ABSTRACT: Quatenary stratigraphy and sedimentology north-central shore Lake Erie, Canada

CGRG Bibliography of Canadian Geomorphology
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Abstract

The Quaternary deposits and features observed within the study area are of Late Wisconsinan age. They record a fluctuating eastward recession of the ice margin during the Port Bruce Stadial and Mackinaw Interstadial, during which time six end moraines were formed. Large ice-contact glacier-fed lakes fronted the ice margin during deglaciation. The Erie Lobe most likely behaved as an ice stream, with its rapid movement controlled predominantly by a deforming bed of glacial debris, separating the glacier sole from underlying pre-deposited sediments. The deforming bed is preserved as a massive diamicton layer, interpreted as subglacial till. Detailed studies of coastal cliff exposures through two end moraines form the basis for a model of ice-marginal sedimentation in large ice-contact glacier-fed lakes. The input to the ice marginal environment directly from the glacier included subglacial till and subaquatic flow tills. The subaquatic flow till (thinly-bedded diamicton) was deposited in an apron (up to 1 km wide) along the ice margin. An upward gradient of porewater pressure immediately beyond the ice margin, causing heaving and dilation of the sediments, initiated debris flows of glacially-derived debris (subaquatic flow tills). Most of the stratified sediments in the ice-marginal zone entered the lake by way of a large proglacial stream. Sedimentation was dominated by quasi- or near-continuous density underflows that resulted in the deposition of a sequence of thick rhythmites. With eastward retreat of the ice margin, water levels in the Erie Basin fell. The sediment sequence of the Jacksonburg Delta records the lowering of water level to approximately 183 m and defines a glacial lake at this level that probably drained westward. The deglaciated area of southern Ontario, Ontario Island, supported a diverse assemblage of plants now found in arctic, boreal, and prairie environments. Spruce trees were probably present as early as 13,400 B.P. A previously unknown postglacial lake level, approximately 5 m above the present level of Lake Erie was identified. A moraine dam across the Niagara River is suggested as the controlling sill of this lake that may have existed only 2,000 to 3,000 years ago.

Bibliography of Canadian Geomorphology