EARLY TO MID-HOLOCENE SEA-LEVEL RISE IN SOUTHEASTERN NEW ENGLAND

The late Holocene record of sea-level rise (SRL) in southeastern New England has been extensively studied over many decades. The foundation of much of the constrained history of SRL in this area has focused on locating paleo salt marsh deposits, to use as sea level index points, overlying glacial deposits in modern coastal mashes. Coastal marshes in southeastern New England formed ~4000 years ago when the rate of SRL decreased to ~1 mm/yr. Over the past 4000 years, salt marshes in southeastern New England have generally kept pace with SRL. However, salt marshes are currently at risk of drowning because of accelerated rates of SRL (currently ~3.0 mm/yr in southeastern New England). Due to the limitation of working in modern terrestrial environments, the record of SRL in southeastern New England is sparse prior to 4000 years ago, leaving many uncertainties about the rate of SRL during the mid-Holocene and the likelihood of salt marsh survival during accelerated rates of SRL.

In our study, we focused on identifying drowned paleo salt and freshwater marshes in modern-day marine environments. Using bathymetric, seismic, and sidescan sonar data from Buzzards Bay, MA, we determined geomorphological features representative of modern salt marshes, collected sediment cores from these areas, and dated peat samples using radiocarbon methods. Additionally, paleo peat samples were collected from marshes and ponds along the Massachusetts and Rhode Island coast. In during this, we have collected a spread of ages from the Holocene to use as sea level, terrestrial limiting, and marine limiting index points. Combining these data with previously published dates from southeastern New England has allowed us to determine rates of SLR during the Holocene and gain insight into the potential for prolonged salt marsh survival during accelerated SRL in southeastern New England.