Regional synthesis of the Ordovician geology and stratigraphy of China

Abstract

Abstract China presently comprises several independent tectonic palaeoplates or terranes and parts of other blocks, which have been assembled over geological time. In the Ordovician, these blocks included South China, North China, Tarim, Qaidam, Junggar, Qiangtang-Qamdo, Lhasa and partially Himalaya, Sibumasu and Indochina, as well as the Altay-Xing'an and Songpan-Garze fold belts, which were discrete but near-adjacent. Twelve stratigraphic megaregions bounded by tectonic sutures or major fault zones can be recognized. Some of them are further differentiated into several regions according to the lithological and biotic facies or distinct stratigraphic sequences. Here, the palaeontologic features and biostratigraphic framework of these stratigraphic megaregions and regions are summarized. The unified biostratigraphic framework presented herein is supported by 33 graptolite biozones and 27 conodont biozones, together with supplementary biozones, communities or associations of brachiopods, trilobites, cephalopods, chitinozoans, acritarchs and radiolarians. With constraints of integrative chronostratigraphy, biostratigraphy, chemostratigraphy, cyclostratigraphy and magnetostratigraphy, along with some geochronologic data, our understanding of the temporal and spatial distribution of the Ordovician lithostratigraphic units on these major blocks has been significantly advanced. Vast amounts of new data accumulated in recent decades also constrain the major Ordovician geological and biotic events evident in China, such as marine anoxia, faunal turnovers and tectonic orogenies.