A re-evaluated glacial chronology for northern East Greenland

Abstract

Abstract The combination of geomorphological, lithostratigraphical and pollen-analytical data from southern Hochstetter Forland and Shannon ø. northern East Greenland, together with 14 C datings and a time/temperature evaluation of amino-acid racemization data, leads to a re-evaluation of the glacial chronology of that area. The most extensive Weichselian glaciation probably culminated not long before 15 000 BP, during the Nanok I stadial. This was a fairly limited glacial advance, compared to older recognized stages represented by older sediments and more weathered landforms. During Nanok I sizeable ice-free lowland areas existed and there was a number of nunataks in the western mountains. Initial deglaciation of the southern rim of Hochstetter Forland took place well before 13000 BP, during the Artemisia interstadial characterized by a pioneer type vegetation. At ca. 10 100 BP the glaciers advanced again, reaching almost the same frontal positions as during Nanok I time. This stadial, Nanok II, ended with the final deglaciation beginning ca. 9500 BP. Nanok II time is characterized by barren interzones in the pollen diagrams. A pioneer type vegetation, similar to that during the Artemisia interstadial, reappeared after 9500 BP and was not succeeded by a true ‘postglacial’ vegetation until ca. 8200 BP. Time/temperature evaluation of amino-acid racemization in mollusc shells from the Peters Bugt marine sediments, immediately underlying the Nanok I moraine, suggests that these sediments date from around the last (Eemian) interglacial. This view is supported by a distinct weathering break at the outer edge of the Nanok moraines. Thus, contrary to earlier interpretations, there would seem to have been no Early or Middle Weichselian glacial advances of any consequence in these parts of Northeast Greenland. Data suggest that the older recognized stages of glacial advance, the Muschelbjerg- and Kap Mackenzie ‘stadials’, were of Saale and older age and that the Weichselian maximum in this high arctic area roughly correlates in time, but not at all in relative amplitude, with the classical Weichselian (and Wisconsinan) maxima around 18000 BP.