The Quaternary Deltaic Series of the St. Lawrence Estuary (Canada): An Analog for the Paleozoic Glacial Reservoir Deposits

Bernard F. Long¹ and Mathieu J. Duchesne^2
1 Institut National de la Recherche Scientifique, Quebec City, QC
² Geological Survey of Canada, Quebec City, QC

Neo-Proterozoic and Permo-Carboniferous glacial and postglacial marine sediments can be found in several places in the world (e.g. Arabic Peninsula, South Africa) but only few recent analogs exist. The St. Lawrence Estuary is one of these few analogs whereas at least five Quaternary glacial and interglacial series are stacked. The geometry of these series is controlled by transverse faults reactivation caused by ice-sheet and sediment loading, and by glacio-isostatic rebound. These geological processes led to the formation of reservoirs located in four grabens. Each of these reservoirs is associated with a series of deep-sea fans linked to lateral deltas constructed during the forced-regression and lowstand periods in a shelf-edge position, and by the progradation of the proximal St. Lawrence delta itself. Throughout the glacial stages, ice eroded the upper portion of the preceding sequence and created two types of till: a coarse till prolonging the coarse-grain delta and a fine till constituting a seal layer for the previous deltaic reservoir. The reservoirs are mostly elongated and distributed on a length of 400 km by a width of 30 km and a thickness of 0.5 to 1.5 km.