Significance of Sedimentological Studies on the Wisconsinan Stratigraphy of Southern Ontario

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>Detailed facies mapping along Lake Erie and Lake Ontario Bluffs, plus other studies illustrate that sedimentological studies, especially those with geomorphic or landform control, have had three main effects on the Wisconsinan stratigraphy of Ontario: (1) improved understanding of depositional processes and environments of several major rock stratigraphic units, without altering the stratigraphic framework, (2) aided correlation of drift sequences, and (3) questioned previous interpretations and stratigraphic correlations of drift sequences. Thus sedimentological analysis can not be separated from stratigraphy because the interpretation of depositional environnments of many mapped strata relies on their geometry and the inclusion of regional data. The geomorphic control provided by sedimentological study of surface landforms is also important because assessment of older buried sediments such as those at the Scarborough Bluffs has been hampered by the failure to determine landform control. The Late Wisconsinan stratigraphy of Southern Ontario generally remains unchanged, except for questions on the role of climate versus ice margin dynamics. The pre-Late Wisconsinan stratigraphy is scarce and not well defined, yet sedimentary studies support the presence of glacial ice in the Ontario Lake basin for all of the Middle Wisconsinan and possibly earlier, including the formation of the Scarborough delta. Large channel cut and fill sequences in the Toronto area (Pottery Road Formation), initially interpreted as resulting from subaerial erosion, were probably formed by subaqueous or subglacial meltwater erosion. If so, the pre-Late Wisconsinan stratigraphy in southern Ontario changes because the Pottery Road Formation may not be an Early Wisconsinan correlative of the St. Pierre beds. The channel example illustrates that stratigraphie correlation without sedimentological investigations may be misleading.</jats:p>

The pre-Late Wisconsin stratigraphy of southern Simcoe County, Ontario: implications for ice sheet buildup, decay, and Great Lakes drainage evolution

“…2) overlies the Scarborough Formation and records the further encroachment of ice into the Ontario basin. Divergent views on the origin of these deposits, i.e., glacial (Karrow 1967;Sharpe and Barnett 1985;Hicock and Dreimanis 1992) sented; however, both interpretations are in agreement regarding the presence of glacial ice well within the Lake Ontario basin. Ice certainly advanced south and west of the Rome outlets (Fig.…”

“…Modified from Dreimanis (1992). a drop in base level causing subaerial erosion of the delta surface (Karrow 1967); enhanced scour by fluvial feeder systems and slumps off the delta front during ice advance from the northeast ; or subglacial meltwater erosion (Sharpe and Barnett 1985). Karrow (1974) suggested that fossiliferous gravels (Pottery Road Formation) partially infilling these valleys may be correlative to the St. Pierre beds in the St. Lawrence lowlands.…”

“…Understanding of previous climatic conditions was deciphered from decades of investigations on isolated exposures of pre-Late Wisconsin sediments in pits and quarries (Coleman 1932;Westgate and Dreimanis 1967), along prominent Lake Ontario shore bluffs at Scarborough (Karrow 1967;Sharpe and Barnett 1985;Eyles and Clark 1988), and Bowmanville (Brookfield et al 1982;Brookfield and Martini 1999), as well as the north shore of Lake Erie (Dreimanis et al 1966;Dreimanis 1992;Dreimanis and Gibbard 2005;Fig. 1a).…”

Subglacial and ice‐marginal landforms in south‐central Ontario: implications for ice‐sheet reconfiguration during deglaciation

“…comm. cited in Sharpe & Russell ), or between deposition of the NT and the HT, during a period of localized ice withdrawal (White ; Chapman & Putnam ; Sharpe & Barnett ; Karrow ; Slomka ). Areas where the ice re‐advanced over lake sediments deposited during ice withdrawal are recorded by deposition (and streamlining) of fine‐grained HT; areas that remained ice‐covered during the flow switching display multiple bedform populations recorded on the surface of the NT, as no new material was available for incorporation into a younger till sheet.…”

The internal structure of glacial landforms: an example from the Halton till plain, Scarborough Bluffs, Ontario

“…In places, boulders occurring at the base of the Sunnybrook diamicton are striated on the top surface (Sharpe & Barnett 1985) and in others they appear to be, but may not be, similar to boulders found projecting from melt-out till sequences within Halton (Fig. 18).…”