Antonio Pedrera
email: a.pedrera@igme.es

Jesús Galindo-Zaldívar

Alejandro Tello

Carlos Marín
email: c.marin@igme.es

Carlos Marín-Lechado

the Húercal-Overa Basin (Eastern Betic Cordillera)

Keywords: Transcurrent fault, neotectonics, active tectonics, paleostress, gravity prospecting

Intramontane basin development related to contractional and extensional structure interaction at

the termination of a major sinistral fault:

Introduction

Intramontane basin development is commonly related to extension of a previously thickened continental lithosphere. The activity of normal faults during the late evolution of the orogens results in subsidence and sedimentation. However, orogens subjected to active horizontal shortening also accommodate sediments: at the front of active thrust systems (e.g. as fore-deep basins, [START_REF] Beaumont | Foreland basins[END_REF][START_REF] Jordan | The Sierras Pampeanas of Argentina: a modern analogue of Rocky Mountain foreland deformation[END_REF][START_REF] Lucente | Topography and palaeogeographic evolution of a middle Miocene foredeep basin, northern Apennines, Italy[END_REF], on the top of active thrust sheets (piggy-back basins; [START_REF] Ori | Sedimentary basins, formed and carried piggyback on active thrust sheets[END_REF]Zoetemeijer et al., 1993), or related to strike-slip faulting (pull-apart basins; [START_REF] Reading | Characteristics and recognition of strike-slip fault systems[END_REF][START_REF] Gürbüz | Middle Pleistocene extinction process of pull-apart basins along the North Anatolian Fault Zone[END_REF]. The coetaneous formation of compressive and extensional tectonic structures has been addressed in some compressional settings [START_REF] Burchfiel | North-south extension within the convergent Himalayan region[END_REF][START_REF] Oldow | Large-scale longitudinal extension in the southern Apennines contractional belt, Italy[END_REF][START_REF] Doglioni | Geological remarks on the relationships between extension and convergent geodynamic settings[END_REF][START_REF] Decker | Tertiary kinematics in the Alpine-Carpathian-Pannonian system: links between thrusting, transform faulting and crustal extension[END_REF][START_REF] Shanker | Normal Fault in contractional tectonics[END_REF]. In these tectonic scenarios, the relation between sedimentation and tectonic structures can be complex with areas dominated by compression, sectors subjected to extension and regions with overprinted deformation. The geometry of the resulting intramontane sedimentary basins becomes irregular and numerous tectonic mechanisms have been proposed to explain their development and paleogeographic evolution. The Neogene evolution of the Betic Cordillera (Fig. 1) is characterized by an atypical tectonic setting where both contractional and extensional structures deform the hinterland of the cordillera inducing uplift and intramontane sedimentation at least since the Tortonian [START_REF] Galindo-Zaldívar | Active faulting in the internal zones of the central Betic Cordilleras (SE Spain)[END_REF]. This setting has been traditionally explained in terms of superposition of different regional stress fields [START_REF] Montenat | The diversity of late Neogene sedimentary basins generated by wrench faulting in the Eastern Betic Cordillera, SE Spain[END_REF]. These tectonic structures have a heterogeneous distribution, dominated by folds and normal faults in the central cordillera and by strike-slip faults in the eastern sector of the cordillera.

The aim of this contribution is to shed light on the relationships between the great varieties of compressive and extensional tectonic structures in order to elucidate the intramontane basin development. This research looks into the interaction of minor structures that deform the Huercal-Overa Basin, located at the southern termination of the sinistral strike-slip Alhama de Murcia Fault (Eastern Betic Cordillera). The primary objective is to discuss the relationships between compressive and extensional deformations in strike-slip fault terminations. Tectonic observations, including mapping and kinematic analysis, are combined with new gravity data to determine the sedimentary thickness distribution in order to constrain the basin development.

Geological setting

The Betic Cordillera (Fig. 1) has been traditionally divided into an external foldand-thrust belt, deformed by thin-skinned tectonics and commonly referred to as the External Zones, and a mostly metamorphic hinterland called the Internal Zones. The External Zones are formed by Mesozoic and Tertiary rocks that were deposited over the The Internal Zones are mainly formed by three major metamorphic complexes that, from bottom to top, are the Nevado-Filábride (Egeler, 1963), Alpujárride (Van Bemmelen, 1927) and Maláguide [START_REF] Blumenthal | Versuch einer tektonischen Gliederung der Betischen Kordilleren von Central und Sùdwest Andalusien[END_REF]. These complexes are separated by low-angle normal faults [START_REF] Aldaya | El contacto Alpujárrides/Nevado-Filábrides en la vertiente meridional de Sierra Nevada. Implicaciones tectónicas[END_REF][START_REF] García-Dueñas | Plisnappes, cisillements syn-à post-métamorphiques et cisaillements ductilesfragiles en distension dans les Nevado-Filabrides (Cordillères bétiques, Espagne)[END_REF][START_REF] Galindo-Zaldívar | Progressive extensional shear structures in a detachment contact in the western Sierra Nevada (Betic Cordilleras, Spain)[END_REF][START_REF] Platt | Extensional collapse of thickened continental lithosphere: A working hypothesis for the Alboran Sea and Gibraltar Arc[END_REF]. Both the Nevado-Filábride and the Alpujárride Complexes Plate-kinematic reconstructions reveal that the main deformation-driving mechanism since the middle Miocene is N-S to NW-SE shortening between Europe and Africa (e.g. [START_REF] Dewey | Kinematics of the Western Mediterranean[END_REF][START_REF] Demets | Effect of recent revisions to the geomagnetic reversal time scale on estimates of current plate motions[END_REF][START_REF] Rosenbaum | Relative motions of Africa, Iberia and Europe during Alpine orogeny[END_REF].

Anticlockwise rotation from N-S to NW-SE occurred around 10 Ma [START_REF] Rosenbaum | Relative motions of Africa, Iberia and Europe during Alpine orogeny[END_REF]. This convergence generated the relief of the Betic Cordillera, characterized by mountain ranges and depressed areas featuring sedimentary basins, respectively coinciding with large E-W to ENE-WSW antiforms and synforms. These large folds mainly interact with normal, strike-slip, and reverse faults (e.g. [START_REF] Booth-Rea | Uppermost Tortonian to Quaternary depocentre migration related with segmentation of the strike-slip Palomares Fault Zone, Vera basin, SE Spain[END_REF]. The compressive and extensional tectonic structures show features indicating simultaneous development since the Tortonian [START_REF] Galindo-Zaldívar | Active faulting in the internal zones of the central Betic Cordilleras (SE Spain)[END_REF]. The Alhama de Murcia Fault and its termination in the Huercal-Overa Basin constitute two major structures of this region.

A c c e p t e d M a n u s c r i p t 5

The Alhama de Murcia sinistral fault (AMF)

The presence of NNE-SSW to NE-SW large sinistral strike-slip faults determines the neotectonic setting in Eastern Betic Cordillera (Fig. 1). This set of faults has been interpreted as a large shear zone (Trans-Alborán transcurrent zone, [START_REF] Larouzière | The Betic segment of the lithospheric Trans-Alboran shear zone during the Late Miocene[END_REF] that represents a crustal discontinuity extending southwestward, crossing the Alborán Sea.

The Alhama de Murcia Fault (AMF) [START_REF] Bousquet | Presence de décrochements NE-SW plio-quaternaires dans les Cordillères Bétiques Orientales (Espagne). Extension et signification général[END_REF] is the northern segment of these transcurrent faults in the Betic Cordillera (Fig. 1). It has a NE-SW orientation showing predominantly reverse strike-slip kinematics [START_REF] Martínez Díaz | Stress field variation related to fault interaction in a reverse oblique-slip fault: the Alhama de Murcia fault, Betic Cordillera, Spain[END_REF].

The AMF extends over 80 km, from Murcia as far as the Huércal-Overa Basin to the south, crossing the northwest boundary of the Guadalentín depression. The most recent fault activity is inferred from Quaternary sediment deformations and their geomorphological expression. The AMF develops mountain fronts related to the sinistral fault segments and associated folds and reverse faults [START_REF] Martínez Díaz | Stress field variation related to fault interaction in a reverse oblique-slip fault: the Alhama de Murcia fault, Betic Cordillera, Spain[END_REF], involving vertical axis rotation, as deduced from paleomagnetic results [START_REF] Mora | Tectonic and sedimentary analysis of the Huércal-Overa region, SE Spain, Betic Cordillera[END_REF][START_REF] Krijgsman | Palaeomagnetic constraints on the geodynamic evolution of the Gibraltar Arc[END_REF][START_REF] Mattei | Neogene tectonic evolution of the Gibraltar Arc: New paleomagnetic constraints from the Betic chain[END_REF]. In addition, the AMF has associated low to moderate seismicity [START_REF] Silva | Paleoseismic indicators along 'aseismic' fault segments in the Guadalentín depresion (SE Spain)[END_REF][START_REF] Soto | Thermal structure of the crust in the Gibraltar Arc: Influence on active tectonics in the western Mediterranean[END_REF]Stich et al., , 2007)).

Despite the numerous structural data obtained from the AMF and its surrounding sedimentary basins, some questions remain open. The initial activity of AMF is under debate; and while some authors propose sinistral behavior since the Tortonian [START_REF] Ott D'estevou | Evolution structurale de la zone Betique orientale (Espagne) du Tortonian à l'Holocène[END_REF][START_REF] Montenat | Tectonic-sedimentary characters of the Betic Néogène Bassins evolving in a crustal transcurrent shear zone (SE Spain)[END_REF]Montenat et al., , 1990;;[START_REF] Krijgsman | The 'Tortonian salinity crisis' of the eastern Betics (Spain)[END_REF]Vennin et al., 2004) other researchers support a latest Miocene-Early Pliocene onset of activity [START_REF] Armijo | La zone des failles Lorca-Totana (Cordillères Bétiques, Espagne). Étude tectonique et neotectonique[END_REF][START_REF] Meijninger | Miocene extensional basin development in the Betic Cordillera, SE Spain, revealed through analysis of the Alhama de Murcia and Crevillente Faults[END_REF]. Likewise, there is no consensus with regard A c c e p t e d M a n u s c r i p t 6 to the spatial and temporal distribution of stress fields proposed for this sector of the cordillera from the Serravallian (Fig. 2). [START_REF] Bousquet | Observations micro-tectoniques sur la compresion nord-sud quaternaire des Cordillères Bétiques Orientales (Espagne Méridional-Arc de Gibraltar)[END_REF] point to E-W extension from the Tortonian up to the Pliocene, plus late regional stress fields characterized by horizontal N-S compression. [START_REF] Armijo | La zone des failles Lorca-Totana (Cordillères Bétiques, Espagne). Étude tectonique et neotectonique[END_REF] [START_REF] Ott D'estevou | Evolution structurale de la zone Betique orientale (Espagne) du Tortonian à l'Holocène[END_REF][START_REF] Montenat | Tectonic-sedimentary characters of the Betic Néogène Bassins evolving in a crustal transcurrent shear zone (SE Spain)[END_REF]Montenat et al., , 1990;;[START_REF] Montenat | The diversity of late Neogene sedimentary basins generated by wrench faulting in the Eastern Betic Cordillera, SE Spain[END_REF]. Recent research evidences the coexistence of NNE-SSW and NNW-SSE horizontal compression and NNW-SSE horizontal extension, active during the Late Miocene to the Quaternary [START_REF] Martínez Díaz | Neotectónica y Tectónica Activa del sector centrooccidental de Murcia y Sur de Almería, Cordillera Bética (España)[END_REF][START_REF] Martínez Díaz | Stress field variation related to fault interaction in a reverse oblique-slip fault: the Alhama de Murcia fault, Betic Cordillera, Spain[END_REF]. [START_REF] Booth-Rea | Extensional attenuation of the Malaguide and Alpujarride thrust sheets in a segment of the Alborán basin folded during the Tortonian (Lorca area, Eastern Betics)[END_REF] described extensional structures with a top-to-the-W-SW transport affecting Late Serravallian age marine sediments, and sealed by Lower Tortonian conglomerates in the southeastern border of the Sierra de la Tercia fold (Fig. 1). These extensional structures are deformed by the Sierra de la Tercia anticline, which shows an intra-Tortonian angular unconformity related to its growth. In the Bajo Segura Basin, which constituted the northern termination of the AMF, [START_REF] Alfaro | Onshore and offshore contractional tectonics in the eastern Betic Cordillera (SE Spain)[END_REF] describe progressive unconformities related to fold development from the Late Miocene up to the present, highlighted by seismic reflection profiles. Recently, [START_REF] Meijninger | Late-orogenic extension and strike-slip deformation in the Neogene of southeastern Spain[END_REF] and [START_REF] Meijninger | Miocene extensional basin development in the Betic Cordillera, SE Spain, revealed through analysis of the Alhama de Murcia and Crevillente Faults[END_REF]

The Huércal-Overa Basin

Previous models for basin development

The Huércal-Overa Basin in the Eastern Betic Cordillera started to develop in the Serravallian-Early Tortonian. The first studies considered it to be a pull-apart basin related to strike-slip activity on NE-SW trending faults (e.g. [START_REF] Bousquet | Presence de décrochements NE-SW plio-quaternaires dans les Cordillères Bétiques Orientales (Espagne). Extension et signification général[END_REF]. [START_REF] Poisson | The origin and development of Neogene basins in the SE Betic Cordillera (SE Spain): a case study of the Tabernas-Sorbas and Huercal Overa Basins[END_REF] proposed a model where the surrounding ranges are interpreted as westward-verging antiforms developed over deep-seated thrust faults, and the Huércal-Overa Basin constitutes a lateral synform oriented parallel to this supposed thrust transport direction. The most recent interpretations suggest the development of the Huércal-Overa Basin in a purely extensional framework that favours the simultaneous exhumation and thinning of the metamorphic middle to upper crust during the Late Miocene (eg. [START_REF] Mora | Tectonic and sedimentary analysis of the Huércal-Overa region, SE Spain, Betic Cordillera[END_REF]Vissers et al., 1995;[START_REF] Augier | Evolution tardi-orogénique des Cordilères Bétiques (Espagne): Apports d'un étude intégrée[END_REF]Augier et al., , 2005;;[START_REF] Meijninger | Late-orogenic extension and strike-slip deformation in the Neogene of southeastern Spain[END_REF][START_REF] Meijninger | Miocene extensional basin development in the Betic Cordillera, SE Spain, revealed through analysis of the Alhama de Murcia and Crevillente Faults[END_REF]. These authors explain the compressive structures as the consequence of a tectonic inversion since Late Messinian-Pliocene times.

Stratigraphy

The Huércal-Overa Basin infill extends from the Middle Miocene up to the Quaternary, and includes several stratigraphic units separated by unconformities (Figs. 3 and4). The oldest sediments that occupy the basin are continental conglomerates (lit-de-vin unit, [START_REF] Briend | Evolution morpho-tectonique du bassin néogène de Huercal-Overa (Cordillères bétiques orientales, Espagne[END_REF][START_REF] Briend | Le bassin de Huercal-Overa[END_REF], possibly deposited during the Middle Miocene, yet poorly represented. A thick continental red conglomerate formation, which includes Nevado-Filábride pebbles, was most likely deposited during the Serravallian and Early Tortonian (~12 Ma exhumation age deduced from fission-track data, [START_REF] Johnson | Neogene tectonics in south eastern Spain: Constraints from fission track analysis[END_REF]1997;[START_REF] Johnson | The role of extension in the Miocene denudation of the Nevado-Filábride Complex, Betic Cordillera (SE Spain)[END_REF], unconformably overlying the previous unit and the basement A c c e p t e d M a n u s c r i p t 8 rocks. The paleocurrents, mainly deduced from imbricate pebbles in this continental red conglomerate formation, are predominantly towards the E and N (Montenat et al., 1990;[START_REF] Meijninger | Late-orogenic extension and strike-slip deformation in the Neogene of southeastern Spain[END_REF], which is consistent with the flow data observed in the nearby Almanzora Corridor [START_REF] Pedrera | Fold and fault interactions during the development of an elongated narrow basin: the Almanzora Neogene-Quaternary Corridor (SE Betic Cordillera, Spain)[END_REF]. These continental deposits pass gradually upwards into a variously colored sequence with alternating beds of conglomerates, sands, grey silts and gypsum, assigned to a fluvial-deltaic environment. An Early Tortonian age is evoked for this unit on the basis of foraminifera sampled in the marine levels [START_REF] Briend | Evolution morpho-tectonique du bassin néogène de Huercal-Overa (Cordillères bétiques orientales, Espagne[END_REF][START_REF] Guerra-Merchán | Tectonosedimentary setting and chronostratigraphy of the Neogene reefs in the Almanzora corridor (Betic Cordillera, Spain)[END_REF][START_REF] Meijninger | Late-orogenic extension and strike-slip deformation in the Neogene of southeastern Spain[END_REF] and micromammals from the continental strata [START_REF] Guerra-Merchán | New data on the Upper Miocene micromammals of the Betic Cordillera and their interest for marine-continental correlations[END_REF]. At the top there is an angular unconformity where, during the Late Tortonian, bioclastic reef limestones and fan delta sediments were deposited (in the southern sector of the basin), passing into yellow marls toward the center of the basin. Foraminiferal [START_REF] Guerra-Merchán | Tectonosedimentary setting and chronostratigraphy of the Neogene reefs in the Almanzora corridor (Betic Cordillera, Spain)[END_REF][START_REF] Meijninger | Late-orogenic extension and strike-slip deformation in the Neogene of southeastern Spain[END_REF] and nannoplankton assemblages (Martín-Pérez, 1997) dated the marls as Late Tortonian. Messinian sediments crop out only in the easternmost part of the study area, close to the village of Huércal-Overa. During the Plio-Quaternary, detrital sediments representing alluvial fan and to the river deposits were unconformably placed over the Miocene rocks.

Tectonic structures in the Huércal-Overa Basin

The Late Miocene sediments that fill the Huércal-Overa Basin are quite deformed by several sets of faults and folds (Fig. 4).

Faults

Faults have been previously studied in the Eastern and Southern Huércal-Overa basin: the earliest research (Groupe de Recherche Neotectonique, 1977), was followed by A c c e p t e d M a n u s c r i p t 9 that of [START_REF] Briend | Evolution morpho-tectonique du bassin néogène de Huercal-Overa (Cordillères bétiques orientales, Espagne[END_REF], and further efforts [START_REF] Mora | Tectonic and sedimentary analysis of the Huércal-Overa region, SE Spain, Betic Cordillera[END_REF][START_REF] Poisson | The origin and development of Neogene basins in the SE Betic Cordillera (SE Spain): a case study of the Tabernas-Sorbas and Huercal Overa Basins[END_REF][START_REF] Augier | Evolution tardi-orogénique des Cordilères Bétiques (Espagne): Apports d'un étude intégrée[END_REF][START_REF] Meijninger | Miocene extensional basin development in the Betic Cordillera, SE Spain, revealed through analysis of the Alhama de Murcia and Crevillente Faults[END_REF]. However, data on the most recent faulting in the western basin sector are scarce. We present a review of the previous data, along with a careful description of the structures that deform this sector.

The most abundant group corresponds to WNW-ESE to NW-SE normal faults that show a widespread distribution in the basin [START_REF] Mora | Tectonic and sedimentary analysis of the Huércal-Overa region, SE Spain, Betic Cordillera[END_REF][START_REF] Augier | Evolution tardi-orogénique des Cordilères Bétiques (Espagne): Apports d'un étude intégrée[END_REF][START_REF] Meijninger | Late-orogenic extension and strike-slip deformation in the Neogene of southeastern Spain[END_REF].

These faults are usually located inside the basin, presenting a length shorter than 1 km, and small values of normal slip, between a few centimetres and a few meters (Fig. 4). They generally dip to the SW in the northern basin sector and to the NE in the southern region.

The presence of conjugate faults with dihedral angles from 50º to 60º is very common (Figs. 4 and 5a). Kinematic analysis of these faults generally shows a pure dip-slip component. However, some fault surfaces show other striae, sometimes overprinted, that suggest a local NW-SE shortening. Only the southwestern basin boundary is limited by normal faults, between the villages of Albánchez and Líjar. These bounding normal faults commonly present planar surfaces and tilt the Early Tortonian continental red conglomerate and the Late Tortonian fan delta towards the SW. Scarce syn-sedimentary features, such as bed thickness variations, show evidence of fault activity during the Tortonian. This set of faults changes its geometry when deforming the multilayer sequence of conglomerates, sands, grey silts, and gypsum of Early Tortonian age (Fig. 5). Flat-andramp normal faults affect this sedimentary sequence, where the soft sedimentary layers mostly concentrate the deformation and constitute detachment levels parallel to the bedding. The sediments are folded by fault activity, forming roll-overs, both in the hanging wall and locally in the footwall (Figs. 4 and5). The most impressive roll-over example is located close to the village of Santopetar, in the north of the study area. This structure is A c c e p t e d M a n u s c r i p t 10 interpreted as the result of Early Tortonian syn-sedimentary deformation in both the footwall and hanging wall, along a major normal fault system composed of several flat and more steeply dipping ramps [START_REF] Briend | Evolution morpho-tectonique du bassin néogène de Huercal-Overa (Cordillères bétiques orientales, Espagne[END_REF][START_REF] Jabaloy | Listric normal faults: constraints to the geometric and kinematic analysis from the study of natural examples[END_REF][START_REF] Mora | Tectonic and sedimentary analysis of the Huércal-Overa region, SE Spain, Betic Cordillera[END_REF][START_REF] Augier | Evolution tardi-orogénique des Cordilères Bétiques (Espagne): Apports d'un étude intégrée[END_REF][START_REF] Meijninger | Late-orogenic extension and strike-slip deformation in the Neogene of southeastern Spain[END_REF].

Our field data show the presence of a second set of scarce ENE-WSW to NE-SW oriented normal faults in the central part of the western Huércal-Overa Basin, deforming Late Tortonian marls (Fig. 4, stations 6 and 7). The southeastern margin of the Huércal-Overa basin is bounded by sub-vertical to NW-ward dipping faults of the same orientation and predominantly sinistral strike-slip kinematics. However, in some fault segments normal striations were observed (Fig. 4). These faults were previously interpreted as transfer fault zones that accommodate the extension produced by the WNW-ESE oriented normal faults [START_REF] Mora | Tectonic and sedimentary analysis of the Huércal-Overa region, SE Spain, Betic Cordillera[END_REF][START_REF] Poisson | The origin and development of Neogene basins in the SE Betic Cordillera (SE Spain): a case study of the Tabernas-Sorbas and Huercal Overa Basins[END_REF], or else considered ancient faults active only during the first stage of the basin evolution and later reactivated as sinistral faults [START_REF] Augier | Evolution tardi-orogénique des Cordilères Bétiques (Espagne): Apports d'un étude intégrée[END_REF]. [START_REF] Meijninger | Late-orogenic extension and strike-slip deformation in the Neogene of southeastern Spain[END_REF] describes a complex history of overprinted slips in one of these faults located close to Huércal-Overa village (Fig. 4), where initial dextral strike-slip striations are originally overprinted by dip-slip, again overprinted by sinistral strike-slip.

E-W to ESE-WNW oriented subvertical dextral strike-slip faults deform the

Tortonian sediments that crop out mainly in the southwestern basin border close to Albox (Fig. 4). These faults deform the Late Tortonian sediments and are usually sealed by the Quaternary deposits (Fig. 5). However, they affect even the Quaternary deposits in the central sector (Rambla el Romeral, Fig. 4). These faults may be conjugate with the NNE-SSW to NE-SW large sinistral-strike-slip faults described above.

The Huércal-Overa Basin is deformed by reverse E-W to ENE-WSW oriented faults with related folds (Fig. 6) that deform the Tortonian and, locally, the Quaternary sediments [START_REF] Armijo | La zone des failles Lorca-Totana (Cordillères Bétiques, Espagne). Étude tectonique et neotectonique[END_REF][START_REF] Briend | Evolution morpho-tectonique du bassin néogène de Huercal-Overa (Cordillères bétiques orientales, Espagne[END_REF]García Meléndez, 2000;[START_REF] Masana | Large Holocene morphogenic earthquakes along the Albox fault, Betic Cordillera, Spain[END_REF]. In the eastern and northeastern sector of the basin, these faults form a splay geometry connected with the AMF [START_REF] Briend | Evolution morpho-tectonique du bassin néogène de Huercal-Overa (Cordillères bétiques orientales, Espagne[END_REF]Silva, 1994). The Late Pliocene-Early Pleistocene faulting activity was established by the interaction of the Alhama de Murcia fault with these E-W reverse faults, generating a progressive syn-tectonic unconformity in the Garita del Diablo sector (Fig. 4) (García-Melendez et al., 2003). In the western sector of the basin, the same reverse fault set deforms the Tortonian and locally the Quaternary sediments, sometimes developing syn-tectonic growth strata during the Middle Pleistocene (Pedrera et al., 2009a and[START_REF] Pedrera | Testing the sensitivity of geomorphic indices in areas of low-rate active folding (eastern Betic Cordillera, Spain)[END_REF].

Folds

Most of the mountain ranges located in the Central and Eastern sectors of the Betic Cordillera correspond to km-scale antiforms, and the surrounding basins to synforms (Marín-Lechado et al., 2006 and references therein). The basin synforms developed coevally with the basin infill. Therefore, the folding age can be deduced from the progressive unconformities of the sedimentary units located near the basin boundaries. The large folds located in the study area are: the Sierra de Los Filabres and Sierra de Almagro antiforms, the Almanzora synform, and the Sierra de Las Estancias antiform (Figs. 1 and4).

The E-W Sierra de Los Filabres antiform growth probably started during Serravallian to Early Tortonian times, as confirmed by the Serravallian-Tortonian age of the folded sediments forming progressive unconformities in the red conglomerate unit, and also in the overlying Late Tortonian sediments [START_REF] Pedrera | Fold and fault interactions during the development of an elongated narrow basin: the Almanzora Neogene-Quaternary Corridor (SE Betic Cordillera, Spain)[END_REF]. The northward and eastward flow directions deduced in the red conglomerate formation during the Serravallian-Early Tortonian (Montenat et al., 1990;[START_REF] Meijninger | Late-orogenic extension and strike-slip deformation in the Neogene of southeastern Spain[END_REF] points to an A c c e p t e d M a n u s c r i p t 12 enhanced topography in the Sierra de Los Filabres, where there was erosion and an abundant sediment supply. The Sierra de Las Estancias does not act as a barrier to sediment transport. In fact, uplift of the Sierra de Las Estancias started later, during the Tortonian [START_REF] Pedrera | Fold and fault interactions during the development of an elongated narrow basin: the Almanzora Neogene-Quaternary Corridor (SE Betic Cordillera, Spain)[END_REF].

The Almanzora Corridor is determined by an N-vergent large synform with direction changing from E-W near the western corridor to ENE-WSW at the eastern end, near the Huércal-Overa Basin. This synform deforms all the Miocene sediments and determines the location of the pelagic sediments in its core. The Quaternary continental alluvial fan beds have initial sedimentary dips towards the centre of the basin, and they lie unconformably over the folded marine sediments, precluding to determine if they are folded.

The Sierra Almagro, located in the Eastern prolongation of the Sierra de Los Filabres (Figs. 1 and4), is also an ENE-WSW oriented antiform that deforms the Tortonian and Messinian sediments. Its limbs are strongly affected by faults, and ENE-WSW oriented North-western dipping reverse faults control its southern mountain front [START_REF] Rutter | Comparative microstructures of natural and experimentally produced clay-bearing fault gouges. In: International structure of fault zones[END_REF][START_REF] Booth-Rea | Influence of strike-slip fault segmentation on drainage evolution and topography. A case study: the Palomares Fault Zone (southeastern Betics, Spain)[END_REF]. The northern limb is deformed by the sub-vertical ENE-WSW to NE-SW oriented faults described above, as they constitute the boundary of the Huércal-Overa basin.

In addition to these large folds, the Huércal-Overa Basin sediment is deformed by minor folds (Figs. 4 and6). They could be grouped, according to the mean strike, as ENE- In the central sector of the Basin, the sediments and the metamorphic rocks of Sierra Limaria (Fig. 4) are deformed by a band of WNW-ESE oriented open folds. The fold wavelengths vary between 1 and 4 km, and their strike is up to 30º oblique to the main normal fault set. There is no a consensus in the interpretation of these folds. While some authors associate them with compression or transpression [START_REF] Poisson | The origin and development of Neogene basins in the SE Betic Cordillera (SE Spain): a case study of the Tabernas-Sorbas and Huercal Overa Basins[END_REF], others interpret them as extensional roll-over anticlines developed above listric normal faults [START_REF] Meijninger | Late-orogenic extension and strike-slip deformation in the Neogene of southeastern Spain[END_REF]. In some places the normal faults are tilted, and in some outcrops the normal faults deform the tilted strata (Fig. 5). In the Huércal-Overa Basin, the roll-overs are usually related to listric or flat-and-ramp normal faults that deform the multi-layered sequence of conglomerates, sands, grey silts and gypsum, or the sediments placed immediately atop this unit (Fig. 5).

Paleostress results

In order to complete the previous paleostress studies in the Huércal-Overa Basin [START_REF] Mora | Tectonic and sedimentary analysis of the Huércal-Overa region, SE Spain, Betic Cordillera[END_REF][START_REF] Augier | Evolution tardi-orogénique des Cordilères Bétiques (Espagne): Apports d'un étude intégrée[END_REF][START_REF] Meijninger | Miocene extensional basin development in the Betic Cordillera, SE Spain, revealed through analysis of the Alhama de Murcia and Crevillente Faults[END_REF], stress inversion of the measured faults located in the western sector of the basin was performed following the Galindo-Zaldívar and Gozález-Lodeiro (1988) method. This method uses a systematic search on a grid pattern and allows determining overprinted stress ellipsoids including main axes orientations and axial ratios. The calculated stress ellipsoids (Fig. 7 and Table 1) could be grouped into three different main sets. (a) The best represented group (type 1) is characterized by a sub-vertical maximum stress axis, NNE-SSW to NE-SW sub-horizontal A c c e p t e d M a n u s c r i p t 14 extension, and variable axial ratios that are in transition to prolate ellipsoids of radial extension. This group is related to normal faults that are 2,3,4,5,8 phase I,17,18 and 19,20,24,[START_REF] Beaumont | Foreland basins[END_REF]26,27 and 28). The maximun axis observed in some stations plunges, suggesting the rotation of the faults by late folds (Table 1, stations 22 and23). (b) The second set (type 2) has a sub-vertical maximum stress axis, E-W to NW-SE extension and low axial ratios, also related to prolate ellipsoids of radial extension (stations: 6, 7, 8 phase II and 29). (c) The third group pertains to stress ellipsoids with a NW-SE sub-horizontal maximum stress axis and low-to-medium axial ratios, likewise suggesting prolate to intermediate ellipsoids related to the development of compressive structures like ENE-WSW reverse faults and folds (9, 10 and 14 phase I).

Gravity survey

In contrast to the widespread geological studies developed in the area [START_REF] Meijninger | Miocene extensional basin development in the Betic Cordillera, SE Spain, revealed through analysis of the Alhama de Murcia and Crevillente Faults[END_REF], and references therein), there are practically no detailed geophysical studies in the sector that help to constraint the thickness of the sedimentary rocks. Vertical electric sounding data alone allowed [START_REF] García-Meléndez | Neotectonics and Plio-Quaternary landscape development within the eastern Huercal-Overa Basin (Betic Cordilleras, Southeast Spain)[END_REF] an approximate reconstruction of the three-dimensional shape of the Cubeta del Saltador, located in the northeastern Huércal-Overa Basin (Fig. 4). For this reason, new gravity data were acquired and interpreted in the light of the available geological information in order to determine the deep structure of the Huércal-Overa Basin.

Gravity data acquisition and processing

Gravity data were acquired by means of a Scintrex cg-5 gravity-meter, with a maximum accuracy of 0.001 mGal. The relative positioning of the gravity stations was A c c e p t e d M a n u s c r i p t 15 done with a e-trex Garmin GPS receiver, and the heights of the stations were determined with a barometric altimeter with an accuracy of 0.5 m. Gravity measurement stations are located along four profiles that are approximately NNW-SSE orientated (Fig. 4). These profiles constitute complete sections of the basin, from the Sierra Almagro-Sierra de Los Filabres up to Sierra de Las Estancias, crossing through the Sierra Limaria. The average distance between stations along the profiles was 250 m.

The gravity measurements were established with reference to the Baza gravimetric base 37º 29' 12.0'';Instituto Geográfico Nacional,www.ign.es), which allows us to determine the absolute gravity values along the profiles. After tidal and instrumental drift, the Bouguer anomaly was obtained using a reference density of 2.67 g/cm 3 and applying the topographic correction to a radius of 22 km, calculated from a digital elevation model with a grid of 90 m, following the Hammer method [START_REF] Hammer | Terrain Corrections for Gravity Stations[END_REF][START_REF] Hammer | Critique of Terrain Corrections for Gravity Stations[END_REF]. The influence of topography outside of this 22 km radius tends to smoothly affect the Bouguer anomaly, and was corrected with the regional anomaly subtraction during the residual anomaly determination. The residual gravity anomaly map (Fig. 8) was calculated from the Bouguer anomaly by profile interpolation, and subtracting the regional anomaly determined on the basis of 46 measurements over basement rocks in agreement with the regional anomaly maps [START_REF]Mapa de España de Anomalía de Bouguer[END_REF]. Finally, residual 2D gravity models along the measured profiles were developed with GRAVMAG v. 1.7 software [START_REF] Pedley | GRAVMAG User Manual -Interactive 2.5D gravity and magnetic modelling[END_REF].

Gravity modelling and deep structure

The new gravity data allow us to illustrate the sedimentary infill thickness (Figs. 8 and9) with a complex pattern where the minimum values (-12 mGal) are reached in the central part of the western Huércal-Overa Basin. Residual gravity anomalies were A c c e p t e d M a n u s c r i p t 16 considered together with surface observations in order to determine the deep structure of the basin by 2D modelling (Fig. 9). For gravity modelling, an average density of 2.35 g/cm 3 was considered for the whole sedimentary infill [START_REF] Robinson | Basic Exploration Geophysics[END_REF][START_REF] Telford | Applied Geophysics[END_REF], also in agreement with gravity studies previously developed in other sedimentary basins of the Betic Cordillera, with similar lithostratigraphic sequences [START_REF] Pedrera | Fault and fold interaction during the development of the Neogene-Quaternary Almería-Níjar basin (SE Betic Cordilleras)[END_REF][START_REF] Pedrera | Fault and fold interaction during the development of the Neogene-Quaternary Almería-Níjar basin (SE Betic Cordilleras)[END_REF][START_REF] Pedrera | Recent large fold nucleation in the upper crust: Inight from gravity, magnetic, magnetotelluric and seismicity data (Sierra de Los Filabres-Sierra de Las Estancias, Internal Zones, Betic Cordillera)[END_REF]. However, to evaluate the uncertainty in the basin infill thickness determination we present alternative gravity models assuming the minimum and the maximum plausible density contrasts (2.2-2.5 g/cm 3 sediments, 2.67 g/cm 3 basement). The obtained gravity anomalies for each profile are irregular in shape, with minimum values between -12 mGal and -2.5 mGal. The sedimentary infill distribution obtained from the models is also irregular, reaching up to 1000 meters of maximum thickness in profile 2 (using the middle density contrast).

The combination of the 2D gravity models and the geological field observations allows us to associate the sediment distribution with the tectonic structures and constrain the geological cross-sections (Fig. 10). The residual anomaly map and the 2D model of profile 2 show the maximum sedimentary thickness to coincide with the ENE-WSW Almanzora synform hinge. Other minor discontinuities could be related to normal faults.

However, the faults bounding the southern sector of the basin have no associated important thickness of sediments, as might be initially expected.

Discussion

The interaction of compressional and extensional structures is recorded by the sedimentary infill of the Huércal-Overa Basin. This tectonic framework could be partially a consequence of the southern termination of the Alhama de Murcia transcurrent fault. In this A c c e p t e d M a n u s c r i p t 17 setting, we first present a discussion of the age of basin development and fault activity so as to highlight their relationships. The main geometric features of the sedimentary basin are then constrained to constitute new data for discussion of previously proposed regional models. This discussion is focused on the coexistence of extensional and compressional deformations responsible for the geological evolution of the region since Tortonian.

Onset and evolution of the Alhama de Murcia Fault deduced from fold growth

In contrast to reverse and normal faults, which usually have associated wedge deposits that record their progressive development, it is quite difficult to date the initial activity of a strike-slip fault. Notwithstanding, one can identify the first occurrence of strike-slip faulting by studying the associated folds, and normal and/or reverse faults.

Local contractional minor structures related to the AMF hold the key to establishing their complete history. The AMF presents a complete set of related folds and reverse faults in its central sector (Sierra de la Tercia fold, [START_REF] Booth-Rea | Extensional attenuation of the Malaguide and Alpujarride thrust sheets in a segment of the Alborán basin folded during the Tortonian (Lorca area, Eastern Betics)[END_REF][START_REF] Martínez Díaz | Stress field variation related to fault interaction in a reverse oblique-slip fault: the Alhama de Murcia fault, Betic Cordillera, Spain[END_REF], and located at its terminations (to the North in the Bajo Segura Basin splay and related folds: Silva, 1994, Alfaro et al., 2002a[START_REF] Alfaro | Onshore and offshore contractional tectonics in the eastern Betic Cordillera (SE Spain)[END_REF]and to the South in the Huércal-Overa Basin: [START_REF] García-Meléndez | Neotectonics and Plio-Quaternary landscape development within the eastern Huercal-Overa Basin (Betic Cordilleras, Southeast Spain)[END_REF]. By the northern termination of the AMF, seismic profiles point to the existence of progressive unconformities related to ENE-WSW folds [START_REF] Alfaro | Onshore and offshore contractional tectonics in the eastern Betic Cordillera (SE Spain)[END_REF]). In the central sector, [START_REF] Booth-Rea | Extensional attenuation of the Malaguide and Alpujarride thrust sheets in a segment of the Alborán basin folded during the Tortonian (Lorca area, Eastern Betics)[END_REF], from field observations, described Tortonian tilted sedimentation related to the Sierra de la Tercia antiform uplift. In the southern termination of the AMF, our structural data point to the presence of a WNW-ESE minor fold band that was active during the Tortonian, before the deposition of Late Tortonian sediments, as deduced from the progressive unconformities associated with the fold limbs. The activity of the AMF continued during the Plio-A c c e p t e d M a n u s c r i p t 18 Pleistocene, as could be deduced from the syn-tectonic progressive unconformity located in the Garita del Diablo sector (García-Melendez et al., 2003), and during the Holocene [START_REF] Masana | Large Holocene morphogenic earthquakes along the Albox fault, Betic Cordillera, Spain[END_REF]. Thus, field observations support the hypothesis of the Late Tortonian to present-day activity of the AMF.

Basin development models

The most recent models proposed for the Huércal-Overa basin by [START_REF] Meijninger | Late-orogenic extension and strike-slip deformation in the Neogene of southeastern Spain[END_REF] and [START_REF] Meijninger | Miocene extensional basin development in the Betic Cordillera, SE Spain, revealed through analysis of the Alhama de Murcia and Crevillente Faults[END_REF] conclude that it is an extensional basin developed on an extending underlying crust and lithosphere since the Middle Miocene. In addition, these authors propose that some parts of the Alhama de Murcia fault zone initiated as normal faults, which were later reactivated as strike-slip-reverse faults. Our results are in agreement with the development of normal faults that mainly accommodate ENE-WSW to NE-SW extension during the Tortonian. However, geological cross-sections constructed from field data and gravity models indicate that there is no great depocenter linked to the southern border faults (Fig. 10).

The Huércal-Overa Basin has to be explained in the framework of the AMF activity together with the large folds and normal faults formed since the Tortonian. Although sedimentary basins commonly form by the extension of the crust, often they develop in sectors subjected to horizontal shortening, where folding significantly influences their location, dimension, and geometry [START_REF] Cobbold | Sedimentary basins and crustal thickening[END_REF]Nicol et al., 1994). In contractional tectonic settings other authors have described the coetaneous formation of compressive and extensional structures, e.g. in the Himalaya [START_REF] Burchfiel | North-south extension within the convergent Himalayan region[END_REF][START_REF] Shanker | Normal Fault in contractional tectonics[END_REF], and in several sectors of the Mediterranean region along the Alpine mountain range [START_REF] Oldow | Large-scale longitudinal extension in the southern Apennines contractional belt, Italy[END_REF][START_REF] Decker | Tertiary kinematics in the Alpine-Carpathian-Pannonian system: links between thrusting, transform faulting and crustal extension[END_REF]. The geometry of these Our structural data prove active NW-SE compression since the Tortonian, causing the development of folds and faults. Progressive unconformities, associated with large and minor folds, evidence continuous deformation. In addition, the maximum sedimentary thickness is related to the eastward continuation of the Almanzora synform (Fig. 10), which represents one of the main compressive structures of the region. The E-W to ENE-WSW synform development favoured a transgression during the Late Tortonian [START_REF] Pedrera | Fold and fault interactions during the development of an elongated narrow basin: the Almanzora Neogene-Quaternary Corridor (SE Betic Cordillera, Spain)[END_REF]. Despite the presence of numerous normal faults, the existence of a succession of antiforms and synforms along fold bands also suggests a compressive origin. In a purely extensional framework, only single and isolated roll-overs occur.

At any rate, WNW-ESE to NW-SE oriented normal faults were active since the Early Tortonian, also indicating the presence of extensional stress ellipsoids -type 1-in the whole basin. Moreover, normal faults that developed in an extensional setting with type 2 ellipsoids, are parallel to the ENE-WSW folds, probably corresponding to external arc extensions, and deform the Tortonian marls close to the Almanzora synform hinge.

In addition, minor folds and reverse faults that are ENE-WSW oriented began to grow probably in the Late Tortonian, favouring basin emersion and erosion. In the western sector of the basin, these structures accommodate NW-SE shortening, related to stress fields represented by type 3 ellipsoids.

Compressive and extensional tectonic structures in a strike-slip fault termination

A c c e p t e d M a n u s c r i p t 20 Associations of compressive and extensional minor structures linked to transcurrence have been widely recognized in the field [START_REF] Freund | Kinematics of transform and transcurrent faults[END_REF]Woodcock and Fisher, 1986), and their mechanisms of development have been tested through analogue models (Tchalenko 1970, Hempton and[START_REF] Hempton | Experimental fracture, strain and subsidence patterns over en echelon strike-slip faults: implications for the structural evolution of pull-apart basins[END_REF][START_REF] Naylor | Fault geometries in basement-induced wrench faulting under different initial stress states[END_REF]. The classical minor structural associations on the transcurrent fault termination are sets of splay faults, either normal or reverse. The new structural data reported in this paper promote the discussion of compressive and extensional tectonic structural interaction in a strike-slip fault termination.

In the surroundings of the Alhama the Murcia sinistral strike-slip Fault, the presence of normal faults and compressive tectonic structures has most often been explained by successive stress field changes since the Serravallian (Bousquet andPhillip, 1976a, 1976b;[START_REF] Armijo | La zone des failles Lorca-Totana (Cordillères Bétiques, Espagne). Étude tectonique et neotectonique[END_REF][START_REF] Montenat | Tectonic-sedimentary characters of the Betic Néogène Bassins evolving in a crustal transcurrent shear zone (SE Spain)[END_REF]Montenat et al., , 1990;;Ott d'Estevou and[START_REF] Ott D'estevou | Evolution structurale de la zone Betique orientale (Espagne) du Tortonian à l'Holocène[END_REF]1999;[START_REF] Augier | Evolution tardi-orogénique des Cordilères Bétiques (Espagne): Apports d'un étude intégrée[END_REF][START_REF] Meijninger | Late-orogenic extension and strike-slip deformation in the Neogene of southeastern Spain[END_REF][START_REF] Meijninger | Miocene extensional basin development in the Betic Cordillera, SE Spain, revealed through analysis of the Alhama de Murcia and Crevillente Faults[END_REF]. Recently, models have proposed attempting to compile the array of tectonic structures under a regional stable stress field (Martinez-Díaz et al., 2002;[START_REF] Pedrera | Fold and fault interactions during the development of an elongated narrow basin: the Almanzora Neogene-Quaternary Corridor (SE Betic Cordillera, Spain)[END_REF], according to the NW-SE regional shortening direction obtained from the plate-kinematic reconstruction models [START_REF] Dewey | Kinematics of the Western Mediterranean[END_REF][START_REF] Srivastava | Motion of Iberia since the Late Jurassic: Results from detailed aeromagnetic measurements in the Newfoundland basin[END_REF]Muller and Roest, 1992;[START_REF] Mazzoli | Neogene patterns of relative plate motion for Africa-Europe: some implications for recent central Mediterranean tectonics[END_REF][START_REF] Rosenbaum | Relative motions of Africa, Iberia and Europe during Alpine orogeny[END_REF].

In the framework of the regional NW-SE Eurasian-African plate convergence (De Mets, 1994), the new data presented suggest a coeval development since the beginning of the Tortonian of compressive and extensional structures under the same regional stress field. The folds are related to regional compression (ENE-WSW oriented folds) as well as to the strike-slip fault termination (both WNW-ESE and ENE-WSW oriented folds). While the ENE-WSW folds deform up to the Quaternary sediments, the WNW-ESE folds only A c c e p t e d M a n u s c r i p t 21 deform Tortonian sediments. We propose that AMF activity produce the clockwise vertical axis rotation of the folds at its ends, the initially ENE-WSW folds thereby become WNW-ESE oriented and inactive (Fig. 11A andB). These changes in fold orientation are also supported by palaeomagnetic data (Mora, 2003;[START_REF] Mattei | Neogene tectonic evolution of the Gibraltar Arc: New paleomagnetic constraints from the Betic chain[END_REF]. Afterwards, the activity of the transcurrent fault was accommodated by new ENE-WSW oriented folds and reverse faults forming a common splay geometry that interacts with all the previous structures (Fig. 11 D).

We propose two possible mechanisms to support the development of normal faults with the same orientations as folds (Fig. 11 C). (a) The first possibility is a decrease in the horizontal compressive stress produced by relaxation after major transcurrent activity pulses of the AMF. In regions subjected to crustal shortening, transcurrent faults generally show highly variable spatial and temporal slip rates [START_REF] Benett | Codependent histories of the San Andreas and San Jacinto fault zones from inversion of fault displacement rates[END_REF][START_REF] Chevalier | Slip-Rate Measurements on the Karakorum Fault May Imply Secular Variations in Fault Motion[END_REF]. When the horizontal stress diminishes, normal faults may start to develop because the vertical stress axis reaches a maximum induced by gravity. (b) The second hypothesis that may explain the normal fault development is related to the progressive thickening of the crust, which was relatively hot at depth. The available geophysical data [START_REF] Banda | Crustal structure under the central and eastern part of the Betic Cordillera[END_REF][START_REF] Banda | Lateral variation of the crust in the Iberian Peninsula, new evidence from the Betic Cordillera[END_REF]Pous et al., 1999) and the most recent thermal model [START_REF] Soto | Thermal structure of the crust in the Gibraltar Arc: Influence on active tectonics in the western Mediterranean[END_REF] suggest a crust relatively hot in its deepest part decoupled from an anomalous mantle in the Eastern Betic Cordillera. A general uplift, together with emersion and erosion of the Late Miocene basins, is well documented since the Early Tortonian (Braga et al., 2003). In addition, crustal anatexix processes occurring at depth between 12 and 9 Ma, as have been deduced from the mineral age of enclaves located in the highcalalkaline volcanic rocks cropping out in the Eastern Betics (Álvarez-Valero and Kriegsma, 2007;[START_REF] Cesare | Do extrusion ages reflect magma generation processes at depth? An example from the Neogene Volcanic Province of SE Spain[END_REF]. In addition, the extrusion of calc-alkaline and A c c e p t e d M a n u s c r i p t 22 tholeitic volcanic rocks extend from Tortotian up to Messinian in the Eastern Betic, Rif cordilleras and in the Alborán Sea (Duggen et al., 2008 and reference therein). Alkali basalts extruded in Mazarrón-Cartagena area during the Pliocene, as occur in other zones of the Rif Mountains [START_REF] Duggen | Geochemical zonation of the Miocene Alborán Basin volcanism westernmost Mediterranean, geodynamic implications Contrib[END_REF]. An isostatic response linked to progressive crustal thickening and the partial melting of the deepest crust would have resulted in a potentialenergy increase and instability in the upper crust, producing normal faulting. Both mechanisms could work together and explain the presence of the sub-vertical maximum stress axis and sub-horizontal extension, NNE-SSW to NE-SW and E-W to NW-SE, in transition to radial extension.

Conclusions

Compressive and extensional structures deformed the Late Miocene-Quaternary Huércal-Overa Basin, located in the southern termination of the Alhama de Murcia sinistral fault (AMF). Progressive unconformities associated with the fold limbs reveal a Tortonian onset of its activity. Analysis of fold and fault development, gravity data, and the paleostress inversion from minor structures altogether reveal the coeval interaction of three main stress fields (ellipsoids 1 to 3) in a setting of regional NW-SE plate convergence and crustal thickening since the Tortonian.

The compressive structures comprise the major NE-SW to NNE-SSW Alhama de Murcia sinistral fault, kilometric folds and small scale ENE-WSW reverse faults and folds that are developed by a NW-SE oriented sub-horizontal maximum stress axis (ellipsoid 3).

In this setting, the eastward extension of the large Almanzora synform constitutes the main structure determining the Huercal-Overa depocenter. Minor folds progressively grew and Vennin, E., Rouchy, J. M., Chaix, C., Blanc-Valleron, M.-M., Caruso, A., Rommevau, V. (2004). Vissers, R.L.M, Platt, J.P., Van der Wal, D. (1995). Late orogenic extension of the Betic Cordillera and the Alboran Domain: A lithospheric view. Tectonics, 14, 786-803. Yin, A. (1993). Mechanics of wedge shaped fault blocks: an elastic solution for contractional wedge. Journal of Geophysical Research, 98. 14245-14256. Zoetemeijer, R., Cloetingh, S., Sassi, W. Roure, F. (1993). Modelling of piggyback-basin stratigraphy: Record of tectonic evolution. Tectonophysics , 226, 253-269. Figure 7. Huércal-Overa tectonic map. Kinematic data and paleostress results compiled from our tectonic data and previous studies [START_REF] Mora | Tectonic and sedimentary analysis of the Huércal-Overa region, SE Spain, Betic Cordillera[END_REF][START_REF] Augier | Evolution tardi-orogénique des Cordilères Bétiques (Espagne): Apports d'un étude intégrée[END_REF][START_REF] Meijninger | Late-orogenic extension and strike-slip deformation in the Neogene of southeastern Spain[END_REF][START_REF] Pedrera | Fold and fault interactions during the development of an elongated narrow basin: the Almanzora Neogene-Quaternary Corridor (SE Betic Cordillera, Spain)[END_REF]. Table 1 Paleostress determination from microfaults. Measurement sites in Figs. 4 and7.

Figure captions

The main axes orientations are defined by their azimuth and plunge. In addition, the axial ratio values (R = (σ 2 -σ 3 )/ (σ 1 -σ 3 )) are given for each station.

Serravallian-Lower Tortonian

A D

A c c e p t e d M a n u s c r i p t

  the Iberian Massif, paleogeographically interpreted as a passive continental margin.

  include several thrust sheets with Paleozoic to Mesozoic lithostratigraphic sequences showing Alpine ductile deformation and metamorphism, in some cases also of Variscan age. The Maláguide Complex is formed by Paleozoic to Middle Miocene rocks that were deformed but not metamorphosed during the Alpine orogeny. The Dorsal and Predorsal complexes also belong to the Internal Zones, and are formed by Triassic to Early Neogene sedimentary rocks.

  studied the Lorca-Totana sector that is located northward of the Huércal-Overa Basin, describing an extension up to the Messinian and a stress field inversion characterized by compression changing from NE-SW to NNE-SSW strike during the Late Pliocene, and NNW-SSE orientation during the Quaternary. Other authors propose a compressive setting since the Tortonian, with horizontal compression varying from NNW-SSE to NNE-SSW (Ott d'Estevou and

  put forth an inversion tectonic model where the NNE-SSW to NE-SW extension was responsible for the Tortonian basin development, with inversion occurring in post-Messinian times.

  WSW or WNW-ESE oriented folds. Both sets of folds have wavelengths of tens to hundreds of meters, being generally open folds, although they occasionally show vertical limbs. Their vergence is variable: for example, in the centre of the basin the antiforms are usually S-vergent with a northern limb characterized by gentle dip to the North and a A c c e p t e d M a n u s c r i p t 13 steeply dipping to vertical southern limb (e.g. La Parata sector). On the other hand, the folds in the Western sector are usually N-vergent (e.g. La Molata fold, Pedrera et al., 2009a).

  irregular, and the relationship between their sedimentation and tectonic structures could be complex, featuring sectors dominated by compression or by extension, or sectors with overprinted deformation.

  -WSW up to WNW-ESE, becoming inactive with the clockwise vertical axis rotation close to the transcurrent fault termination.Meanwhile, a sub-vertical maximum stress axis and sub-horizontal extension NNE-SSW to NE-SW (ellipsoids 1) and E-W to NW-SE oriented, in transition to radial extension (ellipsoids 2) is responsible for the widespread normal fault development. This stress setting could be explained as a consequence of potential-energy increase related to the thickening of a crust relatively hot at depth, or/and by a decrease in the horizontal stress between activity pulses of the Alhama de Murcia fault. Both mechanisms serve to explain a temporary major vertical stress axis induced by gravity.The field example tackled in this contribution illustrates the coalescence of compressional and extensional structures interacting in the termination of a large transcurrent fault. The proposed genetic models reconcile the great amount of apparently incompatible previous data with new geological and geophysical observations.

  R.W. (1927). Bijdrage tot de geologie der Betisch Ketens in de provincie Granada.Ph.D. Thesis, Univ. Delft.

  Paleoecology constraints on reef-coral morphologies in the Tortonian-early Messinian of the Lorca basin, SE Spain. Palaeogeography, Palaeoclimatology, Palaeoecology, 213, 163-185.

Figure 1 .

 1 Figure 1. Geological setting. (a) Simplified geological map of the Betic Cordillera and (b)

Figure 2 .

 2 Figure 2. Paleostress evolution proposed in previous research for the AMF and surrounding

Figure 3 .

 3 Figure 3. Stratigraphic sketch of the Huércal-Overa Basin.

Figure 4 .

 4 Figure 4. Geological map of the Huércal-Overa Basin. The locations of the main faults and

Figure 5 .

 5 Figure 5. Field examples of faults (location indicated in figure 4). (A) Example of WNW-

Figure 6 .

 6 Figure 6. Field examples of folds (location indicated in figure 4). (A) Example of WNW-

Figure 8 .

 8 Figure 8. Residual gravity anomalies (mGal) and tectonic structures. Note the incidence on

Figure 9 .

 9 Figure 9. 2D models constructed from the residual gravity anomalies that allow us to

Figure 10 .

 10 Figure10. Geological cross-sections from structural and gravity data (sedimentary rocks density of 2.35 gr/cm 3 ). The position is marked in Figure4.

Figure 11 .

 11 Figure 11. Evolution of the Huércal-Overa Basin and structural interactions associated with

  Fig. 1B

  Fig. 6A

  Fig. 5E

  Fig. 5C

  Figure 7

  Figure 8

Figure

  Figure

Acknowledgements

We are grateful Reinoud Vissers, John Platt, Jan-Philipp Schmoldt, and an anonymous reviewer the comments and suggestion on an early version of the paper. This study was supported by the projects TOPO-IBERIA CONSOLIDER-INGENIO CSD2006-00041 and CGL 2006-06001 of the Spanish Ministry of Science and Education, as well as by Research Group RNM-149 of the Junta de Andalucía Regional Government. Jean Sanders revised the English manuscript style.