A Seismic Investigation of the Crust and Moho on a Line Perpendicular to the Grenville Front: Reply

Abstract

A major structural feature 50 to 75 km in width has been outlined along the Moho in an area just south of the Grenville Front from a delay-time analysis of Pn waves arriving from a number of different azimuths. The crust in this anomalous region was found to be from 5–10 km thicker than in the surrounding area. The low frequency portion of the gravity low in central Quebec can be attributed to this feature. The fact that the front is deep-seated suggests that it may mark the position of an ancient fault connected tectonically in origin to the mid-continent gravity high and Lake Superior syncline.During the summer of 1968, the University of Western Ontario participated with the Dominion Observatory of Canada and other research groups in a crustal survey of eastern Quebec. Shots of various sizes were fired by the Dominion Observatory at six different locations in central Quebec. Two of the locations were in the Superior (structural) Province, two in the Grenville (structural) Province, and two in the vicini...