Dss Studies Over Deccan Traps Along the Thuadara-Sendhwa-Sindad Profile, Across Narmada-Son Lineament, India

  1. Robert F. Mereu,
  2. Stephan Mueller and
  3. David M. Fountain
  1. K. L. Kaila,
  2. I. B. P. Rao,
  3. P. Koteswara Rao,
  4. N. Madhava Rao,
  5. V. G. Krishna and
  6. A. R. Sridhar

Published Online: 9 APR 2013

DOI: 10.1029/GM051p0127

Properties and Processes of Earth's Lower Crust

Properties and Processes of Earth's Lower Crust

How to Cite

Kaila, K. L., Rao, I. B. P., Rao, P. K., Rao, N. M., Krishna, V. G. and Sridhar, A. R. (1989) Dss Studies Over Deccan Traps Along the Thuadara-Sendhwa-Sindad Profile, Across Narmada-Son Lineament, India, in Properties and Processes of Earth's Lower Crust (eds R. F. Mereu, S. Mueller and D. M. Fountain), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM051p0127

Author Information

  1. National Geophysical Research Institute, Hyderabad 500007, India

Publication History

  1. Published Online: 9 APR 2013
  2. Published Print: 1 JAN 1989

ISBN Information

Print ISBN: 9780875904566

Online ISBN: 9781118666388

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Keywords:

  • Earth—Crust—Congresses;
  • Geophysics—Congresses

Summary

Deep Seismic Sounding (DSS) studies were carried out during 1984–85 along a 260 km long Thuadara-Sendhwa-Sindad profile across the Narmada-Son lineament in central India. Seismic refraction and wide angle reflection data have been recorded in the analog form from a dense coverage of shot points with geophone interval of 200 m. the crustal depth section along this profile was obtained in two parts: shallow and deeper sections. the shallow depth section down to the crystalline basement has been derived from first arrival travel times data of refracted waves from 25 shot points, while the deeper crustal section has been obtained from wide angle reflections data. 1-D velocity models for P waves, derived from several shot points data by forward modeling of travel time observations of refracted and reflected phases, were used to obtain an internally consistent 2-D velocity model along the profile. A low velocity layer probably of Mesozoic sediments (velocity 3.2–4.0 km/sec) with a maximum thickness of about 1.9 km below a thin layer (900 m) of the Deccan Traps (velocity 4.8–4.9 km/sec), has been inferred south of Narmada between Sendhwa and Savkheda from the shallow depth section successively refined by ray tracing. the Deccan Traps layer, with its thickness varying from 500 to 900 m, directly overlies the crystalline basement (velocity 6.0–6.2 km/sec) in the region north of Narmada. the upper crust above the crystalline basement reveals a block structure and the Narmada-Son lineament is reflected as a fault feature, to the south of which we infer a graben consisting of the Deccan Traps and the sub-Trappean sediments above the basement.

The deeper crustal section, initially obtained by migration of wide angle reflection data, has been iteratively refined by 2-D ray tracing and modeling of travel time observations corresponding to various boundaries. the crustal section obtained in the region, reveals a large number of reflectors at various depths down to the Moho boundary indicating a uniform crustal reflectivity, rather than a model consisting of a transparent upper crust and a relatively more reflective lower crust. the Moho depth varies from 38 to 43 km along this profile. the Moho shows a gentle upwarp, with a relief of about 2 km, in the region between Narmada and Tapti where the upper crustal graben above the crystalline basement has been delineated. the P velocity in the lower crust is found to be 6.8–6.9 km/sec. Although a high velocity ‘rift pillow' above the Moho has not been observed, the inferred structural features may be indicative of continental rifting in this region.