Soil chronosequence of brasstown creek, Blue Ridge mountains, USA

A chronosequence of soils on alluvial terraces in the Appalachian highlands of the southeastern United States is identified by simple methods of quantitative soil morphology and chemical analysis. The chronosequence is from Brasstown Creek, a 5th order stream draining 65 km2 of the Blue Ridge Mountains of north Georgia. The portion of the valley studied is about 1 km wide and contains five Quaternary terrace remnants. Radiocarbon dates show that the floodplain (T0) is late Holocene and includes historical (post ca. 1830 A.D.) sediment, and the four older terraces (T1–T5) are pre-Holocene. The floodplain soils are either Entisols in historical sediment or buried Inceptisols with weak Bw horizons in late Holocene to protohistoric sediment. The lowest terrace (T1) is terminal Pleistocene in age, and its soils have Bt horizons that are about 0.9 m thick, 10YR 4/5 to 10YR 5/4 in colour, and contain 25 to 35% clay. Soils on terraces older than T1 become progressively redder and contain more clay with increasing age, culminating with 2.5YR hues and 40 to 52% clay in the Bt horizon of T5. Percent clay in Bt horizons, rubification indices, iron oxide contents, and element ratios progressively change with age of the terraces, but other morphological properties, pH, and individual element concentrations are of less use as chronosequence variables.