Subdivision and correlation of the Ordovician System serve as the time scale for constraining the major geological and biological events during the Ordovician Period. Currently a globally unified scheme has been reached to subdivide the Ordovician System into "Three Series and Seven Stages", established through a process called "the Golden Spikes". However various problems remaining on different palaeo-plates are yet to be resolved. This recent new study reviewed and analyzed the criteria and key remaining issues in the subdivision and correlation of the Ordovician System in China and even in the world.
This article titled "Ordovician integrative stratigraphy and timescale of China" will be published both in Chinese and English in the first issue of SCIENCE CHINA (Earth Sciences) of 2019. It was written by Professor Yuandong Zhang from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and his co-authors. These researchers systematically reviewed and summarized the history and status quo in the subdivision and correlation of the Ordovician System in China and abroad. By analyzing the distribution and preservation features of the Ordovician System in China and the major geological and biological events during the Ordovician, these authors established the correlative relationship of the Ordovician System developed on the major Chinese terranes, and also identified several remaining key issues in this scientific field in China.
One of the problems they raised is the uncertainties existed in the boundary definition, recognition and correlation crossing different mega-facies belts for the Tremadocian, Dapingian and Katian stages. The duration of the Ordovician stages are rather uneven and some stages could potentially be further divided into substages. Others include carbonate δ13C curves from several intervals within the Ordovician in China showing significant differences from the composite global curve; relatively rare record of the Ordovician isotopic dating contrasted to abundant bentonites and other volcanic rocks in China; and requirement for the enhancement of magnetostratigrahic research in China and for reassessment of relationship between Ordovician major bioevents and the reversals of magnetic polarity.
Ordovician experienced several major global geo- and bioevents, particularly the Great Ordovician Biodiversification Event (GOBE), Middle-Late Ordovician tectonic transition, end-Ordovician mass extinction and Gondwana glaciation, which have attracted not only extensive scientific investigation circle but also wide public attention. The advance in the subdivision and correlation of the Ordovician System will be directly beneficial to our better understanding of these major global events. The precise age determination and correlation of the Ordovician strata are critical for petroleum exploration, development and production, as Ordovician System hosts important petroleum resources in China. Among the seven "Golden Spikes", three were established in China, showing the prominence of the Ordovician studies of China in a global context. Therefore, further research to tackle these key issues will promote our leadership position in the international scientific community and advance this field to better serve the mineral and petroleum exploration and development in China.
The experts of the review panel regarded this study with high quality regional synthesis as one of the best works completed in recent years, and hope that it will play an important role to advance the research in the field of the Ordovician chronostratigraphy and integrative stratigraphy in China and abroad.
This study was supported by the National Science and Technology Major Project (2017ZX05036-001-004), the National Natural Science Foundation of China (41290260, 41772005), and the Chinese Academy of Sciences New Frontiers Special Grants, B category (XDB10010100, XDB2600000).
For more details, see:
Zhang Y D, Zhan R B, Zhen Y Y, Wang Z H, Yuan W W, Fang X, Ma X, Zhang J P. 2018. Ordovician integrative stratigraphy and timescale of China. Science China Earth Sciences, doi.org/10.1007/s11430-017-9279-0