Structural Characteristics of the Andaman Forearc Inferred from Interpretation of Multichannel Seismic Reflection Data
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We thank the Director, National Centre for Antarctic and Ocean Research, Goa, for providing facilities and giving permission to submit this manuscript. We are also thankful to the Directorate General of Hydrocarbons for providing the multi-channel seismic (MCS) reflection data. We are grateful to the reviewers for providing detailed reviews and comments that significantly improved the manuscript. This is NCAOR contribution 16/2014.


Structural Characteristics of the Andaman Forearc Inferred from Interpretation of Multichannel Seismic Reflection Data
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    摘要:

    The Andaman Forearc Basin (AFB) is asymmetric in configuration and filled with a ~6 km-thick pile of Neogene to Recent sediments (~4 s in two-way travel time: TWT) with distinct zonation. It shows gradual thinning up to ~3 km (0.8 s in TWT) towards the eastern end with a seabed gradient of 1:30. Thick deformed sediments ~2 s (TWT) of the Outerarc are associated with intense faulting and occasional folding caused by recent tectonics. Development of a series of faults within the upwarped sedimentary column of Oligocene top to Recent is observed with a rotated fault block. These features are manifestations of Recent igneous intrusion, and reveal the presence of a mild N–S compressional regime. Its effect on the AFB resulted in further uplift of sediments, which can now be seen as the Invisible Bank. Forward gravity modelling supporting our seismic interpretation reveals that it is associated with igneous intrusion from the Moho (~9 km depth), and also suggests that continental crust underlies the AFB. Strong Bottom Simulating Reflector (BSR)-like features in the Miocene sediments of Outerarc and Forearc basin at a depth of 0.6 s below the seabed suggest the inferred probable occurrence of gas hydrates in the AFB.

    Abstract:

    The Andaman Forearc Basin (AFB) is asymmetric in configuration and filled with a ~6 km-thick pile of Neogene to Recent sediments (~4 s in two-way travel time: TWT) with distinct zonation. It shows gradual thinning up to ~3 km (0.8 s in TWT) towards the eastern end with a seabed gradient of 1:30. Thick deformed sediments ~2 s (TWT) of the Outerarc are associated with intense faulting and occasional folding caused by recent tectonics. Development of a series of faults within the upwarped sedimentary column of Oligocene top to Recent is observed with a rotated fault block. These features are manifestations of Recent igneous intrusion, and reveal the presence of a mild N–S compressional regime. Its effect on the AFB resulted in further uplift of sediments, which can now be seen as the Invisible Bank. Forward gravity modelling supporting our seismic interpretation reveals that it is associated with igneous intrusion from the Moho (~9 km depth), and also suggests that continental crust underlies the AFB. Strong Bottom Simulating Reflector (BSR)-like features in the Miocene sediments of Outerarc and Forearc basin at a depth of 0.6 s below the seabed suggest the inferred probable occurrence of gas hydrates in the AFB.

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Anitha, GOLI* and Dhananjai K. Pandey.2014. Structural Characteristics of the Andaman Forearc Inferred from Interpretation of Multichannel Seismic Reflection Data[J]. ACTA GEOLOGICA SINICA(English edition),88(4):1145~1156

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  • 收稿日期:2014-02-11
  • 最后修改日期:2014-04-25
  • 在线发布日期: 2014-09-01
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