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| Titel |
Shallow water carbonate platforms (Late Aptian–Early Albian, Southern Apennines) in the context of supraregional to global changes: re-appraisal of palaeoecological events as reflectors of carbonate factory response |
| VerfasserIn |
A. Raspini |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 3, no. 2 ; Nr. 3, no. 2 (2012-08-20), S.225-249 |
| Datensatznummer |
250000985
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| Publikation (Nr.) |
 copernicus.org/se-3-225-2012.pdf |
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| Zusammenfassung |
This paper discusses the palaeoenvironmental significance of the
"Orbitolina Level", the microbial carbonates and the Salpingoporella dinarica-rich deposits
encased in the Aptian/Albian shallow water carbonate platform strata of
Monte Tobenna and Monte Faito (Southern Italy). These facies show a peculiar
field appearance due to their color and/or fossil content. In the shallow
water carbonate strata, the Late Aptian "Orbitolina Level" was formed
during a period of decreasing accommodation space. Microbial carbonates
occur in different levels in the composite section. They reach their maximum
thickness around the sequence boundaries just above the "Orbitolina Level"
and close to the Aptian–Albian transition, and were not deposited during
maximum flooding. S. dinarica-rich deposits occur in the lower part of the Monte
Tobenna-Monte Faito composite section, in both restricted and more open
lagoonal sediments. S. dinarica has its maximum abundance below the "Orbitolina
Level" and disappears 11 m above this layer.
On the basis of δ13C and δ18O values recorded at
Tobenna-Faito, the succession has been correlated to global
sea-level
changes and to the main volcanic and climatic events during the Aptian.
Deterioration of the inner lagoon environmental conditions was related to
high trophic levels triggered by volcano-tectonic activity. Microbial
carbonates were deposited especially in periods of third-order sea level
lowering. In such a scenario, periods of increased precipitation during the
Gargasian induced the mobilization of clay during flooding of the exposed
platform due to high-frequency sea-level changes, with consequent
terrigenous input to the lagoon. This and the high nutrient levels made the
conditions unsuitable for the principle carbonate producers, and an
opportunistic biota rich in orbitolinids (Mesorbitolina texana and M. parva) populated the platform. In
the more open marine domain, the increased nutrient input enhanced the
production of organic matter and locally led to the formation of black
shales (e.g. the Niveau Fallot in the Vocontian Basin).
It is argued that the concomitant low Mg/Ca molar ratio and high
concentration of calcium in seawater could have favoured the development of
the low-Mg calcite skeleton of the S. dinarica green algae.
During third-order sea-level rise, no or minor microbial carbonates formed in
the shallowlagoonal settings and S. dinarica disappeared. Carbonate neritic ecosystems
were not influenced by the environmental changes inferred to have been
induced by the mid-Cretaceous volcanism.
The "Orbitolina Level", the microbial carbonates and the Salpingoporella dinarica-rich deposits in
the studied Aptian/Albian shallow water carbonate strata are interpreted to
be the response to environmental and oceanographic changes in shallow-water
and deeper-marine ecosystems. |
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