1200 NEW YORK STATE MUSEUM 



Dalmanites dentatus zone, which is apparently older 

 than any so far recognized in the Oriskany of New York. This 

 " dentatus fauna " comprises, according to Weller, in addition 

 to a number of Lower Helderberg species and species peculiar 

 to itself, the following Oriskany types: Stropheodonta 

 magnifica, Spirifer murchisoni, Cyrtina ro- 

 stra t a and Orbiculoidea ampla. It seems to occupy 

 a horizon corresponding to the upper part, possibly to the black 

 cherts, of the Port Ewen beds of the Rondout and Whiteport 

 sections. 



The limit between the Port Ewen and the Oriskany has been 

 drawn by us at the bottom of layer 27, the white pebble bed 

 which marks the commencement of new and peculiar conditions 

 of sedimentation and life of Oriskany time. That the pebble 

 beds owe their origin to currents of considerable strength seems 

 evident from the nature of the fragments of which they are com- 

 posed. The pebbles themselves are in all respects small copies 

 of the rolled white quartz pebbles that compose the massive 

 Shawangunk grit, and their source is perhaps to be sought for 

 in masses of this latter formation, which, during that early 

 Devonic time, projected above sea level in the vicinity of what 

 are now the Shawangunk mountains along the eastern shore of 

 the mediterranean basin or trough in which the Helderbergian 

 and Oriskanian sediments were being deposited. No unconformity 

 can be distinguished between the Port Ewen and Oriskany, 

 though small rolled fragments referable to the Port Ewen black 

 chert occur frequently in the Oriskany beds. 



The Oriskany pebble beds are well exposed in the small ridge 

 just west of Gross's residence; farther to the north they are seen 

 along the western slope of the North hill where they are overlain 

 by the upper sandy and cherty limestones of the same formation. 

 Another excellent exposure, where the loose gravellike character 

 of the lower pebble bed is well shown, is along Abeel street 

 that runs from Rondout south along the left bank of the Ron 

 dout creek at a point near the old coal docks and about 14 mile 

 north of the South Rondout ferry. 



The pebble beds are quite constant throughout the southern 

 part of the Little Mountain belt, and they are recorded by Davis 



