334 T 7 ! Carney — Wave-cut Terraces in Keuka Valley. 



Cayuga valley is 2"7 feet per mile." Fairchild measures the 

 warp of the Daua beach in the Seueca valley at 3 feet per 

 mile.+ In reference to the shore phenomena with which we 

 are concerned the latter beach is more pertinent in location, 

 and slightly less dissimilar in age. The pre- Wisconsin shore 

 lines embody whatever tilting is shown by the post-Wisconsin 

 water-levels, plus any earlier deformation that remained uncor- 

 rected by later land movements. 



The shore lines shown in figs. 1 and 2 have obviously a 

 greater tilt than has been reported for the post- Wisconsin 

 beaches. Xo instrumental measurements of the deformation 

 have been made, though an attempt was made by a long series 

 of aneroid readings, checked with a bench aneroid,^: to approxi- 

 mate a degree of correctness ; but the line of contact between 

 cliff and terrace is so obscured by products of weathering and 

 glacial drift that it is impossible to get any T results from this 

 method, although the line is distinct enough when viewed from 

 a distance. It is apparent to the eye that the highest, and 

 presumably the oldest, terrace is the most warped. 



The existence of these wave-cut cliffs, older than the Late 

 Wisconsin stage, and their present attitude in reference to the 

 horizon, suggest a relation of factors that have a bearing on a 

 phase in the drainage history of the St. Lawrence-Susquehanna 

 divide region, and on the question of ice-erosion in the Finger 

 Lake valleys. A reference to the drainage problem was made 

 under the preceding section. The connection with the ice- 

 erosion problem, briefly stated, is this : These old cliffs imply 

 an ice-dammed lake that was not ephemeral ; the topography 

 admits such a lake only when the ice-front is nearby. With 

 such a position for the ice west of the Seneca valley, both it 

 and the Cayuga valley were occupied by lobes from the main 

 body of ice. Such lobes, it has been suggested,! w cmld be 

 competent to accomplish erosion ; the non-existence of such 

 lobes has been hypothecated on the absence of moraine belts, 

 hence it is claimed that there was no erosion. |j But since the 

 stage of glaciation concerned antedated the Late Wisconsin 

 which extended into Pennsylvania, the normal imbrication 

 arrangement of drift sheets may explain the absence of the 

 recessional moraine correlating with the ice-halt that was con- 

 temporaneous with the cliff-cutting and the over-steepening of 



* R. S. Tarr, Journal Geologv, vol. xii, pp. 79-80, 1904. 



■f Bulletin Geol. Soc. Am., vol. x. p. 68, 1899. 



% In the Journal of Geology, vol. xiv. 1907. the writer explains this 

 method of 'working aneroids in pairs. 



§H. L. Fairchild, Ice Erosion Theory a Fallacy, Bull. Geol. Soc. Am., 

 vol. xvi, p. 58. 



|| Ibid!, pp. 59-60. 



