Magnetostratigraphy and Authigenic ¹⁰ Be/ ⁹ Be Dating of Plio‐Pleistocene Abyssal Surficial Sediments on the Southern Slope of Mariana Trench and Sedimentary Processes During the Mid‐Pleistocene Transition

The Mariana Trench is the deepest part of Earth's surface, with a maximum depth of close to 11,000 m in the Challenger Deep. Great progress has been made in studying the trench in the past years; however, several basic issues regarding the sedimentology and geochronology of the abyssal surficial sediments in the trench remain unclear. In this study, two gravity cores of Plio‐Pleistocene sediments were retrieved from the southern slope of the Mariana Trench. They were used for an integrated investigation of magnetostratigraphy, authigenic 10 Be/ 9 Be dating, and element manganese content. The principal results are as follows. (1) Ten magnetozones are recognized for Core A25, which can be correlated to the geomagnetic polarity time scale from Chrons C1n to C3r. (2) The paleomagnetic and 10 Be/ 9 Be‐based ages agree well for both of the two cores, yielding a continuous depositional hiatus since the middle Pleistocene (0.63–0.74 Ma). (3) The sediment accumulation rates prior to ~1.3 Ma are 35–83 cm/Myr and then increased substantially to 167–200 cm/Myr. Based on these results, a sedimentary transition at ~1.3–1.2 Ma is confirmed, which can be potentially correlated to climatic, oceanic, and tectonic changes in the Mid‐Pleistocene transition. In addition, an elemental Mn proxy is derived to reflect changes in bottom‐water ventilation, which is consistent with Lower Circumpolar Deep Water and North Atlantic Deep Water on glacial‐interglacial time scales. We conclude that the sedimentary record of the Mariana Trench provides a unique window for investigating the integrated effects of long‐term climatic, oceanic, and tectonic processes.