Paper No. 24
Presentation Time: 8:00 AM-12:05 PM
A MULTI-PROXY STUDY OF A FIVE METER SEDIMENT CORE FROM SLUICE POND, LYNN, MA: COMPARISON OF LITHOSTRATIGRAPHIC AND SEISMIC RECORDS
A core containing 470.5cm of sediment was taken from the deepest hole in Sluice Pond, Lynn, MA. This pond has a small surface area to depth ratio, and is therefore expected to contain a high-resolution record of sedimentation since the last glaciation (~17,000 years). Various paleoclimactic proxies were measured down core, including wet and dry bulk density, ignition loss at 550°C and 1000°C, magnetic susceptibility, and image (i.e. RGB) analysis. In addition, sub bottom seismic profiles were generated using a StrataBox profiler at 10kHz. This study aims to test two working hypotheses: 1) Density measurements of the core correlate with seismic reflectors found in geophysical sub bottom profiles, and 2) the local history of paleoclimate expressed in the sediment record reflects known regional trends, as well as any local variations that may be present. Magnetic susceptibility data reveal a peak (~42 SI units) over the upper ten centimeters of sediment, reflecting anthropogenic pollutants. Low amplitude magnetic susceptibility variability occurs over the rest of the core. Organic carbon content is fairly high over most of the core, rarely dropping below 10% over the upper 3 meters. It is especially high (over 16%) between 30 and 40 centimeters downcore and between 220 and 230cm downcore. Organic carbon content drops off considerably below 400cm, reaching dry weight percentages below 6% around 455cm. Dry bulk density is found to jump dramatically near the top and over the lower 50 centimeters of the core. These anomalies are interpreted to represent two strong seismic reflectors, found at the sediment-water interface and deeper in the sediment with an apparent depth of 4.5m. Lower amplitude fluctuations in dry bulk density elsewhere in the core are interpreted to represent weaker seismic reflectors. Correlation of the core with seismic reflectors allows for further correlation with other cores taken elsewhere in the pond, and will permit interpretations of sedimentation patterns over the Holocene. Pending radiocarbon dates on terrestrial macrofossils from the core should facilitate correlation with other studies and constrain rates of local sedimentation.