Geo-Marine Letters

, Volume 20, Issue 1, pp 10–19

Gas and fluid venting at the Makran accretionary wedge off Pakistan

Authors

  • U. von Rad
    • BGR, P.O. Box 510153, 30631 Hannover, Germany e-mail: U.vonRad@bgr.de
  • U. Berner
    • BGR, P.O. Box 510153, 30631 Hannover, Germany e-mail: U.vonRad@bgr.de
  • G. Delisle
    • BGR, P.O. Box 510153, 30631 Hannover, Germany e-mail: U.vonRad@bgr.de
  • H. Doose-Rolinski
    • BGR, P.O. Box 510153, 30631 Hannover, Germany e-mail: U.vonRad@bgr.de
  • N. Fechner
    • BGR, P.O. Box 510153, 30631 Hannover, Germany e-mail: U.vonRad@bgr.de
  • P. Linke
    • GEOMAR, Wischhofstr. 1–3, 24148 Kiel, Germany
  • A. Lückge
    • BGR, P.O. Box 510153, 30631 Hannover, Germany e-mail: U.vonRad@bgr.de
  • H. A. Roeser
    • BGR, P.O. Box 510153, 30631 Hannover, Germany e-mail: U.vonRad@bgr.de
  • R. Schmaljohann
    • Institut für Meereskunde, Düsternbrooker Weg 20, 24105 Kiel, Germany
  • M. Wiedicke
    • BGR, P.O. Box 510153, 30631 Hannover, Germany e-mail: U.vonRad@bgr.de
  •  SONNE 122/130 Scientific Parties
    • BGR, P.O. Box 510153, 30631 Hannover, Germany
  • M. Block
    • BGR, P.O. Box 510153, 30631 Hannover, Germany
  • V. Damm
    • BGR, P.O. Box 510153, 30631 Hannover, Germany
  • J. Erbacher
    • BGR, P.O. Box 510153, 30631 Hannover, Germany
  • J. Fritsch
    • BGR, P.O. Box 510153, 30631 Hannover, Germany
  • B. Harazim
    • BGR, P.O. Box 510153, 30631 Hannover, Germany
  • J. Poggenburg
    • BGR, P.O. Box 510153, 30631 Hannover, Germany
  • G. Scheeder
    • BGR, P.O. Box 510153, 30631 Hannover, Germany
  • B. Schreckenberger
    • BGR, P.O. Box 510153, 30631 Hannover, Germany
  • N. von Mirbach
    • GEOMAR, Wischhofstr. 1–3, 24148 Kiel, Germany
  • M. Drews
    • Institut für Meereskunde, Düsternbrooker Weg 20, 24105 Kiel, Germany
  • S. Walter
    • Institut für Meereskunde, Düsternbrooker Weg 20, 24105 Kiel, Germany
  • A. Ali Khan
    • National Institute of Oceanography, 47 S.T., Karachi, Pakistan
  • A. Inam
    • National Institute of Oceanography, 47 S.T., Karachi, Pakistan
  • M. Tahir
    • National Institute of Oceanography, 47 S.T., Karachi, Pakistan
  • A. R. Tabrez
    • National Institute of Oceanography, 47 S.T., Karachi, Pakistan
  • A. H. Cheema
    • Hydrocarbon Development Institute of Pakistan, P.O. Box 1308, Islamabad, Pakistan
  • M. Pervaz
    • Hydrocarbon Development Institute of Pakistan, P.O. Box 1308, Islamabad, Pakistan
  • M. Ashraf
    • Office of Deputy Hydrographer of Pakistan Navy, 11 Liaquat Barracks, Karachi, Pakistan

DOI: 10.1007/s003670000033

Cite this article as:
von Rad, U., Berner, U., Delisle, G. et al. Geo-Marine Letters (2000) 20: 10. doi:10.1007/s003670000033

Abstract

The Makran accretionary complex shows a distinct bottom-simulating reflector, indicating a thick gas-hydrate-bearing horizon between the deformational front and about 1350 m water depth which seals off the upward flow of gas-charged fluids. A field of presently inactive mud diapirs with elevations up to 65 m was discovered in the abyssal plain seawards of the deformation front, suggesting that in the past conditions were favorable for periodic but localized vigorous mud diapirism. Regional destabilization of the gas hydrate leading to focused flow was observed where deep-penetrating, active faults reach the base of the gas-hydrate layer, as in a deeply incised submarine canyon (2100–2500 m water depth). At this location we discovered seeps of methane and H2S-rich fluids associated with chemoautotrophic vent faunas (e.g., Calyptogena sp.). Driven by the accretionary wedge dynamics, the landward part of the gas-hydrate layer below the Makran margin is being progressively uplifted. Due to reduced hydrostatic pressure and rising ocean bottom-water temperatures, gas hydrates are progressively destabilized and dissociated into hydrate water, methane and H2S. Sediment temperatures lie outside the methane stability field wherever water depth is less than 800 m. Above this depth, upward migration of fluids to the seafloor is unimpeded, thus explaining the abundance of randomly distributed gas seeps observed at water depths of 350 to 800 m.

Copyright information

© Springer-Verlag Berlin Heidelberg 2000