Magnetic ‘Fingerprinting’ of Sediments in Taizhou Bay: Implications for Provenance

The reduction in Yangtze River-derived suspended particulate matter significantly impacts adjacent marine sedimentation. Although traditionally considered the primary sediment source for the Zhejiang-Fujian Mud Belt, environmental magnetic evidence contradicts this, indicating local rivers predominantly supply the muddy tidal flats south of central Zhejiang. This study focuses on analyzing sediment provenance in the central Zhejiang offshore area. Magnetic analysis shows the sediments are characterized by low magnetic mineral concentration and fine grain size, highly similar to the adjacent Jiaojiang River’s riverbed sediment and suspended particulate matter, distinct from the Yangtze. Consistent magnetic characteristics in high-energy flood layers further confirm the Jiaojiang River as the stable main source. The robust chronology, established by 210Pb and 137Cs dating, revealed significantly accelerated sedimentation after 1980. End-Member Modeling Analysis shows nearshore sediments are dominated by fine-grained components, with their proportion rising in the long term; meanwhile, coarse-grained components plummeted after 1990, indicating a shift toward stable, low-energy deposition. The contradiction between accelerated sedimentation and weakened hydrodynamics likely stems from Jiaojiang River basin human activities, enhancing local fine-grained sediment supply and trapping efficiency.