The Early Jurassic Stratigraphy And Sporopllen Assemblages Of The Central Depression In The Junggar Basin

The Junggar Basin is one of the largest inland basins in China, and the best-developed Jurassic mother rock in this basin is an important target in oil and gas exploration, therefore, a comprehensive study of the Jurassic is of great significance for the exploitation of the basin. Anyhow, controversies are still remained in the correlation and subdivision of the Jurassic in the eastern and southern Junngar Basin, especially in the central depression, a prospect district for exploration of oil and gas. Relatively weak in the regional geological study of this district greatly limited our evaluation and selection of new target stratum and fresh exploiting field and direction, and made it difficult to reshaping of regional exploration. Therefore, in order to take an integrated evaluation of the petroleum geology, and to get a better understanding of the regularity of hydrocarbon accumulation in Junggar Basin, it is of great important to have a comprehensive study of the Jurassic in central depression, and to furnish a good stratigraphic framework and proof of its correlation in time and space of this basin.Based on the research achievements and exploration data in this basin, relied on the theory of modern stratigaphy and palynology in oil-bearing basin, and with the application of lithological, paleontological and geochronical correlation and subdivision techniques, as well as through the anatomy of the Well Zheng-1, a key exploratory well in the central depression, a systematic study of the Early Jurassic in central depression in Jungar Basin is carried out, and the Early Jurassic stratigraphic framwork (i.e. Badaowan Formation and Sangonghe Formation) in the central depression and its sporopollen assemblages (namely the Cyathidites -Cycadopites and the Cyathidites-Classopollis sporopollen assemblages) are established in refer to a detailed investigation of the field sections and the cores of exploratory wells, to a analysis of important geologic section of wells, and to a describing, counting and identification of the sporopollen fossils of the well zheng-1 and those of the relevant wells. The kinship between the sporopollen assemblages and vegetation types reflects that the Early Jurassic consist mainly of herbaceous Filicinae and arbor, Coniferales and ginkgo belonged to bush and cycad indicative of subtropical climate. Also given is a relative detailed correlation of the Early Jurassic in central depression to that the neighboring area and region.