Abstract
Sediments retrieved from a long core on the floor of glacial Lake Assiniboine, Saskatchewan, expose 106 couplets, consisting of thick, light coloured, silt-rich beds and thin, dark, clay-rich beds. The couplets contain sharp lower and upper contacts of the silt bed, silty and clayey laminations within both the silt and clay beds, and ice-rafted debris in the silt beds, which are features characteristic of glacial varves.
Seasonal variations in runoff are reflected in grain size profiles of individual silt beds in the varves. Mean grain size maxima in the lower portion of the silt bed suggest that snow accumulation during the previous winter had been substantial and that a warm spring combined with a rapid melting rate generated significant volumes of nival meltwater runoff. Coarse laminae higher in the silty part of the couplet imply that substantial meltwater inflow was produced by summer melting of glacier ice.
Vertical trends in clay bed thicknesses, silt bed thicknesses, and total couplet thicknesses were strongly influenced by the proximity of meltwater inflow channels and lake depth. These interpretations, and correlation of the core to varve exposures at the surface, formed the framework for a paleohydrological reconstruction. Close to 11,000 BP, ice dammed the outlet of glacial Lake Assiniboine and the water depth rose about 2 m yr−1. Eventually the lake became deep enough for couplets to form. Varve years 1–40 contain thick clay beds, silt beds, and couplets as a result of the proximal inflow of meltwater. A decline in silt bed and couplet thicknesses from varve years 41–85 occurred in response to ice retreat and more distal inflow. Varve deposition ceased in the shallow part of the basin probably because underflow currents from the distal source were redirected. Varve years 86–106 are distinguished by an increase in silt bed and couplet thicknesses and a decrease in clay bed thickness caused by a reduction in water depth and a return to proximal inflow. Varved sedimentation terminated when Lake Assiniboine drained through the Assiniboine valley to Lake Agassiz.
Similar content being viewed by others
References
Agterberg, F.P. & I. Bannerjee, 1969. Stochastic model for the deposition of varves in glacial Lake Barlow-Ojibway, Ontario, Canada, Can. J. Earth Sci. 6: 625–652.
Anderton, R., 1985. Clastic facies models and facies analysis. In P.J. Brenchley & B.P.J. Williams (eds.), Sedimentology: Recent Developments and Applied Aspects. The Geological Society (London): 31–47.
Ashley, G.M., 1975. Rhythmic sedimentation in glacial Lake Hitchcock, Massachusetts-Connecticut. In A.V. Jopling and B.C. McDonald (eds.), Glaciofluvial and Glaciolacustrine Sedimentation. Society of Economic Paleontologists and Mineralogists Special Publication 23: 304–320.
Ashley, G.M., 1988. Classification of glaciolacustrine sediments. In R.P. Goldthwait & C.L. Matsch (eds.), Genetic Classification of Glacigenic Deposits, A.A. Balkema, Rotterdam: 243–260.
Bannerjee, A., 1973. Sedimentology of Pleistocene glacial varves in Ontario, Canada. Geological Survey of Canada Bulletin 226, Part A. Ottawa, Canada. 44 p.
Catto, N.R., 1987. Lacustrine sedimentation in a proglacial environment, Caribou River Valley, Yukon, Canada. Boreas 16:197–206.
Christiansen, E.R., 1979. The Wisconsin deglaciation of southern Saskatchewan. Can. J. Earth Sci. 16: 913–938.
DeGeer, G., 1912. A geochronology of the last 12,000 years, Compt. Rend. 11e Congr. Geol. Internat., Stockholm 1: 241–258.
Fenton, M.M., S.R. Moran, J.T. Teller, & L. Clayton, 1983. Quaternary stratigraphy and history in the southern part of the Lake Agassiz basin. In J.T. Teller and L. Clayton (eds.), Glacial Lake Agassiz. Geological Association of Canada Special Paper 26: 49–74.
Gilbert, R., 1975. Sedimentation in Lillooet Lake, British Columbia. Can. J. Earth Sci. 12: 1697–1711.
Gilbert, R. & J.R. Desloges, 1987. Sediments of ice-dammed, self-draining Ape Lake, British Columbia. Can. J. Earth Sci. 24: 1735–1747.
Gravenor, C.P. & D.A Coyle, 1985. Origin and magnetic fabric of glacial varves, Nottawasaga River, Ontario, Canada. Can. J. Earth Sci. 22: 291–294.
Kehew, A.E. & M.L. Lord, 1987, Glacial-lake outbursts along the mid-continent margins of the Laurentide ice-sheet. In L. Mayer and D. Nash (eds.), Catastrophic Flooding. Allen & Unwin, Winchester: 95120.
Klassen, R.W., 1972. Wisconsin events and the Assiniboine and Qu'Appelle valleys of Manitoba and Saskatchewan. Can. J. Earth Sci. 9: 544–560.
Klassen, R.W., 1975. Quaternary geology and geomorphology of Assiniboine and Qu'Appelle valleys of Manitoba and Saskatchewan. Geological Survey of Canada Bulletin 228. Ottawa, Canada. 61 p.
Leonard, E.M., 1986. Varve studies at Hector Lake, Alberta, Canada, and the relationship between glacial activity and sedimentation. Quat. Res. 25: 199–214.
Nielsen, E., 1988. Surficial Geology of the Swan River Area. Geological Report GR80-7. Manitoba Energy and Mines, Geological Services, Winnipeg, Canada. 51 p.
O'Sullivan, P.E., 1983. Annually-laminated lake sediments and the study of Quaternary environmental changes — a review. Quat. Sci. Rev. 1: 245–313.
Peach, P.A. & L.A. Perrie, 1975. Grain-size distribution within glacial varves. Geology 3: 43–46.
Perkins, J.A. & J.D. Sims, 1983. Correlation of Alaskan varve thickness with climatic parameters, and use in paleoclimatic reconstruction. Quat. Res. 20: 308–321.
Ringberg, B., 1991. Late Weichselian clay varve chronology and glaciolacustrine environment during glaciation in southeastern Sweden. Sveriges Geologiska Undersokning. Ser Ca, No. 79. Uppsala. 42 p.
Shaw, J. & J. Archer, 1978. Winter turbidity current deposits in Late Pleistocene glaciolacustrine varves, Okanagan Valley, British Columbia, Canada. Boreas 3:123–130.
Shaw, J., R. Gilbert, & J.J.J. Archer. 1978. Proglacial lacustrine sedimentation during winter. Arc. Alp. Res. 10: 689–699.
Smith, N.D., 1978. Sedimentation processes and patterns in a glacier-fed lake with low sediment input. Can. J. Earth Sci. 15: 741–756.
Smith, N.D. & G.M. Ashley, 1985. Proglacial lacustrine environment. In G.M. Ashley, J. Shaw, and N.D. Smith (eds.), Glacial Sedimentary Environments. Society of Economic Paleontologists and Mineralogists Short Course Notes 16:135–216.
Stenborg, T., 1970. Delay of run-off from a glacier basin. Geograf. Ann. 52: 1–30.
St. Onge, D.A., 1972. Sequence of glacial lakes in north-central Alberta. Geological Survey of Canada Bulletin 213. Ottawa, Canada. 16 p.
Tyrrell, J.B., 1892. Report on northwestern Manitoba with portions of the adjacent districts of Assiniboia and Saskatchewan. Geological Survey of Canada Annual Report 5. Ottawa, Canada.
Wolfe, B., 1993. Geological History of Glacial Lake Assiniboine, Saskatchewan. Unpublished M.Sc. Thesis. University of Manitoba, Winnipeg, Manitoba, Canada. 391 p.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Wolfe, B., Teller, J.T. Sedimentological and stratigraphic investigations of a sequence of 106 varves from glacial Lake Assiniboine, Saskatchewan. J Paleolimnol 9, 257–273 (1993). https://doi.org/10.1007/BF00677217
Issue Date:
DOI: https://doi.org/10.1007/BF00677217