paleozoic time — devonian. 677 



1. Oriskany Period, 

 rocks— kinds and distribution. 



The Oriskany sandstone in eastern North America has nearly the limits 

 and distribution of the Lower Helderberg formation. It occurs over the eastern 

 half of New York, between Cayuga Lake and Albany, and reaches northward 

 to Oriskany Falls, northeast of Utica, having a thickness seldom exceeding 

 20 or 25 feet. It overlies the Lower Helderberg in Becrafts Mountain, and 

 abounds in fossils. It extends southward along the Appalachian region, 

 with increasing thickness, being 200 feet or more at Port Jervis, 150 to 200 

 feet along the western border of Kew Jersey, and eastern of Pennsylvania, 

 and of still greater thickness in western Maryland (at Cumberland), West 

 Virginia, and Virginia. It occurs also in eastern Canada, at Gaspe, and in 

 Maine along the Gaspe-Worcester trough, over Parlin Pond and the northern 

 part of Moosehead Lake, where it is reported to be several thousand feet 

 thick (C. H. Hitchcock). It is found also in Ontario, west of Niagara, and 

 in southern Illinois, where, in Union and adjoining counties, its maximum 

 thickness is 250 feet. 



The rock is usually a rough calcareous sandstone, or arenaceous limestone, 

 becoming, where weathered, porous and full of holes, from the dissolving 

 away of its many fossils by percolating waters. It is sometimes cherty lime- 

 stone, a pebbly sandstone, and in part a shale. In its distribution, its great 

 abundance of fossils, and its usually calcareous or semi-calcareous character, 

 it is widely different from the grits which follow it, and bears a close relation 

 to the Lower Helderberg series of impure limestones. At Becrafts Mountain 

 the beds represent the Lower Oriskany, and the rock is a hard, cherty, 

 arenaceous limestone. A similar rock exists at Port Jervis. 



A sandstone containing what appear to be Oriskany fossils has been 

 observed by C. W. Hayes in the highly disturbed region of northern Alabama, 

 in Frog Mountain, between Weisner and Indian mountains. It rests on Lower 

 Silurian and Cambrian unconf ormably ; but the unconformability, though 

 extensive, is described as due to overlap. No intervening Upper Silurian 

 beds occur in the region. The Clinton group (Rockwood beds) exists to the 

 south, but not at that locality (1891, '94). 



The geological connections of the Oriskany are with the Lower Helder- 

 herg formation, its beds thickening to the eastward as in the Lower Helder- 

 berg. It is, however, pronounced Devonian in its fauna and flora, and hence 

 belongs in the Devonian era. 



LIFE. 



The Oriskany fauna, although the rocks are rarely pure limestones, 



included a few Crinoids, of the genera Melocrinus, Mariacrinus, Technocrinus, 



Edriocrinus, etc. , common fossils in western Maryland, but not in New York ; 



some Cystoids ; numerous Brachiopods, of which the two represented 



Dana's manual — 37 



