376 



M. L. FULLER — GEOLOGY OF FISHERS ISLAND 



as far as Marthas Vineyard it seems improbable that the Cretaceous beds 

 stood much, if any, above sealevel, and it is unlikely that they furnished 

 any great proportion of the materials of the Gardiner clay. In eastern 

 Long island and on Plum and Fishers islands the color is suggestive of 

 a derivation from the Triassic area of Connecticut, the silt being brought 

 to the ocean by the Connecticut river, which may be conceived as hav- 

 ing emptied eastward at the time. The amount of clayey sediment now 

 carried by the New England rivers is extremely slight, and the accumu- 

 lation of from 30 to 150 feet of clays over so wide an area would, under 

 the present condition, require a time interval of great length. It is not 

 impossible that the land, although low in the vicinity of Long island, 

 may have been somewhat elevated to the north, in which case erosion 



X 



■<?.-<('•<, •.<=>..-». ,- '-•. <»/--v-;i**v*< 



50' 



Figure 6. — North-south Section across Clay Pit on Fishers Island. 



Showing exposures as seen in June, 1904, with interpreted structure, a, Wisconsin till ; b, sand 

 and granitic gravel (Herod); c, brownish sandy clay interlaminated with sand (Jacob); d, dark 

 gray to almost black plastic clay (Gardiner). 



would be facilitated and relatively large amounts of silt furnished. Of 

 such an elevation, however, the writer knows of no other evidence, unless 

 the cool climate is to be taken as indicating the existence of elevations 

 of some importance in the near vicinity — a not very reasonable suppo- 

 sition. 



Composition of the clays. — In the pit where they are best seen the 

 clays are probably exposed to a thickness of 40 or 50* feet in what 

 appears to be a closed and partly overturned anticline (figure 6). The 

 clay pit was started in a valley where the clay showed at the surface, but 

 has now been worked back until 10 to 30 feet of till or gravel have to be 



* The thickness of the entire series, which includes the Jacob sands, which are here rather 

 clayey, is from 75 to 100 feet. 



