Sedimentology, structure, and age of the Wide Bay Canyon submarine landslide on the southeast Australian continental slope

摘要

Sedimentological analysis and radiocarbon dating of three marine sediment cores collected from the upper continental slope offshore from Fraser Island, Queensland, Australia, indicate the region is dynamic and provide strong evidence for mass movement processes occurring during the Late Pleistocene and Holocene. Two cores were collected within the Wide Bay Canyon submarine landslide scar with a third collected on the adjacent open slope. All three cores present intraformational, mud-clast conglomerates, interpreted to be debris flow deposits comprised of sub-angular to rounded, pebbled and cobble-sized clasts of the hemipelagic muds that typically accumulate in this area. One within-slide core and the open slope core also present coarse-grained, poorly sorted, unconsolidated sand layers that are interpreted to be grain flow deposits derived from continental shelf sands that were driven over the continental shelf edge by the East Australia Current during the Last Glacial Maximum. Radiocarbon dating of unconformities identified in the Wide Bay Canyon slide scar cores indicates that abrasion and sediment removal during the emplacement of debris flows occurred during several separate events prior to similar to 35.1 cal. yr. BP. The sand layers interpreted to be grain flow deposits contain Late Pleistocene age material that was probably re-deposited during the sea level low-stand associated with the Last Glacial Maximum. Consideration of the debris flow ages in the context of ages reported for similar materials and other landslide deposits recorded on the South-eastern Australian Continental Margin supports the previously advanced hypothesis that rare, moderate to large, intraplate earthquakes are a likely triggering mechanism for submarine landslides and/or mass failure events on the South-eastern Australian Continental Margin.