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Glacial Lake Hitchcock and post-glacier Geomorphology of the Connecticut River Valey. Paco DeFrancis 8 May 2014 GE254. Bedrock Geology. Northern Area: Gile Mountain and Waits River Meta wacke Siliceous with calcareous beds. Gile Mountain Formation with a hiker for scale.
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Glacial Lake Hitchcock and post-glacier Geomorphology of the Connecticut River Valey Paco DeFrancis 8 May 2014 GE254
Bedrock Geology • Northern Area: Gile Mountain and Waits River • Meta wacke • Siliceous with calcareous beds Gile Mountain Formation with a hiker for scale
Bedrock Geology • Southern Area: Hartford Rift Basin • N.A. broke of from supercontinent Pangea • Late Triassic sedimentary rock • Unit starts just south of VT-MA border, underlying formation for the rest of extent of Lake Hitchcock • Black shalescommon, anoxic lacustrine environment • Dinosaur ichnofacies common • Less resistant than crystalline rocks to north
Laurentide Ice Sheet • Last large advance was 125,000-18,000 yrs BP • Scoured North American landscape to bedrock, sucking up everything from large boulders to clay-sized particles • Terminal moraines formed in southern New England where the glacier stopped receding
Rocky Hill Dam • Southern Connecticut terminal moraine • Glacio-Marine contact • As the ice finally receded water was unable to flow through • Formed Lake Hitchcock!
Varve Chronology • Varves are an arctic lacustrine rhythmite • Yale geologist Antev studied varve chronology from lake sediments in the 1920’s • The chronological correlation of the varves continues to be debated today • Lake Hitchcock varves are very important for dating the recession of the ice sheet
Why is it important? Deltaic sand and gravel used as a building aggregate
Photographs • http://www.anr.state.vt.us/dec/geo/elizimages/Stop4Dgmpomfret.JPG • http://images.pennwellnet.com/ogj/images/ogj2/9629jfpy05.gif • http://www.highstead.net/publications/maps/southern_ne_sm.jpg • http://alg.umbc.edu/usaq/images/MODIS_RGB_Terra_USNE_20080529.jpg • http://www.anr.state.vt.us/dec/geo/images/GreenMtnGiantpics/IMG_0499.JPG • http://woostergeologists.scotblogs.wooster.edu/files/2012/04/Varve-2.jpg • http://4.bp.blogspot.com/-shyum8MVjxI/UUo-RvbTGeI/AAAAAAAAQTY/W8CNeKxHTjY/s1600/DSCN8284.JPG • http://www.guybiechele.com/portfolio/16-Connecticut_River-Valley_Sunderland-Massachusetts.jpg