Abstract

Rhythmically-bedded glaciofluvial sediments deposited subaqueously and now exposed on an emerged coastal foreland in north-central Newfoundland, exhibit postdepositional deformation structures such as synclinal folds and faulted zones of ground collapse, the result of melting of underlying buried glacier ice. A high rate of glaciofluvial deposition is indicated. The development of fault systems in those sediments overlying decaying glacier ice can be compared with laboratory simulations of vertical foundering in sedimentary rocks. Ice-wedge casts transecting folded and faulted sections in the area are indisputable evidence of subsequent permafrost conditions, i.e. a period when mean annual air temperatures lay below −6 °C. A rise of at least 10.4 °C in mean annual air temperature is indicated since that time. A severe periglacial climate is considered to have existed in the area from 12 000 to 10 000 years BP and ice wedges developed with a minimum growth rate of 1.25 mm/year. Comparison with reports of ice-wedge casts in Nova Scotia and the west coast of Newfoundland indicate that the period which they formed in north-central Newfoundland may be correlated with the tundra pollen zone L-3 of Livingstone and Livingstone, the Greatlakian substage of the Lake Wisconsinan in Midcontinental North America.

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