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Re-evaluation of mobile shale occurrences on seismic sections of the Champion and Baram deltas, offshore Brunei
Van Rensbergen, P.; Morley, C. K. (2003). Re-evaluation of mobile shale occurrences on seismic sections of the Champion and Baram deltas, offshore Brunei, in: Van Rensbergen, P. et al. Subsurface sediment mobilization. Geological Society Special Publication, 216: pp. 395-409
In: Van Rensbergen, P. et al. (2003). Subsurface sediment mobilization. Geological Society Special Publication, 216. Geological Society: United Kingdom. ISBN 1862391416. 522 pp., more
In: Hartley, A.J. et al. (Ed.) Geological Society Special Publication. Geological Society of London: Oxford; London; Edinburgh; Boston, Mass.; Carlton, Vic.. ISSN 0305-8719, more
Peer reviewed article  

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  • Van Rensbergen, P., more
  • Morley, C. K.

Abstract
    3D seismic data in the Baram and Champion delta provinces offshore Brunei show that regions thought to be occupied entirely by chaotic seismic data and conventionally interpreted as shale diapirs, are regions of dimmed, but coherent reflectivity. Such data indicate shale diapir masses are not present, instead dimming can be attributed to sediment intrusive complexes, overpressured fluids and gas clouds, or processing artefacts. In this way significant delta structures are masked on 2D seismic data, which are important to interpret delta tectonic evolution. The Middle Miocene-Recent Champion and Baram deltaic provinces are characterized by typical gravity tectonics-related structures. However, being situated on an active margin they are also affected by episodic development of contractional structures, which are located on older reactive shale bulges and result in inversion of motion on some growth faults. The emplacement of shale pipes, gas clouds and intrusive complexes is generally relatively late (Pliocene) in comparison with the underlying reactive diapirs (Late Miocene) and their emplacement events may be separated in time by several million years. Late overpressured systems may be related to phases of pore fluid pressure increase during or following periods of inversion tectonics, which resulted in phases of enhanced fluid migration in the basin, where fluids were either expelled laterally oceanwards, or vertically.

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