CAPE COD GEOLOGY 



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tocene deposits and on Tertiary and Cretaceous beds. These older deposits 

 in this region form an elevated plateau on which the moraine is superposed. 

 The northeastern limb of the moraine probably lies on the Manhasset forma- 

 tion, but this formation is exposed at but few places. This part of the mo- 

 raine does not rest on an elevated tract, as does the other. The morainal 

 deposits vary in thickness because they consist of ridges. Their average thick- 

 ness is probably not more than 5 or 10 feet. 



Distribution. — The morainal deposits in the town of Gay Head consist of 

 bedded gravel and sand, which form ridges that overlie the Manhasset and 

 older beds. The moraine here is not so conspicuous as it is in Chilmark, but on 

 Nashaquitsa there are prominent typical morainal ridges and knobs. Many 

 of these ridges are distinctly kamelike; and the bedding also suggests kames. 

 The deposits in Stonewall Beach cliffs rest on the Manhasset formation, and 

 those along the shore of Menemsha Pond rest on the Gardiners clay. 



The most extensive morainal area and the largest frontal moraine is in 

 Chilmark. The deposits begin on the east side of Menemsha Pond and rise 

 rapidly to a height of more than 300 feet in Prospect and Peaked Hills, from 

 which they extend northeastward, with interruptions, as far as the region about 

 Norton Point. Their higher parts stand well above 200 feet. Prospect Hill is 

 the most striking morainal ridge on the island, standing up as an isolated hill. 

 A. ridge that runs parallel to the north road, southeast of Prospect Hill, is also 

 typical. The best example of general morainal topography may be seen in the 

 region east of Peaked Hill, and here also Cretaceous deposits are exposed at the 

 base of the ridges in the high area. In Chilmark the moraine is separated 

 longitudinally into two parts by the north road valley. (See Plate 16, fig. 1.) 

 The moraine south of this valley is continuous from Peaked Hill almost to North 

 Tisbury and is a remarkable morainal highland. The moraine north of this 

 valley extends from Menemsha Creek through the town of Chilmark and be- 

 yond, nearly to Chappaquonsett Pond. The topography of this moraine is more 

 accentuated than that of the other and is, perhaps, best shown near the Chil- 

 mark- West Tisbury town line. (See Plate 15, fig. 1.) The deposits here form 

 two sharp ridges that run parallel to the shore and that contain many boulder 

 belts. (See Plate 17, fig. 2.) This moraine is interrupted by several pronounced 

 breaks. One of these breaks, if Nashaquitsa or Gay Head is considered a part 

 of this moraine, is made by Menemsha Pond; another is made by Roaring Brook; 

 and a third by Howlands or Paint Mill Brook. The fact that these two streams 

 were able to maintain their courses in spite of the deposition of the moraine is 

 noteworthy. 



