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Red Sea isolation history suggested by Plio-Pleistocene seismic reflection sequences

Red Sea isolation history suggested by Plio-Pleistocene seismic reflection sequences
Red Sea isolation history suggested by Plio-Pleistocene seismic reflection sequences
High evaporation rates in the desert climate of the Red Sea ensure that, during glacial sea level lowstands when water exchange with the Indian Ocean was more restricted, water salinity and ?18O?18O became unusually extreme. Modeling of the effect on Red Sea sedimentary ?18O?18O has been used previously to reconstruct relative sea level to 500 ka and now poses the question of whether that sea-level model could be extended if continuous core material of older sediment became available. We attempt to address this question here by examining seismic reflection data. The upper Pleistocene hemipelagic sediments in the Red Sea contain intervals of inorganic aragonite precipitated during supersaturated conditions of sea-level lowstands. Seismic impedance changes associated with boundaries to those aragonite-rich layers appear to explain seismic reflection sequences. A segment of Chirp sediment profiler data from the central Red Sea reveals prominent reflections at ?1, ?5, ?23, ?26 and ?36 ms two-way travel time (TWT) from the seabed. Based on depths to the glacial marine isotope stages (MIS) in cores, we relate the upper three reflections to the tops of aragonite-rich layers and hence the sea level rises immediately following MIS 2, 6 and 12. The reflection at 26 ms is related to an unusually rapid fall into MIS 12 predicted by one sea level reconstruction, which may have created an abrupt lower boundary to the MIS 12 aragonite-rich layer. With the aid of seismogram modeling, we tentatively associate the ?36 ms reflection with the top of an aragonite-rich layer formed during MIS 16. Furthermore, some segments of lower frequency (airgun and sparker) seismic data from the central and southern Red Sea show a lower (earlier) Plio-Pleistocene (PP) interval that is less reflective than the upper (late) PP interval. This implies less variability in sediment impedance and that extreme variability in water salinity did not develop; water exchange with the Indian Ocean likely continued throughout this interval. These results suggest that viable relative sea level reconstructions may be recovered from Red Sea sediment ?18O?18O data to at least MIS 16 and perhaps even as far back as the early Pliocene.
sea level, seismogram model, chirp sonar, Red Sea, aragonite layers, oxygen isotopes
0012-821X
387-397
Mitchell, Neil C.
886e2111-8c8a-4c91-acd7-b378948b4779
Ligi, Marco
1a79ed96-f508-4f55-abcd-a8263152caf9
Rohling, Eelco J.
a2a27ef2-fcce-4c71-907b-e692b5ecc685
Mitchell, Neil C.
886e2111-8c8a-4c91-acd7-b378948b4779
Ligi, Marco
1a79ed96-f508-4f55-abcd-a8263152caf9
Rohling, Eelco J.
a2a27ef2-fcce-4c71-907b-e692b5ecc685

Mitchell, Neil C., Ligi, Marco and Rohling, Eelco J. (2015) Red Sea isolation history suggested by Plio-Pleistocene seismic reflection sequences. Earth and Planetary Science Letters, 430, 387-397. (doi:10.1016/j.epsl.2015.08.037).

Record type: Article

Abstract

High evaporation rates in the desert climate of the Red Sea ensure that, during glacial sea level lowstands when water exchange with the Indian Ocean was more restricted, water salinity and ?18O?18O became unusually extreme. Modeling of the effect on Red Sea sedimentary ?18O?18O has been used previously to reconstruct relative sea level to 500 ka and now poses the question of whether that sea-level model could be extended if continuous core material of older sediment became available. We attempt to address this question here by examining seismic reflection data. The upper Pleistocene hemipelagic sediments in the Red Sea contain intervals of inorganic aragonite precipitated during supersaturated conditions of sea-level lowstands. Seismic impedance changes associated with boundaries to those aragonite-rich layers appear to explain seismic reflection sequences. A segment of Chirp sediment profiler data from the central Red Sea reveals prominent reflections at ?1, ?5, ?23, ?26 and ?36 ms two-way travel time (TWT) from the seabed. Based on depths to the glacial marine isotope stages (MIS) in cores, we relate the upper three reflections to the tops of aragonite-rich layers and hence the sea level rises immediately following MIS 2, 6 and 12. The reflection at 26 ms is related to an unusually rapid fall into MIS 12 predicted by one sea level reconstruction, which may have created an abrupt lower boundary to the MIS 12 aragonite-rich layer. With the aid of seismogram modeling, we tentatively associate the ?36 ms reflection with the top of an aragonite-rich layer formed during MIS 16. Furthermore, some segments of lower frequency (airgun and sparker) seismic data from the central and southern Red Sea show a lower (earlier) Plio-Pleistocene (PP) interval that is less reflective than the upper (late) PP interval. This implies less variability in sediment impedance and that extreme variability in water salinity did not develop; water exchange with the Indian Ocean likely continued throughout this interval. These results suggest that viable relative sea level reconstructions may be recovered from Red Sea sediment ?18O?18O data to at least MIS 16 and perhaps even as far back as the early Pliocene.

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More information

Published date: 15 November 2015
Keywords: sea level, seismogram model, chirp sonar, Red Sea, aragonite layers, oxygen isotopes
Organisations: Paleooceanography & Palaeoclimate

Identifiers

Local EPrints ID: 385114
URI: http://eprints.soton.ac.uk/id/eprint/385114
ISSN: 0012-821X
PURE UUID: 217dfc35-4ad2-4c18-a7c8-74337a2909e8
ORCID for Eelco J. Rohling: ORCID iD orcid.org/0000-0001-5349-2158

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Date deposited: 15 Dec 2015 17:20
Last modified: 15 Mar 2024 02:47

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Author: Neil C. Mitchell
Author: Marco Ligi

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