Hudson Bay Lithospheric Experiment (HUBLE)

Abstract

We are carrying out a broadband seismological study of the Hudson Bay region of northern Canada with the view to understanding better the reasons for the Bay’s existence, and the nature of the tectonic processes that shaped the Canadian shield during the Precambrian. The network consists of 10 CMG3T G¨uralp instruments with a combination of Taurus and DCM data loggers recording data at 40Hz in both remote (solar powered) and community (mains powered) locations. Our work is being carried out in conjunction with the Geological Survey of Canada who are providing significant logistical and financial support beyond the scope of the original NERC-funded proposal. To date, data quality has been excellent, with percentage recovery good except during the long Canadian winters when stations powered down. A number of publications have already resulted from analysis of the new dataset showing that: (i) the lithosphere in the region has retained a ∼1.8 Ga fossil fabric, providing strong evidence that modern-day-style plate tectonics was in operation by Paleoproterozoic times (the Trans Hudson Orogen). (ii) Crustal formation of the Canadian Shield likely evolved from one characterised by a hot ductile regime during the Paleoarchean, to one more closely resembling modern-day-style plate tectonics by the Paleoproterozoic. (iii) Crustal stretching, not a mantle down-welling, eclogitised lower-crust, or incomplete glacial rebound are likely responsible for the presence of the Bay.