COI Funded Project: Extending the Documentary Records of Shoreline Change for Martha's Vineyard and Nantucket

Ilya Buynevich and Rob Evans, Geology and Geophysics

Project Funded: 2003
Key Words: Barrier Beaches, Martha's Vineyard, Nantucket, Shoreline Change, Sedimentary Record, Stratigraphy, Erosion, Paleo-inlet, Ground-penetrating Radar

Proposed Research

Coastal barriers and tidal inlets are highly dynamic geological environments that form a vital buffer between the open ocean and ecologically delicate back-barrier wetlands and estuarine environments. Their shape and stability are impacted by recent acceleration in sea-level rise, which exacerbates erosion and flooding during intense storms, by natural and anthropogenic reductions in sediment supply, and by increasing pressure and impacts of development. Our understanding of changes that occur in the coastal zone are often confined to instrumental or documentary records, which in New England span less than 300 years. Therefore, a significant part of the environmental history of our beaches is archived in coastal sedimentary sequences.The islands of Martha's Vineyard and Nantucket experience some of the highest rates of shoreline change in the Northeast. Besides long-term bluff retreat, these changes include beach and dune erosion, breaching and landward migration of sandy barriers, and longshore redistribution of sand. To date, only a few studies have addressed the post-glacial evolution of the islands and the dynamic nature of their rapidly changing coastline. Using a combination of high-resolution geophysical surveying and sediment cores, we propose to extend the documentary records of environmental change over the past 1,000-2,000 years by examining the sedimentary records at a number of coastal sites. The timing of various phases in shoreline evolution will be determined by a combination of radiocarbon and isotopic dating methods.

Our research approach will involve identification and mapping of the geological features beneath the barriers including inlet and breach channels, washover deposits, buried storm scarps, and other erosional unconformities. Geological signatures of most recent events (hurricanes, extratropical storms, sea-level rise) will form the basis for interpreting similar structures in the sedimentary record. Ultimately, this research will allow us to link a variety of subsurface and geomorphic features to the oceanographic processes and climatic events responsible for most dramatic changes along our coasts.