"Source-to-sink" System Coupling Analysis Of The Paleogene,Shaleitian Uplift,Bohai Bay Basin,China

The Shaleitian Uplift and its surrounding areas constituted a complete Palaeogene“source-to-sink" system with several types of coupled models. We analysed the provenance characteristics and sediment-dispersal patterns in the Palaeogene third-order sequence framework on the basis of the recent three-dimensional (3-D) seismic data,lithology, wire-line logs and detrital zircon U-Pb dating. The formation and supplement of provenance, paleogeomorphology and sediment-transport pathways, sediment-dispersal patterns and the coupling relationship of “source-to-sink" systems have been clarified. In addition, the guide of source-to-sink system in continental rift basins is established for exploration prediction of favorable zones in study area as well as similar basins.Based on the sequence stratigraphy theory, the Paleogene, in the Shaleitian Uplift,can be subdivided into five third-order sequences (from base to top: SQS3, SQS12, SQd3,SQd2L and SQd2U), and be investigated combined with three sequence-stratigraphic patterns (fault steep slope, fault gentle slope and slope). Fault steep and gentle slope style sequence patterns were well distributed in a sag-uplift paleostructure during the syn-rift stage (SQS3?SQd3), while the slope sequence pattern was well developed during the post-rift stage (SQd2L?SQd2U). According to the composition and distribution of Pre-Palaeogene bedrocks, catchment areas (a?f zone at the western Shaleitian Uplift,g?t zone at the eastern Shaleitian Uplift) and the variation of different provenance systems, we can draw a conclusion that the large catchment area of source region was well developed (with the maximum area of 2094 km2) and the sink area was mainly supplied by intrabasinal provenance (Shaleitian Uplift) during the rift stage(SQS3?SQd3). The catchment area of source region shrunk largely to 354km2 during the post-rift stage (SQd2L?SQd2U),and the intrabasinal provenance system also gradually changed to relatively distal extrabasinal or intrabasinal provenance systems.The types of sediment transport pathway, the combination pattern of the predominant intervals and their relationships with sand bodies are determined based on the macro provenance tracing. The paleo-geomorphology and stratal slices indicate that three types of sediment transport pathways were developed in the study area, including incised-valley, faulted trough (single fault, double fault and faulted trough) and structural transfer zone. During the syn-rift stage, the sediments were mainly dispersed as large fan-delta through incised-valley pathways in the eastern Shaleitian Uplift controlled by transfer zones in the sink. The sediments were mainly dispersed as the combination of proximal fan-delta and gravity flow deposits through the faulted trough pathways in the western Shaleitian Uplift. And the distribution of banded fan-delta is controlled by the central faulted trough developed between the eastern and western part of the Shaleitian Uplift. During the post-rift stage, the differences between the east and west began to reduce, and the sink is dominated by proximal short axis braided river delta through broad and shallow incised-valley pathways.Paleogene “Source-to-Sink" systems in the Shaleitian Uplift were divided into three types of fault steep slope, fault gentle slope and slope pattern based on the different characteristics of sequence-stratigraphic models. During the syn-rift stage,source (migmatitic granite in the steep slope) - transport pathway (the narrow and shallow incised-valley or faulted trough) - sink (fan delta - gravity flow deposits)systems and source (migmatitic granite or carbonates in the gentle slope) - transport pathway (broad and deep incised-valley or transfer zones) - sink (large-scale fan delta -beach and bar -gravity flow deposits) systems were mainly developed. The comparison with regional “Source-to-Sink" systems indicates that the south structure area of Shaleitian Uplift (fault gentle slope pattern) is the most efficient coupling system where sand bodies are most developed, followed with the southwest and west structure area(fault steep slope pattern) as well as the northeast structure area (fault gentle slope and slop pattern) . During the post-rift stage, the dominated systems were slope pattern source (migmatitic granite or carbonates) - to (incised-valley) - sink (short axis braided-delta). Moreover, there is minor difference between the sand body scales and exploration potential in the various sedimentary zones.