USGS Visual Identifier

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GEOLEX database

Geologic Unit: North River

Publication:
Ratcliffe, N.M., and Armstrong, T.R., 1999, Bedrock geologic 
   map of the West Dover and Jacksonville quadrangles, Windham 
   County, Vermont: U.S. Geological Survey Miscellaneous 
   Investigations Series Map, I-2552, 30 p., 2 sheets, scale 
   1:24,000 [Available online from the USGS PubsWarehouse:  
   http://pubs.er.usgs.gov/pubs/i/i2552]
Usage in Publication:
North River Igneous Suite*

Modifications: Geologic Province: Dominant Lithology:
 Named
 New England province
 Trondhjemite
 Amphibolite
 Gneiss

Summary:
Named the North River Igneous Suite for igneous rocks that intrude the Cram Hill Formation in VT. Unit consists of a massive gneiss unit (white to light-gray, well foliated to blastomylonitic, poorly layered, garnet-biotite-muscovite-chlorite-quartz-plagioclase granofels), quartz-feldspar granofels member (light-brown to tan, chlorite-ilmenite-muscovite-quartz-plagioclase granofels), the Blue Mountain facies (dark-gray to black, poorly layered, porphyritic and nonporphyritic, ilmenite-epidote-chlorite-plagioclase-hornblende amphibolite), the Whitneyville facies (light- to medium-green, massive, epidote-ilmenite-sphene-chlorite-hornblende-plagioclase amphibolite), and the West Halifax Trondhjemite (light- to dark-gray, coarse-grained, massive, ilmenite-chlorite-epidote-muscovite-quartz-plagioclase trondhjemite). The Blue Mountain and Whitneyville facies comprise a dike and sill complex. Rocks of the North River Igneous Suite are younger than the Cram Hill Formation and older than the Northfield Formation. The North River is of Ordovician and Silurian(?) age.
Source: GNU records (USGS DDS-6; Reston GNULEX).