The Blue Ridge-Catoctin anticlinorium extends for more than 300 miles across the State of Virginia, from the Potomac River to the North Carolina and Tennessee lines (Fig. 1). In northern and central Virginia it includes the Blue Ridge proper, which forms its northwestern border, and part of the Piedmont region of foothills, which lies south‐east of the Blue Ridge crest. In Southwest Virginia, as the area south‐west of Roanoke is often termed, the crest of the Blue Ridge does not follow the northwestern front of the anticlinorium but runs diagonal to it, in a direction a little west of south, to the North Carolina border. Between the Blue Ridge crest and the northwestern border of the anticlinorium, which is here formed by the Iron and the Unaka mountains, is an upland plateau 20 miles wide, above which the highest mountains in Virginia rise as monadnocks.
PRE-CAMBRIAN ROCKS OF THE . . .