Use of GPR in developing a facies model for a large sandy braided river, Brahmaputra River, Bangladesh

C. S. Bristow; J. L. Best; P. J. Ashworth

doi:10.1117/12.383543

27 April 2000 Use of GPR in developing a facies model for a large sandy braided river, Brahmaputra River, Bangladesh

C. S. Bristow, J. L. Best, P. J. Ashworth

Proceedings Volume 4084, Eighth International Conference on Ground Penetrating Radar; (2000) https://doi.org/10.1117/12.383543
Event: 8th International Conference on Ground Penetrating Radar, 2000, Gold Coast, Australia

Abstract

A large (2 km X 1 km) sand bar has been surveyed using ground penetrating radar (GPR), augmented by vibracoring and trenching, to investigate the sedimentary structures and three-dimensional alluvial architecture. Around 8 Km of GPR profiles were collected with nine survey lines running transversely across the bar at 250 m intervals with a profile along the bar. Profiles image structures beneath the water table to depths of up to 15 m. Reflectors from GPR profiles are interpreted as sets of cross-stratification, channel erosion surfaces, bar slipface accretion, mud-drapes, upstream accretion surfaces and the water table. Elements of upstream, downstream, lateral and cross-channel accretion are identified. Apart from the preservation of a range of dunes, the dominant style of deposition within the bar is oblique downstream and cross-channel bar margin accretion with large low angle and angle-of-repose foresets. These GPR facies characteristics are used to construct a three-dimensional model of facies architecture which may be applied in the interpretation of ancient braided alluvium. Bounding surfaces on the GPR can be tied to earlier bathymetric profiles, yielding a unique insight into the chronology of sedimentation and bar evolution. Trenching and coring of the bar top confirms that dunes and bar-margin slipfaces are the predominant facies units.

Citation Download Citation

C. S. Bristow, J. L. Best, and P. J. Ashworth "Use of GPR in developing a facies model for a large sandy braided river, Brahmaputra River, Bangladesh", Proc. SPIE 4084, Eighth International Conference on Ground Penetrating Radar, (27 April 2000); https://doi.org/10.1117/12.383543

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