Abstract

This paper describes the seismic stratigraphy of the Quaternary sediments on the inner shelf (< 20 m water depth) of the Canadian Beaufort Sea, seaward of the Tuktoyaktuk Peninsula. Two regional unconformities and three seismic sequences are defined from the high-resolution seismic records. The deeper sequence (sequence III) is characterized by large-scale cross-beds. This sequence has been correlated with the Tingmiark Sand lithostratigraphic unit, which was previously defined farther offshore and is thought to be a glaciofluvial unit deposited during lower-than-present sea-level conditions in the Late Wisconsinan. The lower boundary of the overlying sequence (sequence II) is an unconformity (u/c 2), interpreted as the pre-transgression land surface. Sequence II is discontinuous and consists of localized basin-fill and channel-fill units. Most of these are remnants of thermokarst lakes partially eroded during the Holocene transgression. This sequence is separated from the uppermost sequence (sequence I) by another unconformity (u/c 1), which is the shoreface erosion surface generated by the Holocene sea-level rise. Sequence I is composed of a transgressive sand sheet overlain, in deeper areas, by recent marine muds. Seaward of Hutchison Bay, a large subbottom depression within sequence III in interpreted as a Late Wisconsinan fluviatile channel. According to our seismic interpretation, the Tuk Phase morainal and glaciofluvial deposits existing onland on the Tuktoyaktuk Peninsula, previously assigned to the Early Wisconsinan, would be of Late Wisconsinan age.

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