Carbonates, granulometry, and color of tills on the south‐central Canadian Shield and their implications for stratigraphy and radiocarbon dating

Abstract

Till containing over 10% matrix carbonate extends in a belt 200–300 km wide south of the Hudson Bay Paleozoic basin source. The southern boundary is represented by the ‘carbonate line’, extending from Wawa to near Timmins and Cochrane in the study area. Higher silt content and lighter color are associated with the higher carbonate till. The carbonate tine corresponds approximately to the Chapleau moraine and correlative moraines to the northwest and may signify a discrete stratigraphic unit (possibly identifiable with the Matheson Till) formed by a glacial readvance. Glaciolacustrine sediments have higher carbonate content than nearby till and similarly form widespread sediment blankets even beyond that of the carbonate‐rich till. Radiocarbon dating of amorphous organic sediments may be at risk because of old carbon error on such terrain and there may be some risk even in areas of much smaller carbonate content. A greater effort should be made to establish chronologies based on terrestrial plant matter, now more often possible with AMS radiocarbon dating.

The sedimentary and palynological records of Serpent River Bog, and revised early Holocene lake-level changes in the Lake Huron and Georgian Bay region

“…2) which was possibly sourced from carbonate-rich terrain north of the carbonate line (Fig. 1a) (Karrow 1992). Thus some of the clay sediment in units 9 and 8 may have originated with meltwater flows from the LIS margin north of Huron Basin, and these flows would have been at least partially channeled via the Spanish River valley (Fig.…”

“…1 a Regional map showing location of Serpent River and Espanola West bogs, other stratigraphic sites, Nadoway drift barrier at the eastern end of Lake Superior basin, vicinity of submerged tree stumps (area of Deane-Tovell Saddle) and Flowerpot Island at the entrance to Georgian Bay, French River and North Bay (DPN Depensier Lake), and other places or features mentioned in the text. The inset map of the Laurentian Great Lakes shows locations for Olson (O) and Sanilac (S) forests, sill between basins of lakes Michigan and Huron (M-H Sill), Spanish River (SR), and the carbonate line (CL) (Karrow 1992), north of which glacial sediments are rich in carbonate ([10 %), and south of which their carbonate contents are minor (\3 %). b Map of Serpent River Bog (SRB) and area showing on its southern side the series of bedrock highs which protected the bog from erosion by waves and currents of high lake phases in North Channel (Lake Huron).…”

Regional subglacial quarrying and abrasion below hard‐bedded palaeo‐ice streams crossing the Shield–Palaeozoic boundary of central Canada: the importance of substrate control

“…14) no different from those described from the part of the S-PBz in Ontario that we interpret as rock-cut mega-scale glacial lineations. Widespread glacial erosion of carbonate strata is also suggested by dispersal fans of carbonaterich till that extend southwestward onto the Shield from areas underlain by Palaeozoic limestones south of Hudson Bay (Karrow 1992) and by other prominent rubble-rich dispersal fans of detrital carbonate in the Canadian Arctic such as on Melville Island, Prince of Wales Island, King William Island, and across southern Baffin Island (Andrews & Miller 1979;Dredge 2008;D in Fig. 14).…”