458 A. W. GRABAV PALEOZOIC DELTA DEPOSITS OF NORTH AMERICA 



beds which had been folded and elevated at the end of Ordovicic time, it 

 is probably true that the Clinch sandstone had a similar source, and that 

 hence in the region from which these beds have now been removed by 

 erosion there existed one or more fans of white quartzite beneath the red 

 beds. The fact that the Upper Sevier shale in many places is a sandy 

 bed, and the further fact that on East River Mountain beds of white con- 

 glomeratic quartzite underlie the Bays sandstone, lends a strong element 

 of probability to this supposition. Of course, we have no means of know- 

 ing whether any large part of this pre-Bays or Upper Sevier sandstone 

 deposit was of subaerial origin or whether it was merely a coarse shore 

 deposit which furnished the sands for the Clinch formation. In any 

 case the purity of that sandstone suggests that it is a secondary deposit 

 derived from an older sandstone and not directly from the crystallines. 



Summary of the Bays problem. — Summarizing the preceding discus- 

 sion, we note that the sections indicate a continuous presence of red sand- 

 stones and shales in the Appalachian ridges for a distance of over 300 

 miles northeastward and southwestward. Its greatest thickness. 1,300 

 feet, is in the southernmost portion of the belt, south of which the for- 

 mation, as well as the overlying and underlying one, is wholly wanting. 

 The belt of red rocks extends now over an area of about 90 miles of 

 folded rocks, which would give perhaps 200 miles of area when the folds 

 are straightened out.* The formation probably extended originally to the 

 crystallines on the southeast, by the erosion of which the material was 

 derived. This adds at least 100 miles to the original northwest and 

 southeast extent of this deposit and probably, it was nearer 200 miles. 

 The red formation, known throughout as the Bays sandstone (except in 

 central western Virginia, where it is included in the Massanutten sand- 

 stone), is not a stratigraphic unit. Its lower part is probably everywhere 

 of Upper Ordovicic age. passing into the underlying sandstones and 

 shales with marine fossils. The lower part of the red beds in many 

 places also contains fossils, these generally being of Upper Lorraine or 

 post-Lorraine types. The red beds probably begin earlier in the south- 

 eastern region and later in the northwestern, having the arrangement of 

 a northwesternward-replacing overlap. The highest part of the red 

 series is of early Siluric (Medina) age in many of the sections, especially 

 those in the westernmost belts. This is shown not only by the coarser 

 character of the beds, but also by the few fossils found, especially Sco- 

 lithus verticalis and Arthrophycus harlani. The interpretation which 



* R. D. Chamberlin's studies of the Appalachian folds leads him to conclude that the 

 compression of the folds, west of Harrisburg -was from 81 to 66 miles. 



