GEOLOGY OF LAKE PLEASANT QUADRANGLE 69 



of the mouth of Colombe brook, a very perfect, narrow sandflat 

 at 940 feet extends three-fourths of a mile southward nearly to 

 Dewey creek. Just below this, and crossed by the road, is a stream- 

 cut terrace in the lake deposits at 920 feet. From here down the 

 river for 5 miles there is no distinct terrace above 900 feet, but at 

 5I/2 miles down, or one-half of a mile west of Hope valley (Stony 

 creek sheet) there is a hue large sand flat lying between 900 and 

 920 feet altitude, probably nearer 920 feet. This terrace quite 

 certainly correlates with the ones above mentioned, its somewhat 

 lower level being due to Postglacial warping of the land. A smaller 

 terrace at the same altitude lies one-half of a mile west of the mouth 

 of West Stony creek. Just north of the village of Northville there 

 is a fine delta terrace at 860 to 880 feet which Fairchild correlates 

 with his Amsterdam lake, but this terrace seems too low to be cor- 

 related with that already described farther up the river. Thus it 

 appears most likely that the Hope glacial lake was held by a dam 

 of drift or ice across the valley about i or i;^ miles north of North- 

 ville where much drift still obstru:ts the channel. A possible view, 

 however, is that Hope lake was only an arm of the low water stage 

 of Schoharie lake or a high water stage of Amsterdam lake as 

 described by Fairchild.^ 



Benson Center lake. This small lake occupied the valley bottom 

 at Benson Center, its old shore line closely corresponding to the 

 present 1300-foot contour line. The perfectly developed sand flats 

 at nearly 1300 feet represent the old lake deposits which have been 

 considerably removed by Postglacial erosion of the stream passing 

 through the valley. A dam of drift or ice across the stream chan- 

 nel from I to 2 miles south of the village held up the water. 



Most of the areas now shown as swamps were formerly small 

 lakes but these do not merit special description. 



Existing lakes 



Sacandaga lake and Lake Pleasant. It is certain that these 

 lakes were formerly more extensive than at present, the old shore 

 lines having been some 15 to 20 feet higher. The best sand flats, 

 representing a portion of the lake deposit of the larger lakes, lie 

 one-fourth of a mile southeast of the village of Speculator at an 

 altitude of about 1740 feet. This higher Sacandaga lake sent a 

 small arm northwest to Mud lake, another to Echo lake, and also 

 covered all the swamp area just east of the present lake. The con- 



1 N. Y. State Mus. Bui. 160, p. 26-30. 



