Digital Varves

Varves of the Month for 4/27/2008 - 5/31/2008

Connecticut Valley Varves from Kelsey Ferguson Brickyard, Redland Brick Co., East Windsor, Connecticut.

Scale bar in cm.

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This image shows glacial varves from the Connecticut Valley at the southern end of Lake Hitchcock near Hartford, Connecticut. The winter (W) or non-melt season layers (dark, top part of each annual layer) are labeled for New England varves 3866-3877 (lower Connecticut varve sequence, New England Varve Chronology numbering system of Antevs, 1922). These varves were deposited at least 350 years after ice recession at the site, when the receding ice margin was 45 km to the north near Holyoke, Massachusetts. Sedimentation was still dominantly controlled by the input of sediment from the receding glacier, but with significant contributions from rivers that no longer carried glacial meltwater.

Summer (S) or melt season layers (light-colored units) are composed of a stack of micrograded units of mostly silt with minor amounts of fine sand and clay and are generally non-gradational from bottom to top. Unlike last month's varves from further north in the Connecticut valley at Canoe Brook (Dummerston, Vermont) the upper surfaces of summer layers are abruptly truncated by winter clay and do not appear to be gradational with the winter bed. Variations in summer layer laminae are a reflection of variations in bottom current velocity with occasional clayey (dark) laminae that are periods of diminished bottom current activity during the melting season (see summer layers of varves 3868, 3873, 3874, and 3877). Summer layer thickness is slightly greater than winter layer thickness (except in varves 3870, 3873, and 3874) and also varies about the same as winter layer thickness in these varves. Summer and winter layer thicknesses appear to vary proportionally with summer layer thickness variation mimicking winter layer thick variation. This is another difference between these varves and last month's varves from Canoe Brook in Vermont.

Past Varves of the Month...