Date of Completion

9-27-2019

Embargo Period

9-4-2024

Keywords

Gully erosion, New England, geochemical signatures, Anthropocene, anthropogenic

Major Advisor

William Ouimet

Associate Advisor

Robert Thorson

Associate Advisor

Anji Seith

Associate Advisor

Andrew Jolly-Ballantine

Associate Advisor

Chuanrong Zhang

Field of Study

Geography

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

The proposed Anthropocene epoch provides a novel framework for recognizing, measuring, and interpreting human impacts to landscapes around the world. Important also, is the need to place human impacts in the context of how these landscapes have been behaving over recent geologic time (i.e., the Late Pleistocene and Holocene). In southern New England, widespread Anthropocene landscape changes occurred throughout 17th-20th century following European settlement. Markers of these Anthropocene landscape changes are visible in high-resolution topographic data in the form of historic land use features (e.g., stone walls and charcoal hearths), in gullies that dissect hillslopes, and in the downstream stratigraphic records in wetland and waterways. This study examines the erosional and depositional signatures of human impacts, with special attention to gullies and the geochemical indicators of related sediments. Analysis of LiDAR data and field observations reveal widespread occurrence of gully features dissecting glacial landforms, the deepest and largest of which are likely relate to gully erosion that started in the Late Pleistocene and continued into the Holocene. In addition, data reveals a subset of smaller, shallower gullies that appear directly tied to anthropogenic activity over the last 250 years, as indicated by cultural features indicative of past deforestation and anthropogenic influence. In addition to spatial analysis, temporal and spatial variability in geochemical signatures such as trace metals (primarily Pb and Hg), highlights differences in land use and intensity of impact throughout the region. Overall, there is a time-transgressive nature to the onset of the Anthropocene in this region and as seen in these geochemical signatures. Human impacts associated with coastal sites begin ~100 years before those associated with upstream/upland landscape positions.

Sedimentological analysis, geochronology, and geochemistry of sediment cores collected at the base of gullies help constrain timing of gully activity in the region, and place Anthropocene erosion in the longer-term geologic context of the Holocene and late Pleistocene change. Results indicate a two-pulse sedimentation history in the region- one shortly after deglaciation (i.e. the paraglacial period) and a second erosional reactivation coinciding with 17th -early 20th century Anthropocene landscape change. Existing gullies were likely reactivated in response to forest clearing during the Anthropocene and served as conduits for upland erosion.

Overall, this study demonstrates the complexity and variability in upland response to environmental change and highlights the spatial and temporal variability inherent in addressing onset of the Anthropocene. Understanding evolution of past land-use activities and their impacts on landscape evolution is important as it informs future research, management, and an overall understanding of these landscapes.

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