Indian plate paleogeography, subduction and horizontal underthrusting below Tibet: paradoxes, controversies and opportunities

Indian continental lithosphere horizontally underthrusts and uplifts Tibet, providing the archetype of continental collision. This paper shows how this situation formed in the last 25 million years and outlines the paleogeographic and geodynamic consequences of pre-Miocene models, and the opportunities these provide for fundamental earth scientific research. The India-Asia collision zone is the archetype to calibrate geological responses to continent-continent collision, but hosts a paradox: there is no orogen-wide geological record of oceanic subduction after initial collision around 60-55 Ma, yet thousands of kilometers of post-collisional subduction occurred before the arrival of unsubductable continental lithosphere that currently horizontally underlies Tibet. Kinematically restoring incipient horizontal underthrusting accurately predicts geologically estimated diachronous slab break-off, unlocking the Miocene of Himalaya-Tibet as a natural laboratory for unsubductable lithosphere convergence. Additionally, three endmember paleogeographic scenarios exist with different predictions for the nature of post-collisional subducted lithosphere but each is defended and challenged based on similar data types. This paper attempts at breaking through this impasse by identifying how the three paleogeographic scenarios each challenge paradigms in geodynamics, orogenesis, magmatism or paleogeographic reconstruction and identify opportunities for methodological advances in paleomagnetism, sediment provenance analysis, and seismology to conclusively constrain Greater Indian paleogeography.

Automated summary

This paper explores the process of Indian continental lithosphere underthrusting and uplifting Tibet, and outlines the paleogeographic and geodynamic consequences of pre-Miocene models. By kinematically restoring the initial horizontal underthrusting, it accurately predicts the diachronous slab break-off and unlocks the Miocene of Himalaya-Tibet as a natural laboratory for unsubductable lithosphere convergence. Additionally, the paper discusses three different paleogeographic scenarios and their corresponding challenges and opportunities.