GEOLOGY OF THE GENEVA-OVID QUADRANGLES 29 



Rhinestreet shale, that everywhere in the western part of the State 

 caps the Cashaqua shale, into the Keuka lake valley in the southern 

 part of which the limestone reaches its greatest development so far 

 as it is exposed, but the black band of Rhinestreet shale is reduced 

 in thickness to about lo feet and the light shales intervening be- 

 tween it and the limestone are also very much diminished. 



The Parrish limestone is recognizable in Big Stream ravine with 

 the Rhinestreet shale lo inches thick overlying it, the intervening 

 shales having thinned entirely out. 



The only exposure of their horizon on this quadrangle on the 

 Vv^est side of the lake is on Plum creek half a mile above Himrods. 

 Neither limestone nor black shale appears here but a band of cal- 

 careous olive shale containing many fossils indicates their place in 

 the strata. 



The proportion of santly sediment in the Cashaqua beds is much 

 greater in the upper part and increases toward the east and south 

 to such an extent that only the lower beds conform strictly to the 

 description of the Cashac[ua shale as it appears in Cashaqua creek 

 while the upper contains many flag's and thick layers of hard blue 

 gray sandstone some of which split into even flags while others 

 are compact. 



Exposures at Starkey and North Hector show that with the 

 incoming of the sandy sediments a gradual change in the fauna 

 appeared, brachiopods vdiich are not found in these beds in the 

 Naples valley or farther west occurring in thin calcareous layers, 

 and masses of the coral Cladochonus about lOO feet above the base 

 of the formation. 



From this horizon upward through several hundred feet of shales 

 and sandstones there are irregular alternations and combinations 

 of the Naples and Ithaca faunas and toward the east a gradual 

 segregation of the latter in the formation succeeding the Cashaqua. 

 This formation is well exposed along Plum creek below and above 

 Himrods, in the ravine and along the dugway roads east of Starkey, 

 along the lake shore north of Glenora, and on the east side from 

 the south line of the quadrangle to the north side of North Hector 

 point, and in the ravines of Curry, Breakneck, Lodi, Tommy and 

 Sixteen Falls creeks. The sandstones are ex])osed in old (|uarries 

 in the western part of the village of Ovid and in the vicinity of 

 Scott Corners. The Cashaqua shale is not a very fossilifcrous 

 formation but thin scams in which fossils arc fairly common occur 

 at all horizons. 



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