A SELF-DEFENSE GUIDE TO DEVONIAN PALEOSOLS OF THE APPALACHIAN BASIN

Paleosols are invaluable archives of paleoenvironmental information but, depending on their geologic age and subsequent diagenetic overprints, can be difficult to recognize and interpret. Paleosols within Devonian terrestrial strata of the Appalachian Basin have been subjected to low-grade metamorphism, including weakly foliated strata, overprinting by hematite mineralization, and burial compaction. Despite overprinting, these paleosols preserve a distinct set of macromorphological features that aid in identification of subaerial exposure, general paleoenvironmental conditions, and taphonomic interpretations of important fossil sites. The majority of these paleosols formed on floodplain facies and vary with respect to their distance away from the active channel. Episodes of subaerial exposure are also preserved in transitional/coastal settings and are preserved by marine flooding surfaces and invertebrate fossils. Within fluvial settings, evidence of soil formation is recognized by the presence of roots, soil structures (peds and glaebules), and horizonation. Roots are most commonly preserved as clay infills, but also as drab green haloes. Individual soil profiles commonly preserve detrital plant matter within coarser sediments at their base, either as carbonized films, impressions, or drab-colored reduction haloes. Peds will occur as blocky, platy, and wedge shapes depending on their position within the soil profile and their parent material. Glaebules of calcium carbonate and iron oxide are both common within these soils and can be related to estimates of mean annual precipitation and hydromorphic soil conditions. Horizonation will vary as a function of pedogenic environment but can range from simplistic A-C profiles in proximal floodplain positions to complex associations of A-B-C profiles with numerous subordinant indicators that formed on more stable parts of the landscape. While the base of most profiles can be recognized by a transition to more platy peds and relict bedding at the base of a fining upward overbank deposit, the top of any individual profile is subject to truncation by overlying depositional events. When compared to modern soil taxonomy, these paleosols are most similar to modern entisols, inceptisols, alfisols, and vertisols.