|Name||Cambrian Jim Pond Formation, mafic volcanic rocks|
Metamorphic > Metaigneous > Greenstone (Greenschist)W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith V - Basaltic volcanic rocks; Also GS - Greenschist facies; Protolith V - Basaltic volcanic rocks
|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). W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith V - Basaltic volcanic rocks; Also GS - Greenschist facies; Protolith V - Basaltic volcanic rocks.|
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/.
|Counties||Aroostook - Franklin - Oxford - Penobscot - Piscataquis - Somerset|