Compositional and Geochemical Signatures for the Sedimentary Evolution of the Middle Triassic–Lower Jurassic Continental Redbeds from Western-Central Mediterranean Alpine Chains

Compositional and chemical analyses suggest that Middle Triassic–Lower Liassic continental redbeds (in the internal domains of the Betic, Maghrebian, and Apenninic chains) can be considered a regional lithosome marking the Triassic-Jurassic rift-valley stage of Tethyan rifting, which led to the Pangaea breakup and subsequent development of a mosaic of plates and microplates. Sandstones are quartzose to quartzolithic and represent a provenance of continental block and recycled orogen, made up mainly of Paleozoic metasedimentary rocks similar to those underlying the redbeds. Mudrocks display K enrichments; intense paleoweathering under a hot, episodically humid climate with a prolonged dry season; and sediment recycling. Redbeds experienced temperatures in the range of 100°–160°C and lithostatic/tectonic loading of more than 4 km. These redbeds represent an important stratigraphic signature to reconstruct a continental block (Mesomediterranean Microplate) that separated different realms of the western Tethys from Middle-Late Jurassic to Miocene, when it was completely involved in Alpine orogenesis.

This work was funded by the Ministero dell’Universtità e della Ricerca Scientifica–Progetto di Ricerca Nazionale (MIUR-PRIN) 2001–2003 Project (“Age and Sedimentary Characters of the Mesozoic Continental Redbeds [Verrucano] from Northern Apennines to the Betic Cordillera: Implications for Paleogeographic and Tectonic Evolution of the Central-Western Mediterranean Alpine Belts,” S. Critelli, G. Mongelli, V. Perrone), MIUR-ex60% Projects (“Paleogeographic and Paleotectonic Evolution of the Circum-Mediterranean Orogenic Belts, 2001–2005” and “Relationships between Tectonic Accretion, Volcanism, and Clastic Sedimentation within the Circum-Mediterranean Orogenic Belts, 2006,” S. Critelli), the 2006–2008 MIUR-PRIN Project 2006.04.8397 (“The Cenozoic Clastic Sedimentation within the Circum-Mediterranean Orogenic Belts: Implications for Paleogeographic and Paleotectonic Evolution,” S. Critelli, G. Mongelli, V. Perrone), and Research Project CGL2005-03887 MEC (A. Martin-Algarra).