Mega-scale glacial lineations formed by ice shelf grounding in the Canadian Beaufort Sea during multiple glaciations

Abstract

Mega-scale glacial lineations formed by the raking of ice shelves across the seafloor have been reported from multiple polar regions. Here, we present the first evidence of continental slope situated buried lineations in the southern Canadian Beaufort Sea in present-day water depths of 220 to 800 m. Three separate surfaces with lineations are defined at sub-seafloor depths of 40 m to 390 m. All lineations are mostly parallel to the general trend of slope contours. The uppermost surface is recognized over a distance of 56 km. In water depths > 500 m the lineations are parallel to each other at a consistent direction (43 degrees-44 degrees). The second lineated surface is a regionally occurring erosional unconformity. This event has two sub-sets of lineations: mid-slope situated lineations oriented at 42 degrees-48 degrees, and lineations closer to the continental shelf break at 55 degrees-59 degrees. The third lineated surface is an unconformable horizon buried up to 390 m below seafloor with lineaments oriented between 30 degrees and 55 degrees. All three sets of lineations are interpreted to have been produced by ice-ploughing on the paleo-seafloor through the grounding of an ice shelf. Our observations are similar to those documented along the slope off northern Alaska, Chukchi Rise, and Lomonosov Ridge. Collectively, these observations support the concept of an extensive ice shelf across the Arctic Ocean that grounded locally along its margins during multiple glaciations, including during the penultimate (or an earlier) glaciation. The youngest set of lineations indicates ice movement to the southwest with a suggested source in Amundsen Gulf and/or M'Clure Strait. Tentative age considerations for these youngest lineations indicate the first evidence for an analogous extensive ice shelf configuration for the Last Glacial Maximum.