Abstract:

Sanhecun Sub-sag in Zhanhua sag is an important target zone for future exploration due to its large sediment thickness, and low level of exploration in the lower third member of Shahejie Formation (Es3L). Detailed depiction of the provenance system using Es3L is of practical significance for reconstructing depositional system and forecasting favorable areas. This paper analyzes in detail the provenance system of Es3L in Sanhecun Sub-sag from various aspects and at different levels: the source area and the depositional area are macroscopically distinguished, while sediment transport pathways (valley I to VI) of the southwestern and southern are quantitatively described according to palaeogeomorphology; the types of sedimentary facies and prime material components in deposition area are identified based on cores and debris compositions; the sediment-dispersal patterns of “source-to-sink” systems and the spatial and temporal evolution of fans in the basin are finely pictured according to seismic profile analyses and stratal slices. The results show that of the southwestern gentle slope zone (about 3°) was originated from the western section of Chenjiazhuang Uplift (transport by valley I and II), which developed a gravel-rich fan delta and is mainly composed of carbonates debris; while of the southern slope break zone (about 8°) was originated from the eastern section of Chenjiazhuang Uplift (transport by valley III, IV, V and VI), which developed a sand-rich fan delta and contain quartz or crystal quartz grains. The scales of fan delta system in the deposition area have a positive correlation with the width-to-thickness ratios and the length of sediment transport pathway. The vertical changes show that the fan scale of lowstand system tracts (LST) of Es3L was larger than its highstand system tracts (HST), and the provenance system of convergence zone has transferred from the southern to the southwestern.

Key words: provenance analysis, source-to-sink system, stratal slice, the lower third member of Shahejie Formation, Sanhecun block in Zhanhua Sag