Varve, paleomagnetic, and 14 C Chronologies for late Pleistocene events in New Hampshire and Vermont (U.S.A.)

Abstract

A deglacial chronology for northern New England has been formulated using an atmospheric 14 C calibration of the New England Varve Chronology and paleomagnetic records. This 14 C chronology is based on 14 C ages from macrofossils of non-aquatic plants and is about 1 500 yr younger than existing chronologies that are based primarily on 14 C ages of bulk organic samples. The lower and upper Connecticut Valley varve sequences of Ernst Antevs (NE varves 2 701-6 352 and 6 601-8 500) overlap (lower 6 012 = upper 6 601) based on their crudely matching varve records and their similar paleomagnetic records. Three 14 C ages at Canoe Brook, Vermont (NE varve 6 150 = 12.3 14C ka) calibrate the lower Con necticut Valley sequence. New AMS and con ventional 14 C ages on woody twigs from Newbury, Vermont calibrate the upper se quence from 11.6-10.4 14 C ka (NE varves 7 440-8 660) and are consistent with the over lapping varve and paleomagnetic records, and the Canoe Brook 14 C ages. Deglaciation of the Connecticut Valley in southern Vermont began at 12.6 14 C ka (15.2 cal ka) and the Littleton-Bethlehem Readvance in northern New Hampshire and Vermont reached its maximum at11.9-11.8 14 C ka (14.0-13.9 cal ka) followed by recession of ice into Québec at about 11.5 14 C ka (13.4 cal ka). A lake persisted in the upper Connecticut Valley until at least 10.4 14 C ka (12.3 cal ka) and may have been seen by the first humans in the area.

A catastrophic meltwater flood event and the formation of the Hudson Shelf Valley

“…Water level changes in the Hudson basin associated with the drainage routing of glacial lakes Iroquois, Vermont, and Albany between ∼11,300 and 10,900 14 C year BP (Licciardi et al, 1999;Clark et al, 2001;Rayburn et al, 2005) may have precipitated dam failure at the Narrows. The most likely time interval for breaching of the moraine dam at the Narrows is between 12,300 14 C year BP (Ridge, 1997;Licciardi et al, 1999) and the initiation of the Champlain Sea at about 11,100 14 C year BP (Rodrigues, 1988;Ridge et al, 1999;Richard and Occhietti, 2005). Recently, Donnelly et al (2005) suggested an age of ∼ 11,450 14 C year BP (∼13,350 cal BP) for the flood event.…”

Guidebook for Field Trips in Western Maine and Northern New Hampshire

“…Ridge pinpointed the readvance age much more precisely and confirmed the Older Dryas connection through his work on the New England Varve Chronology and its relation to the Comerford Dam readvance site. His varve correlations in the Connecticut River valley west of Littleton showed that the readvance occurred at 11,900-11,800 14 C ka BP (13.9-13.8 cal ka BP) (Ridge et al, 1999. The Lake Hitchcock varve chronology is now incorporated in the North American Varve Chronology of .…”

Glacial Deposits and Late-Glacial to PostGlacial Alluvial Fans in the Northwestern White Mountians, New Hampshire

“…Ridge pinpointed the readvance age much more precisely and confirmed the Older Dryas connection through his work on the New England Varve Chronology and its relation to the Comerford Dam readvance site. His varve correlations in the Connecticut River valley west of Littleton showed that the readvance occurred at 11, 800 14 C ka BP (13.9-13.8 cal ka BP) (Ridge et al, 1999(Ridge et al, , 2004. The Lake Hitchcock varve chronology is now incorporated in the North American Varve Chronology of Ridge et al (2012).…”