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TitleCorrelation of glaciations: a comparison of northwestern North America and the South American Cordillera
AuthorBarendregt, R W; Duk-Rodkin, A
SourceProceedings of the Amercian Geophysical Union Fall Meeting, 2008; Eos, Transactions of the American Geophysical Union vol. 89, GP11A-0705, no. 53, 2008.
LinksOnline - En ligne
Year2008
Alt SeriesNatural Resources Canada, Contribution Series 20170147
PublisherAmerican Geophysical Union
MeetingAmerican Geophysical Union, Fall Meeting; San Francisco; US; December 15-19, 2008
Documentserial
Lang.English
Mediapaper; on-line; digital
File formathtm
AreaCanada; United States
Subjectsglacial history; glaciers; isotopes; isotopic studies; glacial stages; interglacial stages; Gauss/Matuyama boundary; Milankovitch cycles
AbstractNorthwest Canada is one of the relatively few regions of the world where ice sheets from mountains (valley glaciers) and plains (Laurentide Ice Sheet) coalesced. This also occurred to a minor degree in N.W. Siberia (Arctic Ice Sheet and northern Ural Mountain valley glaciers) while in southern Argentina and Chile large coalescing Piedmont glaciers (Patagonian Ice Sheet) radiated out to the east and west, reaching both the Atlantic and Pacific Oceans. For the most part, build up of continental and Cordilleran ice was coincident in northwestern North America, clearly reflecting the 100 ka Milankovitch cycles. The notable absence of ice from MIS 56 to 38 in both N.A. and S.A. coincides with the low amplitude del 18O values, and bridges the time span during which the transition from 40 ka to 100 ka cycles is seen in the marine isotope record. The Argentinean record, which is the most complete thus far, appears to indicate a record of glaciation which considerably precedes that of N.A. Records from 5-6 Ma in N.A. and S.A have some similarities but the Argentinean record indicates a much earlier initiation of glaciation, dating back as far as 7.5 Ma. Small local glacier occurrences are rare in the earlier N.A. record (e.g. Yakataga Formation, Alaska) but much more common in the Argentinean record, suggesting that Argentinean valley glaciers may have developed earlier in response to cooling associated with the presence of the Antarctic Ice Sheet and the associated northward outflow of cold water along S.A. coasts. In N.A. the major Cordilleran/Montane glacial events commenced immediately preceding the Gauss/Matuyama boundary (2.8-2.6 Ma) and increased in frequency and magnitude with the advance of time. At the time of the Gauss-Matuyama boundary the N.A. and S.A. records are nearly synchronous. Proceeding back in time from the mid-Pleistocene transition (MIS 38), periods of ice free conditions appear to have been more extensive. In southern Argentina the Cordilleran glacial record appears to be somewhat independent from the global ice volume record. The extensive nonglacial periods that are noted in both continents correspond to major periods of tectonic stability and regional denudation. In northwestern North America there are at least 5 and possibly as many as 7 levels of pedimentation documented. In S.A. this record of pedimentation is considerably more extensive.
GEOSCAN ID305356