Silurian integrative stratigraphy and timescale of China

Silurian is a period with the shortest duration in Phanerozoic except for the Neogene and Quaternary. It represents an important and unique interval when the biotic diversity recovered quickly after the end-Ordovician mass extinction, different paleoplates or terranes conjoined, big oceans disappeared or narrowed, climate and sea level changed frequently, global biotic provincialism became weaker, some primitive plants started to occupy the land. Silurian is also the first system of which all the chronostratigraphic stratotypes (i.e. the GSSPs) including four series and seven stages were established by the International Subcommission on Silurian Stratigraphy (ISSS). Nonetheless, during the post-GSSP studies conducted by ISSS in the middle 1980s, some Silurian GSSPs were found to have some congenital defects such as no index fossils available that hinder the high resolution subdivision and correlation on a regional or global scale. In this paper, based on the latest development of Silurian study in China, the progress in biostratigraphy, chronostratigraphy, event stratigraphy (such as facies differentiation, heterochrony of black shales, marine red beds, carbonate rocks and reefs), chemostratigraphy, and tectonic stratigraphy (e.g., widespread of the late Silurian rocks in South China and its tectonic implication) are systematically summarized. Some existing problems and the areas to be focused in future work are also discussed. It is suitable for chronostratigraphic study to concentrate not only on the boundary but also doing multidisciplinary analysis on the biotic, chemical, magnetic, environmental, and chronologic aspects, in order to enhance the reliability and the potential for regional and global correlation of a certain GSSP. Some important achievements are expected in these areas in the Silurian study in China: (1) ecostratigraphy and basin analysis of the Llandovery, and the correlation of integrative stratigraphy with a high resolution; (2) establishment of the Wenlock to Pridoli chronostratigraphic framework; (3) the chemo- and magnetic stratigraphy and the age of some key intervals and horizons; (4) further investigation on paleogeography and plate tectonics; and (5) origin and early evolution of the terrestrial ecosystem. Some new breakthroughs might occur in the restudy on some of those problematic GSSPs of some particular series and stages.