354 G. H. CHADWICK STRATIGRAPHY OF NEW YORK CLINTON 



mass of Herkimer sandstone east of Utica is the trilobite Trimeriis, but 

 Hall says of this that it ranges ^'^as low as the f errnginoiis sandstones of 

 Oneida Coimt}^, which aj^pear to be near the base of the formation" 

 (3:299). 



To complete the adverse evidence on this point,, the nature of the un- 

 conformity at the summit of the Clinton should be studied on the chart 

 (figure 2) and in text-figure 3. The Lockport dolomite, still probably 

 150 feet thick in the Syracuse wells, has become possibly 75 feet (mostly 

 shaly) at Clinton and scarcely separable from the overlying Pittsford 

 horizon (see New York State Museimi Memoir, 14: 4:31), which is prolj- 

 ably the rock that makes its last appearance on Steeles Creek (1:90). 

 At Tisdales all these are gone, and a still higher Silurian formation, the 

 Vernon shale, rests directly on the Herkimer sandstone, with a thickness 

 of possibly 50 feet (1: 96, 258), though it was fully 80 feet at Steeles 

 (1 : 96) and 150 at Clinton (AY. J. Miller, iS^ew York State Museum, Bul- 

 letin 107:150). At Crills, five miles beyond Tisdales, the Yernon is 

 wholly lapped out, and the overlying Camillus gypseous shales of the 

 higher Silurian repose directly on the lower part of the Herkimer sand- 

 stone (1: 100, 258), which does not show itself again beyond this i^lace. 

 At Yanhornsville the upper members of the Camillus come down within 

 a few feet of the red hematitic sandstone (1 : 81, 99), and in a short dis- 

 tance beyond they are in contact with the Ordovician Frankfort shale 

 (9:28; 1:253; New York State Museum Bulletin, 162: 36), the Clin- 

 ton having disappeared; compare text-figure 3. 



There is thus a steady loss of members from both the top of the Clinton 

 and the bottom of the Niagara and Salina as the hiatus enlarges eastward. 

 To whichever group we refer the Eochester, it should therefore be one of 

 the first to go; indeed its sharp reduction in the Lakeport well was our 

 first intimation that this process of elimination had commenced as we 

 came east. Along with it vanishes the upper Irondequoit (Lakeport) 

 and then the Donnelly. The resistant Herkimer, however, persists east- 

 ward as an ancient cuesta, with a steep in-face. 



Stratigraphically, then, the Eochester shale is excluded from the type 

 section of the Clinton. Considering the Waldron aspect of the upper 

 Irondequoit fauna as just observed, the paleontologic testimony is not any 

 more favorable. The comparatively small number of "Eochester" species 

 in the upper Clinton divisions (Brewerton, Phoenix, Donnelly, Kirkland, 

 Herkimer) loses all weight when it is realized that Plectambonites, 

 Spirifer radiatus, Leptaena, Pterinea, Dalmanella, Atrypa, Semicoscinium, 

 Dawsonoceras, Trimcrus, Calymene, Dalmanites, Camarotoecliia neglecta, 

 Dictyonema retiforme and areyi, all get started either in or below the 



