Barrie Creeks, Lovers Creek, and Hewitt's Creek Subwatershed Plan

The Barrie Creeks, Lovers Creek and Hewitt’s Creek Subwatershed Plan
2.4.1.3.
Glacial History
Quaternary Geology
The bedrock within the Barrie Creeks, Lovers Creek, and Hewitt’s Creek subwatersheds is
overlain by unconsolidated sediments, known as the overburden, which was deposited during
the Quaternary Period. The Quaternary period is the most recent time period of the Cenozoic
Era on the geologic time scale. The Quaternary Period can be divided into the Pleistocene
(Great Ice Age) and the Holocene (Recent) Epochs. During the Pleistocene, at least four major
continental-scale glaciations occurred, which include, from youngest to oldest, the Wisconsinan,
Illinoian, Kansan, and Nebraskan Stages (Dreimanis and Karrow, 1972). All of the surficial
deposits within the subwatershed, and within most of southern Ontario, are interpreted to have
been deposited by the Laurentide Ice Sheet during the Wisconsinan glaciation. The Laurentide
Ice Sheet is the glacier that occupied most of Canada during the Late Wisconsinan period,
approximately 20,000 years ago (Barnett, 1992).
Sediments deposited during the Late Wisconsinan substage are extensive in southern Ontario,
and are thought to represent all of the surficial deposits in the subwatersheds. All of the deposits
which outcrop at surface within the subwatershed were likely laid down within the last 15,000
years during and after the Port Bruce Stade. Deep boreholes indicated that older Wisconsinan
deposits do occur at depth; however, it is not always possible to date them (Dreimanis and
Karrow, 1972). These deposits are often quarried by the aggregate industry for use in
infrastructure building. The quaternary deposits are depicted on Figure 2-18.
Quaternary Sediment Thickness
Within the subwatersheds the Quaternary sediment thickness is the difference between the
ground surface and the bedrock surface, as determined from borehole and water well
information within the subwatershed. Figure 2-19 shows the thickness ranges from
approximately 83 to 191 m. The Paleozoic bedrock topography appears to strongly influence the
overlying Quaternary sediment thickness and distribution. The thicker Quaternary sediments
occur in bedrock topographical lows (i.e. within bedrock valleys), while the thinnest areas of
Quaternary deposits occur along the shoreline of Kempenfelt Bay.
Chapter 2: Study Area: The Barrie Creeks, Lovers Creek and Hewitt’s Creek Subwatersheds 43