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Pre-Silurian Stratigraphy in South-Central Massachusetts and North-Central Connecticut

Robert W. Schnabel
Robert W. Schnabel
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January 01, 1976

A sequence of 13 lithologic units persists through the New Hartford, West Granville, Tariffville, and Southwick7-1/2′ quadrangles. The sequence of deposition was deduced from the composition of graded beds and cross-beds that locally are well preserved in many of the units. The units from top to bottom are (1) Oh1; schist, locally graphitic, with thin quartzite, calc-silicate rocks, and coticule rock; minimum 900 m (3,000 ft) thick; (2) Oh2; coarse-grained kyanite-garnet schist with abundant sillimanite; 1,200 m (4,000 ft) thick; (3) Oh3; schist with locally abundant calc-silicate rock and amphibolite; 0 to 600 m (0 to 2,000 ft) thick; (4) Os4; sulfidic and graphitic schist; 600 m (2,000 ft) thick; (5) Os5; graphitic schist with abundant lenses and pods of zoisite amphibolite; 300 m (1,000 ft) thick; (6) Os6; sulfidic nongraphitic schist with abundant thin coticule layers; 180 m (600 ft) thick; (7) Oc7; interlayered felsic and mafic gneiss; minimum 450 m (1,500 ft) thick; (8) OCm8; interlayered fine-grained schist and granular schist with laminated hornblende-epidote amphibolite abundant toward base; minimum 900 m (3,000 ft) thick; (9)Ch9; schist, commonly containing large muscovite porphyroblasts; 900 m (3,000 ft) thick; (10)Ch10; light-gray gneiss; 1,500 m (5,000 ft) thick; (11)Ch11; schist with feldspar porphyroblasts; 1,500 m (5,000 ft) thick; (12)Ch12; light-gray gneiss with schist layers; 0 to 1,050 m (0 to 3,500 ft) thick; and (13)Ch13; heterogeneous interlayered schist and gneiss; 3,000 m (10,000 ft) thick. Units 1, 2, and 3 are members of the Hartland Formation of Connecticut; units 4, 5, and 6 are equivalent to the Straits Schist of Connecticut; and units 1 through 6 are probably equivalent to the Partridge Formation of New Hampshire. Unit 7 is equivalent to the d o me gneiss of Connecticut, the Ammonoosuc Volcanics of New Hampshire, and the Hawley Formation of Massachusetts. Unit 8 is equivalent to the Moretown Formation and Rowe Schist of Vermont and Massachusetts; units 9, 10, 11, 12, and 13 are equivalent to the Waramaug Formation (of local usage) of Connecticut and to the Hoosac Formation of western Massachusetts and Vermont.

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GSA Memoirs

Contributions to the Stratigraphy of New England

Lincoln R. Page
Lincoln R. Page
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Geological Society of America
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Publication date:
January 01, 1976




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