Paleomagnetic age constrains and magneto-mineralogic implications of the Triassic paleosurface in Europe
Autor
Franke, C.; Thiry, M.; Kouakou, Y.; Edel, J.; Gómez, D.; Ihlen, P.; Jelenska, M.; Kadzialko-Hofmokl, M.; Fàbrega, C.; Parcerisa, D.; Lagroix, F.; Szuszkiewicez, A.; Turniak, K.
Tipus d'activitat
Presentació treball a congrés
Nom de l'edició
4th International Congress Eurosoil
Any de l'edició
2012
Data de presentació
2012-07-02
Llibre d'actes
International Congress Eurosoil 2012
Resum
Paleosurfaces represent a unique tool to access the evolution of ancient continents since they contribute to the study of global changes through its paleoweathering crusts, which formed at the interface with the past atmosphere, and which are created through continental uplift and subsidence driven by crustal geodynamics and plate tectonics.
The crystalline basement rocks (such as granites and rhyolithes) of European Variscan massifs often show Permo-Triassic paleomagnetic remagnetization result...
Paleosurfaces represent a unique tool to access the evolution of ancient continents since they contribute to the study of global changes through its paleoweathering crusts, which formed at the interface with the past atmosphere, and which are created through continental uplift and subsidence driven by crustal geodynamics and plate tectonics.
The crystalline basement rocks (such as granites and rhyolithes) of European Variscan massifs often show Permo-Triassic paleomagnetic remagnetization resulting in underestimated age determinations. These rejuvenated ages are attributed to an alteration of
the primary paleomagnetic signal recently carried by the neo-formation of secondary hematite. Hematite forms under oxic conditions. Thus, one may deduce that the remagnetization of Paleozoic crystalline rocks occurs once the basement rocks are exposed at the Permo-Triassic (paleo)surface.
Permo-Triassic remagnetizations are ubiquitous, affecting many emerged Paleozoic rocks in Europe and suggesting a major weathering event under oxic conditions. The extent of the altered zone (> 100 m in depth) points to a sodium enriched groundwater environment. The Na+ enrichment is likely related to the Triassic environment characterized by widespread salt deposits, such as leaching of salt, marine aerosols, periodic/episodic contribution of seawater or evaporative solutions.
Demonstrating that the albitized facies are of supergenic origin and bound to the Triassic paleosurface deeply renews the ideas about the evolution of basement areas. The recognition of the Triassic paleosurface on widespread basements in Europe will provide spatio-temporal benchmarks to constrain the ablation of these massifs since the Triassic. This will be a major contribution to the geodynamic modelling of these areas.
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