Unit B and weathering is lacking, ar- Biii\ - BU ~ro~s Member, Un it A BMB - Burro ws Member, Un it B guing against a clear unconformity. This contact more probably represents a paraconformity.

134 Summary of Investigations 1989 b) Upper Gravelbourg Member d) Upper Shaunavon Member Seven samples taken from the upper member of the The palynomorph assemblage found in four samples of Gravelbourg have a combined palynomorph as the upper member of the Shaunavon Formation differs semblage including: Bennettiteaepollenites canadensis, significantly from Pocock (1972); the only common Calamospora mesozoica, Cerebropollenites macrover palynomorph is Chytroeisphaeridia variabilis. Sedimen rucosus, Concavissimisporites southeyensis, tological evidence suggests that shallow near-shore Gleicheniidites nilssonii, lnaperturopollenites turbatus, sedimentation prevailed during most of upper Lycopodiumsporites pseudoannotinus, Pityosporites Shaunavon time, and that broad shifts in the strand-line divulgatus and Protopicea exilioides, that is quite similar was common (Christopher, 1964). This shifting of en to Pocock's (1972). Pocock noted an abrupt change in vironments may have caused the differences in the character of the palynology of the assemblages at the palynological assemblages, observed between Pocock's boundary between the upper and lower members of the (1972) and the present study. Gravelbourg Formation, indicating an abrupt change in the depositional environment. He also felt that this The palynological assemblage for the upper member of change was indicative of an unconformity at this con the Shaunavon is only similar to Pocock's with respect tact. Pocock suggested that the lack of marine to the relative abundance of terrestrial species, but palynomorphs in the upper member indicated a several marine species were identified that support a lacustrine depositional environment. near-shore depositional environment (Table 1).

While major components of the terrestrial palynological e) Rocanville Member assemblage in both studies are similar, the occurrence of species of Leiosphaeridia, Rugidinium undulatum Most of the eight samples taken from the upper half of and of Tasmanites in the upper Gravelbourg in the the Rocanville Member yielded poorly preserved and present study suggests some marine influence. Taylor commonly unidentifiable specimens. Poor preservation (1981 ) suggests a marine origin for the genera Tas of palynomorphs in the oxidized dolomitic and cal manites. Thus a coastal marine environment is en careous mudstones of this unit is attributed to slow visaged for the upper member of the Gravelbourg For deposition in a high pH environment (Traverse, 1988). mation. Evidence for subaerial exposure is seen in the oxidized and variegated nature of the mudstones. Subaerial ex c) Lower Shaunavon Member posure may have led to further corrosion of palynomorphs by bacterial action (ibid). Additional Palynomorph recovery from four samples from the lithological and stratigraphic evidence of exposure is lower member of the Shaunavon Formation, was rather cited by Kreis (1988). poor. A particularily poor sample (1-17-20-23W2, 2465- 2466 ft) was mounted as a epoxy pellet, examined One sample taken from a one-metre thick car under ultraviolet light, and found to contain abundant bonaceous sandy siltstone unit at the base of the Rocan zoned dolomite rhomboids. Also present were pyritized ville Member (6-33-14-1 W2, 2492 feet) in the Wapella microforams, scattered inertinite and several acritarchs Moosomin area yielded the palynomorphs Calamospora of the Veryhachium type. mesozoica and Protopicea exilioides which are index species for the upper Gravelbourg described by Pocock The lower Shaunavon samples come from what ap (1972). Other palynomorphs found which are index pears to be a transitional unit between the upper mem species for both the Rocanvifle Member and the typical ber of the Gravelbourg Formation and the lower mem assemblage for the upper member of the Gravelbourg ber of the Shaunavon Formation. This lithostratigraphic in this study are: Classopollis itunensis, Concavis zone has also been recognized by Christopher (1989, simisporites southeyensis, Cyathidites minor, and pers. comm.) and is designated as unit 1 of the lower Podocarpidites wapellaensis. The presence of these Shaunavon on the cross section in Figure 1b . It occurs index species supports the idea that some of the lower in well number 6 (i.e. 14-29-7-29W2) of the cross sec most section of the Rocanville Member in the Wapella tion, but is difficult to recognize east of the arbitrary Moosomin area may be correlated on lithological and lithofacies boundary (Figures 1a and 1b, in pocket). palynological grounds with the upper member of the Gravelbourg Formation, west of the arbitrary lithofacies Several palynomorph species found in both this study boundary (Figures 1a and 1b). and Pocock's (1972) are Baculatisporites truncatus, Classopollis c/assoides, Tasmanites suevicus and The presence of Calamospora mesozoica, Concavis Protoconiferus microsaccus, but the abundant simisporites southeyensis, Tasmanites suevicus and dinoftagellates reported by Pocock (1972) are not ap some dinoffagellates (indeterminate) in both the Rocan parent in the present samples. Only scarce specimens ville Member and the lower member of the Shaunavon of the genera Tasmanites and Leiosphaeridia and a few supports the argument that these units are stratigraphic unidentified dinoflagellates are found. The relative scar equivalents. Thus the Rocanville Member appears to be city of dinoflagellates in unit 1 of the lower member of stratigraphically equivalent to both the lower member of the Shaunavon suggests that the lower Shaunavon the Shaunavon Formation and the upper member of the coastline was nearby (probably to the northeast), and Gravelbourg Formation of southwestern Saskatchewan. may also be attributed to slow deposition in a high pH environment.

Saskatchewan Geological Survey 135 f) Moosomin Member these sediments were deposited in open marine condi tions (Williams, 1978). The low frequency of terrestrial A total of 10 samples, 3 from Unit A and 7 from Unit B, palynomorphs also supports an open marine interpreta were taken from the Moosomin Member of the Red tion following Traverse (1988) who suggests that spores Jacket Formation in the Wapella-Moosomin area, yield and pollens are present in virtually all environments but ing an abundant and diverse terrestrial palynological as their abundance decreases towards open ocean. semblage. This suggests that the Moosomin is equivalent to at least part of the upper member of the Gonyaulacysta ornata is the only index species of Shaunavon Formation of southwestern and south Pocock's (1972) assemblage for the upper member of central Saskatchewan which also has an abundant and the Shaunavon Formation found in Unit A of the Bur diverse palynological assemblage. rows. In the present study, Cycadopites minmus, Del toidospora minor and Leiofusa deunffii all belong to the Although both units A and 8 contain a diverse and abun typical palynomorph assemblages for the upper mem dant terrestrial assemblage, unit B shows more marine ber of the Shaunavon Formation and unit A of the Bur forms than unit A of the Moosomin Member (Table 1). rows Member, suggesting that they are stratigraphic This supports the author's opinion that unit A represents equivalents. a sequence of estuarine valley-fill sediments and the overlying unit B was deposited in a near-shore deposi Unhappily, the single sample taken from unit B of the tional setting. Burrows Member did not yield any palynomorphs.

On the basis of geophysical log correlations, the Moosomin Member is most likely equivalent to the 3. References upper member of the Shaunavon Formation. A number of the palynomorphs listed as typical for units A and B Christopher, J.E. (1964): The Middle Jurassic Shaunavon For mation of southwestern Saskatchewan; Sask. Dep. Miner. of the Moosomin Member are found in the upper mem Resour., Rep. 95, 95p. ber of the Shaunavon in this investigation implying that they are stratigraphically equivalent {Table 1). In addi Kreis, L.K. (1988): The Red Jacket Formation of southeastern tion, units A and B have produced a number of Saskatchewan; in Summary of Investigations 1988, Sask. palynomorphs which are index species for Pocock's Geol. Surv., Misc. Rep. 88·4, p211-223. upper member of the Shaunavon, including: Podocar pidites langii, Rugidinium ornatum and Solisphaeridium Milner, R.L. and Thomas, G.E. (1954): Jurassic System in Sas katchewan; in Western Canada Sedimentary Basin; Am. deflandrei. Assoc. Pet. Geo!., Rutherford Mem. Vol., p250-267.

Sedimentological evidence for a disconformity between Pocock, S.A.J. (1970): Palynology of the Jurassic sediments the Rocanville and Moosomin Members is noted by of western Canada; Part 1, Terrestrial Species. Palaeon Kreis (1988), possibly suggesting that some of the tographica, Abt.8., v130, p12-72. palynomorphs found in the Moosomin Member may have been derived from the underlying Rocanville. (1972): Palynology of the Jurassic sediments of Evidence of extensive reworking, however, was not ap - -w-e-s"'"te-rn Canada; Part 2, Marine Species. Paleon tographica, Abt.B., v137: p85-153. parent in samples from this study. Taylor, T.N. (1981): Paleobotany; McGraw-Hill Book Com g) Burrows Member pany, NY, 583p. Three samples were taken from the Burrows Member, Traverse, A. (1988): Paleopalynology; Allen and Unwin, Inc., two from unit A and one from the overlying unit B. The Mass., 600p. mudstone which comprises unit A is marine and con Williams, G.L. (1978): Dinoflagellates, Acritarchs and Tas tains over 45 percent dinoflagellates. The presence of manitids; in Haq, B.U. and A. Boersma, (eds.), Introduc abundant Gonyaulacacean dinoflagellates suggests tion to Marine Micropaleontology, Elsevier, NY, p293-326.

136 Summary of lnwstigations 1989