TY - JOUR

T1 - High-resolution reconstructions and GPS estimates of India-Eurasia and India-Somalia plate motions: 20 Ma to the present

AU - DeMets, C.

AU - Merkouriev, S.

AU - Jade, Sridevi

N1 - Funding Information: We thank Jean-Phillipe Avouac, Jeff Freymueller and Peter Molnar for reviews that significantly improved the manuscript. This work was supported by grant 06-05-64297 from the Russian Foundation for Basic Research and U.S. National Science Foundation grant OCE-1433323. Sridevi Jade acknowledges the support and encouragement of Head, CSIR-4PI for the GPS programme of CSIR-4PI, and all the scientific and technical personnel involved in operating and maintaining the Indian continuous GPS stations. Continuous GPS data were provided by (1) the Global GNSS Network operated by UNAVCO for NASA Jet Propulsion Laboratory under NSF Co-operative Agreement No. EAR-1261833, (2) the Scripps Orbit and Permanent Array Center and (3) the NOAA CORS archive. Figures were drafted using Generic Mapping Tools software (Wessel & Smith 1991).

PY - 2020/2/1

Y1 - 2020/2/1

N2 - We reconstruct the movement of the India Plate relative to Eurasia at ≈1-Myr intervals from 20 Ma to the present from GPS site velocities and high-resolution sequences of rotations from the India-Somalia-Antarctic-Nubia-North America-Eurasia Plate circuit. The plate circuit rotations, which are all estimated using the same data fitting functions, magnetic reversal sampling points, calibrations for magnetic reversal outward displacement, and noise mitigation methods, include new India-Somalia rotations estimated from numerous Carlsberg and northern Central Indian ridge plate kinematic data and high-resolution rotations from the Southwest Indian Ridge that account for slow motion between the Nubia and Somalia plates. Our new rotations indicate that India-Somalia plate motion slowed down by 25-30 per cent from 19.7 to 12.5-11.1 Ma, but remained steady since at least 9.8 Ma and possibly 12.5 Ma. Our new India-Eurasia rotations predict a relatively simple plate motion history, consisting of NNE-directed interplate convergence since 19 Ma, a ≈50 per cent convergence rate decrease from 19.7 to 12.5-11.1 Ma, and steady or nearly steady plate motion since 12.5-11.1 Ma. Instantaneous convergence rates estimated with our new India-Eurasia GPS angular velocity are 16 per cent slower than our reconstructed plate kinematic convergence rates for times since 2.6 Ma, implying either a rapid, recent slowdown in the convergence rate or larger than expected errors in our geodetic and/or plate kinematic estimates. During an acceleration of seafloor faulting within the wide India-Capricorn oceanic boundary at 8-7.5 Ma, our new rotations indicate that the motions of the India Plate relative to Somalia and Eurasia remained steady. We infer that forces acting on the Capricorn rather than the India Plate were responsible for the accelerated seafloor deformation, in accord with a previous study. India-Eurasia displacements that are predicted with our new, well-constrained rotations are fit poorly by a recently proposed model that attributes the post-60-Ma slowdown in India-Eurasia convergence rates to the steady resistance of a strong lithospheric mantle below Tibet.

AB - We reconstruct the movement of the India Plate relative to Eurasia at ≈1-Myr intervals from 20 Ma to the present from GPS site velocities and high-resolution sequences of rotations from the India-Somalia-Antarctic-Nubia-North America-Eurasia Plate circuit. The plate circuit rotations, which are all estimated using the same data fitting functions, magnetic reversal sampling points, calibrations for magnetic reversal outward displacement, and noise mitigation methods, include new India-Somalia rotations estimated from numerous Carlsberg and northern Central Indian ridge plate kinematic data and high-resolution rotations from the Southwest Indian Ridge that account for slow motion between the Nubia and Somalia plates. Our new rotations indicate that India-Somalia plate motion slowed down by 25-30 per cent from 19.7 to 12.5-11.1 Ma, but remained steady since at least 9.8 Ma and possibly 12.5 Ma. Our new India-Eurasia rotations predict a relatively simple plate motion history, consisting of NNE-directed interplate convergence since 19 Ma, a ≈50 per cent convergence rate decrease from 19.7 to 12.5-11.1 Ma, and steady or nearly steady plate motion since 12.5-11.1 Ma. Instantaneous convergence rates estimated with our new India-Eurasia GPS angular velocity are 16 per cent slower than our reconstructed plate kinematic convergence rates for times since 2.6 Ma, implying either a rapid, recent slowdown in the convergence rate or larger than expected errors in our geodetic and/or plate kinematic estimates. During an acceleration of seafloor faulting within the wide India-Capricorn oceanic boundary at 8-7.5 Ma, our new rotations indicate that the motions of the India Plate relative to Somalia and Eurasia remained steady. We infer that forces acting on the Capricorn rather than the India Plate were responsible for the accelerated seafloor deformation, in accord with a previous study. India-Eurasia displacements that are predicted with our new, well-constrained rotations are fit poorly by a recently proposed model that attributes the post-60-Ma slowdown in India-Eurasia convergence rates to the steady resistance of a strong lithospheric mantle below Tibet.

KW - Indian Ocean

KW - Plate motions

UR - http://www.scopus.com/inward/record.url?scp=85085618861&partnerID=8YFLogxK

U2 - 10.1093/gji/ggz508

DO - 10.1093/gji/ggz508

M3 - Article

VL - 220

SP - 1149

EP - 1171

JO - Geophysical Journal International

JF - Geophysical Journal International

SN - 0956-540X

IS - 2

ER -