HIGH RESOLUTION HURRICANE ACTIVITY RECORD FOR SOUTHERN NEW ENGLAND FROM 1,200 YEAR LONG VARVED COASTAL SEDIMENTARY RECORD

A high resolution record of hurricane and tropical storm activity for the Boston area is being developed based on the 1,200 year long varved sedimentary record archived in the Lower Mystic Lake. The Mystic Lake is a low elevation (1 m above sea level), meromictic coastal lake directly connected to Boston Harbor by the Mystic River. Large overwash and storm surge events that drove inland of Boston Harbor delivered marine water to this normally fresh water basin, and these events can be detected by changes in sedimentology (turbidite/detritus layers) and diatom assemblages which indicate marine influence. A varve chronology based on counts from petrographic thin-sections and X-ray densitometry measurements has been developed, and shows excellent agreement with radiocarbon analyses. Additional work to further confirm its validity by other radiometric means is in progress. In conjunction with the varve chronology, event strata in the sedimentary record will be compared with the chronology of known storms during the historical period to calibrate and verify the record. The Mystic Lake record will be compared with a 1 cm resolution loss-on-ignition record developed from Belle Isle Marsh in Boston Harbor. Such marsh records are more typical of studies from other localities which reconstruct past hurricane frequency based on the presence of siliciclastic overwash layers in coastal stratigraphy. The comparison will allow us to determine how accurately both types of records serve as proxies for overwash and storm surge events. The frequency of hurricane events will be placed in the context of long-term climate changes, and may shed light on how hurricane frequencies might be expected to vary under globally warmer conditions in the future.