Geomorphological features of Queen Charlotte Strait, Pacific coast of Canada, and their implications for ice-sheet retreat and relative sea-level changes during the last deglaciation

Queen Charlotte Strait (QCSt), along the glacial Pacific margin of Canada, preserves seabed geomorphological records of past tectonic, glacial, and oceanographic processes, particularly since the Last Glacial Maximum. These records can provide an analogue for predicting future seabed and sediment dynamics in contemporary ice-covered region and their surroundings under global warming. The present study identifies and maps the seabed geomorphology and stratigraphy of QCSt by analyzing extensive multibeam bathymetry data, sub-bottom profiles, seafloor images, surface sediments, sediment cores, and 14 C dates. The analysis of seabed morphology, erosional and depositional patterns, and sedimentary lithofacies of the late glacial marine geology and postglacial stratigraphy in QCSt collectively allows interpretation of the sequence of processes that formed, shaped, and filled this region. Four primary stratigraphic units were delineated: bedrock, moraines, glaciomarine deposits, and postglacial deposits, along with their seafloor distributions. Seabed features recognized in specific areas include active or relict sand and gravel bedforms, gas masking in thick hemipelagic muds, fan deltas, landslide-gully-fan systems, channels, iceberg lineations, and glass sponge reefs. A series of NNE–SSW-oriented moraines generally indicate ice-sheet retreat eastward toward the Coast Mountains during the last deglaciation, while arcuate moraines northwest of Malcolm Island, curving approximately southward, reflect valley-glacier retreat toward the northern mountains of Vancouver Island. The unconformity atop the glaciomarine deposits, leveled banks, terraces, and other truncated bedforms may indicate past lower sea levels.