Tymochtee and Greenfield Formations, Undivided

Dolomite, olive-gray to yellowish- brown, thin to massive bedded, upper two-thirds commonly contains brownish-black to gray shale laminae; locally developed brecciated zones in lower one third.
State Ohio
Name Tymochtee and Greenfield Formations, Undivided
Geologic age Silurian
Lithologic constituents
Major
Sedimentary > Carbonate > Dolostone (Bed)olive-gray to yellowish- brown, thin to massive bedded, upper two-thirds commonly contains brownish-black to gray shale laminae; locally developed brecciated zones in lower one third.
Minor
Sedimentary > Clastic > Mudstone > Shale (Bed)upper two-thirds commonly contains brownish-black to gray shale laminae.
Comments Secondary unit description from USGS Lexicon website (ref. OH017) and OH005:Rock units forming the bedrock in the Maumee, Lucas Co., OH, and that crop out in the walls of a quarry are the Lockport Dolomite and the Greenfield Dolomite. The two form a thick reef complex roughly 600 m in diameter and about 68 m thick. The Lockport contains multistory stromatolite, thrombolite, and coral-microbialite reefs that were probably formed in a subtidal setting within a hypersaline lagoon. Lockport may be Wenlockian or Llandoverian to Ludlovian. In contrast to the mostly massive Lockport, the Greenfield at Maumee quarry is well bedded. It is Wenlockian, according to Shaver (1991), but fig. 16 of this report (after Howell, 1993) depicts the Greenfield as Llandoverian with a significant hiatus between deposition of the two units (Kahle, 1994).
References

Slucher, E.R., (principal compiler), Swinford, E.M., Larsen, G.E., and others, with GIS production and cartography by Powers, D.M., 2006, Bedrock geologic map of Ohio: Ohio Division of Geological Survey Map BG-1, version 6.0, scale 1:500,000.

Kahle, C.F., 1994, Facies and evolution of a Silurian coral-microbialite reef complex, Maumee, Ohio, USA: Journal of Sedimentary Research, v. A6, no. 4, p. 711-725.

USGS Geologic Names lexicon found at: http://ngmdb.usgs.gov/Geolex/

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Counties Allen - Auglaize - Champaign - Clark - Clinton - Fayette - Franklin - Greene - Hancock - Hardin - Highland - Logan - Lucas - Madison - Marion - Mercer - Ottawa - Pickaway - Putnam - Ross - Sandusky - Seneca - Shelby - Union - Van Wert - Wood - Wyandot