F. Carney — Wave-cut Terraces in Keuka Valley. 333 



was also composite ;* but a parallelism of epochs has not been 

 worked out. 



For the purposes of the present paper, however, it is 

 assumed that the Lake Region of New York had been glaci- 

 ated previous to the Late Wisconsin stage, an hypothesis 

 already used by others ;f and that the interval or intervals of 

 deglaciation were not shorter than the time-ratios held tenta- 

 tively for the Mississippian area. 



Illustrations of the wave-cutting work done by some of the 

 Finger Lakes since they were lowered to their present levels 

 are common in geological literature.^: One who is acquainted 

 with Seneca Lake will recall the high cliff on the east shore 

 near Watkins, at the head of the lake ; and other localities 

 along this lake show quite as marked wave-work. Along the 

 present shore of Keuka Lake the cliffs are not so well devel- 

 oped, but benches of 20 feet or more are not uncommon. 



If lakes occupied these longitudinal valleys during the 

 interims of glaciation, cliff-cutting could have proceeded to 

 such an extent as to make survival in certain localities, at 

 least, probable. Even the shortest inter-glacial period, on the 

 assumption that the stages of the ice age represent oscillations 

 of the ice from continuously ice-covered dispersion areas, was 

 much longer than post- Wisconsin time, which has sufficed for 

 defining exact shore lines. But terrace No. 3 has an altitude 

 that is impossible if the body of water with which it is geneti- 

 cally connected discharged over any of the present cols leading' 

 into the Susquehanna area ; all of the overflow channels 

 reported for the Keuka valley are too low. It may be said, 

 however, that many of these interlocking valleys of the St. 

 Lawrence-Susquehanna basins, through which the waters of- 

 the high-level ice-front lakes spilled, have local characteristics 

 which are not normal to the regular development of valleys ; 

 the conditions here alluded to will be discussed in a separate 

 paper, since the problem constitutes a unit of investigation. 

 Nevertheless there is nothing incompatible between the alti- 

 tude of terrace No. 3 and a land ice-locked basin for a body of 

 water. 



Deformation of these old Shore Lines. 



From data supplied by Gilbert, it has been estimated that 

 the post-Wisconsin deformation of the Iroquois shore line in 



*E. D. Salisbury, Geol. Surv. of New Jersey, Ann. Rep. for 1893, pp. 73, 

 etc. ; J. B. Woodworth, N. Y. State Mus., Bulletin 48, pp. 618-670, 1901 ; 

 F. Carney, Journal Geolugy, vol. xv, 1907. 



fR. S. Tarr, American Geologist, vol. xxxiii, p. 284, 1904 ; H. L. Fair- 

 child, Bulletin Geol. Soc. Am., vol. xvi, p. 66, 1905. 



X Natural Hist, of N. Y., Part IV, Geology, p. 192, 1843 ; R. S. Tarr, Ele- 

 mentary Geology, p. 279, 1898 ; LeConte, Elements of Geology, p. 236, 1905. 



