Tertiary In Jiyang Depression Lacustrine Sequence Stratigraphy

In this paper, The Lacustrine sequence stratigraphy of the early Tertiary in the Jiyang depression is systematically studied on the basis of geological data, well logging data,seismic data ,and so on. Firstly, the article deals with the dividing and correlating methods of stratigraphic formation in the early Tertiary ,and sets up the framework of sequence stratigraphy of the whole depression. The early Tertiary in the Jiyang depression is divided into one sequence, The sequence is subdivided into three types of parasequence sets and ten parasequence. Secondly, the forming mechanism of the Lacustrine stratigraphic formation is synthetically analyzed in this paper. Structure sedimentation, sediment supply, paleoclimate and paleotopography are the four main factors affecting the stratigraphic formation structurres which resulted different developing models. Thirdly, this paper discusses the sedimentary facies of the early Tertiary in the Jiyang depression and describes the characteristics of combination plane facies in every development stage. The different sedimentary facies and every section controls the distribution and the thickness of the source rock and the resources. The recogniton of their sequences is based on piling-up of lake sand body and development of the Lacustrine:(1) The early Tertiary includes lowstand systems tract, transgressive systems tract, high systems tract and reflux systems tract are developed ;(2) The different sedimentary facies and every section are in the different places; (3) The different sedimentary facies and every section influences the thickness of the source rock and the resources. The structures of the Lacustrine are affected by each effect between supplying of sediment and producing of accommodation room. There is no record of sediment in the early lowstand systems tract and the transgressive systems tract. In addition, this paper discusses the paleogeography of the early Tertiary in the Jiyang depression.