Evolving strain partitioning in the Eastern Himalaya: the growth of the Shillong Plateau

Yani Najman, Laura Bracciali, Randall R. Parrish, Emdad Chisty, Alex Copley

Research output: Contribution to journalArticlepeer-review


The Shillong Plateau is the only raised topography (up to 2000 m elevation) in the Himalayan foreland. It is proposed to have had a major influence on strain partitioning and thus tectonics in the Eastern Himalaya. Additionally, its position on the trajectory of the summer monsoon means it has influenced the regional climate, with reduced erosion rates proposed over geological timescales in its lee. The timing of surface uplift of the plateau has been difficult to determine. Exhumation rates have been calculated over geological timescales, but these seem at variance with estimates based upon extrapolating the present day velocity field measured with GPS, and it has thus been suggested that exhumation and surface uplift are decoupled. We determine the timing of surface uplift using the sedimentary record in the adjacent Surma Basin to the south, which records the transition from a passive margin with southward thickening sedimentary packages to a flexural basin with north-thickening strata, due to loading by the uplifting plateau. Our method involves using all available 2D seismic data for the basin, coupled to well tie information, to produce isochore maps and construct a simple model of the subsidence of the Surma basin in order to assess the timing and magnitude of flexural loading by the Shillong Plateau. We conclude that the major period of flexural loading occurred from the deposition of the Tipam Formation (3.5–∼2 Ma) onwards, which is likely to represent the timing of significant topographic growth of the Shillong Plateau. Our isochore maps and seismic sections also allow us to constrain the timing of thinning over the north–south trending anticlines of the adjacent basin-bounding Indo–Burman Ranges, as occurring over this same time interval. The combined effect of the uplift of the Shillong Plateau and the westward encroachment of the Indo–Burman Ranges to this region served to sever the palaeo-Brahmaputra drainage connection between Himalayan source and Surma Basin sink, at the end of Tipam Formation times (∼2 Ma).
Original languageEnglish
Pages (from-to)1-9
JournalEarth and Planetary Science Letters
Early online date29 Oct 2015
Publication statusPublished - 1 Jan 2016
Externally publishedYes


  • RCUK
  • NERC
  • NE/F01807X/1
  • NE/F017588/1


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