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Chlorine-36 and C chronology support a limited last glacial maximum across central chukotka, northeastern Siberia, and no Beringian ice sheet |
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| Authors: | Julie Brigham-Grette Lyn M Gualtieri Olga Yu Glushkova Thomas D Hamilton David Mostoller Anatoly Kotov |
| Institution: | a Department of Geosciences, University of Massachusetts, Amherst, MA 01003, USA b Quaternary Research Center, Box 351360, University of Washington, Seattle, WA 98195-1360, USA c Northeast Interdisciplinary Research Institute, Far Eastern Branch Russian Academy of Sciences, 16 Portovaya St., Magadan 685000 Russia d U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508, USA e Weston &; Sampson Engineers, Inc., 195 Hanover Street, Suite 28, Portsmouth, NH 03801, USA f Chukotka Science Center, Anadyr, Chukotka Region, Russia |
| Abstract: | The Pekulney Mountains and adjacent Tanyurer River valley are key regions for examining the nature of glaciation across much of northeast Russia. Twelve new cosmogenic isotope ages and 14 new radiocarbon ages in concert with morphometric analyses and terrace stratigraphy constrain the timing of glaciation in this region of central Chukotka. The Sartan Glaciation (Last Glacial Maximum) was limited in extent in the Pekulney Mountains and dates to 20,000 yr ago. Cosmogenic isotope ages > 30,000 yr as well as non-finite radiocarbon ages imply an estimated age no younger than the Zyryan Glaciation (early Wisconsinan) for large sets of moraines found in the central Tanyurer Valley. Slope angles on these loess-mantled ridges are less than a few degrees and crest widths are an order of magnitude greater than those found on the younger Sartan moraines. The most extensive moraines in the lower Tanyurer Valley are most subdued implying an even older, probable middle Pleistocene age. This research provides direct field evidence against Grosswald’s Beringian ice-sheet hypothesis. |
| Keywords: | Cosmogenic isotopes Last glacial maximum Glacial history Chukotka Arctic Beringia |
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