36 Limnogeology: Sedimentary Records from Modern and Ancient Lakes I

Friday, 29 March 2019
8:30 AM - 11:40 AM
Gold Ballroom

A HIGH-RESOLUTION MILL POND RECORD FROM EASTERN VIRGINIA REVEALS THE IMPACT OF PAST LANDSCAPE CHANGES AND REGIONAL POLLUTION HISTORY

Paper number: 36-4
Program: Theme Sessions
Time: 9:30 AM – 9:50 AM

Authors

Abstract

Mill ponds were formed throughout the eastern United States following European settlement, and sedimentation in these systems has recorded centuries of anthropogenic landscape change, and local and regional pollution. The “legacy sediments” in these artificial waterbodies can potentially impact modern fluvial geomorphic processes and downstream ecosystem health. To date, mill ponds on the Atlantic Coastal Plain have received little attention, however this region was home to the earliest colonial settlements and has the potential to record landscape change and pollution histories at high-resolution because of easily eroded underlying unconsolidated sediments. Here we present a c. 300-year record of sedimentation in Lake Matoaka, a former mill pond in Williamsburg, Virginia, which was a historically active region of the early U.S. We use 210Pb, 137Cs, Pb concentrations, 206Pb/207Pb, and chronostratigraphic horizons to develop a robust chronology, which shows remarkably high sedimentation rates, ~0.5 cm yr-1 allowing for detailed analysis of landscape changes as well as the history of regional atmospheric pollution. Sedimentological data including the analysis of organic matter properties, grain size changes, and scanning XRF elemental data, reveal past conditions within the lake and its watershed, which can be linked to historic developments of the town and surrounding region. We also document detailed changes in the history of Pb accumulation from local and regional industrial activities. Our reconstruction shows the evolution of the basin from an early colonial-era mill pond to an artificially maintained lake. The data contribute to our understanding about the characteristics of sedimentation in mill ponds and other coastal plain environments in reconstructing historic landscape changes and regional pollution history.

Geological Society of America Abstracts with Programs. Vol. 51, No. 3

doi: 10.1130/abs/2019SE-326983

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