|Name||Ordovician graywacke of the Depot Mountain sequence|
Sedimentary > Clastic > Sandstone > GraywackeW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith K - Calcareous feldspathic sandstone
|Comments||Named for Chase Lake, Piscataquis Co., north-central ME. Consists of a lower member composed of slate and graywacke and an upper member composed of conglomerate and graywacke. Thickness is at least 610 m. Unconformably overlies Chase Brook Formation; conformably underlies Bluffer Pond Formation. (ME017) Unit description from USGS GEOLEX website (ME078). W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith A - Pelite|
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.
Roy, D.C., 1989, The Depot Mountain Formation; Transition from syn- to post-Taconian basin along the Baie Verte-Brompton line in northwestern Maine, IN Tucker, R.D., and Marvinney, T.G., eds., Studies in Maine geology; structure and stratigraphy; Volume 2: Maine Geological Survey, p. 85-99.
US Geological Survey, 2005, National Geologic Map Database, Geologic Names Lexicon "GEOLEX", http://ngmdb.usgs.gov/Geolex/.