Evolution of the Chepaizi-Mosuowan Paleo-Uplift, Junggar Basin, China: Evidence from Diagenesis of Late Jurassic Red Beds

Exploration of oil and gas in the central part of Junggar basin has shed light on the evolution of the Chepaizi-Mosuowan paleo-uplift, and the study of red beds beneath the unconformity between Jurassic and Cretaceous indicates that the processes of diagenesis provides information about the evolutionary history of the uplift.It is found that the red beds did not form by syn-sedimentary rubifaction but by diagenetic hematitization which can be explained by models of phreatic oxidation and interlayer oxidation occurring during the development of sandstone hosted uranium deposits.They underwent processes of initial compaction, eluviation (hematitization or brown alteration forming red beds), cementation by dolomite, calcite and/or silica, secondary compaction and deep diagenetic cementation by chlorite.The order of diagenetic events documents the evolutionary history of the Chepaizi-Mosuowan paleo-uplift.Initial compaction indicates that there was continuous deposition in the Jurassic, because the burial was deep and the uplift velocity of the uplift was less than the subsidence velocity of the Junggar Basin.Later eluviation indicates that uplift rates exceeded those of subsidence and Jurassic beds were exposed at the surface where they underwent general phreatic oxidation and interlayer oxidation.Subsequent secondary compaction accompanied by massive cementation indicates that the Jurassic red beds were once again deeply buried as the result of Cretaceous and Cenozoic basin filling.This sequence of diagenetic events thus documents the history of tectonism in the central part of the Junggar basin structure.