Sedimentary Environment and Glacial History of the Northwest Passage (Canadian Arctic Archipelago) Reconstructed from High-Resolution Acoustic Data

摘要

A 2420 km long profile of high-resolution sub-bottom echosounder data (Parasound) is interpreted for facies distribution and stratigraphy across the Canadian Arctic Archipelago including the continental slopes from Baffin Bay to Beaufort Sea through M'Clure Strait. Five units are identified and interpreted as (ⅰ) bedrock (Devonian sedimentary rocks), unconformably overlain by (ⅱ) subglacial till, overlain by (ⅲ) proglacial diamicton deposited during deglaciation with (ⅳ) Holocene muds on top. Subglacial tills have a basinward counterpart of numerous thick stacked debris-flow deposits found on the continental slopes of Baffin Bay and the Beaufort Sea interfingering with stratified deep-sea sediments at the continental rise (ⅴ). The debris flows are interpreted as mostly LGM in age and built up major glacial Trough Mouth Fans at both ends of Northwest Passage. They are indicative of ocean-ward export of glacial debris from fast flowing ice streams at the shelf edge derived from the Laurentide and Innuitian ice sheets. Diamicton deposited during deglaciation is widespread in the inner part of the Northwest Passage but relatively thin. Evidence of moraines as part of the deglaciation deposits points to a re-advance of grounding ice in places, which we interpret as possibly Younger Dryas and early Holocene in age. Postglacial Holocene sediments of significant thickness (>0.2 m) were only found in depressions of the Lancaster Sound and Barrow Strait.