A Record of Holocene Environmental Change Interpreted from Peat in Eastern Maine
This presentation was given at the 48th Annual Northeastern Geological Society of America Meeting in Bretton Woods, NH, March 18-20, 2013.
A multi-proxy analysis of peat deposits in eastern Maine provides a Holocene paleoenvironmental record. A 129 cm core (EB-09-01) was recovered from an abandoned peat mine using a Russian Peat Corer near Penobscot, Maine. A sample of wood collected at a depth of 118 cm in this core has a radiocarbon age of 5.92 ± 0.05 14C ka BP (6.73 ± 0.05 cal ka BP). Continuous sampling of two outcrop sections (WQ-06-01 and WQ-09-02) and a 300 cm core (WQ-09-01) were collected from a raised coastal bog at Quoddy Head State Park, Maine. Six samples of wood from the Quoddy Head bog have been radiocarbon dated, and the basal age of the peat bog is 11.31 ± 0.06 14C ka BP (13.2 ± 60 cal ka BP). Water content, magnetic susceptibility, and loss-on-ignition (LOI) were measured on all samples. Water content in the EB-09-01 core fluctuates between 76% - 90%. Water content at WQ-06-01, WQ-09-01, and WQ-09-02 varies between 69% and 96%. There is an abrupt decrease in LOI at approximately 1.59 ± 0.04 14C ka BP (1.47 ± 40 cal ka BP) at both the Penobscot and Quoddy Head peat bogs suggesting a decrease in productivity and regional cooling at this time. There are at least two other abrupt decreases in LOI at Quoddy Head, interpreted as cooling, at approximately 4.83 14C ka BP (5.54 cal ka BP) and 10.2 14C ka BP (11.9 cal ka BP), and then a significant drop in LOI at the base of the outcrop in the basal sand unit below the peat. A decrease in water content correlates with these decreases in LOI in the peat collected from Quoddy Head State Park. The degree of humification, the extent to which the peat has decomposed, is used as a proxy for precipitation. Measurements of absorbance and percent light transmission were performed on a Spectronic 20 Genesys at 540 nm, and these measurements are used to interpret the degree of humification. Preliminary analyses indicate numerous fluctuations in the degree of humification suggesting fluctuations in wetness throughout the Holocene. Additional analyses are in progress.