ABSTRACT

The Gowganda Formation, which outcrops north of Lake Huron, is a world-famous example of a glacial deposit. It was interpreted by Lindsey as continental in origin in the north (Cobalt area) and marine in the south, near Whitefish Falls. However, drill cores from near the northern limit of the outcrop consist entirely of resedimented glacial diamictites, ice-rafted deposits, and pelagic marine-shelf sediment. No true tills (sediments deposited by grounded ice) are present in these cores or in outcrop near Elliot Lake. Reinterpretation of the diamictites and sandstones is based on recent improvements in our understanding of sediment gravity flows. The conglomerates are debris flows, and the sandstones include liquefied/fluidized and grain-flow deposits and thin-bedded turbidites. These ediments show crude upward-fining cyclicity or grading and probably were deposited on submarine outwash fans.

The presence of marine deposits so far north and the absence of true tills calls for a reappraisal of Gowganda sedimentology by means of modern sedimentological basin-analysis techniques. A depositional model based on an ice shelf is proposed.