Pleistocene History of Glacial Lake Hitchcock

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Pleistocene History of Glacial Lake Hitchcock

• Galen Hammitt

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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

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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

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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

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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

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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

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Questions?
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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.