208 DOUGLAS WILSON JOHNSON 



abundant all along the foot of such slopes, and comparatively little 

 sandstone is seen. Two sections in this vicinity showed the prac- 

 tically continuous limestone ledges up to within 190 feet of the top 

 of the plateau or mountain. For reasons stated in the preceding 

 paragraph, it is highly probable that the limestone continues still 

 higher, no sandstone ledges being seen until nearer the top, and 

 sandstone debris mantling the slopes for some distance. But even 

 if we ascribe the entire thickness of 190 feet to the sandstone, the 

 contrast with conditions at the Tennessee gorge is very marked. 

 North of Scottsboro it appears that the sandstone cap was somewhat 

 thicker, suggesting a progressive thinning toward the western end of 

 the valley, although the possibility that the limestone goes higher 

 up the slope than is apparent makes a definite statement impossible. 

 Such a westward thinning would be in accord with the indications 

 on the geologic folios of adjacent areas, however. 



Turning now to the conditions at the winding gorge through 

 Walden plateau, we find plenty of evidence that the gorge is cut 

 largely in sandstone. Instead of conspicuous limestone ledges well 

 up the mountain slopes, we find the slopes mantled with coarse 

 sandstone debris, generally down to the level of the river. Only 

 near the eastern and western mouths of the gorge was the limestone 

 shown at all prominently, and this is where the gentle rise of the sides 

 of the synclinal trough would naturally bring the limestone to a higher 

 level; while in the Scottsboro valley the limestone is everywhere 

 prominently shown well up toward the plateau summit. Limestone 

 is shown at various other points throughout the gorge, but always, 

 so far as seen, in limited exposures well down at the foot of the slope. 

 Limestone float was little in evidence, usually only close to the 

 small ledges referred to, sandstone debris being everywhere abun- 

 dant. Although the limestone was 'undoubtedly greatly masked by 

 the sandstone debris, exposures of the limestone on the spurs of the 

 mountain, and the careful examination of float and ledges along 

 the courses of side streams emptying into the gorge, indicated that 

 in the main portion of the gorge the limestone-sandstone contact 

 could not be far above the level of the river. In the half-dozen best 

 sections seen, the limestone exposures or limestone debris always 

 stopped short at elevations of between 100 and 200 feet above the 



