452 



INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



almost directly on the Mississippian, or is even absent, is, over most of the area, continuous as 

 the upper member of the Lookout of Hayes. 



The section of the Tennessee coal field lying south of the Briceville tier of quadrangles is 

 included in the area mapped by Hayes at an early date in the work of the United States Geological 

 Survey and is practically covered by the Kingston, Pikeville, McMinnvUle, Chattanooga, and 

 Sewanee quadrangles. The measurements of the Pottsville formations are as follows, from east 

 to wast : 



TMckness, in feet, of Pottsville forrnations in southeastern Tennessee. 



, Some uncertainty exists as to the identification of Safford and Killebrew's Sewanee con- 

 glomerate in the vicinity of Chattanooga. Stevenson, ^'^^ reviewing the details published by 

 Safford "*"' and Colton,^^^ concludes that the top of that terrane is 215 feet Mgher at the White- 

 side (old Etna) mines, 235 feet higher at Daisy, and 234 feet higher at Rathbun than the position 

 assigned it by Hayes at these points, though at Graysville and other points to the northeast in 

 tlie Kingston quadrangle, there is agreement. The Upper Sewanee conglomerate of Safford, 

 in the Walden 240 feet above his Main Sewanee conglomerate (long regarded as equivalent to the 

 Bonair) at Tracy City, in the Sewanee quadrangle, is questionably correlated by Stevenson with 

 the Rockcastle, the top of the Lee, and regarded as probably equivalent to the Raleigh. The flora 

 of the Sewanee coal, about 50 feet above the Lookout at Tracy City, is somewhat like that of the 

 Sewell coal in West Virginia and was therefore made the basis of one of the writer's earliest 

 preliminary correlations in the southern Appalachian region, the underlying conglomerate 

 being then correlated by him with the Raleigh. However, from his later paleobotanic and strati- 

 graphic work it appears that if the sandstone at the top of the Lookout in the Kingston quad- 

 rangle is correctly identified with the "Main Sewanee conglomerate" as developed at Tracy 

 City, as appears to be true, a thickness of over 600 feet intervenes between the top of the 

 Lookout and the top of Keith's Lee in the Emory Gap region of the Briceville and Kingston 

 quadrangles, where the upper massjve Rockcastle conglomerate member, 100 feet thick, about 

 500 feet above the "Sewanee," is the same as Safford's and Killebrew's Emory sandstone,*"" 

 forming the top of the Lee in Emory Gap, near the south border of the Briceville quadrangle. 



The correlation as Corbin (equivalent to Nuttall) by Stevenson of a conglomerate member 

 only 100 feet above the supposed Rockcastle conglomerate member in the Pikeville quad- 

 rangle would seem to assume a too rapid tMnning of the middle Pottsville in passing from the 

 Briceville quadrangle across to Clifty Creek. 



In the Kingston and Chattanooga quadrangles the lower Pottsville seems neither to expand 

 so rapidly eastward nor to exhibit so great a thickness as is found in the eastern basins of 

 Virginia and Alabama. 



