448 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



which he correlates with Campbell's Rockcastle conglomerate lentil. But in the Kenova 

 quadrangle the writer does not recognize pre-Sharon sandstones farther north than the south- 

 east corner of the quadrangle. It is certain, however, that the middle Pottsville beds outcrop 

 at the western border of the coal field not far south of the Kenova quadrangle and that succes- 

 sively lower beds are encountered in passing south through Kentucky; for in the folio on the 

 Richnaond quadrangle Campbell reports a thickness of 250 to 300 feet of Pottsville [part of which 

 is erroneously included as Lee] below a 90-foot conglomerate (Cor bin conglomerate lentil), 

 which is correlated by Stevenson with the Sharon conglomerate member. This underlying 

 series of beds includes the Rockcastle conglomerate member, a transgression deposit, to which 

 reference will again be made. 



In the London quadrangle, next south of the Richmond, including portions of Rockcastle, 

 Jackson, Laurel, and Pulaski counties, Ky., Campbell finds beneath the Corbin 500 to 1,000 

 feet of shales and sandstones that he maps as Lee, with the Rockcastle conglomerate 

 member (0-150 feet), which probably forms the top of the true Lee, near the middle of the 

 thick sections." It is thus shown that in these quadrangles the western border of the coal field 

 has been eroded far enough eastward to cut into the region of the middle Pottsville encroach- 

 ment of the sea. The Rockcastle appears to represent the western extension of the Raleigh 

 sandstone of southern West Virginia. From the London region southward erosion seems to 

 have narrowed the field so that it lies wholly within the limits of the Raleigh-Rockcastle water 

 level — that is, within the lower Pottsville basin. In the southern part of the Standingstone 

 quadrangJe, Tennessee, which lies in the second tier of quadrangles to the south of the London 

 quadrangle, the Bonair conglomerate member, a sandstone over 200 feet below the Rockcastle 

 conglomerate member (top of the lower Pottsville in Tennessee), outcrops along the western 

 border. Farther south the Sewanee conglomerate of Safford and Killebrew is found to lie 

 above the Mssissippian and at some places nearly in contact with it.*"*" This conglomerate, 

 long supposed to be continuous with the Bonair conglomerate member, has been shown by 

 Butts to lie about 200 feet below the Bonair in the Crossville special quadrangle^ Tennessee. 

 The "Sewanee," which forms the top of Hayes's Lookout sandstone, constitutes an important 

 early invasion or trangression member in the old Pottsville basin. 



In the northern part of the Standingstone quadrangle the Rockcastle conglomerate member, 

 100 to 200 feet thick, is underlain by 100 to 300 feet of sandstone and shales belonging to the 

 Walden portion of the Lee. In the south half of the quadrangle the Bonair conglomerate 

 member^ 125 feet below the Rockcastle and 100 to 200 feet thick, locally rests on the eroded 

 Mississippian. The Rockcastle, which in this western region originates at the north as a remark- 

 able gravel wash filling a river valley but a few miles in width, is blended toward the south 

 with a sandstone of wide extent, which, according to Stevenson, is recognizable in nearly all 

 the sufficiently complete sections of Tennessee and Kentucky. 



From the Standingstone quadrangle the coal field is mapped in consecutive quadrangles 

 extending across the coal field from west to east near the southern boundary line of J 16 and also 

 reaching southward to the Alabama line. 



Before referring again to the thick eastern sections the western border will be briefly 

 reviewed. In the southern and eastern of these border quadrangles, whose study by Hayes ante- 

 dates Campbell's work, just cited, the important sandstone designated by Safford and Killebrew as 

 the Main Sewanee conglomerate was made the top member of the Lookout sandstone. Toward 

 the northeast the Bonair conglomerate member, which for a time was, on paleobotanic grounds, 

 considered possibly as young as the Raleigh, was made the top of the Lookout. However, as 

 already noted, the Bonair is, according to Butts, the second sandstone above the Sewanee 

 conglomerate of Safford and Kallebrew, and the Sewanee is more than 600 feet below the top 

 of the Lee formation in the Briceville quadrangle and the corresponding sandstone in the Kingston 

 quadrangle. Accordingly the Lookout sandstone, which ends in the Sewanee conglomerate, 

 represents but about one-half (the lower) of the Lee in this district. The beds above the Look- 



"The Corbin conglomerate member (0-150 feet) is overlain by 500 feet of the Breathitt formation, which is 

 said by Stevenson to extend a little above the limits of the upper Pottsville. 



