CARBON ISOTOPIC BIO-GEOCHEMICAL STUDY ON THE SECTION OF DOUSHANTUO FORMATION IN WENG′AN,GUIZHOU PROVINCE

Secular variations of carbon isotopic composition of organic and carbonate carbon in Doushantuo Formation,which is exposed on the Yangtze Platform at Weng′an,Guizhou Province,south China,were recognized.δ~(13)C values for organic matter varied from -33.4‰ to -26.5‰.The carbon isotopic composition for carbonate carbon displayed variations between -4.9‰ and 3.6‰.A change in the isotopic difference (Δδ_(org-carb)) between both isotope records reflected a difference in the proportional contribution of bacterial biomass to the total sedimentary organic matter.In general,the observed changes were considered to be the primary depositional values,notably variations in the burial of organic matter.The study provided new carbonate carbon and organic carbon isotope data and curves during the Doushantuo interval of terminal Neoproterozoic and early Paleozoic age,and reflected variations of sedimentary environment and also offered important correlation and reference for sedimentary sequence and global stratum of the same period.Furthermore,it presented crucial information for completely understanding for territorial and global events.