PALEOSOLS OF THE CATSKILL CLASTIC WEDGE: IDENTIFICATION, INTERPRETATION, AND APPLICATION

A paleosol is an exposure surface that has been modified from its original parent material by ancient physical, chemical, and biological processes. These processes created structural, chemical, and mineralogical attributes related to specific soil forming processes, and in turn, paleoclimatic and paleoenvironmental conditions at the time of soil formation. Paleosols are abundant within the Catskill Clastic Wedge and have distinct macromorphological characteristics. At the outcrop scale, paleosols tend to be less resistant to weathering and are most commonly found within the vertical accretion deposits of individual fining upward fluvial sequences. Fossil roots define the top of individual soils and tend to be preserved as either greenish haloes or clay infilled voids that branch and taper downward. The size and orientation of root structures provide insights into vegetation type and degree of soil drainage. Depending on the intensity of ancient soil formation, the original depositional fabric can be completely replaced by pedogenic fabrics, which manifests as a downward transition from blocky mudstones (peds) of individual paleosols to laminated and crossbedded strata. Secondary mineral accumulations within paleosols are most commonly clays, carbonates, or iron oxides, and are clues to precipitation and soil drainage conditions. Other features commonly preserved in paleosols of the Catskill Clastic Wedge include vertebrate and invertebrate burrows, and large, curvilinear slickensided planes due to the shrink and swell of soils that were at one time enriched in smectite. At the basin scale, paleosols can define allostratigraphic units and be used to interpret sequence stratigraphy. Vertical successions of paleosols can be used to interpret changes in paleoclimatic and paleoenvironmental conditions, whereas lateral changes along defined paleo-landscapes can be used to understand paleoecological variablility. Within the Catskill Clastic Wedge, paleosols are especially critical to the understanding of the colonization of terrestrial ecosystems during the Devonian.