338 F. Carney — Form of Outwash Drift. 



were also occupied by ice showing more or less dependence 

 upon the lobes lying in the Seneca and Cayuga valleys. But 

 as the general border of the ice retreated, the divide ridges 

 separating these trough-like valleys were revealed farther and 

 farther to the north between the converging lines of ice ; and 

 in an analogous manner the lesser divides marking and forming 

 the valleys contiguous to the Cayuga and Seneca troughs 

 became reentrant angles between converging walls of ice. It 

 is the work of two such lesser valley dependencies that is sup- 

 posed to have given rise to the peculiar drift accumulation 

 with which we are concerned. 



A study of the drift about Penn Yan reveals a massive 

 accumulation, of debris which begins southward a mile or so 

 from Milo Center and continues a mile or more north of Penn 

 Yan. This moraine, approximately three miles wide, suggests 

 a very slow retreat of the ice in this region. It is evident also 

 that this wide band of moraine represents more than the decay 

 of the ice reaching out from the Ontario lobe into Seneca val- 

 ley. It more likely is an indication of the general northwest 

 trend of the ice-front crossing Flint, ^Naples, and Cananclaigua 

 valleys. When the ice stood with a reentrant angle approxi- 

 mately at Milo Center, the Seneca tongue reached many miles 

 southward towards Watkins, while the lesser lobe in the Keuka 

 valley was shorter. A detail of this lesser lobe evidently 

 would give two tongues of ice, one occupying each arm of 

 Keuka lake, with the reentrant angle along the north-sonth 

 axis of Bluff Point, and the drift of our triangular area (fig. 1) 

 in process of construction. 



Along the margin of these valley lobes drift ridges, often 

 widening into morainic areas, w T ere being formed. The uni- 

 formity of such ridges as traced by Tarr on the Watkins quad- 

 rangle has suggested the characterization, " almost diagrammatic 

 in their simplicity."* Each such moraine is indicative of 

 stability in the reach of a valley lobe. Two contiguous valleys 

 as those of Keuka and Seneca lakes would give us contem- 

 poraneously formed contouring moraines. The particular form 

 assumed by the glacial debris at the angle of two such contig- 

 uous moraines will depend in the first place upon the northward 

 slope of the divide ; in the second place, upon the debris melted 

 out of the ice at this particular point; and, in the third place, 

 upon the amount of glacial drainage diverging at this point, 

 carrying the material thus melted along the margin of the 

 valley lobes. 



From a study of these intertrough divides of the Finger Lake 

 region, it is noted that their northward slope is gradual. The 

 *Bull. Geol. Soe. Am., vol. xvi, p. 218, 1905. 



