Devonian Ironbound Mountain Formation (MEDim;0)

State	Maine
Name	Devonian Ironbound Mountain Formation
Geologic age	Devonian
Original map label	Dim
Comments	Ironbound Mountain Formation exposed in two major belts within and beyond Penobscot Lake region. Two minor strike belts are thrust faulted and contained within the region. Southeastern major belt is partly mapped into areas previously identified as Seboomook Formation. Northwestern belt is underlain entirely by the Grenier Ponds Member. Most characteristic lithology of the Ironbound Mountain is thinly bedded, well-cleaved, medium- to dark gray mudstone and siltstone slate. Beds range from 1 to 30 cm. Locally contains minor beds of matrix-supported conglomerate. Stratigraphically underlies North East [Northeast] Carry Formation. Unit may span the Silurian-Devonian boundary and range from possibly latest Pridolian to earliest Gedinnian. (ME011) Unit description from USGS GEOLEX website (ME078). GS - Greenschist facies W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith A - Pelite
Primary rock type	slate
Secondary rock type
Other rock types
Lithologic constituents	Major Metamorphic > Metasedimentary > Metaclastic > SlateGS - Greenschist facies W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite Protolith A - Pelite
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. Marvinney, R.G., 1989, Bedrock geology of the southeastern margin of the Connecticut Valley-Gaspe synclinorium in Somerset County, Maine, IN Berry, A.W., Jr., Guidebook for field trips in southern and west-central Maine: New England Intercollegiate Geological Conference Guidebook, 81st Annual Meeting, Farmington, ME, October 13-15, 1989, p. 212-237. USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Franklin - Oxford - Piscataquis - Somerset