Paper No. 1
Presentation Time: 8:00 AM-6:00 PM
THE EDIACARAN-CAMBRIAN ECOSPHERE REVOLUTION: INSIGHTS FROM CHINESE MICROCONTINENTS
HEUBECK, Christoph E., Department of Geological Sciences, Freie Universitaet Berlin, Malteserstr. 74-100, Berlin, 12249, Germany, ZHU, Maoyan, State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing, 210008, China and JIANG, Shao-Yong, State Key Laboratory for Mineral Deposits Research, Department of Earth Sciences, Nanjing University, 22 Hankou Road, Nanjing, 210093, China, christoph.heubeck@fu-berlin.de
Any outside observer considering the approx. 4500-Million-year history of our planet would likely choose the 150 Ma-time Ediacaran and Cambrian periods as one of the most dramatic intervals in Earth history. The Ediacaran, in particular, is characterized by concurrent profound changes in global tectonics, radical swings in temperature, evolutionary events leading up to largest bioradiation ever, the beginnings of the agronomic revolution, and a significant step-change of atmospheric and oceanic composition. Cambrian strata largely record the gradual establishment of a newly acquired ecologic stability, the beginning of the metazoan conquest, and a profound rearrangement in the chemical composition of Earth’s atmosphere and oceans.
Even though the Ediacaran period records numerous prior evolutionary steps, our interdisciplinary studies using material from the Yangtze Platform favor a “tipping point” character of the PC-C boundary due to near-contemporaneous events in plate tectonics, modified oceanic circulation patterns, changing ocean chemistry, an improved nutrient supply to the oceans, and the rapid increase in shelf sediment bioturbation. These environmental changes likely modified taphonomic conditions significantly. Possibly independently, a biological breakthrough in genomic complexity multiplied the effects of one or several, short-term, tectonically-sourced nutrient pulses and capitalized on the new biomineralization capability, triggering an arms race. Precise global geochronological and stratigraphic correlation would aid in reliably distinguishing cause-and-effect during this time interval but is as yet insufficiently developed.
