Ordovician tuff of the Depot Mountain sequence

Ordovician tuff of the Depot Mountain sequence
State Maine
Name Ordovician tuff of the Depot Mountain sequence
Geologic age Ordovician
Lithologic constituents
Major
Igneous > Volcanic > Felsic-volcanic (Pyroclastic-tuff)W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith T - rhyolitic volcanic rocks
Comments Named as a formation in Meduxnekeag Group (rank raised). Named for Chandler Ridge, Aroostook Co., northern ME. Formerly called slate and graywacke member of Meduxnekeag Formation in Pavlides (1962, 1965). Consists of a lenticular deposit of slate, graywacke, conglomeratic graywacke, and minor amounts of siltstone and quartzite. Thickness about 5,000 ft. Lower contact not exposed; conformably overlain by a thinned sequence of Ordovician and Silurian Carys Mills Formation (new) of Meduxnekeag Group. Because Carys Mills Formation in vicinity of Chandler Ridge is thin and its precise age in this area is not known, underlying Chandler Ridge Formation is provisionally considered to be of Ordovician(?) age. (ME052) Unit description from USGS GEOLEX website (ME078). W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith Q - Interbedded pelite and sandstone
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.

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/.

NGMDB product
Counties Aroostook