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Ground-penetrating radar stratigraphy and dynamics of megaflood gravel dunes

Ground-penetrating radar stratigraphy and dynamics of megaflood gravel dunes
Ground-penetrating radar stratigraphy and dynamics of megaflood gravel dunes
Ground-penetrating radar was used to elucidate the stratigraphy of late Pleistocene gravel dunes in the Altai
Mountains of southern Siberia that formed when a lake emptied as a result of ice-dam failure. Survey-lines across dunes had a resolution of decimetres, with depth penetration of 20 m. The reflections identify bounding surfaces and radar facies. Two classes of unconformities are identified: (1) an erosional unconformity at the base of the dunes; (2) steeply inclined unconformities
that truncate underlying inclined reflections and are downlapped by overlying inclined reflections within the dunes. Unconformities define six radar facies (RF): RF 1, basal subhorizontal discordant reflections; RF 2, poorly defined discordant reflections; RF 3, planar inclined reflections; RF 4, sigmoidal inclined reflections; RF 5, trough fills; RF 6, low-angle inclined reflections. The basal unconformity represents the flood-cut surface, across which the dunes migrated. The inclined unconformities may be interpreted in two ways: (1) erosional surfaces induced by unsteady flow within one flood, or (2)erosional surfaces developed by a series of floods reactivating dunes left stranded by previous floods. The evidence favours the latter model, which is consistent with the occurrence of several dune-forming events within the basin. The broader implications of the study are considered with respect to investigations of megaflood bedforms worldwide.
0016-7649
550-559
Carling, Paul A.
8d252dd9-3c88-4803-81cc-c2ec4c6fa687
Bristow, Charles S.
d3caf6ec-2e17-4f58-8212-0b7a0885c7f0
Litvinov, Alexei S.
4eb598c5-585e-411c-bdd0-b235fbde115f
Carling, Paul A.
8d252dd9-3c88-4803-81cc-c2ec4c6fa687
Bristow, Charles S.
d3caf6ec-2e17-4f58-8212-0b7a0885c7f0
Litvinov, Alexei S.
4eb598c5-585e-411c-bdd0-b235fbde115f

Carling, Paul A., Bristow, Charles S. and Litvinov, Alexei S. (2016) Ground-penetrating radar stratigraphy and dynamics of megaflood gravel dunes. Journal of the Geological Society, 173 (3), 550-559. (doi:10.1144/jgs2015-119).

Record type: Article

Abstract

Ground-penetrating radar was used to elucidate the stratigraphy of late Pleistocene gravel dunes in the Altai
Mountains of southern Siberia that formed when a lake emptied as a result of ice-dam failure. Survey-lines across dunes had a resolution of decimetres, with depth penetration of 20 m. The reflections identify bounding surfaces and radar facies. Two classes of unconformities are identified: (1) an erosional unconformity at the base of the dunes; (2) steeply inclined unconformities
that truncate underlying inclined reflections and are downlapped by overlying inclined reflections within the dunes. Unconformities define six radar facies (RF): RF 1, basal subhorizontal discordant reflections; RF 2, poorly defined discordant reflections; RF 3, planar inclined reflections; RF 4, sigmoidal inclined reflections; RF 5, trough fills; RF 6, low-angle inclined reflections. The basal unconformity represents the flood-cut surface, across which the dunes migrated. The inclined unconformities may be interpreted in two ways: (1) erosional surfaces induced by unsteady flow within one flood, or (2)erosional surfaces developed by a series of floods reactivating dunes left stranded by previous floods. The evidence favours the latter model, which is consistent with the occurrence of several dune-forming events within the basin. The broader implications of the study are considered with respect to investigations of megaflood bedforms worldwide.

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Accepted/In Press date: 13 November 2015
e-pub ahead of print date: 22 January 2016
Published date: May 2016
Organisations: Earth Surface Dynamics

Identifiers

Local EPrints ID: 396748
URI: https://eprints.soton.ac.uk/id/eprint/396748
ISSN: 0016-7649
PURE UUID: 2dc84259-01a7-4423-894d-dc08d78856d7

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Date deposited: 13 Jun 2016 15:14
Last modified: 09 Jan 2018 18:03

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Contributors

Author: Paul A. Carling
Author: Charles S. Bristow
Author: Alexei S. Litvinov

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