Non Marine Stratigraphic Paleobiology

Fossil distribution is determined not only by biological factors such as evolution and ecology but also by stratigraphic processes such as sedimentation and the formation of hiatuses. Disentangling stratigraphic and biological signals is therefore necessary in order to accurately interpret the history of life. Efforts to formulate a robust stratigraphic framework for paleobiological data have transformed our understanding of fossil distribution in the marine sedimentary rock record. However, the effects of stratigraphic architecture on stratigraphic stacking patterns and fossil occurrences in the non-marine realm remain poorly understood. Here I examine stratigraphic paleobiology in non-marine systems that span global, regional, and outcrop scales. A global database study of modern non-marine mammalian spatial ranges and their fossil history indicates that taxa with geographic ranges that intersect modern sedimentary basins have a better fossil record than mammal taxa with ranges outside of sedimentary basins. At the regional scale, the distribution of Jurassic fossil occurrences in the western United States within a comprehensive macrostratigraphic framework suggests that both marine sedimentation and marine diversity track changes in the extent of shallow seas. By contrast, patterns of biodiversity in the non-marine fossil record are strongly overprinted by the temporal and geographic distribution of non-marine sediment storage. At the outcrop-to-regional scale, fossil distribution within the Late Jurassic Morrison Formation in the western United States indicates that distributive fluvial systems preferentially preserve vertebrate fossils in amalgamated channels in proximal zones and in poorly-drained floodplain deposits in distal regions. Combined, this multi-scale analysis indicates that the non-marine fossil record is strongly overprinted by hiatuses, which reflect primarily a failure of sediments to accumulate in non-marine environments. Hiatuses in the marine record, by contrast, largely, reflect shifts in the position of the shoreline relative to the continents and therefore significant changes in habitable marine shelf area. This study acts as an initial non-marine stratigraphic paleobiology model and I anticipate future studies will expand on this work and identify variability between non-marine sedimentary basin types. Within distributive fluvial systems there is a definitive predictive distribution of vertebrate fossils and this body of work illuminates the previously unknown nature of this relationship.