Cambrian Jim Pond Formation

Cambrian Jim Pond Formation
State Maine
Name Cambrian Jim Pond Formation
Geologic age Cambrian
Lithologic constituents
Major
Metamorphic > Metaigneous > Greenstone (Greenschist)GS - Greenschist facies; Protolith W - Mafic to Felsic volcanic rocks
Minor
Metamorphic > Metasedimentary > Metaclastic > Metasandstone > Metagraywacke (Greenschist)
Metamorphic > Metaigneous > Metavolcanic > Metadacite (Greenschist)
Incidental
Metamorphic > Amphibolite (Greenschist)GS - Greenschist facies; Protolith W - Mafic to Felsic volcanic rocks
Sedimentary > Chemical > Banded-iron-formation
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 W - Mafic to Felsic volcanic rocks.
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 - Somerset