624 NKW YOKK STATE Ml'SKUM 



Columbia formation. The rude terraced plains \yk}g north of 

 the ntain moraine on tlie Oyster Bay qiuuh'angle are but the surface 

 of a thick series of gravels and sands on which the niomines have 

 been heaix'd. The reasons for referring to them heretofore as older 

 Pleistocene may now l>e set forth, together with tlie evidence in 

 favor of referring them to the Columbia formation of McGee,' the 

 group to which the deposits appear to have been referred hy that 

 author in 1888. 



F. J. II. Merrill, following the pioneer work of Mather, pointed 

 out in 1880 that these gravels and sands under the name of ''gravel 

 drift" underlie unconfornuibly the moraine, and concluded that 

 they were dej)<>6ited by swift currents carrying along line and coarse 

 materials together." 



The deposits as exposed on the Oyster Bay quadrangle consist of 

 water-worn gravels and sands, clearly divisible in certain sections 

 into an upper and lower series by a thin bed of glacial boulder clay. 

 It has not been possible in the course of the present survey within 

 tlie area to determine whether or not the group thus defined is to 

 be divided into an earlier dislocated and a later undisturbed series, 

 but it is clear that many sections of these gravels, along with what 

 apjjears to l>e the boulder bed named, have been dislocated along the 

 north coast of the island. On Marthas Vineyard and Block island 

 such a division has been made out,^ but the boulder clay parting, on 

 the other hand, has not been found there in the position of an inter- 

 mediate conformable bed. 



The gravels consist of water-worn fragments of quartz derived 

 from veins, granite and gneiss from the ancient Piedmont terrane of 

 the maiidand, of silicified fossils from the metamorphic Paleozoic 

 limestones of the mainland, cherts of the same origin, and ferrugin- 

 ous sandstones and fragments of concretions from the underlving 

 Cretaceous or Potomac section. 



' McGee, W J. Three formations of the middle Atlantic slope. Am. jour. 

 8ci. 8er. 8. 1888. 85 : 867-88. 448-66. It has not seemed possible at present to 

 establish a satisfactory comparison of the deposits in this portion of Long Island 

 with the formations recoKnizr<l in Nt-w Jersey by l^rof. Salisbury. 



^Merrill. F. J. H. N. V. aead. sci. Annals. 18H6. li : 341-64. 



•Woodworth, J. B. Unconformities on ilarthas Vineyard and Block island. 

 Geol. 800. Am. Bui. 1897. 8 : 204-11. 



