Nannoplankton and planktonic foraminifera biostratigraphy of the eastern Betics during the Tortonian (SE Spain)

Abstract

The Serravallian-Tortonian boundary was a time of strong tectonic activity in the Betic Cordillera. The Early Tortonian sediments continue to be under debate because no clear fossil attributions are available. These sediments have been assigned an Early Tortonian age by indirect stratigraphic criteria or by the absence of fossil content older or younger in age. The present work documents the Les Moreres- Albatera composite section, probably the most complete section of the Tortonian age in the Betic Cordillera, despite a major time gap of about 1 Ma due to an intra-Tortonian tectonic event. The section has two limestone units at the bottom (El Castellà) and the top (Las Ventanas) and two intermediate marly units, the lower Les Moreres and the upper Galería de los Suizos divided by the Raya del Búho Conglomerate. The calcareous nannoplankton biozones from CN5b/NN7 to CN9a/NN11a (Okada & Bukry, 1980; Martini, 1971) have been identified, as have the planktonic foraminifera biozones from MMi9 to MMi12a (Lourens et al. 2004). The calcareous nannoplankton biostratigraphy has allowed the identification of a time gap that includes the upper part of the CN7/NN9 biozones to the lower part of the CN9a/NN11a (Okada &Bukry, 1980; Martini, 1971). The integrated palaeomagnetic and biostratigraphic study of Albatera section has allowed to calibrate the C4r.1r/C4n.2n chron boundary.