Surficial Geology of Saint-sylvestre map area, Quebec

The Saint-Sylvestre map-area lies across the boundary between the Eastern Quebec Uplands (northwest half of the area) and the Sutton anticlinorium (southea st half) which forms a steepsided range of hills known as the Notre Dame Mountains. The mountains rise to 2290 feet (695 m) a.s.l. in the area which is 1500 feet (455 m) above the general level of the Eastern Quebec Uplands. The apical segment of the St. Lawrence Lowland at Quebec city a few miles north of the map-area is much lower. Total relief between the Lowland areas around Quebec city and the Notre Dame Mountains is roughly 2000 feet (600 m). Till of Laurentide provenance. i.e. with lithology showing abundance of erratics from Laurentian Shield areas north of St. Lawrence River is typical of the area. Colour and texture of the till vary with those of underlying intensely folded thin-bedded Paleozoic rocks. With few exceptions colour texture and lithology trains in the basal till extend southeastward from outcrops showing that glaciers involved in their deposition moved from northwest to southeast crossing the regional bedrock structure at approximately right angles. The Highland Front morainic system type section lies against the north-facing flank of Notre Dame Mountains. Lithology of the dominant ice-contact stratified drift like that of regional till. shows northern provenance. Lacustrine sediments were ponded in north-sloping valleys on the north flank of Notre Dame Mountains by ice that built the Highland Front system. The ponded sediments occupy depressions in terrain that has been striated by a late northward movement of ice but that was ice free during deposition of the lacustrine sediment. It is concluded therefore that the northward ice movement predates formation of the Highland Front moraine and associated ice-marginal lakes.