GEOLOGY OF THE GEN EVA-OVID QUADRANGLES 



33 



direction of the thickness of nearly all of the formations repre- 

 sented on the map. The amount of dip between different points is 

 greatly affected, however, by the presence of a series of undula- 

 tions or low anticlinal folds that render it exceedingly variable and 

 in many cases reverse it. 



The color line on the map that indicates the position of the 

 Tully limestone shows the irregularity of the dip in the direction 

 of the shores of the lake and fhe larger undulation of the strata, to 

 which attention has been directed in the description of that forma- 

 tion. 



Variations in the western dip are less noticeable to the casual 

 observer on account of their less favorable exposure in rugged and 

 sinuous ravines away from the level lake which on the shore makes 

 the smallest variation from the normal southern dip easily dis- 

 cernible. 



Most of the larger ravines on both sides of the valley show a 

 dip toward the lake, indicating that the location of the depression 

 now partly occupied by the waters of Seneca lake was primarily 

 determined by a synclinal fold o f the rock strata extending in the 

 same general direction as the present valley that was very greatly 

 enlarged and deepened by subsequent erosion. 



At the following localities on the west side of the lake an east- 

 ward dip is seen, at the falls of Wilson creek near the west line of 

 the quadrangle and 3^ miles south of Geneva it is 100 to 150 feet 

 per mile ; on Kashong creek the Tully limestone at the top of the 

 falls dips toward the northeast at the rate of more than 100 feet 

 per mile. On the Keuka outlet a sharp fold in the Tully limestone 

 extending from northeast to southwest, has produced what is almost 

 equivalent to a fault. 



The Tully limestone appears in the top of a conical hill miles 

 southwest from Dresden at 565 A. T. and again at about the same 

 level at the mouth of Bruce gully. It is exposed along up the 

 south side of the gorge to the Cascade mills where it produces a 

 cascade. The bottom and sides of the gorge are covered for 

 nearly a mile west to Seneca mills where the Tully reappears at 

 the top of a second cascade 40 feet higher than at the Cascade 

 mills. This curious phenomenon of a stream of water flowing 

 over the same stratum of rock at two different levels is duplicated 

 in the Great gully ravine 2^ miles south of Union Springs, where 

 a hard band of calcareous shale produces three cascades in a simi- 

 lar manner. The situation is very similar except that but one fall 

 occurs in the Bruce gully where the limestone is exposed in the 



