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| Titel |
The sedimentary expression of the Aptian/Albian OAE 1b in the North Atlantic: a comparative study |
| VerfasserIn |
João Trabucho Alexandre, Roeland van Gilst, Juan Pedro Rodríguez-López, Poppe L. de Boer |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250035965
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| Zusammenfassung |
| In the Mesozoic, the combination of particular basin physiographies with a greenhouse
climate and enhanced tectono-volcanic activity resulted in palaeoceanographic conditions
which were favourable for the production, export and preservation of organic matter in the
marine realm. Oceanic anoxic events (OAEs) are stratigraphic intervals in the Mesozoic
which are defined by excursions in the carbon isotope record resulting from perturbations in
the global carbon cycle. The local lithologic expression of an OAE, i.e. whether marine
sediments are organic-rich or not at a particular location and in what sediment type the OAE
has been recorded, depends on palaeogeographic and depositional setting as well as on local
climate.
The Aptian/Albian OAE 1b is composed of one Aptian event and two Albian events with a
latest Aptian eustatic sea level fall separating them. The second sub-event (Early Albian,
Hedbergella planispira Zone), known as Paquier Level, is defined by a negative excursion in
the carbon isotope record and has an organic-rich sedimentary record in the Western Tethys
(Mediterranean), the North Atlantic and in Mexico. The isotopic signal is remarkably similar
between North Atlantic sites and allows their stratigraphic correlation. Furthermore, the good
agreement between the North Atlantic carbon isotope record and that of the open ocean
Resolution Guyot (Pacific) suggests that the negative excursion associated with this event is
indeed a primary global signal. The other two sub-events are apparently absent in the
North Atlantic, although at least their chemostratigraphic signature is expected to be
present.
For the present study, a total of 124 samples from Deep Sea Drilling Program (DSDP) Site
545 (Mazagan Plateau) and Ocean Drilling Program (ODP) sites 1049 (Blake Nose) and 1276
(Newfoundland Basin) were collected and analysed. The grain size distribution of the
siliciclastic fraction of all samples was determined and the grains examined using a
scanning electron microscope (SEM). Stable carbon isotopes of organic matter, total
organic carbon (TOC) content and Rock-Eval parameters were determined. Sediment
geochemistry was studied using inductively coupled plasma optical emission spectrometry
(ICP-OES).
Based on our results, we show that, despite sharing a common set of global forcing
mechanisms, organic-rich sediments deposited during OAEs are the result of different
combinations of equifinal processes acting on a local scale. |
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