Provenance analysis of the Miocene accretionary prism of the Hengchun Peninsula, southern Taiwan, and regional geological significance

• Hengchun Miocene turbidite sequences mainly derived from Minjiang/Jiulongjiang.
• Lower sea-level favor sediments being transported farther near SW Taiwan.
• Sedimentation is controlled by different river systems and fluctuation of sea-level.
• Tectonic transition from the passive to active continental margin of the Manila system.

Petrographic analysis, detrital zircon U–Pb geochronology and Neodymium isotope are applied to the Middle-Late Miocene turbidite sequences in the Hengchun accretionary prism, southern Taiwan, to constrain the provenance and nature of sedimentation in the Manila subduction system. Both petrographic study and detrital zircon U–Pb ages show that the Middle-Late Miocene turbidite sequences were primarily derived from Mesozoic granites and volcanic rocks of the Cathaysian Block in SE China, which were transported southeastward via rivers like Minjiang and Jiulongjiang to the Taiwan area. This conclusion is further supported by Nd isotope analyses of shales intercalated within sandstone sequences showing negative εNd values (−13.3 to −10.5) of a continental origin. During the Late Miocene when global sea-level fell significantly, the SE China coastline shifted seaward to the eastern part of the present Taiwan Strait, which would have facilitated these continent-derived sediments being transported southeastward to the shelf-upper slope of the Chinese continental margin. These turbidite sequences were then deformed and accreted into the accretionary prism of the Hengchun Peninsula when the South China Sea oceanic lithosphere subducted eastward beneath the Philippine Sea Plate in the Late Miocene. Our study suggests that sedimentary deposition of the turbidite sequences in the Hengchun Peninsula could be strongly controlled by different river system supply, submarine channeling transport and fluctuations of sea-level.