Spatial Trends in Physical and Bulk Sediment Chemistry Composition of Sediments in Andover Lake, CT. abstract by Jennifer N. Vinci
Examination of fourteen 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 three 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 II) 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 (Unit III) with high moisture, organic and inorganic contents cap the sequence at all locations. At the shallow south end of the lake, however the uppermost 0.13 m of Unit III contain discrete layers of sand. Moisture and carbon concentrations are higher for Unit III than Units II 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 III, 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 in the 210Pb dated core suggest that sediment rates in the shallow south end of the lake has always exceeded that in the deep north end of the lake. Increasing rates of mass accumulation as indicated by 210-Pb results from at the deep north end of the lake are likely associated with the progradation of a small sandy delta at the shallow south end of the lake thereby, bringing the source of sediment closer to the 210-Pb coring location.