DEEP-TIME GEOBIOLOGY FROM THE PERSPECTIVE OF ANIMAL-SUBSTRATE INTERACTIONS (Invited Presentation)

Animal-substrate interactions are the scope of ichnology. The fact that trace fossils can be seen as evidence of behavior, and behavior is strongly affected by environmental factors make them powerful tools in paleoenvironmental reconstructions. This has been key in the success of ichnology in sedimentary geology through refinements of a wide spectrum of facies models that are now part of the current paradigm in this field. However, the downside of this perspective is that the activity of animals is seen under this light as completely subordinated to the environment. The explanatory arrow only goes from the environment to the organisms: abiotic factors dictate the fate of the living world. This view of ichnology has been changing in the last couple of decades essentially as a result of the convergence of two lines of thought: marine benthic ecology through the prism of niche construction and ecosystem engineering, and deep-time geobiology, through the understanding that the geosphere and the biosphere co-evolve. Looking at bioturbation as the product of organisms that are active players at the ecologic stage has resulted in the reversal of the explanatory arrow. In this emerging perspective, organisms are no longer simply reacting to stressors: they are actively modifying and recreating their own environment. These recent developments require a re-reading of the trace-fossil record seen as a source of hard data that provides the empirical support to models evaluating bioturbation as a driving force in ecosystem re-structuring and as a key factor in geobiological cycles. This implies using the rich ichnologic toolbox across a broad spectrum of scales, which include not only bioturbation index but also ichnodiversity, ichnodisparity, ichnocoenosis, multidimensional ecospace and ecosystem engineering cubes, spindle diagrams, and movement ecology to tackle a diversity of questions at different scales of analysis. The application of these conceptual and methodological frameworks has illuminated in recent years our understanding of breakthroughs in the history of life, including Paleozoic terrestrialization, evolutionary radiations, and mass extinctions.