Environmental and provenance variations in borehole core CSH-01B from the western edge of the North Yellow Sea: Responses to tectonic movements since the late pliocene

Abstract

To better understand the coupling between sedimentary and tectonic evolution in the East China continental margin, a 120.44-m-long borehole core designated CSH-01B was retrieved from the western margin of the North Yellow Sea. Paleomagnetic measurements revealed B/M, M/G and G/Gil boundaries at depths of 34.82 m, 86.58 m, and 119.98 m, respectively, yielding an extrapolated basal age of ∼3.6 Ma. Alongside systematic investigations encompassing lithofacies discrimination, microfossil examination, and provenance identification based on detrital zircon U‒Pb dating, the studied core was compared with extensively researched boreholes in the Yellow–Bohai Sea region. The sedimentary environment of the North Yellow Sea shifted since ∼2.0 Ma from long-term lacustrine sequences with episodic fluvial deposition, akin to those in the Bohai Sea, to alternating fluvial and marine facies, resembling those in the South Yellow Sea. Additionally, sediments derived from south of the Qianliyan Uplift emerged, in contrast to those primarily delivered by outflows from the Bohai Paleolake previously. Therefore, the Qianliyan Uplift dividing the Yellow Sea must have subsided and/or collapsed at ∼2.0 Ma. Concomitantly, the North and South Yellow Seas experienced subsidence and uplift, respectively, as indicated by their contrasting deposition rate trends. Quaternary marine transgressions began at ∼1.7 Ma were hindered from affecting the Bohai Sea by the Miaodao Uplift until its subsidence and/or fragmentation during the Jaramillo subchron, along with the central South Yellow Sea, establishing a low-lying topographic corridor. Additionally, the provenance analysis in this study contributes new insights into the long-debated evolutionary history of the Yellow River. The prototype of the modern Yellow River must have emerged no later than 2.4 Ma and experienced an interruption at approximately 1.4 Ma. With the commencement of the large-scale marine transgression at ∼0.8 Ma, the reintegrated Yellow River started to influence the East China continental margin widely and constantly.