THE PERMIAN SEQUENCE STRATIGRAPHY IN EASTERN CHINA

The Permian strata are well developed, widespread and contain abundant fossils in eastern China. They can be divided into A, B and c sequences. Sequences A and B correspond to the Early Permian Qixia and Maokou Formations, respectively, while Sequence C to the Late Permian Wujiaping and Changxing Formations. Sequences A and C represent typeⅠsequence, the lower boundary of which is referred to as typeⅠunconformity. Sequence B represents type∏sequence, the lower boundary of which is referred to as typeⅡunconformity. The depositional duration of Sequence A is about 5 Ma, while Sequenceb B and C about 10 Ma.
The lowstand systems tract consists mainly of the coal-bearing series which are assigned to the coastal plain and lower deltaic plain deposits. The condensed sections are composed of radiolarian siliceous rocks, siliceous mudstones and carbon-bearing mudstones, 3 to 15 meters thick, which contain ammonites and brachiopods and represent the starved sediments deposited during maximum rates of sea-level rises. On the carbonate platform, the highstand systems tract is dominated by the aggradational deposits which are composed of light grey grainstones and bioclastic micritic limestones, whereas on the coastal plain, occur the progradatianal deposits which belong to the deltaic coal-bearing series with great thickness. Syndepositional fault activites are closely related with regional sea-level changes, and thus interpreted as the important controlling factors on the coal-bearing series which constitute the highstand systems tract with great thickness.