western quebec and southern ontario - Department of Geology

esearchers investigated the tectonic features of the Grenville orogen by deep seismicreflection imagery from seismic surveys (e.g., White et al., 2000; Forsyth et al., 1994a,b).White et al. (2000) proposed a seismic-based cross-section for the southwest GrenvilleProvince. This section shows that domains within the lithotectonic settings are separatedby a series of northwest-directed thrust sheets. Seismic sections proposed for the orogenbeneath the Great Lakes by Forsyth et al., (1994a,b) and that proposed for areas farthereast in Quebec by Martignole & Calvert (1996) demonstrate similar crustal features.Seismic reflection images of the GFtz, CMBbtz, and EFbz display shallow to moderateeast-dipping reflections that continue to mid-crustal depths (12-20 km) (Green et al.,1988; Milkereit et al., 1992; White et al., 1994). Culotta et al. (1990) proposed that theboundary between the Elzevir and Frontenac terranes could be the eastern edge of thecrustal block of west-dipping features that extends south-west to Alabama.Southern Ontario has continuously experienced relatively small seismic events.Stevens (1994) described the seismicity of this region as “intermittent scattered activity”with no preferred trends. Other authors, however, suggested a link between seismicactivity of this region and magnetic lineaments associated with basement shear zones(e.g., Thomas et al., 1993; Mohajer, 1993; Wallach et al., 1998). Some authors have alsomade a connection between basement features and current seismicity (Mohajer, 1993;Seeber & Armbruster, 1993; Wallach et al., 1998; Boyce & Morris, 2002). Howeverthese studies have been primarily qualitative in nature. Godin et al., (2002) proposed aglaciotectonic origin for most of the deformation features observed in the Rouge Rivervalley in the region of Toronto. Mereu et al. (2002) summarized the existing publicationson seismicity and revised the hypocentre locations in the region for the period 1990 –21