412 



A. W. GRABAU PALEOZOIC DELTA DEPOSITS OF NORTH AMERICA 



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ciatecl fauna, is found at two distinct horizons 

 in the Upper Ordovicic of Kentucky and mid- 

 dle Tennessee, according to Mr. Ulrich. 19 The 

 first is in the Catheys formation, which Ulrich 

 places between the Trenton and the Utica of 

 New York. As I shall more fully show here- 

 after, and have shown in other publications, the 

 stratigraphic break between the Trenton and 

 Utica of New York thus postulated by Ulrich 

 is absolutely non-existent. The Catheys for- 

 mation of the Cincinnati dome is merely a local 

 phase of the higher Trenton, higher, of course, 

 than the New York Trenton, and represented 

 in New York by black Utica shale. The Utica 

 (Fulton) shale overlying the Catheys is merely 

 the last of the westward transgressing mud de- 

 posits, which slowly displaced the calcareous 

 sediments of the interior. This black mud de- 

 posit, the Utica shale type of sediment, is 

 throughout to be regarded as' the stratigraphic 

 equivalent of the Trenton limestone series as a 

 whole, the dividing line between the two being 

 a diagonal one (figure 3). 



The second occurrence of Orthorliynchula 

 linneyi is in the Fairmount formation of the 

 Cincinnati region. This formation, 80 feet 

 thick, is the lowest member of the Maysville 

 series and overlies the Frankfort or Eden shale 

 of the Cincinnati dome region. It is generally 

 correlated with the Lower Pulaski formation 

 of New York. Exact correlation is here out of 

 the question, but even should this be possible, 

 it does not follow that the indications of the 

 Orthorliynchula linneyi fauna found in the 

 Upper Martinsburg beds of the Tyrone Gap 

 prove this to be of Pulaski age. We have no 

 right to assume that, because this fauna occurs 

 in only two horizons in the Kentucky-Tennes- 

 see region, it can not also occur at an interme- 

 diate horizon at another locality. Indeed, the 



in Revision of the Paleozoic Systems. Bull. Geol. Soc. 

 Am., vol. 22, p. r>14. 



