Sedimentary facies and genetic mechanisms of the dolostones in the world-wide end-Permian strata

The statistics and correlation in the present paper are involved into 23 world-wide representative and well-documented Permian-Triassic (late Changxingian) boundary sections and the precursory sedimentary facies of the late Changxingian dolostones. Except from one section from the Liangshan in Hanzhong, Shaanxi, all the other previous deposits of the late Changxingian dolostones belong to the shallow-water sedimentary facies. On the contrary, the known deep-water Upper Permian carbonate deposits have not been dolomitized up to now. This implies that the genetic mechanisms of the world-wide dolostones from the topmost parts of the Upper Permian strata may be related to the rapid global sea-level falls, which led to the exhumation of the shallow-water carbonate deposits to the intertidal and/or supratidal environments. The concentrated brines in these evaporation environments penetrated into the pre-existing carbonate deposits and gave rise to the dolomitization and finally to the formation of the dolostones. A similar example is provided by the Changxing Formation dolostones as excellent reservoir rocks in northeastern Sichuan Basin, where the pervasive dolomitization took place in the pre-existing organic reef facies and shallow-water open platform carbonate deposits, and the dolomitization mechanisms may well be controlled by the same sea-level falling event as the other parts of the world.