14 NEW YORK STATE MUSEUM 



THE ORISKANY SANDSTONE (LOWER DEVONIAN) 



General description. The Oriskany formation in this State in 

 many places is a dark, siHceous, highly fossiliferous limestone; as 

 a sandstone it is best exposed in the type locality, at Oriskany Falls, 

 Oneida county, where it consists of 20 feet^ of nearly pure, white 

 fossiliferous quartz sandrock. 



Less than one-fourth of a mile north of the town, along a 

 road leading out of it in a northeasterly direction, 60-80 feet higher 

 than the road and 500-600 feet west, is exposed a ledge of rather 

 coarsely granular, apparently quite pure quartz sandstone, very 

 friable on weathered surfaces, and with an estimated thickness of 

 12 or 15 feet at the point where the rock was sampled; the dip is 

 very gentle, probably not over 45 or 50 feet to the mile. 



The Oriskany sandstone rests on the Helderbergian limestone, 

 which is locally quarried, the rock being used for road metal and 

 other purposes ; the Onondaga limestone overlies the sandstone, but 

 the limestone capping is not very thick at this point. 



The rock is massive, heavy bedded, and well exposed as a fairly 

 prominent, weathered ledge, for one-fourth of a mile or more. 



Lithologic character. The grains are composed almost wholly 

 of quartz; secondary enlargement has affected most of them, but 

 silicification has not been carried so far as to make the rock a 

 quartzite. 



The texture is decidedly coarser than any of the other rocks 

 described in this report, the grains averaging about 0.6 mm in 

 diameter, with a maximum of about 2 mm. The original rounded 

 grains are plainly outlined, and frequently crowded with inclusions 

 in trains, which terminate at the original grain margins, the added 

 secondary quartz being clear and clean. The inclusions are chiefly 

 liquid and gas ; bubbles of the latter may be seen in constant and 

 rapid motion. 



There is no very firm interlocking of grains so characteristic in 

 most quartzites, which probably accounts for the ready disaggrega- 

 tion of the rock where it is exposed to the action of the weather. 



According to the chemical analysis (table i) the percentage of 

 silica is 99.71 ; the rock crushes readily into granular " sand," the 

 purity of which is slightly improved by washing (table 2). 



Fissure 10 represents a photomicrograph taken with nicols crossed, 

 magnification 65 diameters. The outlines of the original rounded 



^ Grabau, A. W., Guide to the Geology and P?i]eoritolop:\- of the Scho- 

 harie Valley in Eastern New York. New York State Museum Bulletin 92. 

 1906. 



