Cambrian Jim Pond Formation, graywacke

Cambrian Jim Pond Formation graywacke
State Maine
Name Cambrian Jim Pond Formation, graywacke
Geologic age Cambrian
Lithologic constituents
Major
Sedimentary > Clastic > Sandstone > GraywackeGS - Greenschist facies; Protolith E - Feldspathic sandstone
Comments Volcanic and metasedimentary rocks of the ophiolite sequence in central-western Maine are here named the Jim Pond Formation. It consists of a basal chlorite-albite-epidote-actinolite greenstone member with minor metagraywacke, 150 to 500 m thick. Northwest of the Squirtgun fault it is divided into lower and upper units by a metadacite member in the east, 0 to >500 m thick, and a metagraywacke member in the west. The metadacite member is closely associated with hematitic chert iron-formation members. Greenstone is thickly layered with pillowed and massive flows. Patches of altered amphibolite are in contact with the southeastern belt of tonalite of the Boil Mountain Complex. (ME075) Unit description from USGS GEOLEX website (ME078). GS - Greenschist facies; Protolith E - Feldspathic sandstone.
References

Osberg, P.H., Hussey, A.M., and Boone, G.M., 1985, Bedrock geologic map of Maine: Maine Geological Survey, Dept. of Conserv., scale 1:500,000.

Boudette, E.L., 1982, Ophiolite assemblage of early Paleozoic age in central western Maine, IN St-Julien, P., and Beland, J., eds., Major structural zones and faults of the northern Appalachians: Geological Association of Canada Special Paper, 24, p. 209-230.

US Geological Survey, 2005, National Geologic Map Database, Geologic Names Lexicon "GEOLEX", http://ngmdb.usgs.gov/Geolex/.

NGMDB product
Counties Franklin - Oxford