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Ocean Drilling Program Site 1143 of Leg 184 in the southern South China Sea (SCS) recovered a continuous sedimentary sequence since the Late Miocene (~ 10 Ma), which provides a unique record for better understanding the tectonic, environmental, and climatic evolution in the southern part of the SCS. In this study, we conducted a detailed rock magnetism and paleomagnetism study on 637 discrete samples taken from 512.1 m cores of Hole 1143C. Rock magnetic measurements indicate that the main magnetic mineral is single domain magnetite for samples from the upper 200 mcd (meter composite depth). All samples were subjected to stepwise alternating field demagnetization. The demagnetization behaviors of the samples below 200 mcd were erratic and unstable, owing to very weak remanent magnetization. A total of 15 reliable magnetic reversal events were identified in the upper 190 mcd cores of Hole 1143C based on the declination variations of the characteristic remanent magnetization, which can be correlated very well with the Geomagnetic Polarity Time Scale 2012 in combination with biostratigraphic data and astronomical time scales. Our new magnetostratigraphic results provide a more confident age framework for the southern SCS since the Early Pliocene. [ABSTRACT FROM AUTHOR]

The Ocean Drilling Program (ODP) Leg 184 recovered a continuous sedimentary sequence since Miocene at Site 1148 in the northern South China Sea (SCS), which provided a unique record for better understanding the tectonic, environmental and climatic evolution of the SCS. In this study, we report a detailed paleomagnetic study on 881 discrete samples from the upper 460 m cores of Hole 1148A through stepwise alternating field demagnetization (AF) or thermal demagnetization (TD). Rock magnetic results from isothermal remanent magnetization (IRM) acquisition, temperature dependence magnetic susceptibility (κ-T) and hysteresis loop parameters of representative samples indicate that the main magnetic mineral is low coercivity pseudo-single domain magnetite. The characteristic remanent magnetization (ChRM) with moderate downward or upward inclinations was identified after removing a low-stability drilling-induced remanence with steep downward inclinations. A new 23 Myr magnetostratigraphic time framework was established by correlating the magnetic polarity sequence to the Geomagnetic Polarity Time Scale 2012 (GPTS 2012; Ogg, 2012 ) in combination with biostratigraphic data. The mean sediment accumulation rates for lithostratigraphic Units V and IV, Unit III and lower Unit II, upper Unit II, Unit IB and Unit IA are calculated as ∼20.8 m/Myr, ∼15–17 m/Myr, 24.18 m/Myr, 17.07 m/Myr and 49.01 m/Myr, respectively. [ABSTRACT FROM AUTHOR]