Paper No. 11
Presentation Time: 3:30 PM
BIOTURBATION IS THE MAJOR PROCESS IN THE EVOLUTION OF SOILS AND LANDSCAPES––EVIDENCE FROM MODERN AND DEEP TIME
Yes, bioturbation is a major process in the evolution of soils and landscapes based on plant and animal trace fossil evidence in paleosols through deep time, if not THE major process. Bioturbation plays a role in the production of organic material (plants and roots), mixing (animal behavior), and the creation of macropores and macrochannels (active and open plant root channels and animal activity) in the vadose zone. Soils, because of their physical and biological components and biophysicochemical activities, are also referred to as the critical zone—where physical materials and biomass are transformed into soils and its nutrients made available to the community, whose boundaries range from the top of the canopy to the groundwater. Continental strata in deep time record the concomitant evolution of continental bioturbation and paleopedogenesis that is intimately tied to depositional systems and postdepositional conditions in the critical zone. In deep time, ichnofossils (microbial, plant, and animal interactions with each other and physical media) and paleosols together form ichnopedologic facies that record environmental variables and their effects across gradients of time, lithology, disturbances, biological activity, and topography. The study of modern animal bioturbation rates and patterns in soils and landscapes demonstrates the vast amount of work done to mix sediment and create pores and channels into which materials and fluids can be translocated and soil structure produced. Field and laboratory experiments observing and quantifying the burrowing activity of animals demonstrate the great amount of work animals can do in a short amount of time in a particular three-dimensional space. Results of these studies are manifest in the rock record as ichnopedologic facies that record the significance of bioturbation in the evolution of soils and landscapes through time through (i.e., stratigraphic record). Since the Ordovician, ichnopedologic facies became increasingly more diverse, abundant, and penetrative from mid to late Paleozoic, through the Mesozoic and into the Cenozoic. From the Permian to the Neogene, a large number of ichnopedologic patterns are similar to those seen today. Thus, bioturbation mediates biological, pedological, and hydrological processes from micro- to macroscales.