Manhattan Formation, undivided (NYOm;3)

Manhattan Formation, undivided - pelitic schists, amphibolite; Units ?Omb, ?Omc, and ?Omd may be Cambrian eugeosynclinal rocks thrust upon Oma; ?Omd - sillimanite-garnet-muscovite-biotite-plagioclase-quartz gneiss; ?Omc - sillimanite-garnet-muscovite-biotite-quartz-plagioclase schistose gneiss, sillimanite nodules, local quartz-rich layers; ?Omb - discontinous unit of amphibolite and ?Omc-type schist.

State	New York
Name	Manhattan Formation, undivided
Geologic age	Ordovician?
Original map label	Om
Comments	part of Trenton Group and Metamorphic Equivalents up to 8000 ft. (2400 m). All units (?Omb - ?Omd) are mapped under Om in digital map. Only unit Oma is separated out, so I separated it out of this description. Unit is also mentioned under Eugeosynclinal (Allochthonous) Sequence; uses same symbol and color. Age change and second unit description from USGS Lexicon website (ref. NY046) and reference NY004: Manhattan Schist member A replaced by Walloomsac Formation (not new) based on work by Jackson and Hall (1982), Hall (in press), and A.A. Drake (1990, pers. commun.). In addition, L.M. Hall (1985?, pers. commun.) determined that member B of the Manhattan Schist is part of member C and thus recommended the abandonment of member B (Baskerville, 1992) .
Primary rock type	pelitic schist
Secondary rock type	gneiss
Other rock types	amphibolite
Lithologic constituents
Map references	NYS Museum, NYS Geological Survey, NYS Museum Technology Center, 1999, 1:250,000 Bedrock geology of NYS, data is distributed in ARC/INFOr EXPORT format (with ".e00" extension) in 5 seperate files based on printed map sheets, http://www.nysm.nysed.gov/gis.html. [http://www.nysm.nysed.gov/gis.html.]
Unit references	D. W. Fisher; Y. W. Isachsen, L. V. Rickard, 1970, Geologic Map of New York State, consisting of 5 sheets: Niagara, Finger Lakes, Hudson-Mohawk, Adirondack, and Lower Hudson, New York State Museum and Science Service, Map and Chart Series No. 15, scale 1:250000. Baskerville, C.A., 1992, Bedrock and engineering geologic maps of Bronx County and parts of New York and Queens Counties, New York: U.S. Geological Survey Miscellaneous Investigations Series Map, I-2003, 2 sheets, scale 1:24,000. [http://pubs.er.usgs.gov/publication/i2003] USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Bronx - Dutchess - New York - Putnam - Westchester