The morphosedimentary record of glacial to postglacial environmental changes in West Wiyâshâkimî impact crater lake and adjacent areas, northern Québec, Canada

Crater lakes in core regions of former ice sheets have the potential to preserve long‐term sedimentary archives that are otherwise rare in glaciated landscapes due to pervasive glacial erosion. Lake Wiyâshâkimî, an impact crater lake located in the inner core of the Québec‐Labrador Dome of the Laurentide Ice Sheet, provides a rare example of such a setting. The lake was therefore investigated along the region surrounding it through remotely sensed mapping and acoustic sub‐bottom profiling to reconstruct its glacial to postglacial environmental evolution from its morphosedimentary record. Mapping of ice‐flow landforms suggests three distinct glacial flowsets in the region, indicating a transition from external ice‐stream influences to local topographical controls during deglaciation. Contrary to previous hypotheses, mapping evidence suggests that the Tyrrell Sea deglacial marine transgression did not reach Lake Wiyâshâkimî, with surrounding strandlines likely of glaciolacustrine origin. Five acoustic facies were identified from the analysis and interpretation of the acoustic sub‐bottom profiles: AF1, bedrock, till and/or glacifluvial sands forming the acoustic basement; AF2, an acoustically transparent deposit filling the deeper basins of the lake, a fine‐grained diamicton either associated with mass‐movements or full glacial conditions (till); AF3A and AF3B, glaciolacustrine sediments deposited proximally and distally from the ice margin, respectively; and AF4, paraglacial and postglacial deposits that have been partly, at least in the upper tens of metres of the water column, remobilized by bottom currents induced by strong winds prevailing in the large lake. While our analysis shows it is unlikely that sediments pre‐dating the last glaciation were preserved in the lake basin, the findings provide new insights into the lateglacial and deglacial history of the central Québec‐Labrador region and highlight the role of postglacial processes in shaping the lake‐bottom morphosedimentary archives.