Provenance Analysis and Sense of Palaeogeo Graphical of Kongdian Formation of Palaeogene in South Kongdian of the Huanghua Depression
|School||Chengdu University of Technology|
|Keywords||Provenance analysis Palaeogeo graphical Kongdian Formation The south of Kongdian Huanghua Depression|
In south Kongdian area of the Huanghua depression, Bohai Gulf, the top and the bottom boundaries of Kongdian formation are the unconformity. With the vertical development of a complete sedimentary cycle, it has undergone an independent process of basining. The types of sedimentary facies are variety. There are several provenances. The research on provenance analysis of Kongdian formation was unsystematic in the earlier days. Provenance analysis, which includes the matching relationship between spatial distribution of the genetic sand body and uplifted area, is the important territory that rebuilding basin sense of palaeogeo graphical environment, analyzing basin and surveying subtle reservoir exploration. It has the important sense of direction and practice. It has the important sense of direction and practice. the paper chooses Kongdian formation of palaeogene in the south of Kongdian area as a research aid. Guided by the theory of nonmarine sequence stratigraphy, the author uses sequence section of reservoir as the elementary cell to analysis the character of provenance, the types of palaeodrainage pattern and sedimentary system, and then to reveal the provenance characteristics and palaeogeo graphical evolution characteristics of Kongdian formation in the south of Huanghua depression.According to the characteristics of the sedimentary basin palaeogeomorphology and controlling factors of sequences, such as structure, climate, sediment supply and lake-level fluctuation, and so on. Utilizing and realizing the different bounding surfaces on seismic cross-section and borehole log, it divides kongdian formation of palaeogene into one second-order sequence, and four third-order sequences. It uses third-order sequence as the base unit to build the sequence stratigraphic framework of the region. Utilizing conventional analytical methods, which include Gravel composition, Sandstone framework composition, Heavy mineral analysis, and so on, can identify the character of parent rock and the wards of provenances. according to contoured gravity anomaly map, thickness contour of Conglomerate, sand body disperse system, the reflection configuration of seismic and seismic attribution technique, it indicated that there are five major erosion areas, which are corresponding to Cangxian uplift, Chengning uplift, Xuhei bulge, Dongguang bulge and Kongdian bulge. The research indicate there are ten major source port in the edge of the basin, which are corresponding to Zilaitun– Junmazhan - Zaoyuan, Xueguantun - Cangzhou, Shenusi - Jiedi, Dianzijie - Nanpi, Dongguang, Dengmingsi, Wumaying, Jibeitou, Wangguantun - Dongguan, Guxian, etc. Cross channel and longitudinal drainage systems are developed around the basin. According to stratigraphic distribution and lithological composition of the palaeohigh,it can identify the matching relationship between several provenances and uplifted areas of each sequence. According to Dickinson’s trigonometric graphical methods, it can be judged that the tectonic setting typically belong to continental plate and magmatic arc zone.Based on provenance analysis and sedimentary system evolution characteristics, the paper probes into the Palaeogeographic evolution characteristics of each sequence. In summary, it is certain that: during SQ1 period, it was semiarid palaeoclimate of semi-tropical, and undergone fault sag evolutionary phases. There are several enclosed lakelet, and sediment provide basin system though river, which is main of cross channel. It developed delta depositional system and alluvial fan depositional system. During SQ2 period, it was humid climate in depression step. Main body of basin is lake, and mainly developed cross channel. It developed delta depositional system and turbidite fan depositional system. During SQ3 period, it was hot-semiarid climate in resistant step of fault sag. It developed several separate lake in the basin, and sediment was transported into basin though river, which is main of cross channel. It developed alluvial fan depositional system and delta depositional system. During SQ4 period, it was hot arid climate in fault depression step. The basin was distributed brackish-saltwater lake, and mainly developed longitudinal drainage system. It developed alluvial fan depositional system, fan delta depositional system and cream-salt deposit.