Influence of sediment supply rate on sequence stratigraphic architecture change: A case study from the Kaiping Sag, northern South China Sea

Abstract

The sequence stratigraphic architecture change is mainly controlled by three factors: basement subsidence or uplift, sea level change and sediment supply. However, the internal mechanism of the influence of the sediment supply on the sequence stratigraphic architecture change is not clear. In this paper, the Middle-Upper Miocene sequences in Kaiping Sag, northern South China Sea are taken as an example to discuss this issue. First, we divide and correlate the sequence through the comprehensive analysis of drilling and seismic data, and restore the seven seismic sequences in the study interval to their original form of sedimentary stage through the original form structural section restoration technique. Then, based on the original form structural section, the vertical changes of sequence stratigraphic architecture are recognized and the basement subsidence rate and sediment supply rate are estimated. Furthermore, through the correlation analysis between the sediment supply rate and the sequence stratigraphic architecture change, how the sediment supply rate affects the sequence stratigraphic architecture changes is recognized. The results show that the stratigraphic frameworks of the seven sequences are all LST-TST-HST-FRST combination, but the scale of systems tracts of each sequence varies greatly, which is quite different from the sequence stratigraphic architecture of the adjacent Baiyun Sag. The second-order cycle sea level change, basement subsidence, regional tectonic uplift and special paleogeographic environment (Kaiping Sag is located in the lateral edge of the trough zone) in the study area jointly lead to the variation of sediment supply rate in time and space, and this variable sediment supply rate is the main driving force for the change of sequence stratigraphic architecture in Kaiping Sag.