CHAPTER III. 



THE DIFFERENTIATION OF THE CARBONIFEROUS SYSTEM. 



In matters of correlation the Carboniferous system is particularly 

 unfortunate, in that there is nothing in the name nor in the usage 

 to determine precisely the limits of the system above and below. 

 The grand divisions Lower Carboniferous, Millstone Grit, and Coal 

 Measures have been handed down from the early classifications before 

 strict methods were in use. The question whether the Permian shall con- 

 stitute the third age of the Carboniferous period or not must be settled 

 either arbitrarily or by reference to precedent. In order to establish 

 a precedent it must be determined what is the standard Carboniferous 

 system. If the original Carboniferous system excluded the Permian as 

 a distinct system it is important that a name be found to designate that 

 usage and to distinguish it from the present common usage, which 

 includes the Lower Carboniferous, the Coal Measures, and the Permian 

 in the one Carboniferous system. A review of the literature shows that 

 a classification of the rocks to form a system to which first the name Car- 

 boniferous was applied was made by W. D. Conybeare in 1821. 1 It was 

 called the " Medial or Carboniferous order," and was defined to include: 



(1) The Coal Measures, the "independent coal formation" of Werner; 



(2) the Millstone grit and shales; (3) the Carboniferous or Mountain 

 limestone; and (4) the Old lied sandstone. 2 This grouping of the rocks 

 was suggested by their " association together in the districts which 

 afford the principal deposit of fossil coal." 3 



In this classification the "New Red sandstone," including what is 

 now called "Permian" and "Trias," was distinctly excluded, and we 

 discover that the New Red sandstone beds in England generally rest un- 

 comformably upon the Carboniferous. The line of unconformity gave 

 occasion for the distinction between "primary" and "secondary," and 

 later "transition" and "secondary," and for the classification of the 

 rocks and faunas below the line as " Paleozoic " and those above as 

 " Mesozoic." In the Werneriau nomenclature the term " Floetz class" 

 was applied to the flat-lying rocks, beginning with those New Red sand- 

 stones in the English series and running upward. 



Conybeare's Carboniferous order also included rocks correlated as Old 

 Red sandstone, and he recognized that the " Old Red approaches in its 

 lowest beds very nearly to the characters of the gray wacke upon which 



1 Conybeare and Phillip3 : Outlines of the Geology of England and Wales, London, 1822, p. 333. 



*Op.cit.,p.335. 



■Op.cit., p.333. 



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