. Bulletin of the Geological Society of America. Geology. 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 granit
. Bulletin of the Geological Society of America. Geology. 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 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
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1890
