Offered by HMPGA

The Deglaciation of New England and its Relation to Climate and Correlation to Glacial Events in New York

Abstract: The formulation of a complete and accurate chronology of the last deglaciation in the northeastern U.S. is hampered in many places by a lack of radiocarbon ages that can be tied to deglacial ice front positions and events such as readvances, and the formation and drainage of glacial lakes. In most places it prevents us from clearly determining rates of ice recession and the relationship between deglacial events and climate oscillations depicted in North Atlantic climate records, specifically ice core records from north-central Greenland. In New England a continuous and well calibrated record of deglaciation can be derived from a revamped long varve chronology (5659 years) and the radiocarbon dating of plant fossils in the varves. The varve records have the added advantage of representing a record of glacial melting rates for the receding glacier that can be matched to and resemble, down to a sub-century scale, the oxygen isotope temperature record in Greenland. The periods of thinner (low melting) and thicker (high melting) varves in New England all correspond to cooling and warming events in Greenland and indicate that New England deglaciation rates and events are in lock step with North Atlantic climate. Glacial readvances do not appear to be glaciological adjustments such as glacial surges that are not-directly related to climate oscillations. In New York there is no continuous varve record but only a relative age record of the formation and drainage of glacial lakes in which only relatively short varve records have been assembled. Paleomagnetic records of remanent declination can be matched from both New York lakes and varves in New England leading to a correlation between the areas to within ~300 years. This correlation and the calibration of varves in New England allows us to compare and correlate glacial events that match across the region well within the uncertainty of paleomagnetic correlations and radiocarbon ages. Across the Northeast, glacial readvances match and depict periods of ice recession with accelerating rates of deglaciation through time that are punctuated by readvances and end moraine-building events. In order to create such a record, it has been necessary to fuse varve, radiocarbon, morpho-stratigraphic, and paleomagnetic records to create a continuous and expanded chronology of deglaciation.

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