ABSTRACT: Radiocarbon and soil evidence of former forest in the southern Canadian tundra

CGRG Bibliography of Canadian Geomorphology
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Abstract

Radiocarbon dating of charcoal on podzols along a transect reaching 280 kilometers north of the present tree line from Ennadai Lake indicates that former forests were burnt about 3500 years ago and again about 900 years ago. These forests probably were associated with periods of relatively mild climate. The history that emerges from this stratigraphy is as follows. After the draining of great glacier-dammed lakes in southwestern Keewatin not later than 3500 B.C., forest encroached northward to at least about 63°N and remained until about 1500 B.C., developing a typical podzol soil. About 1500 B.C. the forest failed to regenerate after fires, and the tree line retreated south to Ennadai Lake. By A.D. 1000 the forest had again advanced to at least 61°30'N or 62°N. Fires of that time were not followed by forest regeneration north of the present tree line. Thus, the tree line twice advanced north of its present position and was farther south than at present during an intervening period between 1500 B.C. and A.D. 1000. Because the tree line presently coincides with the position of the Arctic front, we infer that these periods of northward forest extension were periods with a more northerly frontal position. Judging that the advances represent periods of relatively milder climate, we correlate the first advance with the Climatic Optimum and the second with the Little Climatic Optimum. The known history of human occupancy of this area also reflects this sequence of biotic and climatic change. Late Paleo-Indian (Protoarchaic) artifacts, like those of buffalo hunters in the Plains and Great Lakes regions 7000 to 9000 years ago, are found on sites exposed after the draining of the proglacial lakes in the Dubawnt and Kazan river systems. These sites were forested until 3500 years ago. The first arrival of Arctic culture in the region (pre-Dorset stage of the Arctic small-tool tradition) probably took place 3000 to 4000 years ago, with the onset of more severe climate and the retreat of the forest border. The recent Caribou Eskimo came after the forest retreat of 900 years ago.

Bibliography of Canadian Geomorphology