STATEN ISLAND DRIFT. 99 



SUMMARY AND CONCLUSIONS. 



There are but few rock outcrops on the island sufficiently 

 hard to preserve the glacial striae, but from the few that are 

 available the direction has been ascertained to be between north 

 13 degrees west and north 20 degrees west, which, if extended 

 northward, may be seen to cross the known outcrops of the 

 rocks represented in the list. 



Satisfactory lithological identifications have also been made of 

 labradorite and other crystalline boulders, which would extend 

 the geographic and geologic range of the morainal material at 

 one extremity into the Archaean of the Adirondack region and 

 of sandstone, conglomerate and gravel which would extend it at 

 the other extremity into the Tertiary of the coastal plain. If 

 the lists alone are examined, however, it may be seen that in the 

 Palaeozoic the range of the fossils is from the Potsdam to the 

 Hamilton while in the Mesozoic there is represented the Trias 

 and the middle and upper Cretaceous. 



There are, therefore, two breaks — the first between the Ham- 

 ilton and the Trias, the second between the Trias and the middle 

 Cretaceous. Indications of either Carboniferous or Jurassic rocks 

 are entirely lacking, which is in accordance with our knowledge 

 in regard to the absence of any rocks of these periods along 

 ■ the line of glacial movement towards Staten Island. 



Probably one of the most interesting facts which may be 

 noted, from an examination of the list of localities, is that the 

 Cietaceous fossils are confined to those parts of the moraine 

 which lie south of the serpentine ridge. Tottenville and 

 Prince's Bay are the two localities at one extremity of the 

 island where they occur, while Clifton is the one locality at the 

 other. Between these two extremities they are absent, and the 

 natural conclusion to be drawn from this fact is that there was 

 never any Cretaceous extending around to the north of the 

 serpentine ridge, otherwise some evidence or at least indications 

 of it ought to occur in that portion of the moraine which rests 

 upon the ridge, but thus far not a fragment of a fossil or piece 



