184 / 2019-06-11 19:05:32

Sequence Stratigraphic Characteristics of Denglouku Formation of lower Cretaceous in Songliao Basin in China

Songliao basin, Sequence stratigraphy, Denglouku Formation, Unconformity surface.

In order to study the sequence interface characteristics of Denglouku formation and find out the regularity of sequence stratigraphic distribution. Using the theory of sequence stratigraphy, we calibrate the bottom surface of Denglouku Formation by combining the core facies sign, logging curve cycle feature and reflection relation of 3d seismic data terminal. The study shows that the sequence stratigraphy of Denglouku Formation was formed in the period when the sequence boundary facing the basin edge was truncated and the in-basin conformity and overlap were the main characteristics. The bottom interface of Denglouku Formation, SB4a, is a regional unconformity formed in songliao basin from fault depression to fault depression. The seismic section shows the reflection relation of seismic terminal, such as cutting, overtopping and overtopping. According to the stratigraphic distribution characteristics, lithological characteristics, top and bottom interface unconformity range and tectonic control of the strata, we divided the original Section IV of Yingcheng Formation into Section I of Denglouku Formation in Xujiaweizi area. And the whole Denglouku Formation is divided into four three-level sequences and ten four-level sequences. The east and west margins in the east and west sections of the four three-level sequences have the characteristics of overlying thinning or pinching. Section I of Denglouku Formation is controlled by the main control faults in each fault depression and the growth faults in the fault depression associated with the main control faults, which mainly show the sedimentary characteristics of fault depressions. It is filled with coarse clastic sediments, mainly alluvial fans and fan deltas, on the topography which has been denuded and leveled under strong compensation. It is mainly developed in Gulong Sag, Sanzhao Sag and Yingshan Miaotai area. In the later sequence filling process, the sedimentation center basically follows the early fault depression belt, and with the continuous expansion of lake basin water body, Section II of Denglouku Formation has the characteristics of expanding to the north and southeast which forms regional deposits of fine particles. But the sedimentation center is still dominated by Gulong and Sanzhao areas. In the sedimentary period of Section III and IV of Denglouku Formation, the compensation effect was relatively enhanced and the sedimentary range was further expanded. Abundant terrigenous debris made the lake water shallow and the water range became smaller, and the climate tended to be dry. During this period, the sedimentary centers such as Sanzhao, yingshan and Miaotaizi tended to merge, and the sedimentary centers were mainly in Gulong area through the process of progradation and filling.