Cosmogenic ¹°Be chronology for the last deglaciation of the southern Scandinavian Ice Sheet

Graduation date: 2004The goal of this dissertation is to develop a chronology of the retreat of the southern margin of the Scandinavian Ice Sheet (SIS) during the late Pleistocene using surface exposure dating with cosmogenic 10Be. A sequence of seven prominent moraines in northeastern Europe (the Leszno Moraine, the Pomeranian Moraine, the Middle Lithuanian Moraine, the North Lithuanian Moraine, the P andivere Moraine, the Palivere Moraine, and the Salpausselka I Moraine) indicates a potential millennialscale record of climate variability. However, there are no direct dating constraints on the timing of this ice sheet retreat. Surface exposure dating using cosmogenic nuclide elements produced by secondary high-energy particles in the upper part of the lithosphere allows for direct dating of moraines deposited by the SIS. Cosmogenic\ud 10Be concentrations were measured in quartz sampled from erratic boulders deposited on top of the moraines. The SIS margin withdrew from its maximum extent at 17,9 ± 2,4 10Be ka, which is correlative to the end of the Last Glacial Maximum period (23,0 to 19,0 ka). Following a recessional period, the ice readvanced to the Pomeranian Moraine. Deglaciation from this moraine is dated at 14,1 ± 1,8 10Be ka, and subsequent deglaciation is marked by the Middle Lithuanian Moraine (13,1 ± 1,7 "Be ka), the North Lithuanian Moraine (13,1 ± 1,7 10Be ka), the Pandivere Moraine (13,0 ± 1,1 10Be ka), the Palivere Moraine (10.0 ± 1,3 10Be ka), and the Salpausselka I Moraine (12,5 ± 1,5 10Be ka). This new chronology is compared to abrupt climate variability recorded in the North Atlantic region during the late Pleistocene. Paleo air temperatures recorded from the GISP2 ice core and paleo sea surface temperatures recorded from the North Atlantic region display warmings at the end of the Last Glacial Maximum period, during the Balling-Allerod interstadial, and at the end of the Younger Dryas stadial. These records also display abrupt coolings during the Oldest Dryas and the Younger\ud Dryas stadials. Based on the 10Be chronology, the margin of the SIS responded to climate changes that occurred in the North Atlantic region. This new chronology contributes the first direct evidence of climate forcing on the southern margin of the SIS