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Proceedings Paper

Use of GPR in developing a facies model for a large sandy braided river, Brahmaputra River, Bangladesh
Author(s): C. S. Bristow; J. L. Best; P. J. Ashworth
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Paper 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.

Paper Details

Date Published: 27 April 2000
PDF: 6 pages
Proc. SPIE 4084, Eighth International Conference on Ground Penetrating Radar, (27 April 2000); doi: 10.1117/12.383543
Show Author Affiliations
C. S. Bristow, Univ. of London (United Kingdom)
J. L. Best, Univ. of Leeds (United Kingdom)
P. J. Ashworth, Univ. of Leeds (United Kingdom)

Published in SPIE Proceedings Vol. 4084:
Eighth International Conference on Ground Penetrating Radar
David A. Noon; Glen F. Stickley; Dennis Longstaff, Editor(s)

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