Geochemistry of the dysaerobic sedimentary environments of the Qixia Formation in Laibing, Guangxi

The geochemical signatures of sediments and/or rocks in the oxygendeficient environments may be employed as important indicators for the interpr etation of palaeor edox conditions.The analyses of twelve laminated limestones and argillaceous limestones samples collected from the Qixia Formation in the Tieqiao section, Laibing, Guangxi, integrated with sedimentological and palaeoecological data, have reflected that the carbonate successions in the study area were accumulated in a dysaerobic envir onment;the pyr ite-bearing black shales and carbonaceous and argillaceous limestones may be formed in an anaerobic environment, and the bioclastic massive limestones should be generated in an oxygen-rich environment.Most of the geochemical indices for the interpretation of palaeoredox conditions inferred from ancient shales, for example, DOP, V/(V +Ni), Ce/La and U/Th ratios are all valid for the interpretation of carbonate rocks.The spatio-temporal distribution of the palaeoredox conditions during the Qixian is always bound up with sea-level changes as well as palaeoclimatic changes.