ABSTRACT: Postglacial faulting within the Temiskaming Graben of Quebec and Ontario; Evidence from Lake Temiskaming.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Lake Temiskaming is a long (100 km) deep (220 m) lake within the Temiskaming Graben of Ontario and Quebec. The graben is an extension of the St. Lawrence Rift System (SLRS) that underlies the St. Lawrence and Ottawa valleys. The SLRS first formed as a Paleoproterozoic `failed rift' and was reactivated during regional extension during Neoproterozic breakup of Rodinia when the Iapetus Ocean opened, and later during the Late Jurassic breakup of Pangea and the opening of the North Atlantic Ocean. The Temiskaming district lies within the Western Quebec Seismic Zone one of the most active in eastern North America characterized by frequently occurring moderate to large magnitude earthquakes such as in 1732 (M5.8; Montreal), 1935 (M6.2 Temiskaming) and 1944 (M5.6; Cornwall). Earthquakes of M$>3$ occur every other year in the Temiskaming area and M6.5 temblers have a 500 yr recurrence interval. High-resolution seismic profiling of the floor of Lake Temiskaming shows that much of the bathymetric relief throughout the lake basin is the product of postglacial neotectonic faulting of the late Pleistocene and Holocene sediment fill. The onshore continuation of prominent faults is marked by linear fault scarps and by straight river valleys. The scale of neotectonic activity is highly unusual for an intracratonic setting, with implications for seismic risk analysis and public safety.

Bibliography of Canadian Geomorphology