Abstract

This paper identifies the sedimentary record of storms and bottom-scouring ice masses that is preserved in upper Pleistocene glaciolacustrine delta sediments. Deltaic sedimentation occurred on the margin of an enlarged, ice-dammed ancestral Lake Ontario with a surface elevation at least 80 m above the modern level. Beds of amalgamated hummocky and swaley cross-strata separated by fairweather muds represent delta-front storm deposits and overlie laminated prodelta clays. The central and thickest part of a 5-km-long outcrop exposes variably cross-stratified sand, in multiple channels, inset within tabular sheets of rippled sand. This complex represents a broad distributary channel system about 1-6 km wide and 20 m deep, cut into delta-front storm sequences. A large scour and related deformation structures are attributed to bottom-dragging ice masses, possibly pressure-ridged lake ice.

The depositional setting outlined in this paper emphasizes the importance of storm waves in large "continental" glacial lakes and provides a contrast with better known low-energy conditions in small glacial lake basins.

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