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Reventilation episodes during the Sapropel S1 Deposition in the eastern Mediterranean based on Holococcolith Preservation

Reventilation episodes during the Sapropel S1 Deposition in the eastern Mediterranean based on Holococcolith Preservation
Reventilation episodes during the Sapropel S1 Deposition in the eastern Mediterranean based on Holococcolith Preservation
Organic‐rich layers (sapropels), preserved in eastern Mediterranean marine sediment records, represent pronounced perturbations to thermohaline circulation and environmental conditions in the basin, in response to enhanced African monsoon activity and subsequent massive freshwater discharge. During the most recent event, Sapropel S1 formed between 10.8 and 6.1 ka, when freshwater‐driven stratification caused seafloor anoxia below ~1,800‐m depth, as a result of both failure of deep water formation and enhanced productivity. Here we analyze coccolith assemblages from the open eastern Mediterranean that form a west‐east transect across the basin and provide insights on past environmental changes. We focus on holococcoliths, which are specifically produced by coccolithophores as part of their life cycle during the haploid phase. Since holococcolith calcification is characterized by nanocrystals highly susceptible to dissolution, we are testing their potential preservation under different bottom environmental conditions, including the effect of postdepositional oxidation. A comparison with benthic foraminifera assemblages in a core recovered close to Lybia reveals that holococcolith preservation is enhanced during seafloor reventilation and benthic foraminiferal repopulation in the middle to upper part of the record, before the actual sapropel termination. There are two such events of improved deep‐water oxygenation in the Aegean and Adriatic Seas at 8.2 and 7.4 ka. The latter episode marks the onset of the transition to restored circulation in the eastern Mediterranean Sea, due to resumption of deep‐water formation in the southern Aegean Sea and the conclusion of enhanced biogenic productivity.
2572-4517
Incarbona, Alessandro
a45b3f2f-cde8-488d-9bd6-5989a7823573
Abu‐zied, Ramadan H.
e4a292ae-b985-464d-819b-e0958194f299
Rohling, Eelco J.
a2a27ef2-fcce-4c71-907b-e692b5ecc685
Ziveri, Patrizia
7c2b4b39-88dd-4765-abac-40405843d220
Incarbona, Alessandro
a45b3f2f-cde8-488d-9bd6-5989a7823573
Abu‐zied, Ramadan H.
e4a292ae-b985-464d-819b-e0958194f299
Rohling, Eelco J.
a2a27ef2-fcce-4c71-907b-e692b5ecc685
Ziveri, Patrizia
7c2b4b39-88dd-4765-abac-40405843d220

Incarbona, Alessandro, Abu‐zied, Ramadan H., Rohling, Eelco J. and Ziveri, Patrizia (2019) Reventilation episodes during the Sapropel S1 Deposition in the eastern Mediterranean based on Holococcolith Preservation. Paleoceanography and Paleoclimatology. (doi:10.1029/2019PA003626).

Record type: Article

Abstract

Organic‐rich layers (sapropels), preserved in eastern Mediterranean marine sediment records, represent pronounced perturbations to thermohaline circulation and environmental conditions in the basin, in response to enhanced African monsoon activity and subsequent massive freshwater discharge. During the most recent event, Sapropel S1 formed between 10.8 and 6.1 ka, when freshwater‐driven stratification caused seafloor anoxia below ~1,800‐m depth, as a result of both failure of deep water formation and enhanced productivity. Here we analyze coccolith assemblages from the open eastern Mediterranean that form a west‐east transect across the basin and provide insights on past environmental changes. We focus on holococcoliths, which are specifically produced by coccolithophores as part of their life cycle during the haploid phase. Since holococcolith calcification is characterized by nanocrystals highly susceptible to dissolution, we are testing their potential preservation under different bottom environmental conditions, including the effect of postdepositional oxidation. A comparison with benthic foraminifera assemblages in a core recovered close to Lybia reveals that holococcolith preservation is enhanced during seafloor reventilation and benthic foraminiferal repopulation in the middle to upper part of the record, before the actual sapropel termination. There are two such events of improved deep‐water oxygenation in the Aegean and Adriatic Seas at 8.2 and 7.4 ka. The latter episode marks the onset of the transition to restored circulation in the eastern Mediterranean Sea, due to resumption of deep‐water formation in the southern Aegean Sea and the conclusion of enhanced biogenic productivity.

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Accepted/In Press date: 25 August 2019
Published date: 3 September 2019

Identifiers

Local EPrints ID: 435092
URI: https://eprints.soton.ac.uk/id/eprint/435092
ISSN: 2572-4517
PURE UUID: 3675924a-3bc0-441a-b1f4-23148783108a
ORCID for Eelco J. Rohling: ORCID iD orcid.org/0000-0001-5349-2158

Catalogue record

Date deposited: 22 Oct 2019 16:30
Last modified: 10 Dec 2019 01:55

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