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Sand wave fields beneath the Loop Current, Gulf of Mexico: Reworking of fan sands

Marine Geology

By:
, , and
DOI: 10.1016/S0025-3227(02)00560-1

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Abstract

Extensive fields of large barchan-like sand waves and longitudinal sand ribbons have been mapped by deep-towed SeaMARC IA sidescan sonar on part of the middle and lower Mississippi Fan that lies in about 3200 m of water. The area is beneath the strongly flowing Loop Current. The bedforms have not been adequately sampled but probably consist of winnowed siliciclastic-foraminiferal sands. The size (about 200 m from wingtip to wingtip) and shape of the large barchans is consistent with a previously observed peak current speed of 30 cm/s, measured 25 m above the seabed. The types of small-scale bedforms and the scoured surfaces of chemical crusts, seen on nearby bottom photographs, indicate that near-bed currents in excess of 30 cm/s may sometimes occur. At the time of the survey the sand transport direction was to the northwest, in the opposite direction to the Loop Current but consistent with there being a deep boundary current along the foot of the Florida Escarpment. Some reworking of the underlying sandy turbidites and debris flow deposits is apparent on the sidescan sonar records. Reworking by deep-sea currents, resulting in erosion and in deposits characterised by coarsening upwards structures and cross-bedding, is a process that has been proposed for sand found in cores in shallower parts of the Gulf of Mexico. This process is more widespread than hitherto supposed. ?? 2002 Published by Elsevier Science B.V.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Sand wave fields beneath the Loop Current, Gulf of Mexico: Reworking of fan sands
Series title:
Marine Geology
DOI:
10.1016/S0025-3227(02)00560-1
Volume
192
Issue:
1-3
Year Published:
2002
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Marine Geology
First page:
297
Last page:
307