312 NEW YORK STATE MUSEUM 



Beds 11 and 10 of the Rondout section show mud crack struc- 

 ture of different sizes. These features have been seen in other 

 regions as well, though the beds showing them do not necessarily 

 belong to the same zone everywhere. Occasionally ripple marks 

 are shown as in the Wilbur Bridge section. Bed 9 is filled with 

 Leperditia a 1 1 a , containing also Beyrichia sp. ?, 

 Modiolopsis dubia and Spirifer vanuxemi. This 

 is a Manlius fauna and reference of these beds to the Rondout 

 appears to be wholly on lithic grounds. Since the two for- 

 mations are so closely related, it does not matter much where 

 the line between them is drawn. The middle ledge (5a) contains 

 Orthothetes interstriatus and C a m a r o t o e c h i a ? 

 lameliata, two typical Cobleskill species, but also found in 

 the Rondout in the Schoharie region [see Section 2]. 



Cobleskill 



Dark, often impure, fossiliferous lime sandrock, with 

 an abundance of Halysites. At Binnewater it is 

 14 feet thick, while at the section near Wilbur 

 bridge it is nearer 18 feet. In both of these locali- 

 ties it is underlain by the Rosendale cement bed, 

 but at Rondout this latter is absent, if my interpre- 

 tations are correct, and the upper 5 to 7 feet of the 

 Cobleskill rest directly on the Normanskill sand- 

 stones. Northward the Cobleskill disappears and 

 is overlapped by the Rondout as shown by Hart- 

 nagel. The relationship of the strata at Rosen- 

 dale and Rondout are shown in the following- 

 diagram [fig. 204]. 



Feet 



14-18 



V. B. 



Fig. 201 Diagram showing- relationship of Champlainic and Siluric strata in Ulster 

 county. R = Rosendale, B Binnewater. W Wilbur bridge, V.B. ■ Vlightberg, Kings- 

 ton, a-a', Normanskill shale, b, Shawangunk conglomerate, c, High Falls shale, 

 d, Binnewater sandstone, ( Wilbur limestone, /-/', Rosendale waterlime, y-y', Cobles- 

 kill, //-/(', Rondout waterlime, i-i , Manlius 



Rosendale cement 



Fine bedded gray lime mudrocks with the proper ad- 

 mixture of silica to make it a natural cement rock. 

 At Rosendale 22 feet are quarried, while near Wil- 



10-21 



