CAPE COD GEOLOGY 



257 



horizon of the beds of clay, gravel, and sand which on the ocean side rise up 

 south of the "clay pounds" and show a clayey section beneath the large bed of 

 clay at the lighthouse. 



A lens of clay was seen in a fresh cut of the bluff about a third of a mile 

 south of the Pamet River Coast Guard station in April, 1916. It presented a 

 rounded termination on its northern border, suggesting that overthrusting had 

 foreshortened the lenticular cross section, unless the whole appearance were 

 due to the dislocation of a once more continuous layer of gray clay. This lens 

 was 25 feet long. 



These lenses of clay in gravel and sand lie below the horizon of the Gardiners 

 clay, if that formation is represented by the clay at Highland Light. 



Fully a dozen beds of blue clay are exposed about Chatham, and along the 

 coast as far north as the north side of Pleasant Bay. The outcrops mapped on 

 the bluff near Chatham Light, at the northeast end of Oyster Pond, and on the 

 sides of a lakelet about a mile northwest of that pond fall into a line extending 

 northwestward and marking either the outcrop of an eroded inclined bed of 

 clay or the axis of a fold. The clay on the south side of the lake mentioned dips 

 rather steeply westward under light-colored sand (Jacob?). In a railroad cut 

 west of the south end of High Hill a sharp fold of clay and overlying sand dips 

 eastward at an angle of 23°. This outcrop lies east of those on the banks of the 

 lake and seems to show that an anticlinal arch brings up the clay along the 

 line described. North of this outcrop, on the west side of Rider's Cove, there 

 is another, and north by east of this is an exposure on the northern part of 

 Nickerson's Neck. North of this outcrop there are exposures on the north shore 

 of Pleasant Bay, on both sides of a small cove. There is also an outcrop of clay 

 on the North Chatham shore about half a mile north of Allen's Point. The 

 alignment of the necks and topographic features, including Great Hill, near 

 Chatham, is due partly to erosion, but this erosion appears to follow the folding 

 of older Pleistocene beds, including what appear to be the Gardiners clay, the 

 Jacob sand, and the Herod gravel. Great Hill is possibly a syncline of Montauk 



till. 



About half a mile west of Harwich railroad station, there is an exposure of 

 reddish clay, which possibly lies at the horizon of the beds of clay here described. 

 Mr. Gilbert Hart, my assistant, noted outcrops of clay under sand along the 

 railway east of South Chatham at two points. This clay appears to be widely 

 distributed under the southeastern part of Cape Cod in low folds, which here 

 and there reach the present surface or he a few feet below it. 



