Alan J. Kaufman, University of Maryland Shuhai Xiao, Virginia Polytechnic Institute and State University Dima Grazhdankin, Russian Academy of Sciences
The PIs will undertake a basin-wide stratigraphic, geochemical, and paleobiological study of the carbonate-dominated Khatyspyt Formation in remote northern Siberia. Ediacaran fossils in this unit are remarkably preserved in fine-grained carbonates, promising a much enhanced anatomical and paleoecological view of Earths earliest animals. Insofar as the Ediacaran biota may have required abundant free oxygen to sustain metabolic activities, we hypothesize that their distribution may track environmental conditions, and propose tests of this linkage through high resolution time-series analyses of carbon and sulfur isotopes in multiple equivalent sections across the Khatyspyt depositional basin as well as other biological, elemental and isotopic indicators of redox conditions. The Khatyspyt Formation contains a wide range of unique carbonate-hosted Ediacaran organisms, as well as carbonaceous macrofossils, small shelly fossils, trace fossils and planktonic microfossils all in a single, 450-m-thick continuous succession cropping out along the Olenek, Khorbosuonka and Lena rivers. Results of the study should provide insights to the phenomenon of soft tissue preservation, increase the ecological resolution of the Ediacaran-Cambrian transition, and provide important constraints on the history of Earths earliest metazoans and the oceans in which they originated, diversified, and ultimately perished. The primary aim of this field and laboratory based proposal is to test whether the geologically brief Ediacaran experiment in complex multicellular life was controlled by the oxidation state of shallow marine environments. The proposed research will establish a new international collaboration with colleagues in Russia, and require two month-long field seasons above the Arctic Circle in northern Siberia. Graduate students from both U.S. institutions will accompany the PIs in the field, providing them with an enhanced learning experience that will promote both scientific and cultural exchange.
Our present understanding of the origin of animals and Phanerozoic ecosystems depends critically on the ability to interpret impressions left behind in siliciclastic sediments by soft-bodied Ediacaran organisms, and to document their spatial and temporal distribution, which conceivably relate to strong environmental gradients in terminal Proterozoic seawater. To enhance paleobiological resolution and track environmental perturbations, however, requires the discovery of new taphonomic windows for the Ediacaran biota in relatively continuous successions dominated by chemical sediments. The main goal of this project is to test whether Ediacaran fossils are temporally and spatially linked with Ediacaran environmental conditions, using paleontological and geochemical data collected from Siberia and South China. The research team, led by Prof. Alan Jay Kaufman at University of Maryland and Prof. Shuhai Xiao at Virginia Tech, in collaboration with Dima Grazhdankin at the Siberian Branch of the Russian Academy of Sciences, has generate a suite of biostratigraphic and geochemical data to address the hypothesized co-evolution between Ediacaran biosphere and physical environment. In addition, they have generated new geochronological data that help constrain the timing and rate of Ediacara biological and environmental evolution. Integrated biostratigraphic and chemostratigraphic data not only provide critical test for the co-evolution hypothesis, but also form the foundation for improved stratigraphic correlation of Ediacaran successions around the world.
