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Precession driven changes in terrestrial organic matter input to the Eastern Mediterranean leading up to the Messinian Salinity Crisis

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)199-211
Number of pages12
JournalEarth and Planetary Science Letters
Volume462
Early online date8 Feb 2017
DOIs
DateAccepted/In press - 24 Jan 2017
DateE-pub ahead of print - 8 Feb 2017
DatePublished (current) - 15 Mar 2017

Abstract

Eastern Mediterranean sediments over the past 12 Myr commonly show strongly developed precessional cyclicity, thought to be a biogeochemical response to insolation-driven freshwater input from run-off. The Mediterranean’s dominant freshwater source today and in the past, is the Nile, which is fed by North African monsoon rain; other, smaller, circum-Mediterranean rivers also contribute to Mediterranean hydrology. Crucially, run-off through all of these systems appears to vary with precession, but there is no direct evidence linking individual water sources to the biogeochemical response recorded in Mediterranean sediments. Consequently, it is not clear whether the North African monsoon is entirely responsible for the Mediterranean’s sedimentary cyclicity, or whether other, precessional signals, such as Atlantic storm precipitation, drive it.
Organic matter in sediments derives from both marine and terrestrial sources and biomarker analysis can be used to discriminate between the two, thereby providing insight into sedimentary and ecological processes. We analysed a wide range of lipids from the Late Miocene (6.6–5.9Ma) Pissouri section, southern Cyprus, and reconstructed the vegetation supplied to this region by measuring the carbon isotopes of the terrestrial component to identify its geographic source. BIT (Branched-Isoprenoidal-Tetraether) indices reflect changes in the relative abundance of marine vs terrestrial (soil) organic matter inputs, and with the exception of records from the last deglaciation, this work is the first application of the BIT approach to the reconstruction of orbital impacts on sedimentological processes. BIT indices show that the organic matter supplied to Cyprus changed over the course of each precession cycle and was dominantly terrestrial during insolation maxima when North African run-off was enhanced. The δ13C values from these intervals are compatible with tropical North African vegetation. However, the δ13C record indicates that during insolation minima, organic material supplied to southern Cyprus derives from a more arid source region. This is likely to have been aeolian-transported organic matter from the Anatolian Plateau demonstrating that even in Mediterranean sedimentary systems influenced by Nile run-off, there is more than one independent precessional organic matter contribution to the sedimentary cyclicity. Pissouri’s organic geochemistry also illustrates a long-term trend towards more saline Mediterranean conditions during the 600kyr leading up to the Messinian Salinity Crisis.

    Research areas

  • Mediterranean , BIT index, carbon isotopes, Messinian Salinity Crisis, terrestrial higher plant waxes, TEX86

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    Rights statement: This is the author accepted manuscript (AAM). The final published version (version of record) is available online via Elsevier at http://www.sciencedirect.com/science/article/pii/S0012821X17300419. Please refer to any applicable terms of use of the publisher.

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    Licence: CC BY-NC-ND

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