BERKEY, GEOLOGY OF SOUTHERN MANHATTAN ISLAND 255 
have been identified with certainty within the area reached by this study. 
Limestone is reported near Newtown Creek a little beyond the eastern margin 
of the map. 1 There has been no opportunity to verify this record. 
The above suggestions on the geology of the region south of Fifty-ninth 
Street are embodied in the accompanying map. Each boring whose record 
and material could be verified and personally inspected is plotted and 
marked to indicate the rock. No dependence was placed upon any records, 
if the material could not be seen. 
There is. no reasonable doubt that folds, faults, crush zones and decayed 
belts occur as frequently in this southern portion of Manhattan as in other 
better known adjacent areas, but they cannot be so definitely traced or 
mapped. It has been found in some places that surface drainage lines 
mark roughly the trace of certain structural weaknesses, even where heavily 
drift covered, but this is not always true. There is nowhere any evidence 
of very important cross structures such, for example, as the Manhattanville 
valley or Spuyten Duyvil Creek of northern Manhattan. 
The problems of this area, therefore, are concerned chiefly with the 
longitudinal structures produced by folding and faulting and subsequent 
disintegration and decay along the crush zones that sometimes accompany 
them. 
A generalized geologic cross-section showing structural relations across 
this area in the vicinity of Williamsburg Bridge based on an interpretation 
of areal geology, as outlined above, is given in Plate XXIII. 
East River Channel 
The East River is still more abnormal with this rearrangement of areal 
and structural geology. Instead of following the belts of limestone as was 
formerly supposed, it seems to have cut across all of the formations twice 
in the great bend below Twenty-seventh Street. There is no structural 
explanation better than the suggestion that it is controlled by a combination 
of intersecting cross fractures and weak zones across the gneiss of enough 
prominence to overcome the usual tendency to follow the strike of the lime¬ 
stone. It is worth noting that the Harlem River has a very similar course 
due rather certainly to cross-faulting, and that Hell Gate, Little Hell Gate 
and Bronx Kills are all of similar structural relation. It is believed that the 
portion of the East River between the Williamsburg and Manhattan bridges 
flows on the gneiss and that this part of the channel has less complexity of 
structure and less uncertainty of condition than any other of the waterways 
about the island. 
1 Veatch, as quoted by W. H. Hobbs: U. S. Geol. Surv. Bull. No. 270, p. S6. 1905. 
