1:45 PM - 2:00 PM
[SIT11-01] Philippine Sea and East Asian plate tectonics since 52 Ma constrained by new subducted slab reconstruction methods
Keywords:Philippine Sea plate, plate tectonic reconstructions, subducted slabs
In this study we show a Philippine Sea and adjacent East Asia plate tectonic reconstruction back to 52Ma constrained by twenty-eight slabs mapped in 3D from global tomography, with a total subducted area of ~25% of global oceanic lithosphere. New slab constraints include subducted parts of existing Pacific, Indo-Australian, and Philippine Sea oceans, plus the wholly subducted proto-South China Sea and the newly discovered "East Asian Sea" ocean. Mapped slabs were structurally restored to a spherical Earth surface using newly-developed unfolding methodologies and input to globally-consistent plate reconstructions using Gplates software.
Important new constraints include:
(1) the northern Philippine Sea Ryukyu slab is short (~1000 km) relative to >2000km northward Philippine Sea motion constrained by paleomagnetism. This requires an intervening, now-subducted ocean south of the Ryukyus and SW Japan in the Eocene. Our plate reconstructions show this to be the 'East Asia Sea' and the Pacific;
(2) the Marianas Pacific subduction zone remained within ±200 km of its present location since 48±10Ma based on a slab wall extending to >1000km depths;
(3) a major (8000 km x 2500 km) swath of lower mantle flat slabs represents a vanished "East Asia Sea" ocean that existed between the Pacific and Indian Oceans at 52Ma. The northern East Asia Sea played the role of the proto-Philippine Sea;
(4) the Caroline backarc basin moved with the Pacific based on an overlapping and coeval Caroline LIPS and hotspot track and proto-Caroline slab locations.
Our preferred plate model involves a Philippine Sea origin near the Manus plume (150°E/0°) at a Pacific-East Asian Sea junction. Large westward motion and post-40Ma clockwise rotation (~60°) were driven by late Eocene-Oligocene collision with the Caroline/Pacific plate. We predict a Miocene arc-arc collision between a northern Philippine Sea arc and the SW Japan-Ryukyu continental margin. Our observed slab age-depths fit within a 1.8±0.8 cm lower mantle sinking rate. Digital files, including plate-model animations and Gplates compatible unfolded slab shapes and rotation files will become publically available to serve as a platform for further refinements or testing alternative tectonic scenarios.