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Sill-controlled salinity contrasts followed post-Messinian flooding of the Mediterranean

Sill-controlled salinity contrasts followed post-Messinian flooding of the Mediterranean
Sill-controlled salinity contrasts followed post-Messinian flooding of the Mediterranean

A mile-high marine cascade terminated the Messinian salinity crisis 5.33 Myr ago, due to partial collapse of the Gibraltar sill that had isolated a largely desiccated Mediterranean from the Atlantic Ocean. Atlantic waters may have refilled the basin within 2 years. Prevailing hypotheses suggest that normal marine conditions were established across the Mediterranean immediately after the catastrophic flooding. Here we use proxy data and fluid physics-based modelling to show that normal conditions were likely for the western Mediterranean, but that flooding caused a massive transfer of salt from the western to the eastern Mediterranean across the Sicily sill, which became a hyper-salinity-stratified basin. Hyper-stratification inhibited deep-water ventilation, causing anomalously long-lasting organic-rich (sapropel) sediment deposition. Model data agreement indicates that hyper-stratification breakdown by diapycnal diffusion required 26,000 years. An alternative hypothesis that Atlantic reconnection occurred after the Mediterranean had largely been refilled is inconsistent with our observations, as this would have led to hyper-stratification and sapropel formation in both basins. Our findings offer insight into the role of stratification in delaying the re-establishment of normal marine conditions following abrupt refilling of a previously desiccated ocean basin.

1752-0894
720-725
Amarathunga, Udara
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Hogg, Andrew Mcc.
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Rohling, Eelco J.
a2a27ef2-fcce-4c71-907b-e692b5ecc685
Roberts, Andrew P.
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Grant, Katharine M.
f9d9fa1b-62f3-4e90-a6f0-b46bc213fdb2
Heslop, David
f32aae36-7f51-40e1-bf7d-54a561369a8d
Hu, Pengxiang
71cac3cf-6094-4ef1-a9ba-3e0a551a5559
Liebrand, Diederik
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Westerhold, Thomas
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Zhao, Xiang
e9d81687-994a-4ffc-9b44-872f8b455693
Gilmore, Stewart
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Amarathunga, Udara
5029978e-bdd2-478f-90b4-2428bad9b1c0
Hogg, Andrew Mcc.
b7d9aa01-9dae-4cfa-ab16-6a1ded2d6575
Rohling, Eelco J.
a2a27ef2-fcce-4c71-907b-e692b5ecc685
Roberts, Andrew P.
bfc571f6-9c7a-4cc5-8df9-2c41ef5ac2a1
Grant, Katharine M.
f9d9fa1b-62f3-4e90-a6f0-b46bc213fdb2
Heslop, David
f32aae36-7f51-40e1-bf7d-54a561369a8d
Hu, Pengxiang
71cac3cf-6094-4ef1-a9ba-3e0a551a5559
Liebrand, Diederik
474825f1-a867-4a2e-96cf-575fb58f4b91
Westerhold, Thomas
7b499943-ba7a-40e8-ae35-797594908d30
Zhao, Xiang
e9d81687-994a-4ffc-9b44-872f8b455693
Gilmore, Stewart
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Amarathunga, Udara, Hogg, Andrew Mcc., Rohling, Eelco J., Roberts, Andrew P., Grant, Katharine M., Heslop, David, Hu, Pengxiang, Liebrand, Diederik, Westerhold, Thomas, Zhao, Xiang and Gilmore, Stewart (2022) Sill-controlled salinity contrasts followed post-Messinian flooding of the Mediterranean. Nature Geoscience, 15 (9), 720-725. (doi:10.1038/s41561-022-00998-z).

Record type: Article

Abstract

A mile-high marine cascade terminated the Messinian salinity crisis 5.33 Myr ago, due to partial collapse of the Gibraltar sill that had isolated a largely desiccated Mediterranean from the Atlantic Ocean. Atlantic waters may have refilled the basin within 2 years. Prevailing hypotheses suggest that normal marine conditions were established across the Mediterranean immediately after the catastrophic flooding. Here we use proxy data and fluid physics-based modelling to show that normal conditions were likely for the western Mediterranean, but that flooding caused a massive transfer of salt from the western to the eastern Mediterranean across the Sicily sill, which became a hyper-salinity-stratified basin. Hyper-stratification inhibited deep-water ventilation, causing anomalously long-lasting organic-rich (sapropel) sediment deposition. Model data agreement indicates that hyper-stratification breakdown by diapycnal diffusion required 26,000 years. An alternative hypothesis that Atlantic reconnection occurred after the Mediterranean had largely been refilled is inconsistent with our observations, as this would have led to hyper-stratification and sapropel formation in both basins. Our findings offer insight into the role of stratification in delaying the re-establishment of normal marine conditions following abrupt refilling of a previously desiccated ocean basin.

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Sill-controlled salinity contrasts main text - Accepted Manuscript
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More information

Accepted/In Press date: 29 June 2022
e-pub ahead of print date: 11 August 2022
Published date: September 2022
Additional Information: Funding Information: We thank D. Garcia-Castellanos for providing essential instructions on developing the Mediterranean reflooding model. We also thank P. Meijer for providing the latest Mediterranean hypsometry reconstruction. Study material on fluid dynamics provided by B. Cushman-Roisin encouraged initial model development. This work contributes to Australian Research Council projects FL120100050 and DP2000101157 (E.J.R.), DE190100042 (K.M.G.), DP190100874 (A.P.R.), and the Australia‐New Zealand IODP Consortium (ANZIC) Legacy/Special Analytical Funding grant LE160100067 (Katharine Mary Grant (K.M.G.), Laura Rodriguez Sanz (L.R.S.)). Publisher Copyright: © 2022, The Author(s), under exclusive licence to Springer Nature Limited.

Identifiers

Local EPrints ID: 470339
URI: http://eprints.soton.ac.uk/id/eprint/470339
ISSN: 1752-0894
PURE UUID: 2f25ba61-0108-45c6-b5f0-aa6ec3db1b85
ORCID for Eelco J. Rohling: ORCID iD orcid.org/0000-0001-5349-2158

Catalogue record

Date deposited: 06 Oct 2022 16:56
Last modified: 08 Oct 2022 01:34

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Contributors

Author: Udara Amarathunga
Author: Andrew Mcc. Hogg
Author: Andrew P. Roberts
Author: Katharine M. Grant
Author: David Heslop
Author: Pengxiang Hu
Author: Diederik Liebrand
Author: Thomas Westerhold
Author: Xiang Zhao
Author: Stewart Gilmore

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