GEOLOGY AND PALEONTOLOGY OP THE SCHOHARIE VALLEY 90 



Chapter 2 



STRATIGRAPHY OF THE SCHOHARIE REGION (continued) 



The Champlainic and Ontario (Siluric) formations and their 



relationships 



Champlainic strata. The lowest beds exposed in the region 

 covered by the accompanying map belong to the Lorraine forma- 

 tion of the Upper Champlainic division. The portion accessible 

 within the area comprises fully six hundred feet of shales and 

 sandstones. In the deep Avell at Altamont, some miles northeast 

 of the eastern limit of the map, 28S0 feet of sandstones and shales 

 v/ere found above the Trenton limestone. This added to about 

 600 feet exposed on the cliff behind Altamont gives a total of 3480 

 feet for the combined thickness of the Lorraine and Utica of this 

 region. 



Continuous exposures are comparatively rare in the Schoharie 

 region, though fragments of the sandstones are common every- 

 where and on account of their flatness are extensively used in 

 stone fences. Good exposures however are found in the gorges of 

 the Bozenkill, Normanskill, and the low^er Schoharie, but all of 

 these are outside the limits of the map. The most accessible and 

 continuous exposure of the upper portion of these strata is in the 

 longer of the two small brooks which hav- incised themselves in 

 the hillside on the west bank of the Cobleskill, and which join 

 that stream halfway between Central Bridge and Howes Cave 

 [map : VII i, 20] . In the banks of this stream above the road the 

 horizontal shales are exposed. The lower beds are chiefly clay 

 rocks, though some beds are quite arenaceous, with mica scales on 

 the bedding planes. All the beds are traversed by tAvo sets of 

 joints, which cause the formation of rhomboidal blocks. Above 

 these micaceous sandrocks are soft gray clay shales with an 

 unctuous feel, and splitting into small fragments. Arenaceous 

 matter seems to be wholly absent from the mass of these shales, 

 with the exception of several one inch layers of sandstone, which 

 appear at intervals. These shales are capped by rather coarse 



