Postglacial Ponds and Alluvial Fans: Recorders of Holocene Landscape History

Abstract

Little is known about rates and patterns of Holocene hillslope erosion in areas once covered by Pleistocene ice sheets and now heavily populated. Yet, understanding past landscape behavior is prerequisite to predicting and mitigating future impacts of human-induced disturbance and climate change. Using northern Vermont as an example, we demonstrate that the sedimentary record preserved in humid-region ponds and alluvial fans can be dated, deciphered isotopically and stratigraphically, and used to understand the history of hillslope erosion. Our data suggest that erosion rates were higher in the early and late Holocene than in the mid-Holocene, perhaps the result of changing climate and the frequency of severe storms. In Vermont, dated alluvial fan sediments reveal that the highest rates of hillslope erosion occurred as a consequence of European settlement. The geologic record of colonial deforestation is clear, revealing significant human impact and suggesting that past landscape response is a meaningful basis for guiding future land management practices.