Silurian - Ordovician Lobster Lake Formation (MESOlb;0)

State	Maine
Name	Silurian - Ordovician Lobster Lake Formation
Geologic age	Silurian - Ordovician
Original map label	SOlb
Comments	Occurs in area adjacent to northwest shore of Lobster Lake. Consists of blue-gray, buff-weathering, calcareous siltstone and calcareous pelmatozoan-columnal-bearing sandstone; siltstone composed of dark, fine-grained silt; calcareous slate composed of fine-grained blue-gray clay; irregular limestone pebble conglomerate; and blue-gray, gray-weathering, massive limestone that contains stromatoporoid debris. Includes basal Big Claw red-bed member consisting of red quartzite, sandstone, shale, and conglomerate, and gray sandstone. Thickness is up to 4,000 ft but is beveled by erosion. Lower contact of main body with Big Claw red-bed member not observed; beds on either side of contact are parallel. Report includes geologic map and correlation chart. (ME003) Unit description from USGS GEOLEX website (ME078). W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith H - Lithic sandstone and conglomerate
Primary rock type	sandstone
Secondary rock type	siltstone
Other rock types	conglomerate; slate; quartzite; shale
Lithologic constituents	Minor Metamorphic > Metasedimentary > Metaclastic > SlateW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith H - Lithic sandstone and conglomerate Metamorphic > Metasedimentary > Metaclastic > QuartziteW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith H - Lithic sandstone and conglomerate Sedimentary > Clastic > Mudstone > ShaleW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith H - Lithic sandstone and conglomerate Sedimentary > Clastic > SiltstoneW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith H - Lithic sandstone and conglomerate Sedimentary > Clastic > ConglomerateW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith H - Lithic sandstone and conglomerate Sedimentary > Clastic > SandstoneW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith H - Lithic sandstone and conglomerate
Map references	Digital bedrock data downloaded from Maine Office of GIS in September 2005 from http://apollo.ogis.state.me.us/catalog/catalog.asp?state=2&extent=cover#bedrock Bedrock units table (publication date 11/15/2002) downloaded from same site. Permission to redistribute these data granted by Dr. Robert Marvinney, State Geologist of Maine, in September 2006. [http://apollo.ogis.state.me.us/catalog/catalog.asp?state=2&extent=cover#bedrock]
Unit 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. Boucot, A.J., 1961, Stratigraphy of the Moose River synclinorium, IN Contributions to general geology, 1959: U.S. Geological Survey Bulletin, 1111-E, p. E153-E188. [http://pubs.er.usgs.gov/publication/b1111E] USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Piscataquis