Alluvial Soil Chronosequence in the Inner Coastal Plain, Central Virginia

摘要: Abstract A chronological sequence of soils formed on a series alluvial depositional surfaces ranging in age from late-middle Miocene to late Pleistocene was characterized clarify soil-geomorphic relations and provide basis for allostratigraphic subdivision the inner Coastal Plain. On Quaternary river terraces, Ultic Hapludalfs containing abundant weatherable mineral species clast types are estimated have 60,000-120,000 yr, whereas Typic Hapludults greatly depleted minerals showing strong weathering be 700,000-1,600,000 yr old. Paleudults with incipient plinthite, duripan, ferricrete development characterize interfluves that been little eroded since early Pliocene time (3.4-5.3 myr ago). Typic-Plinthic intense siliceous clasts moderate duripan found near beginning (10.8-13.0 Chemical chronosequence may classified into three progressive stages: (1) decomposition unstable sand- silt-sized mixed (stable + unstable) clay-mineral suite Fe Al/Si bulk chemical composition, 107 yr). Not all soil properties show unidirectional development, nor is steady state pedon observed even after approximately weathering. Soil episodic. The transition one phase next marked by change rate, sometimes reversal direction, or more properties.