Stratigraphy and palaeoenvironments of Richards Island and the eastern Beaufort Continental Shelf during the last glacial‐interglacial cycle

The Pleistocene lithostratigraphy exposed on northern Richards Island comprises seven units that correlate with the offshore seismostratigraphy of the eastern Beaufort Continental Shelf. Land‐sea correlations, cryostratigraphic observations and proxy indicators of environmental change provide a record of palaeoenvironmental history that commences before the last glacial‐interglacial cycle. After the high sea‐level stand of the Last (Sangamonian) Interglaciation, marine regression exposed a large area of the eastern Beaufort Shelf to cold subaerial conditions and permafrost aggradation. Northward progradation of a braided river system was abruptly replaced by aeolian activity, probably as a result of diversion of the palaeo‐Porcupine River by the advancing Laurentide Ice Sheet during the Late Wisconsinan. Glaciation of Richards Island by the Mackenzie palaeo‐ice stream was brief (sometime between ∼22 000 and 16 000 cal. yr BP), and deglaciation had certainly commenced by 14 300 cal. yr BP and perhaps by ∼16 000 cal. yr BP or earlier. Major fluvial erosion during the Last Glacial‐Interglacial Transition incised cross‐shelf valleys and formed a regional erosion surface. The Holocene marine transgression trimmed some of the erosion surface and offshore, covered it with marine deposits. Copyright © 2009 John Wiley & Sons, Ltd.