HOLOCENE ENVIRONMENTAL CONDITIONS INTERPRETED FROM COASTAL MUDFLATS AND PEAT IN WASHINGTON COUNTY, MAINE

Holocene climate variability is interpreted from coastal mudflats and a raised coastal peat bog from Washington County, Maine. Two short sediment cores (CP-06-01 and CP-06-02) were collected from a semi-protected intertidal sandy mudflat using a Universal Percussion Corer. Two radiocarbon dates constrain the chronology for each core, and linear age models are used. The general stratigraphy for each core includes modern Mytilus edulis shells and organic rich black mud at the top of each core, followed by a layer of large Mya arenaria shells mixed with mud, and a basal unit of stiff gray silty clay. An uncalibrated AMS radiocarbon date on a Mya arenaria shell is 1140 ± 36 ka, and CP-06-01 also contains a brownish, organic peat layer below this shell layer. The organic peat unit is missing in CP-06-2. Basal dates for each core include a basal date on organics (marsh vegetation) of 2824 ± 35 ka from CP-06-01 and a basal date on Macoma balthica of 3942 ± 38 ka from CP-06-02. Each core was sub-sampled at approximately 2 – 4 cm intervals, and standard sedimentology analyses, including water content, magnetic susceptibility, and percent loss-on-ignition (LOI), were completed. An increase in LOI occurs at approximately 2000 ka, but this is only observed in CP-06-01 corresponding to the organic peat layer. The sediments from the mudflats are compared with a Holocene climate record interpreted from a raised coastal bog in Quoddy Head State Park, Lubec, Maine. An approximately 280 cm outcrop of peat is exposed along the shoreline, and wood from the base of the outcrop has an AMS radiocarbon date of 11, 308 ± 57 ka. A second wood layer at 235 cm depth has an AMS radiocarbon age of 4831 ± 39 ka. LOI results are interpreted as relative climatic stability from approximately 4.5 ka through the present, but a sharp drop in LOI at the base of the outcrop is associated with cooler conditions. Variability in the degree of peat humification is visually observed at the site and described with Munsell colors. More detailed analyses of the degree of peat humification, interpreted from measurements of the percent absorbance and percent transmission using a spectrophotometer at 540 nm, are in progress.