GEOLOGIC MAP OF THE BUFFALO QL" \DRAXGLE II 

 DEVONIC 



The division line between the great Siluric and Devonic systems 

 is well marked here on account of the entire absence of Helder- 

 bergian limestones, which in the eastern part of the State repre- 

 sent the earlier stages of Devonic deposition. 



Its peculiarities in this area have been fully noted by Clarke, 1 

 Grabau, 2 and Hartnagel' and are briefly stated below. 



Oriskany sandstone horizon 



The .Cobleskill waterlime is the highest Siluric formation repre- 

 sented on the Buffalo quadrangle. The Paleodevonic strata rest 

 unconformably on it, the Rondout waterlime and the Manlius lime- 

 stone not extending into the western part of the State. The sur- 

 face of the Cobleskill gives unmistakable evidence of having suf- 

 fered considerable erosion in the long period during which those 

 formations were being deposited. The most important facts indi- 

 cating this interval of erosion are the following: 



In the Buffalo Cement Co.'s quarries well defined channels and 

 irregular depressions make the surface of the stratum exceedingly 

 rough and hummocky and its line of contact with the superjacent 

 formation as seen in the quarry walls very uneven. 



In the bottom of some of these depressions there appear thin 

 masses of dark shale and a conglomerate composed principally of 

 small waterworn fragments of waterlime in a matrix of indurated 

 quartz sand. Because of the extremely slender representation of 

 this formation it is not introduced on the map. 



In the quarry wall there are two fissures that extend from the 

 top of the Cobleskill to the bottom of the cement layer. They have 

 been filled with this quartz sand and are covered by a few inches 

 of the conglomerate. This filling of the fissures has been con- 

 sidered as Oriskany sediment by Clarke 1 , and the erosion interval 

 as comprising the Helderbergian and part of Oriskanian ages. 



At Falkirk, Erie co., and Indian Falls, Genesee co., the char- 

 acter of the deposits in the horizon of this erosion interval is still 

 similar to those on this quadrangle, but farther east the broad 

 lentils of characteristic Oriskany sandstone appear in it. 



At Morganville the sandstone is 4 feet thick; in the salt shaft 

 at Livonia, 4 feet, 6 inches; at Honeoye Falls, 1 foot, 2 inches; at 

 North Leroy and Victor only the conglomerate is present; at 



1 N. Y. State Mus. Mem. j. igoo. p.g6-g8. 

 5 Geol. Soc. Am. Bui. igoo. v.ii. p.357-61. 



'State Paleontol. An. Rep't igoj. N. Y. State Mus. Bui. 69. 1903. p.1138. 



