48 NEW YORK STATE MUSEUM 



Deltas at old sea margins. The larger streams have at certain 

 levels well marked deposits of gravel and sand along their courses, 

 evidently deltas built during the time of submergence. 



The English river exhibits such a deposit about 2 miles north- 

 west from Mooers Forks. The stream now makes a turn about 

 the northwestern margin of this deposit. At one time, the stream 

 passed to the east of the delta making a deep trench shown by the 

 contours on the miap. 



The Big Chazy river has a small delta above Mooers Forks 

 mainly developed in the triangular area between this stream and 

 its north branch. The sands of this deposit extend up the valley 

 to about 500 feet above sea level. Along the eastern margin of the 

 delta from 400 feet to about 440 feet the surface is faintly marked 

 by beach and wave-cut lines. 



At Mooers there is another delta on the Big Chazy, whose sur- 

 face is at 280 feet. 



Bullis brook exhibits a slight delta at 300 feet on -the south of 

 Mooers and Shedden brook, also has a slight delta at about 280 

 feet elevation. 



The small streams on the south to the limit of the map show no 

 marked signs of their former local entrance into the sea. 



Clays. The area mapped on this quadrangle lies mainly to the 

 west and above the typical zone of marine clays which borders the 

 present shores of Lake Champlain. The clays however appear 

 along the course of Big Chazy river at Perry Mills in the north- 

 east corner of the area and are said to underlie some of the 

 swamps in the low grounds, probably as high as the 240 foot con- 

 tour line in the region north and east of Mooers. Clays also ap- 

 pear in the banks of Bullis brook near its junction with the Big 

 Chazy river. There is another locality on the north bank of 

 the river about 1J miles east of Mooers. At this locality clay has 

 been worked in recent years in a small way for brickmaking. The 

 clay is decidedly sandy and is overlain by sands representing the 

 outer margin of the Mooers 280 foot delta, a deposit of which the 

 clays are probably an essential part. They are not generally 

 exposed at the surface west of Perry Mills. For an occurrence of 

 early stratified pebbly clays see note on p. 53. 



