88 The ^Iiddle Devonian Deposits of Maryland 



COEEELATION OF THE MIDDLE DEVONIAN 



Onondaga Member * 



The earlier students of the Middle Devonian believed that the Onon- 

 daga member and its equivalents were absent in Maryland and adjoining 

 parts of Pennsylvania and West Virginia and referred the lower beds 

 of the Eomney to the Marcellus. Thus, Prosser, who made a critical 

 study of the Eomney of Marjdand, stated that the Onondaga is absent 

 in Maryland and that the Marcellus rests upon the eroded surface of the 

 Oriskany.' This Avas also the view of OTTarra/ who described the geology 

 of Allegany County, and of Rowe* and Schuchert." Other students of 

 the problem in adjoining areas arrived at the same conclusions." Kindle, 

 who discusses the question elsewhere in this volume, has recently shown ' 

 that the lower beds of the Eomney differ faunally from the overlying 

 strata and has called them the Onondaga member of the Eomney forma- 

 tion, which term has been adopted by the TJ. S. Geological Survey.' 



Before discussing the age of this member it will be helpful to review 

 the conditions that exist in Few York, which is the typical area. The 

 Marcellus of New York was originally made to comprise the dark car- 

 bonaceous shales lying between the Onondaga and Hamilton. It included 

 two limestones, the lower of which is known as the Goniatite and the 

 iipper as the Stafford limestone. Eecently the ]\Iarcelhis formation has 



^ Contributed by Charles K. Swartz. 



' Prosser, C. S., Jour. Geo!., vol. ix, 1900, p. 418, and discussion in ms. of 

 Romney formation for present vohime. 



' O'Harra, C. C, Md. Geol. Survey, Geology of Allegany County, 1900, pp. 

 103, 160. 



*Rowe, R. B., Devonian of Md. Ms. in library of Johns Hopkins Univ. 



= Schuchert, Chas., Proc. U. S. Nat. Mus., vol. xxvi, 1903, p. 414. 



^Darton, N. H., Amer. Geol., vol. x, 1892, p. 16; Stevenson, J. J., 2d Geol. 

 Survey Penn., vol. T2, 1882, pp. 81-83; Ulrich, E. O., and Schuchert, Chas., 

 Bull. N. Y. State Mus., No. 52, 1902, pp. 653-654. 



'Bull. U. S. Geol. Survey, No. 508, 1912, pp. 35-38. 



' U. S. Geol. Survey, Pawpaw-Hancock Folio, 1912, field edition, p. 75. 



