Pleistocene History of Glacial Lake Hitchcock

Galen Hammitt

Location and Formation of GLH

•Connecticut River Valley

•Dammed in by end moraine of the Laurentide Ice Sheet

•Water level controlled by New Britain spillway

•From Ridge, 1990

Drainage of GLH

•Multiple breaches of Rocky Hill Dam

•Breaches preserved in the varve record

•Basins north and south of Holyoke Range, Massachusetts

•Southern basin drains before deeper northern basin

Dating the Formation and Drainage of GLH

•Formation dated to 15.6 ka based on organic material in basal lacustrine deposits

•Estimates for drainage based on varve record and pingo scars

•From Ridge, 1990

Dating Drainage of Southern and Northern Basins

•Southern basin: ~14 ka based on organics in pingo scars

•Northern basin: ~12.4 ka based on varve record

Paleoclimate after the retreat of the Laurentide Ice Sheet

•Glacial retreat was thought to be caused by warming temperatures

•Periglacial formations indicate cold conditions persisted after glacial retreat

•Ice-wedge casts and pingo scars

•Pollen record of cold-climate, tundra vegetation

•From Stone, 1992

Questions?

References Cited:

• Ridge, J. C., 1990: Re-evaluation of Antevs’ New England varve chronology and new radiocarbon dates of sediments from glacial Lake Hitchcock. Geological Society of America Bulletin, v. 102, p.889-899.

• Stone, J. R., 1992: Ice-wedge casts, pingo scars and the drainage of glacial Lake Hitchcock. Guidebook for field trips in the Connecticut Valley region of Massachusetts and adjacent states, v. 66, p. 305-331.