|Name||Manhattan Formation (A Member)|
|Geologic age||Middle Ordovician|
|Comments||part of Trenton Group and Metamorphic Equivalents up to 8000 ft. (2400 m). This unit (Oma) is described under unit ?Om on printed map. Separated out, because it is used separately in digital map. Named it 'A Member' of Manhattan Formation. 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||schist|
|Secondary rock type||marble|
|Other rock types||calc-silicate rock|
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.
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.
|Counties||Putnam - Rockland - Westchester|