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| Titel |
Oceanic Anoxic Event 1b: insights and new data from the Poggio le Guaine section (Umbria–Marche Basin) |
| VerfasserIn |
Nadia Sabatino, Mario Sprovieri, Rodolfo Coccioni, Daniela Salvagio Manta, Silvia Gardin, François Baudin |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104640
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| Publikation (Nr.) |
 EGU/EGU2015-4071.pdf |
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| Zusammenfassung |
| The upper Aptian to lower Albian interval (~114–109 Ma) represents a crucial period during
Earth’s history, with a major evolution in the nature of mid–Cretaceous tectonics, sea level,
climate, and marine plankton communities. Interestingly, it also includes multiple prominent
black shale horizons that are the sedimentary expression of oceanic anoxic event (OAE) 1b.
An high–resolution planktonic foraminiferal and calcareous nannofossil biostratigraphy in
combination with an integrated study of multiple geochemical proxies (δ13Ccarb, δ13Corg,
TOC, HI, CaCO3, trace elements/Al ratios) of the late Aptian–early Albian OAE 1b has been
performed on the pelagic sedimentary sequence of Poggio le Guaine (Umbria-Marche Basin,
central Italy). A comparison of the newly collected stable isotope carbon curve with the
records from the Vocontian Basin (SE France), DSDP Site 545 and Hole 1049C
provided a reliable and precise identification of the four main prominent black
shale levels (113/Jacob, Kilian, Urbino/Paquier and Leenhardt) that definitively
punctuate the OAE 1b. The studied record shows an increase in the marine organic
carbon accumulation rate, in particular in the 113/Jacob and Urbino/Paquier levels. In
the other black shales, TOC values are < 1%, with evidence of degraded marine
organic matter. Completely anoxic conditions were never established during the
sediment deposition, although evidence of oxygen depletion at the bottom of the
basin is clearly documented by the distribution pattern of redox-sensitive trace
metals. The results suggest an increase in organic carbon burial rates during the
OAE 1b due to the effect of enhanced surface productivity, as supported by a major
increase in Ba/Al, and reduced bottom water ventilation. Noteworthy, the Kilian and
Urbino/Paquier levels from the PLG section are characterized by the absence of correlative
shifts in δ13Ccarb and δ13Corg. The increase in the δ13Corg, values in these levels
is explained by an increase in the relative contribution of δ13C enriched marine
planktonic archaeal biomass, while the concomitant negative excursions recorded in the
δ13Ccarb could reflect a major contribution of isotopically light terrestrial carbonate
ions from increased continental runoff during documented more humid conditions. |
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