Resedimented conglomerates of Huronian (lower Aphebian) age, from the north shore of Lake Huron, Ontario, Canada

Abstract

Conglomeratic rocks are present near the top of a dominantly arenaceous sequence, previously ascribed entirely to the Huronian Mississagi Formation, in a belt extending for about 60 km east of Blind River, on the north shore of Lake Huron. These conglomeratic rocks and the massive and planar laminated sandstones which overlie them are herein named the Lauzon member, after the thickest exposed development of the sequence at Lauzon Lake in Striker Township. The presence of dropstones in the sequence at Lauzon Lake suggests that the member is best considered as part of the Bruce Formation. Conglomeratic rocks within the Lauzon member include granule-supported boulder, cobble, and pebble conglomerate; sand-supported cobble and pebble conglomerate; intact framework graded and non-graded pebble and cobble conglomerates; stratified conglomerates and conglomeratic sandstones; and disrupt framework conglomerates. These conglomeratic rocks lack abundant mud-grade matrix material and, hence, are readily distinguished from (glaciogenic?) mixtites of the Ramsay Lake, Bruce, and Gowganda Formations. Conglomerates of the Lauzon member were probably deposited from sediment gravity flows within a series of subaqueous fans or fan head valleys which may have been initiated by contemporaneous movements along a precursor to the Murray Fault system at the onset of the Bruce glaciation.