Seismic sedimentology of continuous translation point bars in meandering rivers: a case study of the Pingyuan Formation (Quaternary) in eastern Shaleitian Uplift, Bohai Bay Basin, China

The depositional architectures of continuous translation point bars (TPBs) in single meandering channel belts are increasingly being identified with modern seismic data imaging, yet they remain poorly characterized. This study uses 3D seismic and well-logging data to assess the spatial distribution patterns of depositional thickness and sand fraction of continuous TPBs, and discusses the factors that control the differences in sedimentary characteristics among the different TPBs. In the eastern Shaleitian Uplift of the Bohai Bay Basin, five translation point bars with counter-point bars (TPB1–TPB5) were recorded, two of them (TPB1 and TPB2) being built by a combination of downstream migration and rotation, the others only by translation (TPB3–TPB5). Regardless of whether TPBs undergo apex rotation, the bar thickness of TPBs shows a strong positive correlation with the sinuosity variation (R 2 = 0.80), as increased sinuosity in a channel segment leads to deeper scour along the outsides of river bends. Along the flow direction, a declining bar sand fraction of pure TPBs links to diminished flow transportation capacity (TPB3–TPB4). Apex rotation resulted in the bar sand fraction rapidly decreasing in TPB1 and abnormally increasing in TPB2 along the flow direction, through enhanced localized scouring. In an area with significant slope changes, the sand fraction of a TPB tends to respond to the slope gradient (TPB5). This research illustrates the depositional architectures of continuous TPBs under different controlling factors, providing significant implications for characterizing the sand distribution and reservoir heterogeneity in subsurface translation point bars.