GARDINER CLAY 



377 



stripped off. The outer or upper part of the material worked at the pit 

 is a brownish sandy clay interlaminated with sand and perhaps 40 feet 

 in thickness. The remainder, including the part now worked, is a dark- 

 gray, blue to nearly black plastic clay, with a slight brownish tinge, 

 almost identical in appearance with the thick clays at Nashaquitsa 

 cliffs, on Marthas Vineyard, and at Highland light, cape Cod. No peb- 

 bles could be found by the writer except in the lowest part of the clay 

 exposed, where a lens of granitic gravel was seen, possibly due to the 

 incorporation of some of the underlying Jameco materials. No fossil 

 shells or leaves are reported. Some rounded clay concretions occur, and 

 dendritic markings are found between some of the laminae. At Isabella 

 beach brownish and gray clays are seen in alternating laminse, while a 

 greenish-gray clay, probably representing a weathered phase of the 

 Gardiner, is seen three-quarters of a mile to the north. 



50' 



Figure 7 .—Northeast-southwest section along Isabella Beach. 



Showing, a, Herod gravels; b, Jacob sands, and, c, Gardiner clay. As elsewhere throughout the 

 island, there is a noticeable agreement between the topography and the geologic structure. 



Details of occurrence. — The best exposures of the Gardiner clay, as 

 has been indicated, are at the clay pit where the section shown in figure 6 

 is exposed. The dip at the pit commonly averages 45 degrees to the 

 north, pointing to a fold of considerable magnitude and indicating con- 

 ditions of folding much more marked than was supposed by Dr H. Ries, 

 who reported the disturbance to extend only to a depth of 20 to 30 feet.* 

 That the folding is essentially superficial is likewise believed by the 

 present writer (figure 4), but, as indicated by figures 3, 6, and 7, which 

 are drawn to scale, is certainly much greater than the figures quoted. 

 Besides the main folding there are many minor contortions which appear 

 to be due to movements of the clay layers over one another. 



Besides the clay pit there is only one point where the Gardiner clay is 

 well exposed, the clayey sands in the lower portion of the high bluff on 

 the south shore just south of West harbor belonging to the Jacob sands. 

 The exception is at Isabella beach, where, in the sections represented in 



♦ Bull. New York State Mus., no. 135, 1900, p. 603. 



