THE UPPER DEVONIAN DEPOSITS 

 OF MARYLAND 



BY 

 CHARLES S. PROSSER AND CHARLES K. SWARTZ 



IXTRODUCTORY' 



As stated under the description of the Middle Devonian, the Devonian 

 period was often separated in a general way into the lower, middle, and 

 upper divisions. For the latter Prof. H. S. Williams proposed the 

 name Neodevonian " which in general included, in New York, the Tully 

 limestone, Genesee shale. Portage, Chemung, and Catskill stages, the 

 latter being a local facies of the Chemung, or Portage, Chemung and 

 perhaps early Carboniferous, occurring in southern and southeastern New 

 York. 



In 1840, Prof. James Hall named and described the following "groups" 

 as succeeding the "upper Black shale" (Genesee shale) in the Genesee 

 Valley, in the order named : Cashaqna shale, Gardeau or Lower Fucoidal 

 group, and Portage or Upper Fucoidal group.' He also stated that " the 

 two groups just described [Gardeau and Portage], occupy a thickness of 

 more than 1000 feet, and are interposed between the Cashaqua shale and 

 the Chemnng group." * In succeeding accounts, the base of the Chemung 

 formation has generally been considered as resting on top of the sand- 

 stones which Professor Hall described as composing the Portage group; 

 but the following statement is important, especially when the classi- 

 fication of the rocks of this part of the Genesee Valley by Dr. J. M. 

 Clarke, is considered. Professor Hall said, " Indeed, if we consider the 

 Chemung group as commencing with the occurrence of its characteristic 

 marine fossils, then several hundred feet more of rocks may be noticed 



* Contributed by Charles S. Prosser. 

 => Jour. Geol., Vol. II, pp. 155, 157. 



•Mth Ann. Rep., Fourth Geol. Dist. [N. Y.J (Assembly Doc. No. 50, 1840), pp. 

 390, 391. 



'Ibid.,X). 392. 



