Definición de la Formación Cehegín para los carbonatos de faciès Muschelkalk depositados en un área intermedia-externa del Paleomargen Sudibérico

The Cehegín Formation (Ladinian) is defined as a formal lithostratigraphic unit to characterize the Muschelkalk facies deposited on intermediate-external area of the southern Iberian continental margin. This formation consists of dark limestones and marly limestones. Two main members can be distinguished in this formation. In the lower member, two o three massive carbonate thick beds appear with bedded marly limestone intercalations. The upper member consists of a more marly succession of carbonate beds with burrows and intercalations of bioclastic limestone. Pot and gutter casts are frequent in the lower member, and tempestites occur mainly in the upper member. The sediments of this formations are interpreted as epicontinental marine deposits. The holostratotype, parastratotypes and hypostratotype which characterize this formation in the Betic Cordillera are described

Bioestratigrafía del Ladiniense Inferior en la región de Calasparra (Murcia, España)

A bioestratigraphic study has been carried out with the aid of ammonoids from the Lower Ladinian of the SE Calasparra section (Eastern of the Betic Cordillera). The section is formed by 89 m of do- lostones and fossiliferous limestones from the Muschelkalk facies. From the study of 11 successive levels with ammonoids, three biozones have been distinguished: Brotzeni Zone (Upper Anisian), Curionii Zone (Lower Ladinian) and Epigonus Zone (Upper Ladinian). Moreover, the Curionii Zone could be subdivided in two Subzones: Curionii Subzone and Awadi Subzone. The ammo- noid assemblages are typical from the Sepharadic Province, which include numerous species in common with Sinai and Negev (Israel). These assemblages can be correlated with other areas of Spain (Catalonia and Minorca) and the Tethys Province, due to the presence of two species of wide geographic distribution, Eoprotrachyceras curionii and "Eoprotrachyceras" cf. gredleri, which are recorded in the lower part of the Curionii and Epigonus Zones respectively

An evaporite-bearing accretionary complex in the northern front of the Betic-Rif orogen

The Guadalquivir Accretionary Complex forms a largely oblique prism at the northern edge of the Betic-Rif orogen, where Miocene sediments plus allochthonous evaporite-bearing units were accreted during the displacement of the Alborán Domain toward the west. Traditional interpretations end the tectonic structuring of the Betic Cordillera at the present topographic front, beyond which gravitational and/or diapiric processes would predominate. However, this study shows pervasive tectonic deformation in the outer prism with coherent oblique shortening kinematics, which is achieved through an alternation of roughly N-S arcuate thrust systems connected by E-W transfer fault zones. These structures accord well with the geophysical models that propose westward rollback subduction. The main stage of tectonic activity occurred in the early-middle Miocene, but deformation lasted until the Quaternary with the same kinematics. Evaporite rocks played a leading role in the deformation as evidenced by the suite of ductile structures in gypsum distributed throughout the area. S- and L- gypsum tectonites, scaly clay fabrics, and brittle fabrics coexist and consistently indicate westward motion (top to 290°), with subordinate N-S contraction almost perpendicular to the transfer zones. This work reveals ductile tectonic fabrics in gypsum as a valuable tool to elucidate the structure and deformational history of complex tectonic mélanges involving evaporites above the décollement level of accretionary wedges.This study was supported by research projects CGL2012-33281 and CGL2013-46368-P (Secretaría de Estado de I+D+I, Spain), CeacTierra-Universidad de Jaén, RNM-0451 (Junta de Andalucía), and by the Junta de Andalucía Research Groups RNM 208, 325, and 370

The oldest post-Paleozoic (Ladinian, Triassic) brachiopods from the Betic Range, SE Spain

Triassic brachiopods from the Betic Range were unknown hitherto. Herein we describe the first brachiopod occurrences in the early Ladinian of this domain referable to a new genus and species Misunithyris goyi derived from three localities of the south-Iberian Triassic outcrops. The analysis of internal and external characters of this brachiopod allowed to characterize systematically and biogeographically this fauna in a chronostratigraphic interval when the paucity of brachiopod records is attributable to the entire peri-Iberian epicontinental platform system established in the westernmost Tethyan margin. The new record is endemic to the Betic Range and represents a new faunal constituent of the multicostate zeillerids stock. This fauna inhabited the epicontinental seas of the Sephardic bioprovince since a closer affinity with the low-latitude Tethyan assemblages is revealed. The possible linkage of the Triassic stock with the Early–Middle Jurassic multicostate zeillerid representatives suggests feasible phylogenetic relationships between both groups.This research was supported by projects CGL2015-66604-R (MINECO, Government of Spain), the Research Groups VIGROB-167 (University of Alicante), and RNM 325 (Junta de Andalucía)

Active Tectonics, Quaternary Stress Regime Evolution and Seismotectonic Faults in Southern Central Hispaniola: Implications for the Quantitative Seismic Hazard Assessment

Present-day convergence between Caribbean and North American plates is accommodated by subduction zones, major active thrusts and strike-slip faults, which are probably the source of the historical large earthquakes on Hispaniola. However, little is known of their geometric and kinematic characteristics, slip rates and seismic activity over time. This information is important to understand the active tectonics in Hispaniola, but it is also crucial to estimate the seismic hazard in the region. Here we show that a relatively constant NE-directed shortening controlled the geometry and kinematics of main active faults in southern central Hispaniola, as well as the evolution of the Quaternary stress regime. This evolution included a pre-Early Pleistocene D1 event of NE-trending compression, which gave rise to the large-scale fold and thrust structure in the Cordillera Central, Peralta Belt, Sierra Martín García and San Juan-Azua basin. This was followed by a near pure strike-slip D2 stress regime, partitioned into the N-S to NE-SW transverse Ocoa-Bonao-La Guácara and Beata Ridge fault zones, as well as subordinate structures in related sub-parallel deformation corridors. Shift to D2 strike-slip deformation was related to indentation of the Beata Ridge in southern Hispaniola from the Early to Middle Pleistocene and continues today. D2 was locally coeval by a more heterogeneous and geographically localized D3 extensional deformation. Defined seismotectonic fault zones divide the region into a set of simplified seismogenic zones as starting point for a seismic hazard modeling. Highest peak ground acceleration values computed in the Ocoa Bay establish a very high seismic hazard.The research was funded through PID2019-105625RB-C22 project of the MCIN/AEI/10.13039/501100011033 of the Spanish Government. Some works also received funding from the DR-T 1190 Project of the Banco Interamericano de Desarrollo (World Bank) and the FONDOCYT project 2015-1b3–118 of the MESCyT of the Dominican Republic Government

Ammonoideos del Ladiniense en la Unidad de Cabo Cope (Zonas Internas, Cordillera Bética)

In the Cabo Cope Unit (Maláguide Complex, W Aguilas, Murcia), two members have been distinguished within the Triassic Unit. The lower member consists of detritic deposits with interbedded gypsum. The upper member is composed of carbonates. A level containing ammonoids has been found at 21m above the base of the upper member. Due to the inusual presence of fossils of this taxonomic group in the whole Malaguide Complex, their study has a special biochrnostratigra- phycal and palaeogeographyc relevance. The studied fossils belong to Clydonitaceae, Trachyce- ratidae, of the genus Anolcites Mojsisovics, 1893. This genus which has a wide biogeographical distribution in Alpine Europe, Balkans, Himalaya and North America, has been recognised here for the first time in the Betic Cordillera. The tipe species A. doleriticus (Mojsisovics, 1882) which was defined in the Upper Ladinian of Southern Alps, is present in the Cabo Cope section. This presence allows supposition that during the Upper Ladinia, a palaeogeographic connection between the southeastern domain of the Betic Cordillera and the Tehys Province existed

Sharp-based, mixed carbonate–siliciclastic shallow-marine deposits (upper Miocene, Betic Cordillera, Spain): The record of ancient transgressive shelf ridges?

Isolated sharp-based sedimentary bodies in shelf settings can develop via the reworking of regressive deposits during transgressions. An example of these are shelf ridges, formed under a wide range of processes, and widely studied due to their high reservoir potential. However, there is still a lack of examples in mixed (carbonate–siliciclastic) successions. This study presents an outcrop example from the Upper Miocene of the Betic Cordillera (Spain), with the aim to propose a model for the development of transgressive sharp-based mixed carbonate–siliciclastic deposits, and to provide criteria to differentiate these from their regressive counterparts. The studied succession is ca. 300 m-thick, and shows a cyclic alternation of coarse and fine-grained mixed deposits. Depositional cycles start with siliciclastic-dominated offshore to offshore transition deposits, progressively replaced by lower shoreface deposits. These are abruptly truncated by sharp erosive contacts bioturbated by passively-infilled large burrows; their ichnological features allow assignation to the Glossifungites ichnofacies. These contacts are interpreted as ravinement surfaces. They are overlain by mixed carbonate–siliciclastic barforms, rich in skeletal fragments and extraclasts, and displaying large-scale cross bedding. These form several m-thick and hundreds of m-long depositional elements interpreted as mixed shelf ridges. These ridges formed in a fine-grained, shallow-water shelf, which occasionally received coarse siliciclastic sediment supply via gravity flows, but had a coeval offshore carbonate factory, which provided the skeletal fragments. The sharp-based, coarser-grained nature and lithological break at the base of these mixed carbonate–clastic deposits could lead to their misinterpretation as forced-regressive wedges. However, the nature of their lower contact, combined with the reworked offshore skeletal fragments, and their stacking pattern are consistent with these mixed units forming during transgression. Other studies in relatively time-equivalent deposits have demonstrated the existence of coeval regressive, coarser siliciclastic-dominated shoreline systems in relatively close localities. These evidence a complex basin configuration in the area during the upper Miocene, with the development of local depocentres and relatively narrow corridors or seaways in the Mediterranean–Atlantic connection, which could have favoured shelf reworking processes, but also promoted the development of diverse stacking patterns, reflecting the differential interaction between active tectonics and sedimentation across the region.FEDER AndalucíaSecretaría de Estado de I+D+IAker BPUniversitetet i OsloUniversidad de Granada PID2019-104625RB-100, PID2020-114381GB-100European Regional Development Fund CGL2017-89618-RJunta de Andalucía B-RNM-072-UGR18, P18-RT-4074Agencia Estatal de Investigació

La falla de Tíscar: su significado en la terminación sudoeste del arco Prebético

10 páginas, 11 figuras, 1 tabla.[EN] The Tíscar fault, located towards the SW end of the Prebetic arc, is an important feature within the Betic External Zone which contributed to the separation of two different geologic domains. This fault affected the Mesozoic and Tertiary cover detached from the Palaeozoic basement and was developed as consequence of the blockage of the thrust sheets of the western border of the arc, because they could not advance farther over the basement situated progressively in a shallower position. Hence, this fault encouraged the continuation of the NW displacements in the western block, formed by Subbetic olistostromic masses and part of the Prebetic situated in the end of the arc. Although the Tíscar fault has been defined by one main line, there are in fact other parallel faults that form a broad fault zone. Its displacement began during the late Miocene and continued till Pliocene, within a near N-S compressive setting with a perpendicular extension.[ES] La falla de Tíscar, localizada en la terminación SO del arco Prebético, es un rasgo importante dentro de la Zona Externa Bética, donde ha contribuido a la separación de dos dominios geológicos diferentes. Esta falla afectó a la cobertera mesozoica y terciaria despegada del basamento paleozoico y se formó como consecuencia de que los cabalgamientos del borde occidental del arco quedaron bloqueados al no poder avanzar más sobre el basamento cada vez menos profundo. Entonces la falla permitió la continuación de los movimientos hacia el NO de su bloque occidental formado por materiales del Subbético, dispuesto en masas olistostrómicas, e incluso parte del propio Prebético del extremo del arco. Aunque la falla de Tíscar se ha definido por su traza principal, existen otras paralelas que en conjunto forman una amplia zona. Sus movimientos iniciados en el Mioceno superior continuaron hasta el Plioceno, en un contexto de compresión N-S y extensión perpendicular.Este estudio se ha financiado a través de los proyectos BTE2001-5230-E, CGL200401636/BTE, CGL2004-03333/ BTE, CGL2005-01520/BTE y BTE2001-5230-E y los grupos de la Junta de Andalucía RNM 163 y 217.Peer reviewe

Reconstructing the Crustal Section of the Intra-Oceanic Caribbean Island Arc: Constraints From the Cumulate Layered Gabbronorites and Pyroxenites of the Rio Boba Plutonic Sequence, Northern Dominican Republic

Located in northern Dominican Republic, the Early Cretaceous Rio Boba mafic-ultramafic plutonic sequence constitutes a lower crust section of the Caribbean island arc, made up by gabbroic rocks and subordinate pyroxenite. Modal compositions, mineral chemistry, whole-rock compositions and thermobarometric calculations indicate that pyroxenites and gabbronorites represent a cumulate sequence formed by fractionation of tholeiitic magmas with initially very low H2O content in the lower crust of the arc (0.6–0.8 GPa). Melts evolved along a simplified crystallization sequence of olivine → pyroxenes → plagioclase → Fe-Ti oxides. The magmatic evolution of the Rio Boba sequence and associated supra-crustal Puerca Gorda metavolcanic rocks is multi-stage and involves the generation of magmas from melting of different sources in a supra-subduction zone setting. The first stage included the formation of a highly depleted substrate as result of decompressional melting of a refractory mantle source, represented by a cumulate sequence of LREE-depleted island arc tholeiitic (IAT) and boninitic gabbronorites and pyroxenites. The second stage involved volumetrically subordinate cumulate troctolites and gabbros, which are not penetratively deformed. The mantle source was refractory and enriched by a LILE-rich hydrous fluid derived from a subducting slab and/or overlying sediments, and possibly by a LREE-rich melt. The third stage is recorded in the upper crust of the arc by the Puerca Gorda “normal” IAT protoliths, which are derived from an N-MORB mantle source enriched with a strong subduction component. This magmatic evolution has implications for unraveling the processes responsible for subduction initiation and subsequent building of the Caribbean island arc.This research was funded through CGL2012-33669/BTE and PID2019-105625RB-C22 of the MCIN/AEI/10.13039/501100011033 projects and PRX18/00055 stay grant to the J. Escuder-Viruete of the Ministerio de Ciencia e Innovación of the Spanish Government