LONG-DISTANCE TRANSPORTED ERRATICS AT THE ENTRY OF THE SAGUENAY RIVER

Long-distance transported erratics at the entry of the Saguenay River. Many hundred erratics have been observed and mapped at the mouth of t he Saguenay Fjord, both on the present shoreline cut into Quaternary d eposits and in situ in these deposits. Two groups of indicators have b een recognized: those of distal origin (400 to 500 km) and those of pr oximal origin (100 to 200 km). The first group of erratics is composed mainly of the following Precambrian lithologies: conglomerate, stroma tolitic dolostone, and various kinds of dolostones. The second group i s dominated by Ordovician (Trenton) limestone and anorthosite clasts. Based on the glacial flow in the Saguenay area (determined from striae s, and other micro-forms), the limestone erratics originated from the Upper Saguenay area (Saint-Honore) or from the southern part of Lac Sa int-Jean; similarly the anorthosite erratics are from the large anorth osite massif located in the Saguenay-Lac Saint-Jean area. Tillite and dolostone erratics originated from the area of Mistassini, Albanel and Waconichi lakes in the central Quebec area. This implies a Wisconsina n glacial flow to the SE from that area downstream the Saguenay Fjord (Tadoussac), and consequently the existence of a dome and a regional i ce divide located somewhere to the W or the NW of the Lac Mistassini b asin. These data emphasize the validity of the models suggested recent ly by a few workers and stress the interest of mapping long-distance t ransported erratics to determine more accurately the major ice flows.