Genesis of a Late-Holocene Soil Chronosequence at the Lubbock Lake Archaeological Site, Texas

Field and laboratory data combined with geochronological information were used to investigate the nature and rates of pedogenesis of three late Holocene soils at the Lubbock Lake archaeological site (Southern High Plains of Texas). A variety of pedologic characteristics become better expressed with time, and aerosolic additions and burial of the soils significantly affect the development of these characteristics. Organic carbon accumulates rapidly in initial stages of development of the A horizon: mollic epipedons form in about 100 years and steady-state conditions of organic carbon content are attained in about 1000 years. Upon burial, organic carbon content of the A horizon quickly decreases. Calcic horizons form in 200 years and minimally developed argillic horizons form in 450 years, the result of infiltration of clay and carbonate derived from aerosolic dust. Horizonation is better expressed with time, and B-horizon hues redden from 10YR to 5YR in 3500 years. Locally, landscape position is an important factor: along the valley axis A horizons become cumulic and mixed-layer illite-smectite clays form at the expense of illite because more moisture is availabe and there are strong seasonal contrasts in wetting and drying.