Source Rock Distribition And Its Main Controlling Factor Of The Upper Cretaceous In SK-I Borehole

In this paper,source rock of the Upper Cretaceous in SK-I borehole were evaluated to determine the distribution of high-quality source rocks at first.astronomical cycles of the Upper Cretaceous in the southern SK-1 borehole were identified with a cycle stratigraphy method,and then by using moving window spectral analysis method,sedimentation rate of each window was calculated.We use ostracod abundance as well as its shell Carbon Isotope to qualitatively describe paleoproductivity in this area.Base on the proportion of organic carbon source,we corrected the paleoproductivity which was calculated by ancient ocean productivity formula.The ratio of pristane and phytane and mudstone color were used as an indicator redox conditions to determine the preservation condition of the SK-I borehole in each interval.The relationship between total organic matter content and sedimentation rate were discussed under different environment and paleoproductivity condition.The research shows that the first member of Nenjiang Formation and Qingshankou Formation are the main high-quality source rock in this area.TOC is mainly controlled by palaeo-productivity under the reduction condition,and however,the influence of SR is very little.In a high palaeo-productivit y environment the TOC value is bigger than 1% and it is less than 1% in contrast.But under the oxidation and low palaeo-productivity condition,the TOC value tends to increase with SR when the sedimentation rate is less than 11cm/ka and then decrease in a higher SR background.Compared two favorable conditions caused the differences in organic matter,we find that TOC has greater difference under conditions of high productivity redox environment.Redox conditions is the main controlling factor for source rock of the upper Cretaceous in SK-I borehole.