ORIGIN AND PHYSICAL AND CHEMICAL CHARACTERISTICS OF GLACIAL OVERBURDEN IN ESSEX AND KENT COUNTIES, SOUTHWESTERN ONTARIO

The overburden of Essex and Kent counties, southwestern Ontario, has b een described as consisting of a clayey silt to silty clay till overly ing a gravelly unit resting on bedrock. Recent Quaternary geology mapp ing has identified additional materials and redefined the origin of ot hers by determining the stratigraphic position and physical and geoche mical properties of materials encountered in a sonic drilling program and field mapping. Catfish Creek Till was deposited on the bedrock sur face during the Nissouri Stadial as ice advanced south over the area. As ice retreated during the Erie Interstade, fine-grained glaciolacust rine material was deposited in glacial Lake Leverett and overlay Catfi sh Creek Till. Tavistock Till was deposited over glacial Lake Leverett material as the Huron lobe readvanced south during the Port Bruce Sta dial. As the Huron lobe retreated north, coarse-grained glaciolacustri ne materials were deposited in the Leamington area. Ice from the Erie lobe deposited the Port Stanley Till along the north shore of Lake Eri e in Rent County and deflected meltwater southward from the Huron lobe in the Blenheim area. A series of recessional moraines were deposited by the Huron lobe as it retreated north. The area is capped by a fine -grained glaciolacustrine deposit.