Spatial and temporal trends in Ediacaran-Cambrian ichnofaunas

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The Ediacaran-Cambrian boundary represents a major divide in the history of life. Ediacaran biotas were dominated by soft-bodied organisms that are now considered for the most part to be unrelated with modern multicelular faunas. Ediacaran organisms flourished after a global glaciation that is presently known as the Snowball Earth episode. On the other hand, the Cambrian witnessed the rapid development of almost all modern groups of animals, including the rise of skeletal faunas, a major evolutionary innovation known as the Cambrian explosion. The majority of evolutionary studies on the Ediacaran-Cambrian transition have been based on the analysis of body fossils. However, the ichnologic record (that consisting of tracks, trails and burrows produced by animals) provides an independent line of evidence to calibrate the Cambrian explosion. Many recent studies have stressed the anactualistic character of the Ediacaran ecosystems by showing that, unlike modern environments, these ecosystems were dominated by benthic communities that developed in direct association with resistant microbial mats. Sediment stabilization by microbial binding was a major factor in Ediacaran ecosystems. During the Early Cambrian, matgrounds became rare due to the onset of vertical bioturbation and were replaced by mixgrounds in an event referred to as the "agronomic revolution". Integrated sedimentological and ichnological analysis provides a glimpse into the ecology of these ancient ecosystems and is particularly relevant to understanding the benthic communities of the terminal Proterozoic-Cambrian transition. The aim of this project is to analyze the spatial and temporal patterns of Ediacaran-Cambrian ichnofaunas. Planned activities include: (1) fieldwork in several Ediacaran-Cambrian successions, (2) revision of trace fossil collections, (3) construction of a database of Ediacaran-Cambrian ichnofaunas, and (4) study of modern biogenic structures associated with microbial matgrounds in stressed environments. Fieldwork will be done in northwest Argentina, South Africa, Spain, China, the Canadian Rockies and Kenya.