Zhu, Dr Xiangkun1, Wang, Dr Xun1, Zhang, Dr Kan1, Sun, Dr Jian1, Poulton, Dr Simon2
1Institute Of Geology, Chinese Academy Of Geological Sciences, China, 2School of Earth and Environment, University of Leeds, UK
The Mesoproterozoic Era (1,600-1,000 million years ago; Ma) has long been considered a period of relative environmental stasis, with persistently low levels of atmospheric oxygen, and sluggish biological evolution. There remains much uncertainty, however, over the evolution of ocean chemistry during this time period, which may have been of profound significance for the early evolution of eukaryotic life. Here, we present multiple geochemical proxies, including rare earth element, iron speciation, Fe-, Ca- and Sr isotopes to investigate the redox evolution, and its relationship with tectonics, and effects on bio-essential elements, of the 1,600-1,550 Ma Yanliao Basin, North China Craton. These data confirm that the ocean at the start of the Mesoproterozoic was dominantly anoxic and ferruginous. Significantly, we find evidence for a progressive oxygenation event starting at ~1,570 Ma, immediately prior to the occurrence of complex multicellular eukaryotes in shelf areas of the Yanliao Basin. Interestingly, the onset of the oxygenation is coincident with the transition from rift to drift of the North China Craton. Moreover, the oxygenation is most likely progressive rather than a short-lived pulse, which resulted in depletion of bio-essential elements such as P. Our study thus demonstrates that oxygenation of the Mesoproterozoic environment was far more dynamic and intense than previously envisaged, and establishes an important link between rising oxygen and the emerging record of diverse, multicellular eukaryotic life in the early Mesoproterozoic. Furthermore, It sheds significant light on the reason of the sluggish evolution of eukaryotes during the protracted period.
Dr Xiangkun Zhu obtained a Ph.D. from Cambridge University. His researches mainly focus on isotopes of transitional metals and their implications in geochemistry, cosmochemistry and biogeochemistry.