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Few data are available to infer the thinning rate of the Laurentide Ice Sheet (LIS) through the last deglaciation, despite its importance for constraining past ice sheet response to climate warming. We measured 31 cosmogenic 10 Be exposure ages in samples collected on coastal mountainsides in Acadia National Park and from the slightly inland Pineo Ridge moraine complex, a ~100-km-long glaciomarine delta, to constrain the timing and rate of LIS thinning and subsequent retreat in coastal Maine. Samples collected along vertical transects in Acadia NationalPark have indistinguishable exposure ages over a 300 m range of elevation, suggesting that rapid, century-scale thinning occurred at 15.2 ± 0.7 ka, similar to the timing of abrupt thinning inferred from cosmogenic exposure ages at Mt. Katahdin in central Maine (Davis et al

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Marked differences in bedrock meander dimensions in the Appalachian Valley and Ridge province, at times in adjacent reaches of a single stream, are related to differences in relative erodability of the bedrock. Meanders cut in thick-bedded to massive lithologies, typically carbonates, are distinctly smaller overall than meanders cut into shaly lithologies.Empirical relations developed from meander geometry measurements and estimated bedrock erodability for 78 bedrock meander reaches, containing a total of 1089 individual meander loops, show that meanders cut in shaly lithologies (ML = 105 QF.50, where ML = meander length and Qf = most probable annual flood) are about twice the length of meanders cut in non-shaly lithologies (ML = 39.3 Q:.s6). The valley floor width of the meanders cut in shaly bedrock (VF = 28 QF"' ) is two to three times wider than the valley floor width of the meanders cut in the more resistant non-shaly bedrock (VF = 8 Q:.'"). The mean and median meander length values for individual reaches typically differ by less than 10 per cent.Other factors that could affect bedrock meander dimensions were considered and none appeared to offer any help in explaining the dimensional differences observed above.In plateau regions underlain by essentially horizontal strata, the meander form characteristic of one lithology may become superimposed upon another as incision progresses, producing anomalous relationships between bedrock meandel dimensions and lithology.

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