ABSTRACT

Lower and upper tills from the area along the north shore of Lake Erie were studied by various field and laboratory methods in order to determine which of them would be the most suitable for later and more detailed investigations.

Where only differentiation of two tills is required the following methods were found to give the best results: determination of color and grain-size, petrographic analyses, particularly of the 0.5-1.0 mm grade, heavy mineral investigations and determination of carbonate content of the silt+clay grade.

Where provenance is the dominant consideration field studies of till fabric and till stones (alignment of stones, orientation of pentagonal pebbles, striage on boulder pavements), petrographic investigation of sand and pebble grades, heavy mineral investigations, particle size analyses, and determination of carbonate content, seem to be most suitable as illustrated in this paper.

Some preliminary conclusions are drawn in respect to provenance of the two tills and ice flow directions. The upper till has a higher percentage of local materials from the Lake Erie basin, such as Devonian shales and Pleistocene lacustrine deposits. This indicates an intensive erosion of the lake depression during the period of deposition of the upper till.

Differences in the pre-Cambrian components of the two tills suggest that the earlier ice flow, depositing the lower till, came from north-northeast, but the later one, depositing the upper till, was along the Lake Ontario and Lake Erie basins.