Abstract

In the Piedmont of North Carolina and Virginia, northeast-flowing tributaries of southeast-flowing rivers such as the Catawba, Yadkin, and James are long and subparallel. Opposing tributaries on the northeast sides of the main streams are short and irregular in direction. This asymmetry suggests the former existence of a subsequent drainage flowing northeastward toward the Potomac. Apparently it was dismembered by multiple captures effected by short southeast-flowing streams of steeper gradient.

The drainage area of this former stream system is delimited by an enclosing zone of monadnocks on the southeast and southwest, and by the Blue Ridge Scarp on the northwest. It is developed largely upon the crystalline rocks, while the marginal monadnocks (Uwharie Hills, etc.) which mark the former divide on the southeast are developed largely on the Carolina slates. The zone of terminal monadnocks which marks the headwater divide extends across the strike, on the crystalline rocks approximately along the boundary between North Carolina and South Carolina.

Apparently, a succession of captures progressed across the area as the stronger southeast-flowing streams insinuated their headwaters northwestward, dismembering and diverting each of the northeast-flowing streams in turn, beginning at the southeast and ending at the foot of the Blue Ridge on the northwest. Elbows of capture are sharper in the northwestern streams where captures were later. There, also, gravel-coated strath terraces are preserved across the divides between present major streams such as the Yadkin and Catawba.

Present stream profiles show lower gradients in the area of the former northeast-flowing drainage than in the slate belt to the east.

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