Characteristics and Deposition of Marker Beds in the Yanchang Formation of the Northern Shaanxi Province

• 责任者：Pang Jungang (State Key Laboratory of Continental Dynamics ; Geological Department ; Northwest University ; Xi’an 710069 ; China) ; Li Wenhou
• 刊名：Journal of Stratigraphy
• 出版年：2010
• 卷期：34(2)
• 关键词：延长组 ; Yanchang Formation ; 标志层 ; index beds ; 陕西 ; Shaanxi Province
• 页码：p.173-178
• 图表：5 illus., 1 table, 8 refs.
• 分类号：1200
• issnNo：ISSN0253-4959
• isbnNo：CN32-1187/P

The authors applied traditional sedimentology and sequence stratigraphy methods in the study of a large volume of well log and outcrop data. The lithostratigraphic and well log characters of marker beds in the Yanchang Formation of the northern Shaanxi are described systematically. Regionally extensive oil shale is associated with the maximum flooding surfaces of five third order sequences in the Yanchang Formation, these flooding surfaces are characterized as condensed sections, the marker beds are volcanic tuffs. The distribution of these marker beds is controlled by the depositional environment, and they are mainly found in deep lake sub-facies, with some in shallow sub-facies. There are certain differences in lithology and well log characteristics of these marker beds in different facies. These marker beds, together with well log data and stratum thickness data, can be used to facilitate stratigraphic correlation and subdivision.