RELATIONSHIP BETWEEN GEOMORPHIC SURFACES AND LOW ACTIVITY CLAY ON THENORTH-CAROLINA COASTAL-PLAIN

The adoption of the kandic horizon for use in recognizing the predomin ance of low activity clay has resulted in reclassification of several major soil series on the Atlantic Coastal Plain of the Southeastern U. S. To provide a more definitive basis for predicting the geographic di stribution of the kandic feature, 41 sites correlated to successive ge omorphic surfaces in North Carolina were sampled and characterized. Th e locations represented five defined Coastal Plain surfaces encompassi ng the Upper, Middle, and Lower Coastal Plain. Well to poorly drained upland soils were included. Results indicate that both the cation exch ange capacity 7 and the effective cation exchange capacity requirement for the kandic horizon were consistently satisfied only in the well d rained soils on the Upper Coastal Plain surface. Soil with greater wet ness and soils on lower, younger geomorphic surfaces (Middle and Lower Coastal Plain) did not consistently satisfy requirements for the kand ic horizon.