MASSIVE OVERWASH AT SEAL COVE, MAINE: EVIDENCE FOR THE GREAT COLONIAL HURRICANE OF 1635

Seal Cove is part of mid-coastal Maine's extensive paraglacial barrier system. Its southeastern exposure and protection by bedrock headlands make it the ideal site to study the role of southerly storms on beach evolution. We combine ground-penetrating radar (GPR) surveys with deep auger cores and vibracores to reconstruct the evolution of the back-barrier, presently a freshwater cranberry bog. GPR and cores reveal extensive landward-dipping overwash deposits above a basal layer of freshwater peat. Several heavy-mineral lag horizons rich in garnet were present in the overwash deposits overlying the peat unit. These units are evidence of landward barrier translation in the background of sea-level rise. Freshwater peat immediately underlying washover deposits obtained from two cores has yielded calibrated radiocarbon ages of AD 1470-1650 and AD 1470-1640. These dates suggest that the overlying sand has been likely deposited by the Great Colonial Hurricane of 1635. We develop a storm surge model using various scenarios to determine storm surge and wave height conditions necessary for deposition of the observed overwash package. Considering a maximum storm surge based on the data from the 1978 storm of record and assuming the height of the paleodune at the time of the storm was similar to its present elevation, the observed deposits could have only resulted from penetration of the swash after the waves broke ahead of the dune. If the topography has changed over time, and the paleobarrier was at least 1 m lower than its present height, the storm surge and associated waves could have completely overtopped the dune and deposited the overwash unit, heightening the Seal Cove barrier.