Sedimentary evolution and lithofacies palaeogeography of the 4thsub-member of Member 5 of Majiagou Formation in Ordovician of central and eastern Ordos Basin
Yu Zhou1, Ding Zhenchun1, Sun Liuyi2, Ma Zhanrong2, Wu Xingning1, Dong Yan3
1 Hangzhou Research Institute of Geology,PetroChina,Hangzhou 310023,Zhejiang;
2 Research Institute of Exploration and Development,Changqing Oilfield Company,PetroChina,Xi'an 710018,Shaanxi;
3 Heavy Oil Production Company,Xinjiang Oilfield Company,PetroChina,Karamay 834000,Xinjiang
Based on the analysis of outcrops,drilling core samples and thin sections,this paper summarized the sedimentary microfacies and its vertical sequence types of the 4th sub-member of Member 5 of Majiagou Formation in Ordovician of central and eastern Ordos Basin. The palaeogeography of four periods which are M543,M542,M541b and M541a of Majiagou Formation is studied,mainly based on the parameters including the cumulative thickness of gypsum-salt rock and its ratio to the whole formation. The result shows that the study area is an arid environment with a low sea level during the 4th sub-member of Member 5 of Majiagou depositional period. The sedimentary pattern was uplifts alternate with depressions. From the early to later,the relative sea-level gradually rose and the salinity reduced,which controlled the development and spatial distribution of sedimentary microfacies of these sub-members.
Yu Zhou,Ding Zhenchun,Sun Liuyi et al. Sedimentary evolution and lithofacies palaeogeography of the 4thsub-member of Member 5 of Majiagou Formation in Ordovician of central and eastern Ordos Basin[J]. JOPC, 2015, 17(6): 787-796.
