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NEW YORK STATE MUSEUM 



type. As already noted, similar ones are found on the surface 

 of the upper quartzite of the Oriskany. 



The thickness of the Esopus on West hill is scarcely over 90 

 feet, 1 while on East hill the measurements give only about 80 feet. 

 At Countryman hill near New Salem the thickness of this forma- 

 tion is 121 feet ; at Clarksville 121 feet ; at Becraf t mountain and 

 at Rondout about 300 feet including the Schoharie, and at Port 

 Jervis about 700 feet. Except the structure described as 

 Spirophyton (Taonurus) cauda-galli no fossils 

 have been found in the Esopus shales of this region. 



Sequence of events during Lower Devonic time 



With the completion of the deposition of the Manlius limestone, 

 i. e. at the end of Siluric time, there appears to have been a gen- 

 eral elevation of the North American continent into dry land, 2 

 with the exception of a long narrow sea, which extended along the 

 western border of the old Appalachian continent ( Appalachia) 

 and between it and the newly elevated continent on the west. In 

 this sea which has been named the Cumberland basin, 3 the Hel- 

 derbergian strata were deposited, resting directly on the Manlius 

 formation and continuous with it in the central portion of the 

 basin. Western New York and the whole Mississippi region, be- 

 ing above sea level at that time, were actively eroded, till at the 

 beginning of Oriskany time, only 7 feet (the Cobleskill member) 

 of the Manlius remained in western New York ; from 300-400 feet 

 in Michigan; and not over 30 feet in southeastern Wisconsin 

 where it rests directly on the Guelph. 4 Westward from this point 

 the Manlius, if once present, was entirely removed by erosion, and 

 farther west the whole Siluric is wanting. The fact that late 

 Devonic rests on late Lower Siluric in some localities suggests 



1 These measurements are made by careful leveling from the top of the 

 Oriskany to the base of the Schoharie or the Onondaga [see sections in 

 ch. 5]. The thicknesses heretofore published for this formation in the 

 Schoharie region are mostly too large. 



2 The Cayugan emergence of Ulrich and Schuchert. 



3 Ulrich & Schuchert. Paleozoic Saas and Barriers in Eastern North 

 America. N. Y. State Paleontol. An. Kept for 1901. p.G47. 

 4 These dolomites (Monroe) may in part represent the Salina. 



