68 PROCEEDINGS OF THE AXX ARBOR MEETING 



CHEMUXG STRATIGRAPHY IX WESTERN XEW YORK ^ 

 BY GEORGE H. CHADWICK 



i Abstract) 



The upper Devonian of western New York consists of several thousand feet 

 of terrigenous strata in whicli tlie outstanding terms have been "Genesee."' 

 "Portage," "Cliemung/' and ''Catskill.'' It is now many years, however, since 

 John M. Clarke, H. S. Williams, D. D. Luther, and others began to point out 

 that these familiar subdivisions are not strictly successive units, but local and 

 overlapping (or dovetailing) facies. 



Field studies under Dr. Clarke's direction have now shown that the prin- 

 ciples enunciated by him are applicable to these strata across the entire State 

 of New York and beyond, into Ohio. The fossiliferous "Chemung'" strata 

 prove to occupy progressively higher horizons in passing westward, as do the 

 red "Catskill" beds that overlie them throughout mo.st of this stretch. Like- 

 wise the comparatively barren "Portage"' strata rise steadily in the scale in a 

 westerly direction, while black shales of "Genesee" type pursue them upward. 



The careful tracing of key horizons across the State into Pennsylvania, to- 

 gether with the writer" s previous study of the literature for the Ohio equiv- 

 alents, leads to the correlations in the table herewith presented, in which ver- 

 tical dark bands indicate the portions of each section usually ascribed to the 

 "Chemung." The units beneath Lake Erie are checked on well borings.- The 

 defense of the upper portion for Ohio and Pennsylvania will be published 

 separately. 



Presented in abstract extemporaneously. 



Brief remarks were made by Mr. David White and Dr. I. C. White, 

 with reply by the author. 



CORRELATION OF THE POTTSVILLE AND LOWER ALLEGHEXY FORMATIONS' 



IX WESTERX PEXXSYLVANIA 



BY B. COUEMAX REXICK ^ 



(Ahstract) 



The reports of the Second Pennsylvania Geological Survey covering the 

 region along the Beaver River and its tributaries, in Lawrence, Mercer, and 

 Butler counties, show that the average interval between the Yanport limestone 

 of the Allegheny formation and the Homewood sandstone, the youngest mem- 

 ber of the Pottsville formation, is 50 feet. In the Foxburg quadrangle along 

 the Allegheny River the average interval is 120 feet from the Yanport lime- 

 stone to what is called the Homewood sandstone in that folio. 



The geologic section from the base of the Pottsville to the Yanport limestone 

 was studied along the Beaver River between Homewood and Mercer. The 

 same members were then traced along the outcrop up one of the tributaries to 



1 By permission of the Director of the New York State Museum. 

 -Title in this Bulletin, vol. .'5.*'.. p. 1.")L'. 

 1 Introduced by G. F. Kay. 



