Magnetostratigraphy of core XT06 and Quaternary sedimentary dynamics of the deep-sea deposits in the West Philippian Basin

The Philippine Sea, as a key area in the Western Pacific Warm Pool, is a characterized by wind-dust deposition. Sedimentary and paleo-environmental researches are relatively rare in the region due to large water depth and other reasons. In this paper, magnetic stratigraphy and sediment grain size data from the gravity core XT06, which is located in the central Philippine Sea, are used as the raw materials to establish the chronological sequence and to reveal the sedimentary processes. Upon the basis, the controlling factors on regional sediment distribution pattern and paleoenvironmental processes are discussed. The results suggest that: (1) After alternative demagnetization, the core XT06 can be subdivided into 6 magnetic polarity intervals, corresponding to the Brunhes (C1n) chron, the Jaramillo (C1r.1n) subchron, the Olduvia (C2n) chron, and the successive polarity-reversed intervals of the Matuyama chron respectively. After calibrated with the geomagnetic polarity timescale (GPTS), it is found that the sedimentation rate of core XT06 had an obvious change from fast to slow at 1.0～1.5 Ma, indicating a regional deep-water environment transition event, probably controlled by the tectonic activities related to the interaction between the Asian continent and the Pacific plate. (2) The core sediments are dominated by pelagic suspended matters, reflecting a weak sedimentary dynamic environment. Grain-size data further suggest that there occur two, coarse and fine, dynamic components in a compensated relationship, indicating a relatively stable dynamic environment. By comparisons with the proxies of global ice volume, deep-sea ventilation, and Inner Asian aridification, we proposed that regional tectonic activities with enhanced aridification and increased flux of aeolian input are the major factors to control the regional sedimentation on tectonic timescales, and the bottom-water circulation is the dominating factor on glacial-interglacial timescales. This paper presented some key sedimentary features for the central part of the Philippine Sea which may contribute much to the in-depth study of the coupling process of some key Earth systems.