Evidence for the Carboniferous hydrocarbon generation in Qaidam Basin

There have been controversies whether or not the Carboniferous has the potential of hydrocarbon generation in Qaidam Basin.Based on a great deal of geological field surveys and lab tests,this paper obtained the related evidence for the Carboniferous hydrocarbon generation in the basin.Recently,thick-layered oil sands were firstly found in many Carboniferous outcrops in peripheries of Qaidam Basin and they are mainly distributed within interlayers and fractures of the thick Carboniferous Huaitoutala Formation biogenic limestone,especially in bioherms and fossil belts.On the basis of comparison and analysis of biomarker parameters for source materials,sedimentary environments and thermal maturity,the oil-source correlation testified that these oil sands have no affiliations with any Mesozoic or Cenozoic source rocks of the basin but a good comparability with Carboniferous source rocks.Therefore,the oil in these Carboniferous oil sands originates from Carboniferous source rocks in Qaidam Basin.This evidence shows that Carboniferous source rocks have a hydrocarbon generation process,and probably generate oils that accumulated in Carboniferous traps.Therefore,there would be a great exploration potential in the Carboniferous of Qaidam Basin.