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Reconstruction of the formation history of the Darwin Mounds, N Rockall Trough: How the dynamics of a sandy contourite affected cold-water coral growth

Reconstruction of the formation history of the Darwin Mounds, N Rockall Trough: How the dynamics of a sandy contourite affected cold-water coral growth
Reconstruction of the formation history of the Darwin Mounds, N Rockall Trough: How the dynamics of a sandy contourite affected cold-water coral growth
Cold-water coral mounds, formed through a feed-back process of cold-water coral growth and sediment baffling, have been studied all along the NE Atlantic continental margin. However, major questions remain concerning their formation history, especially their initiation and early development in relation to the surrounding sediment dynamics. For the first time, two small mounds located in a sandy contourite have been cored from the top to mound base: here, the formation history of the Darwin Mounds, located in the Northern Rockall Trough was investigated and reconstructed from two piston cores using a multidisciplinary approach. This consisted of CT-scanning for quantifying coral density changes with depth, grain-size analysis to obtain the hydrodynamic trends and radiocarbon and U-series dating to place the results into a wider paleoceanographic context. The results show that the Darwin Mounds formed during the early Holocene (~ 10 ka BP) through sediment baffling, mainly by Lophelia pertusa. The initiation of both mounds shows a similar pattern of increased current velocities resulting in coarser sediment deposition and a relatively high coral density with a peak of 23 vol%. The mound growth was rapid between ~ 10–9.7 ka BP (up to 277 cm ka? 1 in one of the mounds), with further vibrant growth periods around ~ 8.8 ka BP, 6.5 ka BP and 3.4 ka BP. The demise of the mounds ca. ~ 3 ka BP was likely caused by an intensification in bottom current velocities causing a hostile environment for coral growth in the contourite setting. In a wider context, the development of the Darwin Mounds appears to have responded to the relative strength and position of the Subpolar Gyre, which affected food supply to the corals, sedimentation rates, current speeds and other water mass properties in the area.
Lophelia pertusa, Cold-water coral mounds, North-east Atlantic, Darwin Mounds, Contourite, CT-scan
0025-3227
186-195
Victorero, Lissette
b9c0ee3a-6324-4276-8f40-6156d6e81c02
Blamart, Dominique
f1460df6-1b51-45a4-b6ec-405ecd83e4a8
Pons-Branchu, Edwige
0cc88582-3ff9-42a4-b5b7-2520c610c246
Mavrogordato, Mark N.
f3e0879b-118a-463a-a130-1c890e9ab547
Huvenne, Veerle A.I.
f22be3e2-708c-491b-b985-a438470fa053
Victorero, Lissette
b9c0ee3a-6324-4276-8f40-6156d6e81c02
Blamart, Dominique
f1460df6-1b51-45a4-b6ec-405ecd83e4a8
Pons-Branchu, Edwige
0cc88582-3ff9-42a4-b5b7-2520c610c246
Mavrogordato, Mark N.
f3e0879b-118a-463a-a130-1c890e9ab547
Huvenne, Veerle A.I.
f22be3e2-708c-491b-b985-a438470fa053

Victorero, Lissette, Blamart, Dominique, Pons-Branchu, Edwige, Mavrogordato, Mark N. and Huvenne, Veerle A.I. (2016) Reconstruction of the formation history of the Darwin Mounds, N Rockall Trough: How the dynamics of a sandy contourite affected cold-water coral growth. Marine Geology, 378, 186-195. (doi:10.1016/j.margeo.2015.12.001).

Record type: Article

Abstract

Cold-water coral mounds, formed through a feed-back process of cold-water coral growth and sediment baffling, have been studied all along the NE Atlantic continental margin. However, major questions remain concerning their formation history, especially their initiation and early development in relation to the surrounding sediment dynamics. For the first time, two small mounds located in a sandy contourite have been cored from the top to mound base: here, the formation history of the Darwin Mounds, located in the Northern Rockall Trough was investigated and reconstructed from two piston cores using a multidisciplinary approach. This consisted of CT-scanning for quantifying coral density changes with depth, grain-size analysis to obtain the hydrodynamic trends and radiocarbon and U-series dating to place the results into a wider paleoceanographic context. The results show that the Darwin Mounds formed during the early Holocene (~ 10 ka BP) through sediment baffling, mainly by Lophelia pertusa. The initiation of both mounds shows a similar pattern of increased current velocities resulting in coarser sediment deposition and a relatively high coral density with a peak of 23 vol%. The mound growth was rapid between ~ 10–9.7 ka BP (up to 277 cm ka? 1 in one of the mounds), with further vibrant growth periods around ~ 8.8 ka BP, 6.5 ka BP and 3.4 ka BP. The demise of the mounds ca. ~ 3 ka BP was likely caused by an intensification in bottom current velocities causing a hostile environment for coral growth in the contourite setting. In a wider context, the development of the Darwin Mounds appears to have responded to the relative strength and position of the Subpolar Gyre, which affected food supply to the corals, sedimentation rates, current speeds and other water mass properties in the area.

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Accepted/In Press date: 4 December 2015
Published date: 1 August 2016
Keywords: Lophelia pertusa, Cold-water coral mounds, North-east Atlantic, Darwin Mounds, Contourite, CT-scan
Organisations: Ocean and Earth Science, Marine Geoscience

Identifiers

Local EPrints ID: 385630
URI: http://eprints.soton.ac.uk/id/eprint/385630
ISSN: 0025-3227
PURE UUID: f9b89dee-bf87-4ce7-bfb8-43604d4be92d
ORCID for Veerle A.I. Huvenne: ORCID iD orcid.org/0000-0001-7135-6360

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Date deposited: 14 Jan 2016 14:04
Last modified: 10 Jan 2022 02:48

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Contributors

Author: Lissette Victorero
Author: Dominique Blamart
Author: Edwige Pons-Branchu
Author: Veerle A.I. Huvenne ORCID iD

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