ijSS E. O. ULRICH REVISION OF THE PALEOZOIC SYSTEMS 



preferable to place the latter in the Ozarkian.^^ This conclusion is of 

 considerable consequence, since it means that the Jonesboro area was 

 emerged throughout the Ozarkian period. It means, further, that the 

 Canadian seas failed to cover most of the valley of east Tennessee to the 

 west and southwest of Jonesboro. 



Eegarding the relations of the upper Knox to the Jefferson City dolo- 

 mite, the evidence is not altogether conclusive. It will be noticed that 

 the upper Knox is placed beneath the Chepultepec formation and that 

 this is correlated — the fossil evidence is very satisfactory on this point — 

 with the Gasconade of the Missouri section. This arrangement is based 

 on two facts: First, that the physical break between the Copper Eidge 

 and the upper Knox is not as sharply defined as it should be if a long 

 time had intervened between them ; second, that in Murphrees and Cahaba 

 valleys, in Alabama, the only localities in the southern Appalachian re- 

 gion in which the Chepultepec is yet known, the topography indicates a 

 relatively non-resistant zone between the Chepultepec and the Copper 

 Eidge that in all probability corresponds to the upper Knox in Tennessee 

 and Virginia. 



The Chepultepec chert formation (new). — The western part of Chert 

 Eidge, in Murphrees Valley, Alabama, just west of the old town of Che- 

 pultepec (see northeastern angle of Birmingham quadrangle), is made 

 by a formation that seems to be but seldom included in the Eopaleozoic 

 sequence of the Appalachian Valley. So far as known, it represents the 

 last of Ozarkian deposits in this province. Chepultepec is located in a 

 narrow depression or irregular valley that, as noted in the preceding 

 paragraph, probably represents the "upper Knox" of this work. This 

 narrow valley extends an unknown distance northeastward from Chepul- 

 tepec. Southward from the town where its width is sufficient to include 

 about 300 feet of beds, it is traceable about 3 miles. Beyond this point 

 the beds which are responsible for its existence apparently wedge out. 

 Further on in the latter direction Gravelly Eidge, which may be described 

 as a continuation of Chert Eidge, seems, moreover, to consist only of the 

 Copper Eidge division of the Knox. 



Through the observed extent of the valley-making band of supposed 

 upper Knox the ridge to the east is composed of the underlying Copper 

 Eidge Knox. To the west is another highly cherty formation that is the 

 subject of these paragraphs and for which the new term Chepultepec for- 

 mation is proposed. Fossils are relatively common in the new formation 



^ In accord with this older view, K. S. Bassler, in his report on "The Cement Re- 

 sources of Virginia" (Virginia Geological Survey, Bull. No. II-A, 1909, pp. 151-157), 

 refers these upper Knox beds to the Beekmantown. 



