SCOYENIA-DOMINATED TRIASSIC RIPARIAN PALEOSOLS, BUCKS COUNTY, PENNSYLVANIA

In a largely sandstone-dominated succession of the Upper Triassic Stockton Formation, a 3–4-m-thick riparian section is exposed along the Neshaminy Creek, Bucks County, Pennsylvania. Immature red paleosols interbedded with siltstones are incised by fining-upward channel sequence. The paleosols contain abundant Scoyenia isp. burrows, which are also known from other locations in the Newark Basin. Circular to vertically compressed burrows are exposed in epirelief and have bimodal diameter classes of 6 and 12 mm. These traces are attributed to Scoyenia gracilis based on the surficial morphology (bundles of longitudinal striations) and clay-lined meniscate backfill. They are often clustered and are dominated by subhorizontal tunnels that occasionally are traceable into shafts. Intersecting burrows clearly show crosscutting relationships. Tunnel curvature varies from 5–30° (U-shaped bends are rare) and orientations are confined to a 115° azimuth sector. On fully weathered burrow fragments, some menisci separate along curved surfaces covered by thin organic film, which is common on adjacent bedding planes and pedogenic slickensides. These findings indicate a low-biodiversity ecosystem, likely dominated by insects or morphologically similar taxa that were part of the temporary soil biota within a well-drained setting.