• Fulltext

       

        Click here to view fulltext PDF


      Permanent link:
      https://www.ias.ac.in/article/fulltext/jess/123/01/0033-0047

    • Keywords

       

      Afanasy Nikitin seamount; 85°E Ridge; Indian Ocean; 40Ar/39Ar dating; Conrad Rise hotspot; Marion Dufresne seamount.

    • Abstract

       

      The Afanasy Nikitin seamount (ANS) is a major structural feature (400 km-long and 150 km-wide) in the Central Indian Basin, situated at the southern end of the so-called 85°E Ridge. Combined analyses of new multibeam bathymetric, seismic reflection and geochronological data together with previously described magnetic data provide new insights into the growth of the ANS through time, and its relationship with the 85°E Ridge. The ANS comprises a main plateau, rising 1200 m above the surrounding ocean floor (4800 m), and secondary elevated seamount highs, two of which (lie at 1600 and 2050 m water depths) have the morphology of a guyot, suggesting that they were formed above or close to sea-level. An unbroken sequence of spreading anomalies 34 through 32n.1 identified over the ANS reveal that the main plateau of the ANS was formed at 80–73 Ma, at around the same time as that of the underlying oceanic crust. The 40Ar/39Ar dates for two basalt samples dredged from the seamount highs are consistent, within error, at 67 Ma. These results, together with published results of late Cretaceous to early Cenozoic Indian Ocean plate reconstructions, indicate that the Conrad Rise hotspot emplaced both the main plateau of the ANS and Conrad Rise (including the Marion Dufresne, Ob and Lena seamounts) at 80–73 Ma, close to the India–Antarctica Ridge system. Subsequently, the seamount highs were formed by late-stage volcanism c. 6–13 Myr after the main constructional phase of the seamount plateau. Flexural analysis indicates that the main plateau and seamount highs of the ANS are consistent with Airy-type isostatic compensation, which suggest emplacement of the entire seamount in a near spreading-center setting. This is contrary to the flexural compensation of the 85°E Ridge further north, which is interpreted as being emplaced in an intraplate setting, i.e., 25–35 Myr later than the underlying oceanic crust. Therefore, we suggest that the ANS and the 85°E Ridge appear to be unrelated as they were formed by different mantle sources, and that the proximity of the southern end of the 85°E Ridge to the ANS is coincidental.

    • Author Affiliations

       

      K S Krishna1 J M Bull2 O Ishizuka3 R A Scrutton4 S Jaishankar1 V K Banakar1

      1. CSIR – National Institute of Oceanography, Dona Paula, Goa 403 004, India.
      2. School of Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Southampton SO14 3ZH, UK.
      3. Geological Survey of Japan/AIST, Ibaraki, 305-8567, Japan.
      4. School of Geosciences, Edinburgh University, Edinburgh, EH9 3JW, UK.
    • Dates

       
  • Journal of Earth System Science | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.