THE NORTH AMERICAN VARVE CHRONOLOGY IN THE CONNECTICUT VALLEY: A RECORD OF GLACIAL MELTWATER, CLIMATE, AND ICE SHEET RESPONSE

New varve records and radiocarbon ages have allowed the correction, expansion, and calibration of Ernst Antevs’ original New England Varve Chronology. Varves are renumbered with corrections and filled gaps as the North American Varve Chronology, a continuous 5659-yr sequence (18.2-12.5 kyr BP) spanning most of the last deglaciation. Changes in varve thickness record changes in glacial meltwater production that are tied to summer climate variations and have been matched to the δ¹⁸O record of ice from the GISP2 Greenland ice core (original measurements interpolated to the GICC05 time scale) and Greenland Stadial (GS) and Interstadial (GI) events. Independent time scales for the varve (¹⁴C calibration) and ice core (layer counts) records are consistently different by 15 yr when features similar in magnitude and spacing are matched between the two records from 15.0-12.5 kyr BP. Varves record: 1) cold events as periods of thinner varve deposition (reduced ablation and meltwater production) associated with glacial stillstands and readvances lasting no more than a few centuries, and 2) warm events as periods of thicker varve deposition (higher ablation and meltwater production) associated with rapid ice recession. The chronology of major events from S to N is: ice recession of 50-100 m/yr in northern Connecticut (GS-2b); Chicopee Readvance (beginning GS-2a); recession of 30-40 m/yr in central Massachusetts; Hatfield event (mid-GS-2a); recession of 80-90 m/yr from Massachusetts to central NH; North Charlestown moraines (end GS-2a); ice recession of 300 m/yr to northern NH (GI-1e); Littleton Readvance (GI-1d); recession >100 m/yr to Quebec (GI-1c). There are also sub-century scale events in the Greenland record that are recorded by the varves and are now precisely linked to changes in ice recession. An example is a small readvance at Walpole, NH lasting <50 yr. Coupling of the varve and deglaciation record depicts an ice sheet that is extremely sensitive to local climate but it is also fully synchronous with Greenland climate at stadial to sub-century scales after ~15 kyr BP. Prior to 15 kyr BP, the varve and deglaciation records appear to be in sync, but Greenland climate changes were more subtle and the ice core record has lower resolution, which makes the comparison of New England and Greenland climates more difficult.