Bedrock geology of Hudson Strait and Ungava Bay

This paper summarizes information regarding the bedrock geology underlying Hudson Strait and Ungava Bay interpreted from seismic reflection data together with shallow borehole information, published data from adjoining terrestrial areas, and from an exploratory well on Akpatok Island. Hudson Strait is underlain primarily by Lower Paleozoic sedimentary rocks (mainly calcareous carbonate rocks) that contact Precambrian metamorphic rocks of the adjacent land masses not far from the coasts of Baffin Island and Ungava and Labrador peninsulas. These sedimentary rocks also form the central platform in Ungava Bay. Younger strata, possibly of Mesozoic age occur locally in Eastern basin and their presence has also been postulated in parts of western and southwestern Hudson Strait. Three half-graben structures, downfaulted against older rocks at their southern margins, form prominent structural features in the floor of Hudson Strait. Phanerozoic (mainly Lower Paleozoic) sedimentary rocks thicken southward in these structures reaching 2000 m or more in Eastern basin. These basins have been sites for deposition of Quaternary sediments that locally reach more than 100 m in thickness. Calcareous sediments and erratics derived from glacial erosion of the Paleozoic strata are important markers in interpreting ice-flow patterns in the region and sediment dispersal seaward.