Constraints of subducted slabs under the Indian Ocean on the northward motion of India from Gondwanaland towards Eurasia
We find an extensive swath of slabs in the lower mantle under the Indian Ocean at depths of 1000-2200km, with shallower slabs to the north under India and Eurasia at ~200-1500km. These slabs closely correspond to the well-known track that India has travelled northward from Gondwanaland toward its collision with Eurasia, viewed in the Indo-Atlantic moving hotspot reference frame, and account for a significant proportion of the predicted loss of the Ceno- and Neo-Tethyan Oceans since ~140Ma. Our work is based on our methodology of  mapping subducted slabs in global tomography (MITP08, Li et al. 2008) as 3D mid-slab surfaces in the Gocad environment,  quantitatively unfolding these surfaces to the surface of the earth in a spherical Earth model, minimizing changes in area and distortion, and  incorporating them into Gplates global plate tectonic reconstructions (http://www.earthbyte.org). These unfolded subducted slabs provide substantial quantitative constraints for the original location and extent of India and Greater India and for the nature and history of Ceno- and Neo-Tethys. We observe a distinct discontinuity in amplitude of p- and s-wave velocity anomalies between the higher-amplitude Neo-Tethyan slabs to the north under India and the Middle East and the lower-amplitude Ceno-Tethyan slabs under the central Indian Ocean, which is in agreement with a predicted large ~100Ma discontinuity in age-at-subduction between Neo- and Ceno-Tethys in existing plate-tectonic models (e.g. Müller et al., 2008; Seton et al, 2012). We present a plate tectonic reconstruction that incorporates these mapped slab constraints, with the implication that a substantial fraction of the Tethyan Ocean (~3000km) subducted southward under India at an early stage in the northward motion of India from Gondwanaland.
EGU General Assembly Conference Abstracts
- Pub Date:
- April 2013