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Ages for the Big Stone Moraine and the oldest beaches of glacial Lake Agassiz: Implications for deglaciation chronology

2007; Geological Society of America; Volume: 35; Issue: 7 Linguagem: Inglês

10.1130/g23665a.1

1943-2682

Kenneth Lepper, Timothy G. Fisher, Irka Hajdas, Thomas V. Lowell,

Geological formations and processes

Research Article| July 01, 2007 Ages for the Big Stone Moraine and the oldest beaches of glacial Lake Agassiz: Implications for deglaciation chronology Kenneth Lepper; Kenneth Lepper 1Department of Geosciences, North Dakota State University, Fargo, North Dakota 58105, USA Search for other works by this author on: GSW Google Scholar Timothy G. Fisher; Timothy G. Fisher 2Department of Environmental Sciences, University of Toledo, Toledo, Ohio 43606, USA Search for other works by this author on: GSW Google Scholar Irka Hajdas; Irka Hajdas 3Ion Beam Physics, Paul Scherrer Institute and ETH Zurich, 8093 Zurich, Switzerland Search for other works by this author on: GSW Google Scholar Thomas V. Lowell Thomas V. Lowell 4Department of Geology, University of Cincinnati, Cincinnati, Ohio 45226, USA Search for other works by this author on: GSW Google Scholar Geology (2007) 35 (7): 667–670. https://doi.org/10.1130/G23665A.1 Article history received: 31 Dec 2006 rev-recd: 08 Mar 2007 accepted: 12 Mar 2007 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Kenneth Lepper, Timothy G. Fisher, Irka Hajdas, Thomas V. Lowell; Ages for the Big Stone Moraine and the oldest beaches of glacial Lake Agassiz: Implications for deglaciation chronology. Geology 2007;; 35 (7): 667–670. doi: https://doi.org/10.1130/G23665A.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Glacial Lake Agassiz has been implicated as the trigger for numerous episodes of abrupt climate change at the close of the last ice age, yet the beginning age of the lake has never been determined. Here we report the first numerical age data on the Big Stone Moraine and the oldest beaches of glacial Lake Agassiz. Organic remains from lakes, bogs, and channels distal to, and inset to, the Big Stone Moraine require that glacial activity at this moraine ceased prior to 12,000 14C yr B.P. (13,950 cal [calendar] yr). A site near New Effington, South Dakota (United States), implies full glacial recession north of the topographic divide prior to 11,810 14C yr B.P. (13,670 cal yr), synchronous with the beginning of glacial Lake Agassiz. Lake Agassiz shorelines inset to the moraine yield optically stimulated luminescence (OSL) ages from 14,200–12,600 yr cal. Lower strandlines are younger, but the similarity of ages suggests that initial lake lowering was faster than OSL ages can currently resolve. Nevertheless, the OSL ages represent the first numerical age assignments for the Herman, Norcross, and Upham beach ridges, setting the stage for future numerical age assignments within the Lake Agassiz basin. These two dating methods yield strongly consistent results within stated uncertainties. The age of the Big Stone Moraine implies an interval of rapid retreat for the Des Moines lobe of the Laurentide Ice Sheet during the Bölling-Alleröd warm interval. The overlapping ages for the uppermost beach levels and abandonment of the highest Lake Agassiz spillway indicate a rapidly evolving lake until at least 13,500 yr cal. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.