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| Titel |
Record of palaeoenvironmental changes in the Mid-Polish Basin during the Valanginian Event |
| VerfasserIn |
Chloé Morales, Ariane Kujau, Ulrich Heimhofer, Joerg Mutterlose, Jorge Spangenberg, Thierry Adatte, Isabela Ploch, Karl B. Föllmi |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250082645
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| Zusammenfassung |
| The Valanginian stage displays the first major perturbation of the carbon cycle
of the Cretaceous period. The Valanginian Weissert episode is associated with a
positive excursion (CIE) in δ13Ccarb and δ13Corg values, and the occurrence of
a crisis in pelagic and neritic carbonate production (Weissert et al., 1998; Erba,
2004, Föllmi et al., 2007). As for Cretaceous oceanic anoxic events (OAEs), the
carbon anomaly is explained by the intensification of continental biogeochemical
weathering triggering an increase in marine primary productivity and organic-matter
preservation. However, to the contrary of OAEs, the organic matter trapped in the Tethyan
Ocean during the Valanginian is both marine and continental and the occurrence of
a widespread anoxia could not be evidenced (Westermann et al., 2010; Kujau et
al., 2012). The resulting marine Corg burial rates were probably not sufficient to
explain the shift in δ13C values and an alternative scheme has been proposed by
Westermann et al. (2010): the carbonate platform crisis combined with the storage of
organic-matter on the continent may be the major triggers of the δ13C positive shift.
(Westermann et al., 2010). We present the results of an analysis of the Wąwał drilling core
(Mid-Polish Trough), which is of particular interest because of its near-coastal
setting and its exceptional preservation, demonstrated by the presence of up to 17
wt.% aragonite. The section consists in marine silty to sandy clays deposited on
top of a lower Berriasian karstified limestone. It covers the Early and early Late
Valanginian, and displays the onset of the positive excursion. The lack of anoxia is
evidenced by trace-element and Rock-Eval data. Two intervals of phosphogenesis
are emphasised that appear equivalent in time to the condensed horizons of the
northern Tethyan region (Helvetic Alps). A rapid climate change toward less humid
and seasonally-contrasted conditions that is similar to the northern Tethyan areas
is observed closed to the early-late Valanginian boundary. This is associated to a
decoupling of the δ13Ccarb and δ13Corg, which is interpreted as a change in atmospheric
pCO2.
References Erba, E., Bartolini, A. and Larson, L.R. (2004) Valanginian Weissert oceanic
anoxic event. Geology, 32, 149-152. Föllmi, K.B., Bodin, S., Godet, A., Linder, P. and van de
Schootbrugge, B. (2007) Unlocking paleo-environmental information from Early
Cretaceous shelf sediments in the Helvetic Alps: stratigraphy is the key! Swiss journal of
geosciences, 100, 349-369. Kujau, A., Heimhofer, U., Ostertag-Henning, C., Gréselle, B.
and Mutterlose, J. (2012) No evidence for anoxia during the Valanginian carbon
isotope event - an organic-geochemical study from the Vocontian Basin, SE France.
Global and Planetary Change, doi: 10.1016/j.gloplacha.2012.04.007. Weissert, H.,
Lini, A., Föllmi, K.B. and Kuhn, O. (1998) Correlation of Early Cretaceous carbon
isotope stratigraphy and platform drowning events: a possible link? Palaeogeography,
Palaeoclimatology, Palaeoecology, 137, 189-203. Westermann, S., Caron, M., Fiet, N.,
Fleitmann, D., Matera, V., Adatte, T. and Föllmi, K.B. (2010) Evidence for oxic conditions
during oceanic anoxic event 2 in the northern Tethyan pelagic realm. Cretaceous
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