Linking Ichnology and Paleopedology to Infer Landscape Evolution, Paleoenvironments, Paleohydrology, and Paleoclimate: Future Directions of Integrated Soil and Trace-Fossil Studies

The study of trace fossils (ichna) in paleosols has greatly been enriched by research on the activity of organisms and their role in soil formation in modern landscapes. Organisms characterized as epigeon, geophiles, and geobionts impact a variety of media at different spatial and temporal scales to produce soils. Laboratory and field studies with soil biota reveal burrowing mechanisms and burrow morphologies analogous to but different from marine ichna. The record of organism activity preserved as ichna in paleosols is surprisingly abundant and diverse in rocks as old as the Late Ordovician. Ichna in paleosols can be used as proxies of soil organisms and their size, behavior, presence in soil, and role in soil formation and nutrient cycling. Ichna also record the rate of landscape aggradation, soil-moisture and water-table level, environmental setting, and relative amount of precipitation and its seasonality because they are the result of organisms interacting and responding to the other four soil-forming factors. The integration of interpretations from ichnologic, paleontologic, sedimentary, paleopedogenic, and geochemical associations has been used to reconstruct environments, hydrology, climate and their variation through time in Mesozoic and Cenozoic strata. The future of integrated soil and trace-fossil studies lies in the combined efforts of field and laboratory investigations to understand better how traces of organism behavior in modern soils record the biophysicochemical factors under which they form. Under experimental conditions the morphology, depth, and distribution of animal and plant traces can be quantitatively evaluated under specific conditions of moisture and temperature as well as under increased or decreased levels to simulate changes in temperature and precipitation. Such studies can be used to more accurately interpret the behavior and significance of trace fossils in paleosols and retrodict their environmental and climatic settings.