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A Proxy Late Holocene Climatic Record Deduced from Northwest Alaska Beach Ridges,

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A climatically sensitive, oscillatory pattern of progradation and erosion is revealed in late Holocene accretionary sand ridge and barrier island complexes of Seward Peninsula, northwest Alaska. Archaeological and geological radiocarbon dates constrain our chronology for the Cape Espenberg beach ridge plain and the Shishmaref barrier islands, 50 km to the southwest. Cape Espenberg, the depositional sink for the northeastward longshore transport system, contains the oldest sedimentary deposits 3700 - 90 B.P. B-23170 old grass from a paleosol in a low dune. The oldest date on the Shishmaref barrier islands is 1550 - 70 B.P. B-23183 and implies that the modern barrier is a comparatively recent phenomenon. Late Holocene sedimentation along the Seward Peninsula varied between intervals of rapid progradation and erosion. Rapid progradation predominated from 4000-3300 B.P. and from 2000-1200 B.P., with the generation of low beach ridges without dunes, separated by wide swales. During erosional periods higher dunes built atop beach ridges as between 3300-2000 B.P. and intermittently from 1000 B.P. to the present. Dune formation correlates with the Neoglacial and Little Ice Age glacial advances and increased alluviation in northern and central Alaska, while rapid progradation is contemporaneous with warmer intervals of soil andor, peat formation atop alluvial terraces, dated to 4000-3500 and 2000-1000 B.P.

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This article is from 'Proceedings of the International Conference on the Role of Polar Regions in Global Change Held in Fairbanks, Alaska on 11-15 June 1990. Volume 2', AD-A253 028, p649-657. See also Volume 1, AD-A253 027.



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