ORISKANY SANDSTONE. 169 



and the singular association of fossils which arc found in it. Sometimes, though it is but 

 a thin mass, not exceeding a foot in thickness, it is composed almost wholly of organic 

 bodies, being so crowded together that they appear a mass of shells. In addition to the 

 number of the fossils, it is highly interesting to observe the sudden transition of genera 

 and species that occurs in passing from the Delthyris and Encrinal limestones to the 

 Oriskany. Almost every species in the two former rocks seems to have perished about 

 the time the latter was in the process of deposition. To learn at this late day the cause of 

 this sudden extinction of life in so many animals, is certainly no easy matter. 



The Oriskany sandstone, being a clean sandy deposit, does not seem a sufficient cause 

 in itself for occasioning such a loss of life among the tenants of the deep ; though there is 

 no doubt of the position that the mollusca have their favorite habitations, a choice in the 

 materials in which they bury themselves, and in which they may seek their food. Still 

 one would hardly suppose that simple sand would prove so injurious to life, as to destroy 

 entire races. Hence it is more natural to suppose that some change preceded the deposi- 

 tion of the rock, to which must be attributed the catastrophe under consideration. This 

 change may have consisted simply in the elevation of the bottom of the sea, while the 

 preceding deposits were accumulating. This seems to be a rational hypothesis, inasmuch 

 as there is a change in the kind of materials which compose the sandstone. Previous to 

 this rock, there were calcareous deposits, mixed with sandy argillaceous ones ; afterwards 

 there were siliceous deposits, which must have come from another direction. The reader 

 of course will understand, that all the rocks which we have had under consideration in this 

 chapter, are formed of sediments abraded from preexisting rocks, brought from a distance 

 by rivers, to the oceans or seas which existed at this era. Again, the beings belonging 

 to the era of the sandstone were not only suddenly ushered into life, but they were as 

 suddenly put out of life, or, in other words, were destroyed as suddenly and as uncere- 

 moniously as their predecessors, and after an extremely brief period of existence. 



Characters of the Oriskany sandstone. It is composed in the main of coarsish angular 

 sand : in this respect, it is unlike many of the sandstones in the New- York system. The 

 sand is usually gray or yellowish, but sometimes white. Pebbles or rounded stones are 

 not common, if they ever exist in it : it is, at any rate, far from being a conglomerate. 

 Although the sand seems to be held together without cement, yet the presence of lime is 

 indicated by effervescence in a very large proportion of the rock, even in that portion which 

 to the eye appears altogether sandy. 



Localities where this rock is developed. Near the village of Leeds in Greene county, this 

 rock is crushed in, and concealed or greatly obscured by contortions which it has suffered 

 along with its associates (See PI. XX. sec. 5) . But the Helderberg range is the region 

 where this rock, for a thin one, is quite conspicuous, namely, on the road to New-Scotland, 

 near Mr. Clark's ; in Knox, on the road to Schoharie ; at Schoharie, on both sides of 

 the valley, but more particularly on the western terrace, and also at Cherryvalley ; at 

 Auburn, and four miles west of Auburn, on the road to Cayuga bridge. It forms an 



[Agricultural Report.] 22 



