A Window Into Eastern Mediterranean Productivity Conditions Over Three Pliocene Precession-Forced Climate Cycles
Cutmore, A.; Bale, N.; De Lange, G. J.; Nijenhuis, I. A.; Lourens, L. J.
(2023) Paleoceanography and Paleoclimatology, volume 38, issue 4, pp. 1 - 19
(Article)
Abstract
Here, we explore the importance of export productivity versus anoxia in the formation of sedimentary layers with enhanced total organic carbon (TOC) content. We use geochemical, sedimentological and micropaleontological records from two SW Sicily outcropping successions, Lido Rossello (LR) and Punta di Maiata (PM), over three Early Pliocene precession-forced climate
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cycles (4.7–4.6 million years ago [Ma]). Gray marls, deposited during precession minima, show enhanced TOC in both records. We suggest that basin-wide, low-oxygenated bottom-waters, resulting from freshwater-induced stratification during precession minimum, was integral to preserving gray marl TOC. Furthermore, prolonged eastern Mediterranean stratification may have produced a deep chlorophyll maximum (DCM), leading to “shade-flora” dominated productivity. The LR succession displays two unique laminated layers containing enhanced TOC. These laminations do not occur at specific times in the precession cycle or in time-equivalent PM samples. They are likely to have been produced by an intermittent dysoxic/anoxic pool at LR, caused by a local depression, which enhanced TOC preservation. Consequently, the laminations provide a rare window into “true” eastern Mediterranean productivity conditions during precession maxima, as organic matter is typically poorly preserved during these period due to enhanced ventilation. The laminated “windows” indicate that eastern Mediterranean export productivity may not have been significantly lower during precession maxima compared to precession minima, as previously thought. During these periods, productivity conditions are likely to have been comparable to the modern eastern Mediterranean, with a spring-bloom caused by enhanced winter/spring deep-water mixing preceding a summer “shade-flora” bloom caused by a summer-stratification induced DCM.
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Keywords: anoxia, Mediterranean, Pliocene, preservation, productivity, sapropel, Oceanography, Atmospheric Science, Palaeontology
ISSN: 2572-4517
Publisher: Wiley Online Library
Note: Funding Information: Samples would not have been collected without the aid of F.J. Hilgen, W. Krijgsman and C. E. Duermeijer. For technical support with the geochemical, micropaleontological, and stable isotope analyses we thank P. Anten, D. van de Meent, A. van Dijk, G. Nobbe, H. de Waard, T. Zalm, T. Broer, G. J. van het Veld and G. Ittman. We also thank L. Pronk and L. Stille for picking and analyzing the planktonic and benthic foraminiferal specimen for their stable isotope composition. Special thanks goes to H. Schrader and L. Beaufort, whom carried out preliminary studies on the diatom and nannofossil contents of the samples, respectively. This long‐standing study was partly funded by the Netherlands Organization for Scientific Research (NWO), through the PIONEER program of F.J. Hilgen, VIDI program of L. J. Lourens, and the Netherlands Earth System Science Centre (NESSC). Publisher Copyright: © 2023 The Authors.
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