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| Titel |
Bridging the Faraoni and Selli oceanic anoxic events: late Hauterivian to early Aptian dysaerobic to anaerobic phases in the Tethys |
| VerfasserIn |
K. B. Föllmi, M. Bôle, N. Jammet, P. Froidevaux, A. Godet, S. Bodin, T. Adatte, V. Matera, D. Fleitmann, J. E. Spangenberg |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 8, no. 1 ; Nr. 8, no. 1 (2012-01-30), S.171-189 |
| Datensatznummer |
250005367
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| Publikation (Nr.) |
 copernicus.org/cp-8-171-2012.pdf |
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| Zusammenfassung |
A detailed geochemical analysis was performed on the
upper part of the Maiolica Formation in the Breggia (southern Switzerland)
and Capriolo sections (northern Italy). The analysed sediments consist of
well-bedded, partly siliceous, pelagic carbonate, which lodges numerous
thin, dark and organic-rich layers. Stable-isotope, phosphorus,
organic-carbon and a suite of redox-sensitive trace-element contents (RSTE: Mo, U, Co, V and As)
were measured. The RSTE pattern and Corg:Ptot
ratios indicate that most organic-rich layers were deposited under
dysaerobic rather than anaerobic conditions and that latter conditions were
likely restricted to short intervals in the latest Hauterivian, the early
Barremian and the pre-Selli early Aptian.
Correlations are both possible with organic-rich intervals in central Italy
(the Gorgo a Cerbara section) and the Boreal Lower Saxony Basin, as well as
with the facies and drowning pattern in the Helvetic segment of the northern
Tethyan carbonate platform. Our data and correlations suggest that the
latest Hauterivian witnessed the progressive installation of dysaerobic
conditions in the Tethys, which went along with the onset in sediment
condensation, phosphogenesis and platform drowning on the northern Tethyan
margin, and which culminated in the Faraoni anoxic episode. This episode is
followed by further episodes of dysaerobic conditions in the Tethys and the
Lower Saxony Basin, which became more frequent and progressively stronger in
the late early Barremian. Platform drowning persisted and did not halt
before the latest early Barremian. The late Barremian witnessed diminishing
frequencies and intensities in dysaerobic conditions, which went along with
the progressive installation of the Urgonian carbonate platform. Near the
Barremian-Aptian boundary, the increasing density in dysaerobic episodes in
the Tethyan and Lower Saxony Basins is paralleled by a change towards
heterozoan carbonate production on the northern Tethyan shelf. The following
return to more oxygenated conditions is correlated with the second phase of
Urgonian platform growth and the period immediately preceding and
corresponding to the Selli anoxic episode is characterised by renewed
platform drowning and the change to heterozoan carbonate production. Changes
towards more humid climate conditions were the likely cause for the
repetitive installation of dys- to anaerobic conditions in the Tethyan and
Boreal basins and the accompanying changes in the evolution of the carbonate
platform towards heterozoan carbonate-producing ecosystems and
platform drowning. |
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