Abstract

The 14C ages of the earliest organic deposits in 32 small lakes located higher than or near the altitudinal limit of proglacial Lake Barlow, in the Timiskaming region, span the period 10 400 – 6490 years BP. Identification of lags in organic accumulation by means of pollen and macrofossil assemblages allows the rejection of 14C dates later than 8500 BP as the minimum dates for local ice retreat in each lake basin. However, because of the absence of synchronous pollen zones, the pollen stratigraphy cannot be used to correlate the individual 32 sites and illustrate the geography of deglaciation between 10 400 and 8500 years BP. The directions of ice retreat are nevertheless apparent when the sites are grouped according to age, despite some geographical dispersion of sites with closely related 14C ages. The usefulness of pollen analysis in determining the age of deglaciation in the Timiskaming region is consequently nil, in contrast to the situation in northwest Europe. This unexpected characteristic is attributed to the peculiar palaeoenvironmental context of the proglacial Lake Barlow episode. At the scale of the Great Lakes – St. Lawrence River watershed, the differences in the pollen stratigraphies at the transition between the Pleistocene and the Holocene sediments and in the lower Holocene sediments appear to be the result of contrasting palaeoclimatic conditions existing in front of the ice sheet on both sides of Longitude 76°W, approximately.

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