CONTROLS ON THE INFILLING OF LACUSTRINE BASINS: INFERENCES AND UNCERTAINTIES FROM A REGIONAL STUDY OF LAKES IN THE NORTHEASTERN UNITED STATES

The rate of sediment infilling in lacustrine basins is controlled by a variety of factors related to both processes and conditions acting within a lake and in the surrounding environment, including lake water chemistry, aquatic productivity, climate, land-use, lake and watershed morphology, human activity, and the legacy of past geologic events. Quantifying the impact of any one of these factors requires examining records of sediment infilling from a wide variety of lakes of differing characteristics and over time periods relevant to both human induced changes and longer-term natural variability related to climatic and landscape changes. We have approached this topic by compiling existing records of sediment age-depth relationships from lakes located throughout the northeastern United States. This region is ideal for examining controls on lake sedimentation due to the high density of lakes of various morphologies and drainage basin sizes and because of the significant landscape and environmental changes that have occurred subsequent to regional deglaciation, including widespread deforestation and subsequent reforestation related to changes in human land-use patterns. Lakes in the study range in size from less than 1 ha to several hundred ha in surface area and have drainages basins ranging up to about 70 km². Age-depth models are constrained by some combination of radiocarbon dates, pollen stratigraphic horizons, short-lived Pb and Cs radioisotopes, and industrial pollution horizons. Records fall into three categories: (1) records spanning significant portions of the pre-historic period (late-glacial through Holocene) with centennial to millennial scale resolution, (2) short-term records spanning the post-European settlement period, and (3) records extending into or through the Holocene and which also include historical age constraints. This combination of records provides insight into geographic, morphologic, climatic, and anthropogenic controls on lake sedimentation while at the same time highlights limitations of existing sedimentary records and remaining uncertainties in our understanding of the depositional history of lacustrine basins in the northeastern United States.