Magnetostratigraphy of Abyssal Deposits in the Central Philippine Sea and Regional Sedimentary Dynamics During the Quaternary

The Philippine Sea is a typical region of aeolian dust reposition and is located within the Western Pacific Warm Pool. Here, we use the paleomagnetic stratigraphy and the grain-size distributions of Quaternary abyssal deposits in the Central Philippine Sea to investigate the factors controlling regional sedimentary and paleoenvironmental changes. Our principal results are as follows: (a) A reliable geochronologic framework for Quaternary sediments in the Central Philippine Sea is established. (b) An eastward expansion of the regional depocenter in the Middle Pleistocene is observed. (c) The mean grain size of the abyssal sediments is 7-8 mu m, and there are only minor differences between the sites. Comparison of the geochronological framework with various paleoenvironmental events during the Mid-Pleistocene Transition shows that sedimentary processes can be correlated to a major transition in global climate which affected regions from the Asian interior to the tropical Pacific, and that changes in aeolian sedimentation are likely the predominant factor responsible. A derived grain-size proxy of the sedimentary dynamics and its comparison with various paleoenvironmental proxies show that the relative contributions are roughly estimated as 23%, 9%, and 68% for aeolian inputs, oceanic circulation, and the tropical Pacific zonal SST gradient, respectively, in the studied region. The relative importance of tropical processes in abyssal sedimentary dynamics highlights the possibility of the long-term influence of (sub)mesoscale eddies in the upper ocean, via regional upwelling and unique submarine topography, on the deepest part (>5,000 m) of the Central Philippine Sea, from meteorological to geological timescales.