Ordovician Munsungun Lake Formation

Ordovician Munsungun Lake Formation
State Maine
Name Ordovician Munsungun Lake Formation
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
Minor
Igneous > Volcanic > Mafic-volcanic > Basalt (Dike or sill)W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith T - Rhyolitic volcanic rocks
Incidental
Sedimentary > Clastic > Mudstone > ShaleW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith T - Rhyolitic volcanic rocks
Sedimentary > Chemical > ChertW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith T - Rhyolitic volcanic rocks
Sedimentary > Clastic > SandstoneW - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith T - Rhyolitic volcanic rocks
Comments Named for Kennebec River. Type locality is 1/4 mi northeast of Somerset Junction on northwest side of abandoned railroad right-of-way on northwest side of west branch of Kennebec River, Brassua Lake 15-min quad, northern Somerset Co., western ME. Occurs in belt about 5 mi long northeast to southwest through Somerset Junction. Consists of olive-drab, white-weathering, massive felsite and rhyolite tuff. Thickness unknown, probably from a few hundred feet to a thousand feet. Contact relationships unknown. Report includes geologic map and correlation chart. (ME003) Unit description from USGS GEOLEX website (ME078). W - Weakly metamorphosed; contains local occurrences of prehnite and pumpellyite; Protolith T - Rhyolitic volcanic rocks
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.

Hall, B.A., 1970, Stratigraphy of the southern end of the Munsungun anticlinorium, Maine: Maine Geol. Surv., Bull. 22, 63 p.

Pollock, S.G., Hamilton, N.D. and Doyle, R.A., 1994, Geology and archaeology of chert in the Munsungun Lake Formation; B6, IN Hanson, L.S., ed., Guidebook to field trips in north-central Maine: New England Intercollegiate Geological Conference Guidebook, [86th] Annual Meeting, Millinocket, ME, September 23-25, 1994, p. 159-181.

NGMDB product
Counties Aroostook - Piscataquis