Mineral Resources On-Line Spatial Data
Mineral Resources > Online Spatial Data > Geology > by state > Connecticut
|Name||Upper member [of Bigelow Brook Formation]|
|Geologic age||Silurian and perhaps Ordovician|
|Original map label||SObu|
|Comments||Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Merrimack Synclinorium; Hebron Gneiss and equivalent formations (including equivalents of Paxton and Oakdale Formations of Massachusetts) (including Bigelow Brook and Southbridge Formations) (Silurian and Ordovician). The age of the Brimfield Group and its Bigelow Brook, Hamilton Reservoir, and Mount Pisgah Formations in this area is considered to be Cambrian(?) based on the intrusion of 440 m.y. Hedgehog Hill gneiss emplaced near the top of the Hamilton Reservoir Formation in the upper part of the Brimfield, although the top of the Brimfield, at least, may be Ordovician or older Paleozoic (Pease, 1989) per CT013.|
|Primary rock type||schist|
|Secondary rock type||granofels|
|Other rock types|
Metamorphic > SchistChiefly gray, rusty-weathering, medium-grained, generally well layered and locally fissile schist, composed of plagioclase, quartz, biotite, garnet, and sillimanite, locally with K-feldspar or cordierite, fissile layers commonly with graphite and pyrrhotite.
Metamorphic > Granoblastic > Granofelsinterlayered with quartzose granofels with less biotite but with calc-silicate minerals
Connecticut Geological and Natural History Survey, DEP, in cooperation with the U.S. Geological Survey, 2000, Bedrock Geology of Connecticut, data format: shapefile, file name: bedrock, downloaded from: http://magic.lib.uconn.edu/cgi-bin/MAGIC_DBsearch2.pl?Geography=37800&Loc=0000 on 9/18/2003, scale 1:50,000.
Rodgers, John, compiler, 1985, Bedrock Geological Map of Connecticut: Connecticut Geological and Natural History Survey, Hartford, Connecticut, 2 sheets, scale 125,000.
|Geographic coverage||Tolland - Windham|
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