ABSTRACT: Reconnaissance sub-bottom profiling results from selected basins along the lower French River, Ontario.

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Abstract

During the late Pleistocene and early to mid-Holocene, lake levels within the Lake Huron and Georgian Bay basins experienced a sequence of major transgressions and recessions due to the deglaciation of successively lower outlets, periods of major melt water influx from glacial lakes Agassiz and, possibly, Ojibway, and/or the progressive isostatic tilting of the basins . Of specific interest are three intervals of low water levels known as the early-, mid-, and late Stanley-Hough stages that existed at approximately 10.1-9.7, 9.4-9.3 and 8.3-8.1 ka BP, respectively. During at least the earliest of these stages, separate water bodies existed in the Lake Huron and Georgian Bay basins. Outlet flow from Lake Hough, which occupied the Georgian Bay basin and was the lower of the two lakes, was towards the east-northeast through the French River–Lake Nipissing–North Bay corridor, down the Mattawa-Ottawa river system (Fig. 1A), and into the Champlain Sea that occupied the lower Ottawa Valley. Recently, it has been hypothesized that one or more of the Stanley-Hough low stages may have entered climatically-driven, closed-basin phases, when water levels receded below the level of the controlling outlet sill causing outflow to cease through the French River–Lake Nipissing–North Bay corridor. A project within the Reducing Canada’s Vulnerability to Climate Change Program has been investigating the evolution and controls of lake level fluctuation in the Great Lakes basins, specifically focusing on the possible occurrence of and controls upon the closed-basin phases during the Stanley-Hough low stages. The project includes a research activity that is examining the lower French River area, Ontario (which was part of the ancient outlet of the upper Great Lakes) for evidence that can confirm or reject the closed-lake phase hypothesis. This research has collected sub-bottom profiling data from selected bays and lakes within the lower French River system (Figs. 1B and 2). The profiling was undertaken specifically to: 1) determine if late Pleistocene and Holocene deposits are preserved in the watershed basins; 2) develop a sub-bottom stratigraphy of the deposits; and 3) identify locations for coring to investigate the composition and depositional history of the deposits. This Open File report presents the methodology, locations and results of the sub-bottom profiling surveys, and generalized stratigraphy of the sub-bottom deposits. The integration and interpretation of the sub-bottom stratigraphy with core data will be reported elsewhere after the coring program is completed.

Bibliography of Canadian Geomorphology