Molecular Microbiology Research In Black And Red Mudstones Of Cretaceous Continental Scientific Drilling

In the geological history, Cretaceous is regarded as the exemplar of Greenhouse climate, punctuated by dramatic events such as the mid-Cretaceous ocean anoxic events (OAEs) and the Cretaceous Oceanic Red Beds are thought to provide a clue for researching the carbon recycle during the geological history. Songliao Basin is the largest oil and gas producing basin in China., with the most integrated and continuous Cretaceous terrestrial strata and geological records in the world. Cretaceous Continental Scientific Drilling situates in the northern central of Songliao Basin and aimed to obtain the complete cores of Cretaceous.This thesis uses molecular microbiological method to analyze the black and red mudstones sampling from the Cretaceous continental scientific drilling, and discusses the causes and the influences to the environment from the biological and geological aspects.The main experimental means contain X-ray Diffraction analysis, phospholipid fatty acid analysis, 16S rRNA gene analysis and gene sequences diversity analysis. According to the object, two samples, B2-03 (dark black, 1117 m depth) and B2-05 (red, 1215 m depth) were selected for microbial analyses. The PLFA-determined biomass is similar between the two samples, i.e.,～2 x 10~7 cells/g. Polymerase chain reaction (PCR) was able to successfully amplify bacterial 16S rRNA gene, but failed to amplify any archaeal 16S rRNA gene. Bacterial clone sequences mostly belong to low G + C Gram positives and Proteobacteria. Based on relatedness of clone sequences to close relatives and to other clone sequences from known environmental conditions, the bacterial community composition in both samples appeared to be dominated with halophilic, and alkaliphilic microorganisms. In the black sample (supposedly more reducing), clone sequences were mostly related to aquatic metal and sulfate (sulfur) reducing bacteria, whereas in the red sample (supposedly more oxidizing), clone sequences were related to aquatic sulfite and sulfur oxidizing bacteria. By XRD analyzing, there is pyrite in the black sample, which is formed in more reducing environment, whereas analcime exists in the red sample which is formed in more oxidizing environment.This is the first time using molecular microbiological methods to the systematic study of cretaceous terrestrial sedimental records. This research founds a feasible geomicrobiological methods and obtains a similar result with cretaceous marine sedimental records. And these data are encouraging and appear to suggest that microbial record (fossil DNA and biomarker) may be used to reflect paleo-environmental conditions.