Microstructures in Diamictites of the Lower Gowganda Formation (Huronian), Near Elliot Lake, Ontario: Evidence for Deforming-Bed Conditions at the Grounding Line?

Abstract

ABSTRACT Diamictites examined in the lower Gowganda Formation (2.5-2.2 Ga) to the north of Elliot Lake reveal a large number of macrostructures and microstructures. From micromorphological analyses the microstructures show a group of structures indicative of both ductile and brittle deformation likely developed during glacial sedimentation. The diamictites possibly were deposited in a proximal subglacial or subaqueous environment as a product of soft deforming-bed sediments being extruded beneath an active ice sheet at its grounding-line margin as it entered a marine basin. This is the first known example of glacial deforming-bed conditions being shown to have possibly developed beneath Precambrian ice sheets.