Evidence of late glacial permafrost in Newfoundland

Structures interpreted as ice-wedge pseudomorphs are developed in postglaci al sediments at several locations in coastal areas of western, central, and eastern Newfoundland. The ice-wedge casts indicate that permafrost was pre valent in exposed coastal locations following Late Wisconsinan deglaciation and marine regression due to isostatic uplift. Formation of the ice-wedge casts indicates that the mean annual temperatures were colder than at prese nt along the Newfoundland coast; and that snow pack depths were less and sn ow cover less persistent. The environment following marine regression was m arked by cold, windswept conditions, which permitted the development of per mafrost in the coastal regions. Much of the interior of Newfoundland remain ed covered by glacial ice, and consequently did not support subaerial perma frost. Direct numerical dating of the ice-wedge casts is not possible at pr esent. However, the geomorphic settings and stratigraphic positions of the features indicate that they developed subsequent to Latest Wisconsinan glac ial retreat, and followed regression from the postglacial marine limit. Per mafrost formation preceded climatic warming and establishment of arboreal v egetation in the Early Holocene. The time of formation of the ice wedges, t herefore, is constrained between the initiation of postglacial marine regre ssion, ca. 12,300-11,000 BP (uncal.), and the initiation of climate amelior ation, ca. 10,400 BP (uncal). This chronological range corresponds to the c ombined duration of the initial postglacial cooling episode and the subsequ ent Younger Dryas cold climate event, documented in palaeoenvironmental rec ords from Newfoundland as lasting from shortly before ca. 11,200 to ca. 10, 400 BP. (C) 2000 Elsevier Science Ltd and INQUA. All rights reserved.