336 F. Carney — Form of Out wash Drift. 



Art. XXXI. — A Form of Outwash Drift; by Frank 



Carney. 



The triangular area indicated in fig. 1 encloses a formation 

 of outwash drift in an association nndescribed in the literature 

 so far as the writer is aware. This drift forms a terrace in the 

 gradual slope to the north, the decline being about 500 feet in 

 three and one-half miles. Approaching the area along the 

 highway from Bluff Point postoffice (v. Penn Tan Quadrangle, 

 JS\ Y.), one notes the closeness of rock to the surface and the 

 general absence of glacial drift. The slope, though gradual, is 

 presumably the resultant of stream work, being the south wall 

 of an old valley, and of ice-corrasion ; but the marked change 

 as one nears this triangle is due to an unusual accumulation of 

 drift which is somewhat interlobate in origin ; but the further 

 differences between this and the typical outwash plain are so 

 marked as to warrant a more definite description, and possibly 

 a distinct designation. 



Topography of the Region. 



The drift under consideration lies on the north slope of 

 Hall's peninsula,"* designated on the Penn Yan quadrangle as 

 Bluff Point, which attains an elevation of TOO feet above lake 

 level. A nine-mile cross section, having a general east-west 

 direction through the highest part of Bluff Point, resembles 

 the letter " W", the inner legs being steepest but symmetrical 

 to a vertical axis, while the left or west of the outer legs is the 

 longer and has a gentler slope. The general relation of the 

 two arms of Lake Keuka is strikingly suggestive of an origin- 

 ally south-flowing stream, the valley of which has been blocked 

 by a great mass of glacial drift southwest of Hammondsport, a 

 village at the southern end of this body of water, thus giving 

 rise to the lake, which now has an outlet past Penn Yan into 

 the Seneca valley. Obviously this cross-section, AV-like in 

 shape, is made at the junction of the old south-flowing river 

 and a tributary. 



The general topography of the Finger Lake region, so fre- 

 quently alluded to in geological articles, is a systematic assem- 

 blage of trough-like valleys opening into the Ontario lowland. 

 Presumably the bed rock of these troughs slopes northward, as 

 do also the divides between them. The Penn Yan quadrangle 

 extends almost to the eds-e of this Ontario lowland. The 



• 



Drumlin region reaches its maximum southern extension north 



* James Hall. Geology of the Foui'th District, Natural History of N. Y. , 

 Part IV, p. 459, 1843. 



