Cosmogenic Be-10 and Al-26 ages for the Last Glacial Maximum, eastern Baffin Island, Arctic Canada

Citation
Ka. Marsella et al., Cosmogenic Be-10 and Al-26 ages for the Last Glacial Maximum, eastern Baffin Island, Arctic Canada, GEOL S AM B, 112(8), 2000, pp. 1296-1312
Citations number
97
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
GEOLOGICAL SOCIETY OF AMERICA BULLETIN
ISSN journal
0016-7606 → ACNP
Volume
112
Issue
8
Year of publication
2000
Pages
1296 - 1312
Database
ISI
SICI code
0016-7606(200008)112:8<1296:CBAAAF>2.0.ZU;2-U
Abstract
A chronology for the Last Glacial Maximum based on cosmogenic exposure dati ng in the Pangnirtung Fjord area, eastern Baffin bland, Arctic Canada, is a t adds with many decades of land-based, glacial stratigraphic research. Mos t previous chronologies focused primarily an relative weathering criteria a nd suggested that ice extent was restricted during the late Wisconsinan (ca . 24-8 ka). In contrast, by directly dating glacial features, we conclude t hat late Wisconsinan ice was far more extensive than previously believed. There are 36 gneissic boulders and 8 samples of ice-molded gneissic bedrock that yield late Wisconsinan Be-10 and Al-26 exposure ages for the last gla ciation of Pangnirtung Fjord. The prominent Duval moraines, which were prev iously interpreted to represent a significant early Wisconsinan (100-60 ka) ice advance on southern Cumberland Peninsula, were actually deposited betw een 24 and 9 ka. Two boulders from a raised glaciomarine delta, stratigraph ically related to the Duval moraines, date to about 10 ka. Two recessional moraines and striated bedrock along Pangnirtung Fjord, as well as erratics on the floor of the Kolik River valley, a tributary to Pangnirtung Fjord, i ndicate that deglaciation began between 12 and 9 ka. In situ produced Be-10 and Al-26 abundances indicate that ice filled Pangni rtung Fjord for about 15 k.y. (either continuously or intermittently) prior to 10 ka, which is compatible with C-14 chronologies for adjacent Cumberla nd Sound. Thus, our data support other recent studies that suggest the nort hern and southern margins of the Laurentide ice sheet were generally in pha se during the latest Wisconsinan, contrary to earlier interpretations.