Characterizing the sedimentary architecture of successions of shallow-water deltas fed by braided rivers is crucial for the prediction of sandbody development in potential field. However, the complex distribution and diverse sedimentary characteristics of these deltas have led to insufficient insight into the controlling factors for different types. Based on high-resolution seismic data and well-logging data from the P Oilfield in the Bohai Bay Basin, two zones (I 1 and III 2 ) within the Neogene upper member of Guantao Formation were selected. Utilizing palynological analysis, elemental geochemical analysis, and frequency-division seismic-attribute fusion technology based on an ensemble-machine-learning algorithm, paleoclimate analysis and detailed architectural characterization of the studied stratigraphic interval were conducted. The findings indicate that: (1) Two palynological assemblages were identified in the upper member of Guantao Formation: Assemblage I suggests a subtropical-temperate monsoon climate, while Assemblage II indicates a continental semi-arid climate. (2) Zone I 1 represents a lobate shallow-water braided-river delta, whereas zone III 2 represents a lobate shallow-water braided-river delta with bar-finger. (3) Stable discharge conditions and a high bedload fraction under a subtropical-temperate monsoon climate facilitate the formation of the lobate shallow water delta. A low bedload fraction provides a favorable condition for the development of bar-finger, but flood events under a continental semi-arid climate enhance channel-mouth deposition driving the formation of the lobate delta with bar-finger. • Subtropical-temperate monsoon climate and continental semi-arid climate are identified of the upper Guantao Formation in the P Oilfield, Bohai Bay Basin. • Climatic evolution drives changes in sediment supply and discharge, which in turn alters fluvial hydrodynamics, thereby controlling the sedimentary morphology of shallow-water braided-river deltas.
Jingyang et al. (Wed,) studied this question.