Testing Proto-South China Sea Plate Reconstructions by Data Assimilation into TERRA Global Mantle Convection Models
Abstract
The South China Sea lies at a key junction between major plates (i.e. Pacific, Eurasian and Indo-Australian), which is one of the most tectonically complex regions in the world. A great diversity of plate reconstructions has been proposed for the South China Sea area since the Cenozoic. The conventional plate model suggested one-sided, southward Proto-South China Sea subduction beneath Borneo during Eocene and Early Miocene (e.g. Hall and Breitfield, 2017; Holloway, 1982; Taylor and Hayes, 1983) whereas an alternative study proposed double-sided Proto South China Sea subduction within the same time period (Wu and Suppe, 2017). A recent mantle flow model assimilated a conventional-style plate model (Zahirovic et al., 2016) and, despite many valuable insights, did not clearly reproduce a well-known, sub-horizontal fast slab anomaly in the mantle below present-day South China Sea at 500-700 km depth from tomography. Furthermore, the predicted dynamic topography from a conventional-style plate model implied dynamic subsidence since 40 Ma in Sundaland (Yang et al., 2016). In contrast, slow shear wave velocities, free-air gravity anomalies, and mafic magmatic histories suggest positive dynamic support since 20 Ma at Borneo and the Sunda Shelf (Roberts et al., 2018).
This study assimilates these two end-member plate models into otherwise similar TERRA numerical models, with an aim to compare the predicted mantle structure against imaged mantle structure from tomography and the dynamic topography to test plate model viability. The computational domain is discretized on a regular grid based on the icosahedron, for a total of 80 million grid points and a resolution of 25 km, allowing us to simulate convection in the same regime as the real Earth. We implement the plate models as a set of continuously closing plates in order to generate a global self-consistent velocity field to be assimilated into the convection models. We will compare our mantle model prediction with seismic tomography, and our implied dynamic topography with regional topography variations, to test the likelihood of proposed proto-South China Sea plate tectonic reconstructions.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T31D0339L
- Keywords:
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- 8104 Continental margins: convergent;
- TECTONOPHYSICSDE: 8105 Continental margins: divergent;
- TECTONOPHYSICSDE: 8157 Plate motions: past;
- TECTONOPHYSICSDE: 8178 Tectonics and magmatism;
- TECTONOPHYSICS