HAL : hal-00498288, version 1

DOI : 10.1016/j.palaeo.2010.06.007

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Palaeogeography Palaeoclimatology Palaeoecology / Palaeogeography Palaeoclimatology and Palaeoecology 295, 1-2 (2010) 293-306

Integrated chronostratigraphy of an intra-arc basin: 40Ar/39Ar datings, micropalaeontology and magnetostratigraphy of the early Miocene Castelsardo basin (northern Sardinia, Italy)

J. Oudet 1, Philippe Munch 2, 3, C. Verati 1, M. Ferrandini 4, M. Melinte-Dobrinescu 5, J. Gattacceca 6, Jean-Jacques Cornee 2, G. Oggiano 7, F. Quillévéré 8, J. Borgomano 3, J. Ferrandini 4

(01/09/2010)

The chronostratigraphy of the lower Miocene deposits of northwestern Sardinia is refined in the Castelsardo Basin. The combination of new 40Ar/39Ar isotopic datings, 19 micropalaeontological datings (calcareous nannofossils, planktonic and large benthic foraminifers) and 16 palaeomagnetic polarity measurements led to a new chronostratigraphic framework. The continental deposits of the first megasequence (Valledoria and Casteldoria members) are possibly Aquitanian. The overlying marine sediments are early Burdigalian (Vaginella depressa Molasse). The marine transgression can be dated to around 19.7 Ma. Marine conditions ceased 18.83 ± 0.13 Ma, the age of the index aerial τ2 ignimbrite. The continental part of the second megasequence (“Lacustre” unit) is early–middle Burdigalian, between 18.8 and 18 Ma. The overlying marine part (Campulandu and Sedini members) is middle–late Burdigalian. The second marine transgression began in the earliest–late Burdigalian, during the Chron C5Dr reversal, at the time of the eustatic Bur 4 event. The Castelsardo basin went through two main extensional tectonic episodes. The first one occurred as the Valledoria Member was deposited and possibly dates back to the Aquitanian. The second one occurred as the uppermost part of the Vaginella depressa Molasse was deposited during the early Burdigalian. The second extensional episode is related to a rapid rotation of Sardinia. Palaeomagnetic results confirm that Corsica and Sardinia acted as a single block which suffered a 28 ± 17° ccw rotation after 19.2 Ma. The Castelsardo basin is held to be an Aquitanian–early Burdigalian intra-arc rift basin that later evolved in a thermally controlled subsident margin of the Ligurian-Provençal Basin during the middle–late Burdigalian.

1 :	Géoazur (GEOAZUR)
	Université Nice Sophia Antipolis [UNS] – CNRS : UMR6526 – Institut de recherche pour le développement [IRD] – Observatoire de la Côte d'Azur – INSU – Université Pierre et Marie Curie [UPMC] - Paris VI
2 :	Géosciences Montpellier (GM)
	CNRS : UMR5243 – Université Montpellier II - Sciences et techniques
3 :	Laboratoire de Géologie des Systèmes et Réservoirs Carbonatés EA 4229
	Université de Provence - Aix-Marseille I
4 :	CNRS UMR 6134, Faculté des Sciences et Techniques, laboratoire des Sciences de la Terre
	Université de Corte
5 :	National Institute of Geology and Marine Geoecology
	National Institute of Geology and Marine Geoecology
6 :	Centre européen de recherche et d'enseignement de géosciences de l'environnement (CEREGE)
	CNRS : UMR6635 – Institut de recherche pour le développement [IRD] – INSU – Université de Provence - Aix-Marseille I – Université Paul Cézanne - Aix-Marseille III
7 :	Istituto di Scienze Geologico-Mineralogiche
	Istituto di Scienze Geologico-Mineralogiche
8 :	Paléoenvironnement et paléobiosphère (PP)
	CNRS : UMR5125 – INSU – Université Claude Bernard - Lyon I

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Planète et Univers/Sciences de la Terre/Géochimie Sciences de l'environnement/Milieux et Changements globaux

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Soumis le : Mercredi 7 Juillet 2010, 10:59:23

Dernière modification le : Vendredi 21 Janvier 2011, 18:40:39