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Oceanographic and climatic evolution of the Miocene Mediterranean deduced from Nd, Sr, C, and O isotope compositions of marine fossils and sediments

Oceanographic and climatic evolution of the Miocene Mediterranean deduced from Nd, Sr, C, and O isotope compositions of marine fossils and sediments
Oceanographic and climatic evolution of the Miocene Mediterranean deduced from Nd, Sr, C, and O isotope compositions of marine fossils and sediments
Isotopic compositions of marine sediments and fossils have been investigated from northern basins of the Mediterranean to help constrain local oceanographic and climatic changes adjacent to the uplifting Alps. Stable C and O isotope compositions of benthic and planktonic foraminifera from the Umbria-Marche region (UMC) have an offset characteristic for their habitats and the changes in composition mimic global changes, suggesting that the regional conditions of climate and the carbon cycle were controlled by global changes. The radiogenic isotope composition of these fossil assemblages allows recognition of three distinct periods. In the first period, from 25 to 19 Ma, high Nd values and low 87Sr/86Sr of sediments and fossils support intense tectonism and volcanism, related to the opening of the western Mediterranean. In the second period, from 19 to 13 Ma the 87Sr/86Sr ratio of Mediterranean (UMC) deviate from the global ocean, which is compatible with rapid uplift of the hinterland and intense influx of Sr from Mesozoic carbonates of the western Apennines. This local control on the seawater was driven by a humid and warm climate and indicates restricted exchange of water with the global ocean. Generally, the Nd values of the fossils are very similar to those of Indian Ocean water, with brief periods of a decrease in the Nd values coinciding with volcanic events and maybe sea level variation at 15.2 Ma. In the third period, from 13 to 10 Ma the fossils have 87Sr/86Sr similar to those of Miocene seawater while their Nd values change considerably with time. This indicates fluctuating influence of the Atlantic versus the Paratethys and/or locally evolved seawater in the Mediterranean driven by global sea level changes. Other investigated localities near the Alps and from the ODP 900 site are compatible with this oceanographic interpretation. However, in the late early Miocene, enhanced local control, reflecting erosion of old crustal silicate rocks near the Alps, results in higher 87Sr/86Sr.
isotopes, Miocene, Mediterranean
0883-8305
PA4211
Kocsis, L.
e36a251b-9630-4769-b517-9e223968e601
Vennemann, T.W.
c91252fe-d4da-41ee-a331-ec072df75c66
Fontignie, D.
0f6fb746-03be-4d79-8c07-9047a17edd8e
Baumgartner, C.
7acb0659-4ef8-41e3-b40d-c8a8b97e7bc7
Montanari, A.
05bdc8ce-59ae-4a7b-b936-54ac369420ae
Jelen, B.
f4e49b29-c16d-48a7-b4fe-be66a32cd773
Kocsis, L.
e36a251b-9630-4769-b517-9e223968e601
Vennemann, T.W.
c91252fe-d4da-41ee-a331-ec072df75c66
Fontignie, D.
0f6fb746-03be-4d79-8c07-9047a17edd8e
Baumgartner, C.
7acb0659-4ef8-41e3-b40d-c8a8b97e7bc7
Montanari, A.
05bdc8ce-59ae-4a7b-b936-54ac369420ae
Jelen, B.
f4e49b29-c16d-48a7-b4fe-be66a32cd773

Kocsis, L., Vennemann, T.W., Fontignie, D., Baumgartner, C., Montanari, A. and Jelen, B. (2008) Oceanographic and climatic evolution of the Miocene Mediterranean deduced from Nd, Sr, C, and O isotope compositions of marine fossils and sediments. Paleoceanography, 23, PA4211. (doi:10.1029/2007PA001540).

Record type: Article

Abstract

Isotopic compositions of marine sediments and fossils have been investigated from northern basins of the Mediterranean to help constrain local oceanographic and climatic changes adjacent to the uplifting Alps. Stable C and O isotope compositions of benthic and planktonic foraminifera from the Umbria-Marche region (UMC) have an offset characteristic for their habitats and the changes in composition mimic global changes, suggesting that the regional conditions of climate and the carbon cycle were controlled by global changes. The radiogenic isotope composition of these fossil assemblages allows recognition of three distinct periods. In the first period, from 25 to 19 Ma, high Nd values and low 87Sr/86Sr of sediments and fossils support intense tectonism and volcanism, related to the opening of the western Mediterranean. In the second period, from 19 to 13 Ma the 87Sr/86Sr ratio of Mediterranean (UMC) deviate from the global ocean, which is compatible with rapid uplift of the hinterland and intense influx of Sr from Mesozoic carbonates of the western Apennines. This local control on the seawater was driven by a humid and warm climate and indicates restricted exchange of water with the global ocean. Generally, the Nd values of the fossils are very similar to those of Indian Ocean water, with brief periods of a decrease in the Nd values coinciding with volcanic events and maybe sea level variation at 15.2 Ma. In the third period, from 13 to 10 Ma the fossils have 87Sr/86Sr similar to those of Miocene seawater while their Nd values change considerably with time. This indicates fluctuating influence of the Atlantic versus the Paratethys and/or locally evolved seawater in the Mediterranean driven by global sea level changes. Other investigated localities near the Alps and from the ODP 900 site are compatible with this oceanographic interpretation. However, in the late early Miocene, enhanced local control, reflecting erosion of old crustal silicate rocks near the Alps, results in higher 87Sr/86Sr.

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Published date: November 2008
Keywords: isotopes, Miocene, Mediterranean

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Local EPrints ID: 64702
URI: http://eprints.soton.ac.uk/id/eprint/64702
ISSN: 0883-8305
PURE UUID: 0978ad92-c166-4b55-807a-ba25ce2c59e1

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Date deposited: 07 Jan 2009
Last modified: 15 Mar 2024 12:01

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Contributors

Author: L. Kocsis
Author: T.W. Vennemann
Author: D. Fontignie
Author: C. Baumgartner
Author: A. Montanari
Author: B. Jelen

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