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ENVIRONMENTAL CONTEXT OF EARLY ANIMAL EVOLUTION

THURSDAY OCTOBER 10 - 4 PM

HUAN CUI
AMGC, VRIJE UNIVERSITEIT BRUSSEL

ABSTRACT: The terminal Ediacaran Period witnessed the first appearance of macroscopic organisms including the earliest biomineralizing animals in Earth history. However, the biogeochemical context for this evolutionary milestone remains uncertain. To fill this knowledge gap, comprehensive chemostratigraphic investigations were conducted for the fossiliferous Dengying Formation in South China and the Khatyspyt Formation in Arctic Siberia. In the Dengying Formation, the first appearance of biomineralizing animal fossil Cloudina is closely associated with positive anomalies of δ13Ccarb, δ34Spyrite, and Sr/Ca values. We propose that the coupled paleontological and biogeochemical transition may have coincided with an increase in terrestrial weathering fluxes of sulfate, alkalinity, and nutrients to the depositional basin, which stimulated primary productivity and the spread of an oxygen minimum zone. The environmental and physiological pressures from an increase in seawater alkalinity may set the stage for animal biomineralization. In the Khatyspyt Formation, the development of oceanic euxinia may have locally prohibited the colonization of Ediacara-type organisms. The progressive secular transition from euxinic to non-euxinic and more habitable conditions may have allowed for the colonization of Ediacara-type and other macro-organisms at that time.

BIO: Huan Cui is a postdoc sponsored by the ET-HOME astrobiology research consortium and based at the AMGC group of Vrije Universiteit Brussel (Free University of Brussels-VUB), Brussels, Belgium. He conducts multi-disciplinary research that integrates sedimentology, stratigraphy, geochemistry, and paleontology to investigate the co-evolution of paleoenvironment and life in Earth’s history. Sedimentology and field investigations are typically the essential basis of the more topical, lab-based, hypothesis-driven projects in his research.

AMGC-Seminar-HC

Top: an artist's interpretation of what the Ediacaran sea floor looked like.
Bottom: modern-day South Australian Ediacaran fossils.
Illustrator: Peter Trusler; © Australian Postal Corporation 2005