Stratigraphic, Structural, and Correlation Considerations 25 



stones in Ohio. In general, the change is from red sands and conglomerates 

 to gray, fine-grained sandstones to dark siltstones, thin to dark-gray and black 

 shales, and finally to calcareous shales and limestones containing coral planta- 

 tions and bioherms. The pattern of these shifts is now so well known that 

 relationships not yet recognized in parts of the Appalachian geosyncline can 

 be anticipated.^^ 



According to Weller:^^ 



Facies variation is not peculiar to the Mississippian system [North Amer- 

 ica], but the problems which result from certain types of rapid lateral variation 

 in sediments, in the fields of both practical stratigraphy and stratigraphic 

 nomenclature, have received more attention in the Lower Mississippian and 

 Upper Devonian rocks of Ohio, Pennsylvania, Indiana, and Kentucky than in 

 other parts of the stratigraphic column and other regions of the continent. 



The work of Hyde,^^ Stockdale,!^ ^'^ Chadwick,!^ and Caster ^^ is partic- 

 ularly important. Both Hyde and Stockdale recognized certain major forma- 

 tions, each of which, they presumed, was deposited contemporaneously through- 

 out its extent. Each formation was then divided vertically into different 

 facies developments, which were given geographic names. Finally the facies 

 were divided horizontally into members which were also partially or completely 

 named. This system has proved to be flexible and convenient for description. 

 The facies names are, in effect, synonyms of the formation names but have 

 only local significance. Although this system introduces a large number of 

 names, many of them can be ignored by persons having no interest in the 

 detailed stratigraphy of these formations. 



Caster was more concerned with the interrelationships of rock-stratigraphic 

 and time-stratigraphic units. To units of more or less uniform lithologic char- 

 acters which transgress time lines he applied the term "magnafacies"; these are 

 rock-stratigraphic units and correspond to the original lithologic formations 

 of the northern Appalachian region. He used the terms "stage," "formation," or 

 "stratigraphic unit" for time-stratigraphic units. The magnafacies and stages 

 intersect each other, and for the intersected strata Caster introduced the term 

 "parvafacies." According to this system, which is an elaboration of conclusions 

 reached earlier by Chadwick and others, each magnafacies consists of a suc- 

 cession of parvafacies of similar lithologic character but unequal age, and each 

 stage consists of a succession of parvafacies of similar age but different litho- 

 logic character. Geographic names were introduced for all so that strata at any 

 place have three major names: a more or less local parvafacies name, extensive 

 magnafacies, and stage names. In addition, named members are also recog- 

 nized. This system is of considerable theoretical interest and may be very 

 useful in the detailed study and description of the strata deposited near the 

 margin of an expanding delta. It is not likely, however, to be widely applicable 

 to other types of facies problems. 



^^ Cooper, A. G., et al., Conelation of the Devonian Sedimentary Formations of North America: Ceol. 

 Soc. America Bull., vol. 53, no. 12, pp. 1729-1794, 19<12. 



^'' Weller, J. M., et al.. Correlation of the Mississippian Formations of North America: Geol. Soc. 

 America Bull., vol. 59, uo. 2, pp. 91-196, 1948. 



■•^ Hyde, J. E., Stratigraphy of the Waverly Formations of Central and Southern Ohio: Jour. Geology, 

 vol. 23, pp. 655-682, 757-779, 1915. 



^° Stockdale, P. B. , The Borden (Knobstone) Rocks of Southern Indiana: Indiana Dept. Cons. 

 Pub. 98, 1931. 



'' Stockdale, P. B,, Lower Mississippian Rocks of the East-Central Interior: Geol. Soc. America 

 Special Paper 22, 1939. 



^^ Chadwick, G. H., Faunal Differentiation in the Upper Devonian: Geol. Soc. America Bull., vol. 

 46, pp. 305-342, 1935. 



Caster, K. E., The Stratigraphy and Paleontology of Northwestern Pennsylvania, pt. 1: Am. 

 Paleontology Bull., vol. 21, no. 71, 1934. 



