SPATIAL TRENDS IN THE PHYSICAL AND BULK SEDIMENT CHEMISTRY COMPOSITION OF SEDIMENTS IN ANDOVER LAKE, CONNECTICUT

Examination of ten sediment cores (to 1.5m in length) from Andover Lake, CT, dammed in 1927, reveal spatially variable trends in physical properties and bulk sediment chemistry within two well defined stratigraphic Units. Basal Unit I varies with location and consists of coarse grained gravel and sands to sandy silts that often retain buried soil horizons indicating a terrestrial setting prior to damming. These sediments are draped by up to 0.88 m of stratified sand and silt (Unit IIA) at locations near primary inflows to the lake indicating rapid deposition soon after damming. This facies is absent in cores collected from the deep, north end of the lake. Fine-grained and massive lacustrine muds with high moisture, organic and inorganic contents cap the sequence at all location. At the shallow south end of the lake, however the uppermost 0.13 m of Unit IIB contain discrete layers of sand. Moisture and carbon concentrations are higher for Unit IIB than Units IIA or I, although buried soil A-horizons in Unit I also have high concentrations. Bulk sediment chemistry concentrations by aqua-regia digestion and ICP-AES are also highest in Unit IIB, except for Cr, Mg, and Ni.

210-Pb dating for a single core at the deep north end of the lake, indicates a pronounced increase in mass accumulation beginning between 1964 and 1972, a time when power line construction across the primary inflow likely increased sediment delivery to the lake. Cross lake correlations, based on Al concentrations suggest that increasing rates of accumulation at the deep north end of the lake are associated with the progradation of a small sandy delta at the shallow south end of the lake.