PRESERVATION OF A PALEO-VERTISOL AND AN ESTIMATE OF LATE MISSISSIPPIAN PALEOPRECIPITATION

A Late Mississippian paleosol satisfying all of the morphological crit eria required for classification of Holocene Vertisols provides quanti tative paleoclimate information, in addition to the now commonplace in terpretation of precipitation seasonality based on the presence of ver tic features, Paleoprecipitation was estimated using the empirical rel ationship between depth to pedogenic carbonate horizon in Quaternary s oils. Burial compaction, erosional truncation, and high paleoatmospher ic CO2 concentration, all factors that complicate paleo-precipitation estimates, are unusually well constrained for this paleosol, Allowing for 10% compaction, the paleosol had a pre-burial depth of 100 cm for the pedogenic carbonate horizon, yielding a mean annual paleo precipit ation estimate of 648 +/- 141 mm. This is comparable to the mean annua l precipitation for Brownsville, Texas, where similar soils are found today, A dolomicrite crust, developed in gilgai micro-lows, is well pr eserved in the paleo-Vertisol. Higher Late Mississippian paleotemperat ures and rates of evapotranspiration associated with a lower-latitude paleogeography for central Tennessee during the Late Mississippian may explain in part why Holocene coastal Vertisols in the Brownsville reg ion lack surficial crusts similar to that of the paleo-Vertisol. We qu alitatively define the Late Mississippian climate of central Tennessee as semiarid.