-PALEOZOIC DELTA DEPOSITS OF NORTH AMERICA 



angle of 27° to 30° to the southeast and were well exposed for measure- 

 ment and observation : 



Section on Clinch Mountain near Mendota, Virginia 



9. Clinch sandstone. p ee t 



8. Bays sandstone, more or less well exposed; red. often cro ss- bedded . . . . 295 



7. Interval 10 



6. Red sandstone and shale, typical Bays 214 



5. Red sandstone containing pelecypods, poorly preserved, but resem- 

 bling Amnigenia 40 



4. Red fossiliferous sandstone and shale, grading downward into the 



underlying bed by a gradual change in color 8 



The fossils obtained are: Hormotoma cf. bellicmcta, crushed 

 molds: Tetranota cf. obsoleta U. and S., internal molds. 

 3. Greenish, yellowish, and pinkish sandstones with Byssonichia cf. 

 radiata, mostly crushed but common; B. cf. prcecursa Ulrich, rare; 

 B. cf. obcsa Ulrich ; Modiomorpha ? and other pelecypods, 3% feet 

 above the base occurs a 4-iuch calcareous bed full of fossils, in- _ 

 eluding: Byssonychm cf. radiata; B. cf. richmondcnsis Ulrich; B. cf. 

 obesa Ulrich, and other pelecypods. Above this occur the following 

 species up to 30 feet from the base: Hchertella sinuata, Zygospira 

 modesta, Zygospira larger species, Pterinea demissa, Byssonychia cf. 

 walkerensis sp. now Red beds appear commonly far down in this 



division, establishing a perfect gradation to the bed overlying 35 



2. Calcareous beds alternating with shales, exposed at the turn in the 

 road. Fossils mainly brachiopods, including: Zygospira modesta, 



Zygospira sp., and others, including a number of pelecypods 4 



1. Shale, gradually becoming more sandy upwards; the beds of sand- 

 stone increase in thickness and frequency until the formation is 

 mostly a sandstone, some of which is of a reddish color, while most 

 of it is greenish or gray. Fossils abound. This is typical Sevier 

 shale. Thickness not measured. The total thickness of the Sevier 

 shale for this section is given as about 1,300 feet by Campbell 

 (Bristol folio). 



There is no question here of the intimate relation existing between the 

 Sevier and Bays. The former grades upward into the latter. At first 

 marine conditions still prevailed, while the deposition of "red" sands and 

 muds had already begun, and the last of the survivors of the Cincinnati 

 fauna of this region were embedded in the basal sandstones of the grow- 

 ing Bays delta. The total absence of fossils in the overlying beds and 

 the general character of the formation clearly indicate that here was 

 forming a subaerial deposit of highly oxidized sands and dust, similar to 

 that which formed the Juniata farther to the north. The fossils indicate 

 the age of the basal beds of the Bays to be late Upper Ordovicic, the 

 precise correlation being perhaps Upper Maysvillian — that is, post-Lor- 

 raine. A decided Richmond element is also observable. 



