Division of the Ordovician geographic units of China – a synopsis
Eleven geographic units,corresponding mainly to different allochthonous continental masses(plates and terranes)in the Ordovician in China,are divided on the basis of evidence from regional tectonics,palaeogeography and stratigraphy. The paper is aimed at defining the boundaries of geographic units. Units or regions now in close proximity were distantly separated during the Ordovician. Except for the southern boundary of the North China Region and the northern boundary of the South China Region,which are well demarcated by the coeval intervening Qinling mobile belt,boundaries of most other regions have to be delimited by the conjunctional zones,along which tectonic amalgamations took place after the Ordovician. In detecting boundaries between the Northern Xinjiang/Central Tianshan Beishan/ Tarim regions,it is of particular significance to trace the remains of sutural zones that represent the relics of finite ocean basins or deep marine basins,which were developed between the Siberia Plate/Kazakhstan Mid Plate/Tarim Plate during the Ordovician. The final assembly of these Chinese landmasses likely underwent a long sustained process that extended from the Late Carboniferous to the Cenozoic,essentially involving the consumption of the mobile zones and the dispersion,accretion and collision of the relevant plates and terranes.