History and evolution of the North-Betic Strait (Prebetic Zone, Betic Cordillera): A narrow, early Tortonian, tidal-dominated, Atlantic–Mediterranean marine passage José M. Martín ⁎, Juan C. Braga, Julio Aguirre, Ángel Puga-Bernabéu Departamento de Estratigrafía y Paleontología, Facultad de Ciencias, Campus de Fuentenueva s.n., Universidad de Granada, 18002 Granada, Spain abstract article info Article history: Received 15 October 2008 Received in revised form 23 January 2009 Accepted 23 January 2009 Keywords: North-Betic Strait Large-scale cross-bedding Miocene Betic Cordillera Prebetic The North-Betic Strait, located in the Prebetic Zone (outermost part of the Betic Cordillera), was a narrow seaway connecting the Atlantic Ocean and the Mediterranean Sea through the Betic Cordillera during the Early Late Miocene. Strait facies consist of heterozoan bioclastic carbonates and mixed siliciclastics– carbonates. Local fan-delta deposits (conglomerates) also occur. The North-Betic Strait deposits exhibit huge trough cross-bedded structures. Single troughs are up to 5 m high and point to the east in easternmost outcrops. In central outcrops, they reach up to 15 m in height and some tens of metres in length and point both to the east and to the west. The westernmost outcrops show the largest cross-bedded structures, up to 20 m in height and some hundred of metres in length, all pointing to the west. The large-scale cross-bedding was generated by the migration of very large dunes moved by tides. The largest structures are inferred to have formed at depths of 90 m. Depth estimations indicate that the North-Betic Strait shallowed to the east and deepened to the west. The Miocene evolution towards the formation of the North-Betic Strait can be divided into a series of steps. The palaeogeography evolved from a south-facing platform, marginal to a northeastern relief, to a wide-open marine passage limited by a southern platform and, finally, to a tidal- dominated strait. The closing of the North-Betic Strait is recorded by the presence of lagoonal, silty sediments covered by a stromatolite layer and crowned by a red soil in the westernmost outcrops. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Tectonic movements open and close marine passages connecting oceans and seas, which can substantially modify the interchange of water masses and major oceanographic patterns throughout geologi- cal time. Such was the case of the Atlantic-Mediterranean connec- tions, which underwent significant variations during the Miocene and Pliocene, dramatically affecting the oceanography of the Mediterra- nean basin (Esteban et al., 1996; Comas et al., 1999; Krijgsman et al., 1999; Barbieri and Ori, 2000; Martín et al., 2001, Betzler et al., 2006; Martín et al., in press). Among these connections, the North-Betic Strait was long considered as the main way of communication between the Atlantic Ocean and the Mediterranean Sea through the Betic Cordillera during the Miocene (e.g. Benson et al., 1991). In this regard, Hsü et al. (1973, 1977) believed that its closure prompted a Mediterranean desiccation and the formation of huge evaporite deposits at the bottom of the Mediterranean during the Messinian (uppermost Miocene). Although the influence of its closure in triggering the Messinian Salinity Crisis has been discarded (Esteban et al., 1996), its existence has been an accepted fact up to now. Despite continued references to the North-Betic Strait since it was first mentioned (Colom, 1952), its precise location has remained an open question. It was thought to be located somewhere in the Prebetic Zone, the outermost part of the External Zones of the Betic Cordillera, at the southern margin of the Iberian Massif (Fig. 1), where it developed at some time during the Miocene (e.g. Sierro et al., 1996; Meijninger and Vissers, 2007). The identification of ancient straits can be difficult as strait deposits are very local and prone to erosion after emersion. Never- theless, fossil strait deposits exhibit, as a very distinctive character- istic, large-scale cross-bedded structures, which are well exemplified in two other Late-Miocene straits, reported from the Betic Cordillera connecting the Atlantic Ocean and the Mediterranean Sea. The Dehesas de Guadix Corridor joined the Atlantic-linked Guadalquivir basin and the Mediterranean Guadix-Baza basin during the late Tortonian (Betzler et al., 2006), while the Guadalhorce Corridor was active during the early Messinian as a narrow Atlantic–Mediterranean connection through the Guadalquivir and Málaga basins (Martín et al., 2001). In both cases, bottom currents flowing from the Mediterranean to the Atlantic moved very large dunes on the seafloor, generating large-scale cross-beds of mixed siliciclastic and carbonate particles, with grain sizes ranging from medium sand up to pebbles. Sedimentary Geology 216 (2009) 80–90 ⁎ Corresponding author. Fax: +34 958 248528. E-mail address: jmmartin@ugr.es (J.M. Martín). 0037-0738/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.sedgeo.2009.01.005 Contents lists available at ScienceDirect Sedimentary Geology journal homepage: www.elsevier.com/locate/sedgeo