CGRG Bibliography of Canadian Geomorphology
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Author : Coulthard, R.D.; Miller, G.H.; and Briner, J.P.
Date : 2004.
Title : Glaciation of the Aston Lowland, Baffin Island, Nunavut: implications for glacial climate and Laurentide Ice Sheet dynamics.
Publication : 49th Annual Meeting of the Geological Association and the Mineralogical Association of Canada. May 12-14, 2004. Brock University, St. Catharines, Ontario.
Issue :
Page(s) :
Abstract
The history of the Laurentide Ice Sheet (LIS) during the last glaciations of the eastern Canadian Arctic remains poorly understood despite over 40 years of field research. The Aston delta, a > 25 km2, 80 m asl raised marine delta on the Aston Lowland of eastern Baffin Island, has frequently been cited as evidence of ice free conditions during the last glaciation. Nine non-finite radiocarbon dates confirm the pre-last glacial age (> 54,700 yr BP) of this delta and the associated 80 – 90 m asl shoreline; amino acid racemization of in situ marine molluscs suggests it to be ~95 ka. However, a new finite radiocarbon date of 36,490 yr BP on ice-transported molluscs on the Aston delta surface, and post-depositional lateral meltwater channels crossing the delta and lowland to the Holocene marine limit indicate the area was inundated by minimally erosive cold-based ice during the last glaciation. During early Holocene retreat from the last glacial maximum, the marine limit was 23 m asl and dates to ~12 ka (cal). Eustatic sea level has risen ~60 m since 12 ka, combining for almost 85 m of post-glacial rebound since deglacierization. In contrast, the Aston delta formed in a relative sea level of 80 – 90 m asl, indicating at least this much total rebound without considering post-glacial eustatic sea level rise. Thus, the penultimate glacial loading of the Aston Lowland was greater than the last glacial loading of the area. This thicker ice sheet was also relatively non-erosive: amino acid racemization of in situ marine molluscs indicates undisturbed sediment > 260 ka is preserved adjacent to the fiords. These new data indicate a relatively thin LIS covered most of the Aston Lowland during the last glaciation, terminating beyond the modern shoreline. However, preserved sediment and landform assemblages indicate the most distal portions of the LIS were composed of minimally erosive, cold-based ice during at least two glacial episodes. Undisturbed sediment > 260 ka adjacent to the fiords indicates fiord ice has not been sufficiently erosive to remove this sediment. Thus, rapidly moving, erosive, warm-based ice was probably restricted to the centres of the major fiord troughs during glaciations younger than > 260 ka. This suggests the eastern Baffin Island landscape is ancient in origin and has not been substantially modified during several glacial cycles. Late Quaternary glacial climate was probably too cold and dry to support large, warm-based ice sheets along the outer coast.
Bibliography of Canadian Geomorphology