A DROWNED PALEO-FOREST ALONG A CAPE COD BARRIER BEACH: LESSONS FROM THE PAST, MASHPEE, MASSACHUSETTS, USA

In March 2010 a series of nor’easters swept the New England coastline resulting in significant erosion along South Cape Beach, a barrier system located on the south shore of Cape Cod, Massachusetts. The erosion revealed 111 subfossil stumps, some of which were rooted in a preserved peat horizon. Based on physical characteristics, the subfossils were identified as Chamaecyparis thyoides (Atlantic White Cedar). Subfossil stumps, macrofossils, and sediments were aged at the National Ocean Sciences Accelerator Mass Spectrometry Facility in Woods Hole, Massachusetts, using both traditional and continuous-flow Atomic Mass Spectroscopy radiocarbon methods. Continuous-flow radiocarbon aging of bivalve artifacts from an ancient Native American midden located 3.5 km from the paleo-forest provides evidence of human exploitation of area resources between 542 ±79 and 1958 ±126 (1σ) calibrated years before present.

Subfossils stumps ranged in age from 413 ±80 to 1239 ±53 (1σ) calibrated years before present. Based on subfossil elevation and radiocarbon dates a linear regression rate of submergence was calculated at 0.73 mm/yr with an R² value of 0.43. Six sediment cores were used to decipher subsurface stratigraphy and interpret environmental setting. Microfossils identified within the preserved peat horizon indicate a fresh to brackish water environment. High resolution geospatial data was used within a GIS to visualize past and future changes along the barrier. An endpoint rate of erosion was calculated at 0.41 m per year for the period between 1846 and 2010. This rate is far greater than that which occurred during the submergence of the paleo-forest.

The ancient Native American midden and preserved peat deposits in the vicinity of the paleo-forest indicates the area holds preservation potential for cultural resources and provides insights into past human interactions with climate change. The preserved paleo-landscape provides a time sensitive opportunity to elucidate the character and timing of late Holocene transgression along the barrier. The site also provides a pre-anthropogenic context for current and future marine inundation of terrestrial landscapes in response to accelerated rates of sea-level rise and increasing reoccurrence and intensity of extreme storm events.