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Abstract Direct measurements of erosional response to past climate change are scarce, but mid‐latitude landscapes can record how shifts between cold and warm periods altered erosion outside glacial margins. To study hillslope responses to periglaciation, we measured bulk geochemistry and cosmogenic10Be and26Al concentrations in colluvium and weathered bedrock in an 18 m regolith core from Bear Meadows, Pennsylvania, ∼100 km south of maximum glacial extent. Using core lithology, cosmogenic nuclide concentrations, and regional10Be‐derived erosion rates, we show the onset of 100‐Kyr glacial cycles at the Mid‐Pleistocene Transition (1.2–0.7 Ma) instigated multiple periglacial episodes in central Appalachia, increasing erosion rates compared to the relatively warmer Neogene. Our results show the higher efficiency of periglacial versus temperate erosion processes and highlight a pervasive Pleistocene periglacial erosion signal preserved in the10Be inventory of surface sediments in central Appalachia, where erosion rates are slow enough to integrate previous cold‐climate processes.
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Hurricanes alter 10 Be concentrations in tropical river sediment but do not change regional erosion rate estimates
Abstract Tropical islands, including many in island arcs, are subjected to recurring disturbances from extreme storms such as tropical cyclones. To test whether such storms influence cosmogenic nuclide concentrations such that they do not reflect long‐term rates of erosion, we measured meteoric andin situ10Be in river sediment samples from Dominica, an andesitic island in the Caribbean, before and after category five Hurricane Maria (in 2017). Populations of before‐ and after‐storm concentrations are statistically indistinguishable (n = 7 pairs forin‐situ10Be,n = 11 pairs for meteoric10Be).10Be concentrations vary from −138% to +73% within before–after sample pairs relative to the mean of the pair. These new data suggest that the effects of extreme storms on the depth and amount of near‐surface erosion on Dominica vary spatially. Our data support the calculations of Niemi et al. (2005) and Yanites et al. (2009) suggesting that basin‐by‐basin comparisons of erosion rates based on cosmogenic nuclides should be approached with caution in small (<~100 km2) watersheds affected by mass movements and extreme storms. Erosion rates determined fromin‐situ10Be on Dominica (geometric mean = 0.102 mm y−1,n = 12) are low compared to similarly steep and wet areas globally and correlate positively with the spatial density of mass movements.
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- PAR ID:
- 10367825
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Earth Surface Processes and Landforms
- Volume:
- 47
- Issue:
- 5
- ISSN:
- 0197-9337
- Page Range / eLocation ID:
- p. 1196-1211
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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