University of the State of New : ftrk' Bulletin 



Entered as second-class matter August 2, 1913, at the Post Office at Albany, N. Y., under the 



act of August 12, 1912 



Published fortnightly 



No. 573 ALBANY, N. Y. AUGUST 15, 1914 



New York State Museum 



JOHN M. CLARKE, Director 

 Museum Bulletin 172 



GEOLOGY OF THE ATTICA AND DEPEW 

 QUADRANGLES 



BY D. D. LUTHER 



The area embraced within these quadrangles lies between the 

 lines of 42 45' and 43 north latitude, and 78 15' and 78 45' 

 west longitude and contains 455 square miles. 



It is situated just where the sloping front of the great Allegany 

 plateau begins to bend from a generally east and west line to a 

 direction nearly southwest and parallel to the southern shore of 

 Lake Erie. 



The point of lowest altitude is in the northwest corner of the 

 Depew quadrangle where it is 585 feet above sea level, or 338 feet 

 above Lake Ontario and 12 feet higher than Lake Erie, while the 

 crest of the ridge west of Varysburg reaches, on the southern 

 boundary line of the Attica quadrangle, the height of 1780 feet, 

 showing a difference in elevation of 1195 feet. 



The rock strata of this region have an average southward dip 

 or declination estimated to be about 33 feet a mile, or 577 feet 

 on a north and south line across the quadrangles. Adding this 

 thickness which is lost from the difference in elevation, the total 

 thickness of the rock section or Surface rocks shown on the maps 

 is approximately 1772 feet. 



The basal strata of this rock section to the thickness of about 

 100 feet belong to the Ontaric or Siluric system, and lie at the 

 foot and to the north of the rocky declivity known as the Helder- 

 berg escarpment that extends from Albany county to the Niagara 

 river, and crosses the Depew quadrangle near its northern bound- 

 ary. The Siluric strata and their contact with the overlying basal 

 formation of the Devonic system are finely exposed in several 

 quarries along the front of the escarpment. 



The rocks exposed in the upper part of the escarpment and the 

 surface rocks south of it on these quadrangles belong to the 



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