Sedimentary evolution and lithofacies palaeogeography of the 4th sub-member of Member 5 of Majiagou Formation in Ordovician of central and eastern Ordos Basin
Author(s): Yu Zhou, Ding Zhenchun, Sun Liuyi, Ma Zhanrong, Wu Xingning, Dong Yan, Hangzhou Research Institute of Geology, PetroChina, Research Institute of Exploration and Development, Changqing Oilfield Company, PetroChina, Heavy Oil Production Company, Xinjiang Oilfield Company, PetroChina
Pages: 787-796
Year: 2015 Issue: 6
Journal: Journal of Palaeogeography
Keyword: sedimentary microfacies; Majiagou Formation; Ordovician; Ordos Basin;
Abstract: 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 5of Majiagou Formation in Ordovician of central and eastern Ordos Basin. The palaeogeography of four periods which are M543,M542,M541 band M541aof Majiagou Formation is studied,mainly based on the parameters including the cumulative thickness of gypsum-salt rock and its ratio to the whole formation. Theresult 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.
Pages: 787-796
Year: 2015 Issue: 6
Journal: Journal of Palaeogeography
Keyword: sedimentary microfacies; Majiagou Formation; Ordovician; Ordos Basin;
Abstract: 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 5of Majiagou Formation in Ordovician of central and eastern Ordos Basin. The palaeogeography of four periods which are M543,M542,M541 band M541aof Majiagou Formation is studied,mainly based on the parameters including the cumulative thickness of gypsum-salt rock and its ratio to the whole formation. Theresult 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.
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