Pyroclastic Quartz Grains from the Late Battle Formation of Southwestern Saskatchewan

P.L. Binda I and B.R. Watters 1

Binda. P.L. and Watters, B.R. ( 1997): Pyroclastic 4uartz grains from the Battle Formati on of southwestern Saskatchewan; in Summary of In vestigations 1997. Saskatchewan Geological Survey, Sask. Energy Mi nes, Misc. Rep. 97-4.

Unahradcd quartz crystals and ··rounded" grains. It has also been traced over a large area in the isolated from the Late Cretaceous Battle Formation of subsurface or (Elliott, 1960). East of the southwestern Saskatchewan, have heen studied by Cypress Hills, the unit is cut by a major regional scanning electron microscopy and nuid inclusion disconformity (Furnival, 1946). thermometry in order to determine their mode of formation and occurrence in a lacustrine mudstone. In outcrop, the Battle Formation can be easily recognized by its chocolate-brown colour in stark contrast with the underlying white heds of the 1. Geological Setting Whitemud Formation (Figure 1). It is a blocky, massive-bedded mudstone with typical popcorn The Battle Formation is a IO to I 2 m thick, brown weathering; however, in thin section, it displays a fine, claystone that occurs 50 to 60 m helow the Cretaceous­ hut irregular, layering of clayey laminae, generally less Tertiary boundary (Lcrbckmo et al., 1979) and than 0.1 mm thick, and silty-sandy laminae, commonly outcrops in river cuts and badlands of southern Alberta less than 1.0 mm thick (Binda, 1992). The clay is and in the Cypress Hills of Alberta and Saskatchewan. predominantly smectite wi th minor kaolinite (Binda, 1970). The microfossil content of the Battle Formation is quite

LITHOST RA TIO RAP HY unusual, consisting of silicified MAGNETO- ANO ISOTOPIC DATES spores and pollen grains, STRATIGRAPHY >­ chrysomonad cysts, and siliceous VEOETAL a: sponge gemmoscleres (Binda and :Ii MICROFOSSILS ... Ardley < Srivastava, 1968; Srivastava and Coal DINOSAURS .... Binda, 1984), indicating a 83 M• a: lacustrine to paludal depositional Wodehoueele w c Nevi• Coal flmbrlau z. .... environment. a: 8-' Ma --- (/) In the Cypress Hills, a tu ffaceous -< • ::::, ::, c bed (Kneehills Tuft), occurring ..J "~ • 0 c.:,:, w near the top of the unit, yielded a ..J 0 ~. Wod•hou••I• u K-Ar date of 65 Ma from - :, . eplnata z. u 0 •• 0 < sanidinc and biotite (Folinsbce et • c I- (.) w al.. 1965). The Knechills Tuff is ~ ~ : . a: ~ 0 ~ • a crystal-vitric luff composed of ...... ;,,, • u "' ... :I fresh fragments of quartz and feldspar in a groundmass of ..,,__ K neehlll• chry1omonad1 devitrilied glass and fibers of - Tuff .,• BATTLE elllcllled chalccdonic silica. A few FM 85 M• ' m•gaaporea WHITEMUO ,•~· volcanic glass shards have been Azoll•- FM Thompeon B••m•leporlt•a identified by Binda ( 1970). w :I Coal Scollardla Zircons separated from the tuff ~ II. tr•p•formla z. ~ suggested a derivation from "'z :.;-·- ::, WO I • explosive phases of the Butte U) >­ .>< • tr % u O rhyolite (Ritchie, 1957). A 0 -< :, c ::c O "t> .; southern provenance for the ash is also indicated by the northerly decrease in grain size of the coarse fraction of the tuff (Binda, Figure 1 - Stratigraphic colum11 and palynomorph w nation of the late 1969). sequence in Alberta and Saskatchewan (from Nambudiri and Hinda, 1991).

' Department of Geology, University of Regina, Regina, SK S4S OA2.

Saskatchewan Gn1/u,:ical Survey 213 2. Field and Laboratory Methods bipyramidal habit which typically have six ident ical pyramid faces capping each end of the crystal (Figure Samples were collected west of the town of 28). These crystal forms are typical of high-quartz that Ravenscrag, in the northeastern comer of Section 22, forms al temperatures above 573°C and arc commonly Township 6, Range 24, west of the third meridian. A found in acidic volcanic rocks (Fisher and Schmincke, 12 m vertical sec tion was sampled at I m intervals. The 1984). mudstone was disaggregated in water and detergent and wet sieved at 100 and 200 mesh. The quartz grains, The "rounded" surfaces on the crystals do not show the which were found in all samples, were hand picked pitted character typical of particles abraded by from the residue under a binocular microscope. Further sedimentary processes, rather the rounding is believed random sampling in abandoned kaolin quarries in the to represent resorption or magmatic corrosion (Figure Cypress Hills of Al berta revealed similar quartz grains. 2), and provides further evidence for a magmatic The grains range in size from approximately 80 to origin. As such, the quartz crystals would have 200 µm . developed as phenocrysts in an acidic magma and suffered varying degrees of resorption prior to being erupted as volcaniclastic components. 3. Results and Discussion Many of the quartz crystals contain fluid indusions The quartz grains represent single crystals, the external which were subjected to heating experiments using a form of which varies from well-preserved with flat U.S.G.S.-type gas-now heating/freezing system. crystal faces and angular or slightly smoothed face Instrumental limitations did not allow the crystals to be intersections (Figures 2A and 28) to rounded with heated to temperatures above 500°C but at that remnant crystal faces (Figure 2C), or no crystal faces at temperature the fluid inclusions were still unchanged. all (Figure 20 ). All crystals display a short prismatic These results, while inconclusive on their own, support

Figure 2 - SEM photographs ofpyro claslic quartz g~ains from the Battle Form_ation of southwesterr, Sas~atc~ei.:a11. . . A) bipyramidal crystal with well-defi11ed crysta_l flab1t, lo11g axi~=/30 ~m; B) b1pyra,mdal '!uai:z ~rysta~ w1th.h,mted prismatic development and incipient resorption, long axu=ISO µm; C) b1pyramida/ quartz crystal with limited pnsmatzc development and advanced resorption, lor,g axis=/60 µm; D) egg-shaped quartz ~rain it1 which th~ crystal faces h_ave been completely obliterated by resorption, conclwidal fra ctures at one end ofthe gram may be due to impact, long ax1s=l JO µm.

214 Summary of lnves1igations / 997 the interpretation that the quartz grains represent Srivastava, S.K. and Binda, P.L. ( 1984): Siliceous and crystals formed at high (magmatic) temperatures. silicified microfossils from the Maastrichtian Battle Formation of southern Albena, Canada; Paleobiologie Contincntale, 24p. 4. Conclusions Unabraded bipyramidal, short prismatic, and "rounded" quartz grains of the late Maastrichtian Battle Formation arc recogni zed as magmatic in origin and represent a pyroclastic component of the lacustrine mudstone. Their occurrence throughout the vertical extent of the unit shows that volcanic ash was falling into the " Battle Lake" from its inception and not just during the time of deposition of the Kneehills Tuff.

5. References Binda, P.L. ( 1969): Provenance of the Upper Cretaceous Kneehills Tuff, southern Albena; Can. J. Earth Sci., v6, p510-513.

____ ( 1970): Sedimentology and vcgetal micropaleontology of the rocks associated with the Cretaceous Kneehills Tuff of Alhena; unpuhl. Ph.D. thesis, Univ. Albena, 273p.

_____ ( 1992): The Battle Formation: A lacustrine episode in the Late Maastrichtian of western Canada; in Mateer. N.J. and Chen, Pei-ji (eds.), Aspects of Non­ marine Cretaceous Geology, Proceedings of the First International Symposium of IGCP 245, C hina Ocean Press. Beijing,, p220-236.

Binda, P.L. and Srivastava. S.K. ( 1968): Silicified megaspores from Upper Cretaceous beds of southern Alberta, Canada; Micropaleo., v l4. pl05- l 13.

Elliott. R.H.J. ( 1960): Subsurface correlation of the Edmonton Formation; J. Alta. So<.:. Petrol. Geo!.. v8. p324-338.

Fisher, R.V. and Schmincke, H. ·U. (1984): Pyroclastic Rocks; Springer-Verlag, New York, 472p.

Folinsbce. R.E.. Baadsgaard, H., Cumming, G.L., Nascimbcnc. J. , and Shafiqullah, M. ( 1965): Late Cretaceous radiomeLric dates from the Cypress Hills of western Canada; Alta. Soc. Petrol. Gcol., 15th Annual Field Confcren<.:e Guidebook, Part l. Cypress Hills Plateau, p 162- I 74.

Furnival, G.M. (1946): Cypress Lake map area, Saskatchewan; Geo!. Surv. Can., Men1. 242, 161 p.

Lerbekmo. J.F. , Evans, M.E., and Baadsgaard, H. (1979): Magnetostratigraphy. hiostratigraphy, and geochronology of Cretaceous-Tertiary boundary sedime nts. Red Deer Valley; Nature. v279, p26-30.

Nambudiri, E.M.V. and Binda, P.L. (1991): Paleobotany, palynology, and depositional environment of the Maastrichtian Whitemud Formation in Alberta and Saskatchewan, Canada; Cretaceous Resear., vl 2, p579- 596.

Ritchie, W.D. ( 1957): The Knechills Tuff: unpubl. M.Sc. thesis, Univ. Alhena. 66p.

Saskatrheww1 Geological Swvey 215 Summary of !nves1igatio11S !997 216