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



persists southward about one and one-lialf miles ; much of this 

 distance it forms a prominent bench. 



The next formation that might include beds for registering 

 differential weathering effects is the Hatch shales and flags, 

 which attain a thickness of about 300 feet.* Along the slopes 

 of Bluff Point the sand} 7 layers of this formation, though irregu- 

 lar in both horizontal and vertical distribution, are conspicu- 

 ous. The greatest thickness of shale noted in any exposure is 

 about 12 feet ; the base of this horizon is 261 feet (corrected 

 aneroid reading) above lake-level ; it could not be demonstrated 

 that this horizon of shale had much horizontal extension. 

 Likewise the arenaceous layers, the heaviest noted being under 

 2 feet, do not persist horizontally. 



Next in rising section is the Grimes sandstone, estimated by 

 Luther to be 75 feet thick. f Tins formation is above the ter- 

 races in question, so its characteristics do not concern us. 



It appears, therefore, that there is no factor in the strati- 

 graphy of this area to account for the marked benches. No 

 conditions could be more favorable for registering the differ- 

 ential effects of weathering than the topography formed by 

 this peninsula of rock dividing the two arms of Keuka Lake. 



Cliffs in Keuka Valley. 



The succession of post-Wisconsin high level lakes that for- 

 merly occupied this region has been worked out by Fairchild. 

 He designates the overflow channels of the principal stages, 

 correlates the deltas, and points out some localities of wave- 

 work.^: 



The terraces and cliffs which occasion the present paper 

 have been studied in some detail along the flanks of Bluff 

 Point. Terraces apparently of the same age have been noted 

 elsewhere on the walls of Keuka valley, but have not been 

 critically examined. 



The most obvious reason for not associating these cliffs and 

 terraces with the work already done is the fact that they are 

 overlain and intersected by lines of Wisconsin drift. This 

 drift is in place, and so far as observed, shows no evidence 

 of wave-work along the planes of the terraces in question ; 

 furthermore, the drift is particularly well developed where it 

 crosses the terraces (fig. 3). 



These terraces, designated by numerals, are described in 

 regular order ascending from present lake-level : 



No. 1. This is not a clear case. For some distance south- 



•• D. D. Luther. N. Y. State Mus., Bulletin 101, p. 47, 1906. 

 •flbid., p. 49, 1906. 



{This Journal, vol. vii, pp. 255-56. 258. 1899; Bulletin Geol. Soe. Am., 

 vol. x, pp. 4-41. 1899. 



