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Deep-water sediment wave fields, bottom current sand channels and gravity flow channel-lobe systems: Gulf of Cadiz, NE Atlantic

Deep-water sediment wave fields, bottom current sand channels and gravity flow channel-lobe systems: Gulf of Cadiz, NE Atlantic
Deep-water sediment wave fields, bottom current sand channels and gravity flow channel-lobe systems: Gulf of Cadiz, NE Atlantic
A study of the seafloor of the Gulf of Cadiz west of the Strait of Gibraltar, using an integrated geophysical and sedimentological data set, gives new insights into sediment deposition from downslope thermohaline bottom currents. In this area, the Mediterranean Outflow (MO) begins to mix with North Atlantic waters and separates into alongslope geostrophic and downslope ageostrophic components. Changes in bedform morphology across the study area indicate a decrease in the peak velocity of the MO from >1 m s-1to <0·5 m s-1. The associated sediment waves form a continuum from sand waves to muddy sand waves to mud waves. A series of downslope-oriented channels, formed by the MO, are found where the MO starts to descend the continental slope at a water depth of &ap;700 m. These channels are up to 40 km long, have gradients of <0·5°, a fairly constant width of &ap;2 km and a depth of &ap;75 m. Sand waves move down the channels that have mud wave-covered levees similar to those seen in turbidite channel-levee systems, although the channel size and levee thickness do not decrease downslope as in typical turbidite channel systems. The channels terminate abruptly where the MO lifts off the seafloor. Gravity flow channels with lobes on the basin floor exist downslope from several of the bottom current channels. Each gravity flow system has a narrow, slightly sinuous channel, up to 20 m deep, feeding a depositional lobe up to 7 km long. Cores from the lobes recovered up to 8·5 m of massive, well-sorted, fine sand, with occasional mud clasts. This work provides an insight into the complex facies patterns associated with strong bottom currents and highlights key differences between bottom current and gravity flow channel-levee systems. The distribution of sand within these systems is of particular interest, with applications in understanding the architecture of hydrocarbon reservoirs formed in continental slope settings.
CADIZ GULF, SEDIMENT TRANSPORT, BOTTOM CURRENTS, CONTOURITES
0037-0746
483-510
Habgood, Edward L.
153de3e3-0bea-4df2-9d15-5bde240f43df
Kenyon, Neil H.
fc3aeb3d-7211-4765-b767-b91692b52724
Masson, Douglas G.
edd44c8b-38ca-45fb-8d0d-ac8365748a45
Akhmetzhanov, Andrey
20fd3070-f76f-4a05-8795-992dfa3ab10a
Weaver, Philip P. E.
c73e149f-6860-4a54-bbd9-0a4a40b85924
Gardner, Joan
4022531c-9129-4bdd-bcd0-b6774783606d
Mulder, Thierry
835eb1d7-c04d-4263-b6d5-3868e1485181
Habgood, Edward L.
153de3e3-0bea-4df2-9d15-5bde240f43df
Kenyon, Neil H.
fc3aeb3d-7211-4765-b767-b91692b52724
Masson, Douglas G.
edd44c8b-38ca-45fb-8d0d-ac8365748a45
Akhmetzhanov, Andrey
20fd3070-f76f-4a05-8795-992dfa3ab10a
Weaver, Philip P. E.
c73e149f-6860-4a54-bbd9-0a4a40b85924
Gardner, Joan
4022531c-9129-4bdd-bcd0-b6774783606d
Mulder, Thierry
835eb1d7-c04d-4263-b6d5-3868e1485181

Habgood, Edward L., Kenyon, Neil H., Masson, Douglas G., Akhmetzhanov, Andrey, Weaver, Philip P. E., Gardner, Joan and Mulder, Thierry (2003) Deep-water sediment wave fields, bottom current sand channels and gravity flow channel-lobe systems: Gulf of Cadiz, NE Atlantic. Sedimentology, 50 (3), 483-510. (doi:10.1046/j.1365-3091.2003.00561.x).

Record type: Article

Abstract

A study of the seafloor of the Gulf of Cadiz west of the Strait of Gibraltar, using an integrated geophysical and sedimentological data set, gives new insights into sediment deposition from downslope thermohaline bottom currents. In this area, the Mediterranean Outflow (MO) begins to mix with North Atlantic waters and separates into alongslope geostrophic and downslope ageostrophic components. Changes in bedform morphology across the study area indicate a decrease in the peak velocity of the MO from >1 m s-1to <0·5 m s-1. The associated sediment waves form a continuum from sand waves to muddy sand waves to mud waves. A series of downslope-oriented channels, formed by the MO, are found where the MO starts to descend the continental slope at a water depth of &ap;700 m. These channels are up to 40 km long, have gradients of <0·5°, a fairly constant width of &ap;2 km and a depth of &ap;75 m. Sand waves move down the channels that have mud wave-covered levees similar to those seen in turbidite channel-levee systems, although the channel size and levee thickness do not decrease downslope as in typical turbidite channel systems. The channels terminate abruptly where the MO lifts off the seafloor. Gravity flow channels with lobes on the basin floor exist downslope from several of the bottom current channels. Each gravity flow system has a narrow, slightly sinuous channel, up to 20 m deep, feeding a depositional lobe up to 7 km long. Cores from the lobes recovered up to 8·5 m of massive, well-sorted, fine sand, with occasional mud clasts. This work provides an insight into the complex facies patterns associated with strong bottom currents and highlights key differences between bottom current and gravity flow channel-levee systems. The distribution of sand within these systems is of particular interest, with applications in understanding the architecture of hydrocarbon reservoirs formed in continental slope settings.

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Published date: 2003
Keywords: CADIZ GULF, SEDIMENT TRANSPORT, BOTTOM CURRENTS, CONTOURITES

Identifiers

Local EPrints ID: 2033
URI: http://eprints.soton.ac.uk/id/eprint/2033
ISSN: 0037-0746
PURE UUID: 78141e86-e542-438e-8488-4bdd779f25d0

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Date deposited: 07 May 2004
Last modified: 15 Mar 2024 04:44

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Contributors

Author: Edward L. Habgood
Author: Neil H. Kenyon
Author: Douglas G. Masson
Author: Andrey Akhmetzhanov
Author: Philip P. E. Weaver
Author: Joan Gardner
Author: Thierry Mulder

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