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New neodymium isotope data quantify Nile involvement in Mediterranean anoxic episodes

Record type: Article

The development of widespread anoxic conditions in the deep oceans is evidenced by the accumulation and preservation of organic-carbon–rich sediments, but its precise cause remains controversial. The two most popular hypotheses involve (1) circulation-induced increased stratification resulting in reduced oxygenation of deep waters or (2) enhanced productivity in the surface ocean, increasing the raining down of organic matter and overwhelming the oxic remineralization potential of the deep ocean. In the periodic development of deep-water anoxia in the Pliocene–Pleistocene Mediterranean Sea, increased riverine runoff has been implicated both as a source for nutrients that fuel enhanced photic-zone productivity and a source of a less dense freshwater cap leading to reduced circulation, basin-wide stagnation, and deep-water oxygen starvation. Monsoon-driven increases in Nile River discharge and increased regional precipitation due to enhanced westerly activity—two mechanisms that represent fundamentally different climatic driving forces—have both been suggested as causes of the altered freshwater balance. Here we present data that confirm a distinctive neodymium (Nd) isotope signature for the Nile River relative to the Eastern Mediterranean—providing a new tracer of enhanced Nile outflow into the Mediterranean in the past. We further present Nd isotope data for planktonic foraminifera that suggest a clear increase in Nile discharge during the central intense period of two recent anoxic events. Our data also suggest, however, that other regional freshwater sources were more important at the beginning and end of the anoxic events. Taken at face value, the data appear to imply a temporal link between peaks in Nile discharge and enhanced westerly activity.

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Citation

Scrivner, A.E., Vance, D. and Rohling, E.J. (2004) New neodymium isotope data quantify Nile involvement in Mediterranean anoxic episodes Geology, 32, (7), pp. 565-568. (doi:10.1130/G20419.1).

More information

Published date: 2004
Keywords: anoxia, Mediterranean, Nile River, monsoon, foraminifera, neodymium isotopes

Identifiers

Local EPrints ID: 11048
URI: http://eprints.soton.ac.uk/id/eprint/11048
ISSN: 0091-7613
PURE UUID: b479fdb8-ae02-4f36-975f-a0138cc99d8c
ORCID for E.J. Rohling: ORCID iD orcid.org/0000-0001-5349-2158

Catalogue record

Date deposited: 18 Oct 2004
Last modified: 17 Jul 2017 17:05

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Contributors

Author: A.E. Scrivner
Author: D. Vance
Author: E.J. Rohling ORCID iD

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