256 



CAPE COD GEOLOGY 



about Chatham and Pleasant Bay; on the Bay side of Truro; and in the so-called 

 "clay-pounds" at Highland Light. The base of these beds is nowhere exposed 

 to view except at Highland Light. Shaler called them the ' 'Barnstable series," 

 a term that was apparently intended to include also certain gravelly clay. 

 Whether the beds of clay on Cape Cod are all of the same age is still uncertain. 

 The only well exposed section that strongly resembles the typical Gardiners 

 section is that at Highland Light, where the dark clay occurs in the form of a 

 large lens that crops out on the coast above the gravel that Fuller called Jameco 

 and below beds of sand that represent either the Jacob sand or a younger 

 deposit. (See Plate 33). 



HIGHLAND 

 LIGHTHOUSE 



A WIRELESS 



TOWER 



O O O 



BEACH 



Fig, 20.— Section at Highland Light, in North Truro, showing the "clay pound" or supposed Gardiners clay resting on gravel 

 identified by Fuller as Jameco gravel and overlain by sands that resemble the Jacob sand. 



The bed of clay that crops out at Highland Light lies in a shallow syncline, 

 the axis of which appears to trend south of west and to pitch in that direction, 

 so that the clay is brought out beneath the North Truro plain to the bluff on 

 the bay side between North Truro station and Truro, on the Pamet River. 

 But the clay on the bay side is prevailingly sandier than the typical Gardiners 

 clay, and it passes laterally into sand and gravel. At a point a mile south by 

 east from Truro station there was exposed in the bluff, in 1916, the typical 

 Gardiners succession, namely, gravel below a brownish clay less than 20 feet 

 thick, and above that a fine yellow sand resembling the Jacob sand. The clay 

 bed thickened toward the north, but the sand became gravelly. There is a down- 

 fold in the series and beds of clay extend along the bluff nearly to North Truro, 

 but whether at the same or at a higher horizon cannot be ascertained because 

 of the slumping of the cliff. The clay south of the sharp downfold may he at the 



