FIFTH REPORT OF THE DIRECTOR I908 



I I 



assembled a body of data of extraordinary importance bearing upon 

 the physiography and geological structure of the lower Hudson 

 valley and the adjoining region. Two years ago the areal survey 

 of the Highlands quadrangles was placed in charge of Dr Charles 

 P. Berkey who has also become associated as geologist with the 

 Eoard of Water Supply. This double professional interest en- 

 ables Dr Berkey to assemble and combine all the data most effect- 

 ively. During the past season more time was spent upon struc- 

 tural and petrographic details of this work than on a continuance 

 of areal mapping, as this was made necessary from the accumu- 

 lation of drill records and similar data. It is of interest to note 

 that these deep seated data do not intimate any inaccuracy in the 

 determination from the surface, of the stratigraphic succession or 

 of general interpretation. On the contrary these well established 

 factors were a constant guide to the engineering exploration and 

 to the interpretation of data gathered throughout the work. But 

 the data available are so abundant and well distributed as to enable 

 the construction of cross sections with exceptional accuracy. The 

 preliminary explorations of the Catskill Aqueduct are largely 

 finished. More complete data, such as may be gathered as the 

 tunnels progress will not be obtainable for several years and it 

 therefore seems advisable to arrange the present matter for imme- 

 diate use. This is being done in the form of a bulletin which 

 will present an outline of the geology of southeastern New York as 

 now understood, and a discussion of the significance of the newer 

 factors. 



In further areal work in the Highlands additional limestone 

 occurrences have been noted some of which at least are clearly 

 interbedded or included in the gneisses. These interbedded lime- 

 stones (probably of Grenville age) are now known in the High- 

 lands proper at occasional points from the vicinity of Brewster 

 near the Connecticut line to Tuxedo lake near the New Jersey 

 line, but they appear to be most frequent in the central or Hudson 

 River belt. An important connecting link between the gneisses of 

 New York city and of the Highlands proper was found in the 

 discovery of interbedded limestones in the city at the type locality 

 of the Fordham gneiss. Three points were found near Jerome 

 Park reservoir in the Borough of the Bronx where the limestones 

 are surely of this interbedded relation. In two of them the struct- 

 ural relations are unusually clear. They are small beds but lie 

 within small anticlinal folds in such a way as wholly to preclude 

 the possibility of infolding of overlying strata. In all cases these 



