THE POTENTIAL INFLUENCE OF DISTRIBUTIVE FLUVIAL SYSTEMS ON PALEOCLIMATIC INTERPRETATIONS OF THE DEVONIAN CATSKILL WEDGE

The Late Devonian of North America is marked by a change from hothouse to icehouse conditions and the continued evolution and expansion of nonmarine biota. The terrestrial strata of the Catskill Wedge preserve a multitude of paleosols and associated facies that can be used to interpret these paleoclimatic and paleoenvironmental changes. To date, paleosols similar to modern entisols, inceptisols, histosols, alfisols, and vertisols have been documented by various researchers in strata of the Catskill Wedge from New York to West Virginia, as have associated shifts of facies architecture in transitional and nonmarine depositional environments. These paleosols record variable climatic conditions ranging from aquic to sub-humid, differences in vegetative cover, and punctuated changes in parent material, but the majority of studies to date are limited in their areal and temporal extent. In order to accurately interpret the paleopedological record of climate change in the Catskill Wedge, the influence of changing sedimentation styles and subsequent shifts in depositional environments associated with the evolution of distributive fluvial systems (DFS) must be considered. Modern DFS form in tectonically active areas and display proximal to distal changes in fluvial style, facies, and pedology that are mediated by lateral changes in hydrologic budgets. Down-gradient flow of groundwater manifests as spring lines, with deposits below the spring line dominated by relatively wetter soils and depositional environments. As DFS prograde, areas previously dominated by wetter environments and soils are replaced by deposits and soils of drier environments. In the rock record, the progradation of such a DFS would generate up-section changes in nonmarine facies and paleopedology, with lower parts of the section dominated by paleosols influenced by greater amounts of water and lower sedimentation rates yielding to progressively drier soil conditions. At any one locality this upward trend could be interpreted as paleoclimatic change. Comparisons of temporally constrained sections across a broad region within a particular depositional system are required to test hypotheses of climate change versus DFS within the Catskill Wedge.