NOTES ON SILURIAN FOSSILS FROM OHIO AND OTHER 



CENTRAL STATES. 



Aug. F. Foerste. 



The order of succession of Silurian strata in southeastern 



Indiana and the adjacent parts of Kentucky, in descending 



order, is as follows: 



Louisville limestone, 

 Waldron shale, 

 Laurel limestone, 

 Osgood clay and limestone, 

 Brassfield limestone. 



The Waldron clay shale has not been traced north of 

 Waldron, St. Paul, and Milroy, the latter village being seven 

 miles south of Rushville, Indiana. The Louisville limestone 

 thins out eastward, beneath the Devonian, there being an 

 unconformity between the top of the Louisville exposures and 

 the base of the Devonian. Typical Louisville limestone can 

 be traced eastward as far as Madison and the outcrops along 

 Big Creek, southeast of Dupont. Between Vernon and Milroy 

 the equivalent of the Louisville limestone is poorly supplied 

 with fossils and rarely exceeds ten feet in thickness. Farther 

 north it has not been recognized as a distinct horizon, separable 

 from the general upper Niagaran section. Neither the Waldron 

 nor the Louisville member has been recognized in Ohio. 



The order of succession of Silurian strata in the northern 

 tier of counties in southwestern Ohio, including Preble, Mont- 

 gomery, Greene, Clarke, Champaign, Miami and Darke 

 Counties, in descending order, is as follows: 



[Cedarville dolomite 

 Durbin formation < Springfield dolomite 



[Euphemia dolomite 

 Laurel limestone 

 Osgood clay shale 

 Dayton limestone 

 Brassfield limestone. 



The Euphemia dolomite is the very porous Mottled Zone 

 of Prosser (The Classification of the Niagaran Formations of 

 Western Ohio, Journal of Geology, 1916, pp. 334-365), and 

 was identified by Orton with his West Union formation, of the 

 more southern counties of Ohio. The Euphemia dolomite 

 can not be identified west of New Paris, nor south of Cedarville, 

 Ohio. 



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