 |
| Titel |
Environmental and climatic change during the Valanginian event: Case study of the Wawal section, Polish Basin |
| VerfasserIn |
Chloé Morales, Ariane Kujau, Ulrich Heimhofer, Joerg Mutterlose, Jorge E. Spangenberg, Thierry Adatte, Stéphane Westermann, Izabela Ploch, Karl B. Foellmi |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056222
|
|
|
|
|
|
| Zusammenfassung |
| The Valanginian positive δ13C excursion, also known as the Weissert event, records the first
major perturbation of the carbon cycle in the Cretaceous period. A general hypothesis to
explain this anomaly is that an intensification in continental biogeochemical weathering
occurred, which led to an increase in marine primary productivity and preservation. A recent
study has shown, however, that organic-matter trapped in the Tethyan Ocean is of
both marine and continental origin, and that there is no evidence for widespread
anoxia during the Valanginian (Westermann et al., 2010). This implies that the
resulting marine Corg burial rates may not be sufficient to explain the shift in δ13C
values. As controlling factors leading to the Valanginian event, Westermann et al.
(2010) suggest therefore a combination of a decrease in shallow-marine carbonate
production and the storage of organic-matter on the continent. Enhanced nutrient input
into the ocean led indeed to an increase in marine primary productivity, which did,
however, not materialize in enhanced organic-matter preservation, at least not in the
Tethys.
We studied the section and drill cores of Wąwał, located in the Polish basin. This section
is of particular interest because of its paleogeographic location within the Polish basin, which
represents a narrow straight connecting the Boreal and Tethyan oceans, and because of its
exceptional degree of organic-matter preservation. The section covers the Early and early
Late Valanginian, its δ13Corg and δ13Ccarb records display the onset of the positive
excursion and P contents indicate two intervals of phosphogenesis. Its clay-mineral
composition shows a strong diminution in kaolinite contents during the positive δ13C shift.
These trends are comparable to trends in Tethyan sections and confirm the importance of
environmental change prior and during the onset of the positive δ13C excursion. However the
study of this section should be continued to gather more information about this specific
paleoenvironment.
References:
Westermann, S., Föllmi, K.B., Adatte, T., Matera, V., Schnyder, J., Fleitmann, D., Fiet,
N., Ploch, I. and Duchamp-Alphonse, S. (2010). "The Valanginian δ13C excursion may not
be an expression of a global oceanic anoxic event." Earth and Planetary Science
Letters |
|
|
|
|
|
|