luams.] SAFFORD'S GEOLOGY OF TENNESSEE. 1 G5 



The " Lower Carboniferous," or " Formation VIII," is primarily defined 

 as "the great group of strata intervening between the black shale and 

 the Coal Measures," with a maximum thickness of 1,200 feet. 1 This is 

 subdivided into (8a) the "Siliceous group" and (8b) the "Mountain 

 limestone." This, as the author remarks, " is the most useful division 

 that can be made, so far at least as the consideration of the topo- 

 graphical and agricultural features of the State are concerned." 



The Coal Measures are classified by the author in three divisions: 

 (a) the " Lower Coal Measures," varying from a few feet to 300 ; (b) the 

 "Conglomerate;" (c)the "Upper Coal Measures," from 200 to 2,000 i'vot 

 thick. 



It is evident that this classification is primarily a natural classification 

 of the rock formations according to their prominent petrographic fea- 

 tures. To take them in detail: Saiford's "Siliceous group" ($a) em- 

 braces about the same rocks as were previously defined by Troost under 

 the name Siliceous stratum." The name is suggested by the fact of the 

 predominance of siliceous material in the rocks in the form of "chert, 

 fine sandstone, silicocalcareous rock or siliceous shale." The " Siliceous 

 group " as it appears in Middle Tennessee, is subdivided, into " a lower," 

 the " Protean member ," and an upper or " Lithostrontion bed." From 

 a study of the characters distinguishing the two it is evident that the 

 presence of the Lithostrontion in the upper member is chiefly relied 

 upon, the lithologic characters not presenting any constant distinction, 

 and the author states that no division is practicable in East Tennessee. 2 

 Two characters are mentioned as pertaining to the "Lithostrontion 

 bed " — the fossiliferous character of the cherts and the liberation of oxide 

 of iron in the decomposing of the cherts. The author also thinks the 

 two members become one below Huntsville, on the anticlinals of Ala- 

 bama, 3 being characterized throughout by Lithostrontion Canadense. 

 He correlates the " Protean member " in general with the " Lower Car- 

 boniferous limestone below the St. Louis limestone " of the Iowa ami 

 Illinois and Missouri classification, and the "Lithostrontion bed "he 

 correlates with the " St. Louis limestone." The " Mountain limestone" 

 is "a heavy group of limestones and shales, the latter constituting in 

 the aggregate about one-fourth of the mass," including a sandstone near 

 the base which in the northern part of the State is 40 or 50 feet thick. 

 This formation reaches its maximum thickness in the southern part of 

 the State (720 feet), decreasing going northward until near the Ken- 

 tucky line it is reduced to 400 feet. 4 The limestones are often argilla- 

 ceous, sometimes oolitic, but rarely cherty. The fauna is considered 

 equivalent to that of the Kaskaskia limestone (Hall) of the Northwestern 

 States (=the Chester limestone of Worthen). Thus the name " Moun- 

 tain limestone " is used in a restricted sense. 



The author's classification is primarily a lithologic classification of the 



1 Geology of Tennessee, by James M. Safford, State geologist, Nashville, 1869, p. 338. 

 ■ Ibid., p. 347. » Ibid., p. 340. 4 Ibid., p. 352. 



