Abstract

The Pleistocene sequence at the Canada Cement Plant No. 4 quarry at Zorra is remarkable for the large number of till sheets it contains; nine physically distinct tills, intercalated with stratified drift, are present. These glacial deposits, laid down by Erie, Huron, and Georgian Bay ice lobes, are continuously exposed along a graphic-mile long face that reaches a height of 70 ft in places.Lithologic and till fabric studies, analysis of striae on bedrock and boulder pavements, plus observations on the orientation of streamlined glacial landforms in the Zorra district, were carried out in an attempt to determine the parent ice lobe of each till. Erie lobe deposits constitute the lower part of the sequence (units A and B); units C and D were deposited by Georgian Bay and Huron ice lobes respectively; units E, F, and G are related to an Erie lobe whereas units H and I were laid down by a Huron ice lobe.On the basis of lithology, till fabric, and stratigraphic position, the Zorra tills have been correlated with tills exposed along the Nith River and in the area between Thames River and Lake Erie, southwestern Ontario. From the proposed correlation it follows that units A and B are of Early Wisconsin age; units C and D, of Mid-Wisconsin age; all younger units are of Main or Late Wisconsin age.

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