Paleoclimate, burial compaction, and perched water tables: Carboniferous vertic paleosols, Ohio and Tennessee

A Late Mississippian paleosol, in central Tennessee, satisfying all of the morphological criteria set forth in Soil Taxonomy for Holocene Vertisols provides quantitative paleoclimate information, in addition to the now commonplace interpretation of precipitation seasonality based on the presence of vertic features. Paleo-precipitation was estimated using the empirical relationship between depth to pedogenic carbonate horizon in Quaternary soils. Burial compaction, erosional truncation, and high paleoatmospheric CO{dollar}sb2{dollar} concentration, all factors which 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-precipitation estimate of 648 mm {dollar}pm{dollar} 141. The Late Mississippian climate of central Tennessee is qualitatively defined as semi-arid.; Burial compaction is one of several major obstacles to estimating paleo-precipitation from depth to pedogenic carbonate in favorable preserved paleosols. Paleosols must be decompacted and pre-burial depth to pedogenic carbonate obtained. Vertic paleosols may be particularly good candidates for paleoprecipitation estimates, because of an increased likelihood of preserving clastic dikes, one of the best features for estimating burial compaction. Compaction estimates from clastic dikes and literature--based depth of burial estimates suggest that vertic paleosols undergo significantly less burial compaction than may be commonly assumed. Late Carboniferous vertic paleosols, buried to 2.5 to 3.0 km, compacted to 93% of their original thickness. In contrast, clastic dikes in a non-pedogenic shale directly underlying one of the Late Carboniferous paleosols records compaction to 70% of original thickness. Similarly obtained burial compaction and burial depth estimates for Early Carboniferous, Ordovician, and Proterozoic vertic paleosols are used to test a burial compaction curve and equation specific for vertic paleosols.; The Harlem coal (Upper Pennsylvanian) is genetically related to the underlying, vertic, sub-Ames paleosol complex. Color patterns in the paleosol complex appear to have survived burial diagenesis and provide sensitive data on soil drainage and redox conditions. Catenary relationships preserved by the paleosol complex, indicate that soil drainage setting, largely a reflection of subtle topographic differences on the paleolandscape, controlled initiation of the Harlem coal swamp. Paleotopography reflected the presence of an abandoned fluvial channel tract, or perhaps a marginal-marine bar complex stranded on a broad, newly exposed surface created by withdrawal of the pre-Ames sea from the Appalachian basin. The Harlem peat accumulated in isolated topographic lows following local establishment of saturated zones in the top of the paleosol complex. Development of perched water tables was facilitated by formation of clay-enriched subsoil intervals. The clay-enriched intervals record the onset of long-wet/short-dry seasonality in precipitation and a corresponding decrease in the intensity of churning in the soil body. As the new, wetter climate became established, perched zones of saturation grew upwards to intersect the soil surface and initiated coal swamps. During the subsequent "Ames" transgression, the paleolandscape influenced deposition such that marine limestones were deposited on local topographic highs. (Abstract shortened by UMI.)...