STUDY ON THE MICRO CHARACTERISTICS OF DEEP -WATER SANDY CLASTIC FLOW AND TU IDITE SANDSTONE IN CONTINENTAL LAKE BASIN A CASE STUDY OF CHANG 7 MEMBER OF YANCHANG FO ATION IN 0 I OS BASIN

In this paper, we conducted a systematic study on the micro -sedimentary characteristics of the sandy elastic flow and turbidite sedimentary rocks of the Chang 7 member of Yanchang Formation in Xunyi and Yaoqu areas of Ordos Basin, based on thin section observation, image analysis, environmental scanning electron microscopy, X-ray diffraction and x Fluorescence element analysis. Observation under the microscope shows that the elastic particles of sandy elastic flow sandstone are arranged in a disorderly manner, while the turbidite has obvious characteristics of directional arrangement. It reflects that the former has the characteristics of secondary transport of block flow, while the latter has the characteristics of turbulent transport. The results of particle size analysis show that the particle size probability curve of sandy elastic flow sandstone has an obvious two -stage type, which better inherits the particle size characteristics of delta sediments; while the turbidite is a single -stage type. which reflects the turbulent transport feature. Clay analysis shows that the clay types are similar, but the content of chlorite in sandy elastic flow sandstone is slightly higher than that of turbidite. In elemental analysis. the ratio of Sr/Ba in turbidite sandstone is higher than that of sandy elastic sandstone. which confirms that turbidite sediments are closer to the deep lake area. The Zr content of sandy elastic flow sandstone is much higher than that of turbidite, indicating that it has stronger elastic transport ability. Quantitative analysis results of the whole rock and clay show that there is no significant difference in the clay composition and mixed layer ratio of the sandy elastic flow and turbidity current sediments, but there is a difference in the mineral composition of the whole rock.