Arthropic Epipedons in the Tombigbee Valley of Mississippi

Anthropic epipedons resulting from prolonged habitation were characterized in midden mounds of natural fluvial origin in the Tombigbee River Floodplain of Mississippi. Radiocarbon ages ranged from 300 yr before present (YBP) in surface layers to 7000 (YBP) in deeper zones of the dark‐colored epipedons. The loamy epipedons ranged from 1‐ to 1.5‐m thick and contained 0.6 to 3% organic C and 1 to 5% charcoal fragments. Munsell hues were 5YR and 7.5YR with values and chromas of 3 or less due to particle coatings of humic materials that promoted granular structure and H 2 O repellency. Base saturation ranged from 24 to 73% with pH levels one unit higher than adjacent off‐site soils. Calcium/Mg values exceeded 10:1 due to Ca enrichment. Total N decreased with depth and C/N ratios exceeded 30:1 due to C accumulation and N depletion. Phosphorus extracted with 1% citric acid exceeded 250 mg kg −1 in the anthropic epipedons and readily distinguished the habitation sites from adjacent soils. Nonoccluded‐P and occluded‐P were dominant P forms with lesser organic‐P and Ca‐P.