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Sedimentary Geology, 47 (1986), 27-52

PLEISTOCENE GLACIO-LACUSTRINE DELTAIC DEPOSITS OF THE SCARBOROUGH FORMATION, ONTARIO, CANADA

R.I. KELLY and I.P. MARTINI

Department of Land Resource Science, University of Guelph, Guelph, Ont. N1G 2W1 (Canada)

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image_37.jpg (438018 ×Ö½Ú)The late Pleistocene Scarborough Formation of the Lake Ontario Basin represents a lacustrine-deltaic sequence strongly affected by a nearby glacier. It shows gradual upward coarsening and thickening of layers from varve-like, clay-rich rhythmites at the base to channelized cross-bedded sands at the top. Thick, lensing, "massive" layers (Cm) of silty sand are found interstratified with thin layers of silt and clay in the lower and middle parts of the sequence. These" massive" layers were probably formed by subaqueous gravity flows of material in part derived directly from a glacier. Absence of pebbles and of other features such as glacial silt-pellets suggests dispersal away from the foot of the glacier rather than deposition under floating ice. Varve-like rhythmites, pollen and insect fauna indicate subarctic to arctic climatic conditions at the time of sediment deposition. The large amount of sand in the upper part of the formation is best explained as derived from active outwash fans. Similar fans were formed during the last deglaciation in southern Ontario and can be observed on the landscape.

 

 

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