Betic Internal Zone Research Articles

A Python Application for Visualizing an Imbricate Thrust System: Palomeque Duplex (SE, Spain)

This paper introduces a Python application for visualizing an imbricate thrust system. The application uses the traditional geologic information to create an HTML geological map with real topography and a set of geological cross-sections with the essential structural and stratigraphic elements. On the basis of the high geological knowledge gained during the last three decades, the Palomeque sheets affecting the Cenozoic Malaguide succession in the Internal Betic Zone (SE Spain) were selected to show the application. In this area, a Malaguide Cretaceous to Lower Miocene succession is deformed as an imbricate thrust system, with two thrusts forming a duplex, affected later by a set of faults with a main strike-slip kinematic. The modeled elements match well with the design of the stratigraphic intervals and the structures reported in recent scientific publications. This proves the good performance of this Python application for visualizing the structural and stratigraphic architecture. This kind of application could be a crucial stage for future groundwater, mining, and civil engineering management.

Barrovian metamorphism in nominally lowermost Alpujarride Complex units: tectonic implications for the development of the orogenic wedge in the Western Mediterranean

ABSTRACT The sedimentary successions of the Permian-Triassic rifting related to the Alpine Tethys in the easternmost Lower Alpujarride units (Internal Betic Zone, south Spain) host shallow-intrusive basic bodies of Mesozoic age. These gabbroic bodies experienced low-grade Alpine metamorphic overprint, singularly recorded in three outcrops nearby Alicante city in southeast Spain: Callosa and Orihuela Ranges and Nueva Tabarca Island. Overall, the metabasic bodies still preserve magmatic ophitic/subophitic texture and relicts of magmatic augite and ferropargasite-ferroedenite-edenite and kaersutite. In contrast, metamorphic minerals include magnesioriebeckite, actinolite, albite, stilpnomelane, phengite, and chlorite. Major and trace element geochemical data suggest crystallization of the igneous protoliths from subalkaline (tholeiitic) to alkaline within-plate (continental) basaltic magmas slightly enriched in incompatible elements. These magmas with E-MORB geochemical affinity very likely intruded at shallow crustal levels in an extensional-synrift-geodynamic setting related to the breakoff of Pangea in the region. Pressure-Temperature (P-T) conditions estimated by average P-T method and pseudosection calculations suggest metamorphic peak at ca. 6 kbar at 340°C consistent with burial metamorphism down to ca. 18 km depth with intermediate thermal gradients of ca. 18°C/km. These conditions are different to the typical subduction-related blueschist facies conditions of the Lower Alpujarride units and suggest, instead, a collisional (Barrovian) event. This can be explained by a late-stage accretion of the studied units after the main subduction-related event, pointing to the dispersion of the corresponding Lower Alpujarride sections along the margin in different palaeogeographic positions before deformation and movement to their actual structural position. The metamorphic correlation of the studied units with the accreted passive margin of South Iberia (Subbetic zone) is also discussed.

The Eocene carbonate platform of the central-western Malaguides (Internal Betic Zone, S Spain) and its meaning for the Cenozoic paleogeography of the westermost Tethys

The Eocene Peñicas (Almería) and Harania (Málaga) stratigraphic sections from the Malaguide Complex (Betic Cordillera, South Spain) belonging to the Mesomediterranean Microplate from the westernmost Tethys (about-35°N and 0° to 5°E according to the Eocene coordinates) have been studied. The Eocene sections cover the Cuisian to middle Lutetian deposits, which show several lithofacies representing shallow marine platform realms. Based on the fossiliferous assemblage, texture and fabrics, eight microfacies related to inner to outer ramp settings were defined. In the inner ramp of the Harania section abundant colonial corals have been recognized. The Eocene deposits are arranged into a transgressive succession composed by three minor transgressive-regressive sedimentary cycles. The Eocene fossiliferous assemblage shows a mixture of photozoan (Larger Bentic Foraminifera –LBF–, green and red calcareous algae and corals) and heterotrophic (mollusks, echinoids, bryozoans, small benthic and planktic foraminifers) elements, suggesting euphotic to mesophotic conditions in oligo-mesotrophic marine warm-waters at low-middle latitudes. This assemblage indicates a transition from photozoan to heterozoan carbonates and in particular a shift towards outer marine ramp settings. During the Early Eocene, the widespread distribution of LBF leads in the Tethyan domains to disappearance or extreme reduction of coral constructions. Nevertheless, abundant corals associated to inner ramp realms have been observed in the Harania stratigraphic section indicating that corals could continue to develop in the westernmost Tethys at the transition to the Atlantic Ocean, in contrast with respect to other Tethyan sectors. Therefore, the Ypresian-Lutetian time-span is a transitional period for the global temperature during which corals locally survived only where optimal ecologic conditions occurred, preferably in marginal contexts, as it seems to have happened in the studied area. • Westernmost Tethys (about-30° N and 0° to 5°E according to the Eocene coordinates) • Cuisian to Middle Lutetian deposits • Shallow marine platform realms • Photozoan elements (LBF, green and red calcareous algae and corals) • Abundant corals associated to inner ramp realms

Provenance of quartz grains from soils over Quaternary terraces along the Guadalquivir River, Spain

The characterisation of quartz grains’ chemical and mineralogical properties in sediments and sedimentary rocks is widely used in provenance studies. This paper analyses quartz grains from the coarse sand fraction in soils in Quaternary fluvial terraces (Guadalquivir River, southern Spain). The tentative soil ages are 0.3 ka (Haplic Fluvisol), 7 ka (Haplic Calcisol), 70 ka (Cutanic Luvisol), 300 ka (Lixic Calcisol) and 600 ka (Cutanic Luvisol). The quartz grains analyses shed light on the sedimentological history of these terraces. Scanning electron microscope cathodoluminescence (SEM-CL) characteristics, micro inclusion inventory established by Energy-dispersive X-ray spectroscopy (SEM-EDX) and trace element contents determined with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of quartz grains permitted distinguishing six types of grains in the soils studied: metamorphic quartz (type 1), undeformed granitic quartz (type 2), strongly altered granitic quartz (type 3), recrystallised (deformed) granitic quartz (type 4), sandstone-derived quartz (type 5) and hydrothermal quartz grains (type 6).Metamorphic quartz grains (type 1) come from the Sierra Morena (Iberian Massif) and Sierra Nevada (Internal Betic Zone). Granitic quartz grains (types 2 to 4) come from Los Pedroches batholith and its associated plutons (Santa Elena and Linares). The sandstone-derived quartz type 5 comes from the numerous sandstone outcrops scattered in the central catchment area of the Guadalquivir River. Finally, hydrothermal quartz grains (type 6) originate from hydrothermal veins associated with subvolcanic rocks of the Los Pedroches batholith.Variations were noted in the proportions of quartz types in soils of different ages, attributed to spatial and temporal changes in the catchment area. The most remarkable change occurred between 500 and 240 ka ago when the catchment area extended into Sierra Nevadás metamorphic rocks, well reflected in type 1 content (lower in P2, P4, P5 and PM) and their characteristics (quartz with less healed fractures, less Al content, bigger mica microinclusions, smaller Al/Ti ratio) in the post-500–240 ka soils.Our study shows that the combined study of SEM-CL characteristics, micro inclusions (SEM-EDX), and trace element contents (LA-ICP-MS) of quartz grains is an efficient approach for characterising the provenance of quartz grains in the sand fraction of soils.

The Cenozoic Malaguide Basin from Sierra Espuña (Murcia, S Spain): An Example of Geological Heritage

The Cenozoic Malaguide Basin from Sierra Espuña (Internal Betic Zone, S Spain) due to the quality of outcropping, areal representation, and continuity in the sedimentation can be considered a key-basin. In the last 30 years, a large number of studies with very different methodological approaches have been done in the area. Models indicate an evolution from passive margin to wedge-top basin from Late Cretaceous to Early Miocene. Sedimentation changes from limestone platforms with scarce terrigenous inputs, during the Paleocene to Early Oligocene, to the deep basin with huge supplies of turbidite sandstones and conglomerates during the Late Oligocene to Early Miocene. The area now appears structured as an antiformal stack with evidence of synsedimentary tectonics. The Cenozoic tectono-sedimentary basin evolution is related to three phases: (1) flexural tectonics during most of the Paleogene times to create the basin; (2) fault and fold compartmentation of the basin with the creation of structural highs and subsiding areas related to blind-fault-propagation folds, deforming the basin from south to north during Late Oligocene to Early Aquitanian times; (3) thin-skin thrusting tectonics when the basin began to be eroded during the Late Aquitanian-Burdigalian. In recent times some works on the geological heritage of the area have been performed trying to diffuse different geological aspects of the sector to the general public. A review of the studies performed and the revisiting of the area allow proposing different key-outcrops to follow the tectono-sedimentary evolution of the Cenozoic basin from this area. Eight sites of geological interest have been selected (Cretaceous-Cenozoic boundary, Paleocene Mula Fm, Lower Eocene Espuña-Valdelaparra Fms, Middle Eocene Malvariche-Cánovas Fms, Lowermost Oligocene As Fm, Upper Oligocene-Lower Aquitanian Bosque Fm, Upper Oligocene-Aquitanian Río Pliego Fm, Burdigalian El Niño Fm) and an evaluation has been performed to obtain four parameters: the scientific value, the educational and touristic potential, and the degradation risk. The firsts three parameters obtained values above 50 being considered of “high” or “very high” interest (“very high” in most of the cases). The last parameter shows always values below 50 indicating a “moderate” or “low” risk of degradation. The obtained values allow us considering the tectono-sedimentary evolution of this basin worthy of being proposed as a geological heritage.

The Andalusian E-W coast. Discussion on its geological significance

The Andalusian coast from the Cabo de Gata to Malaga has as a whole an E-W direction. The tectonic units are arranged obliquely along it, in general with the lower ones outcropping the in the eastern part and the upper ones in the western part. Since the continental shelf is narrow, this obliquity cannot be recovered before the slope, which suggests the existence of a fault along the slope. In support of this interpretation, it should be noted that in the westernmost part of the Betic Internal Zone there are significant dextral E-W faults (i.e. parallel to the E-W coast), which are some of the E-W faults cutting up the Internal Zone facilitating its westwards translation, greater in the southern most sectors displaced by the faults. These westwards displacements were linked to the opening of the Alboran Sea, due to the pressure that this produced especially on its northern border (on the other hand, deformations also occurred on the Rifian border). Later, important E-O antiforms were formed and the erosion of the S flank of the antiform situated directly to the N of the coast produced the existing scarp.

Sedimentary history and palaeogeography of the Cenozoic clastic wedges of the Malaguide Complex, Internal Betic Cordillera, southern Spain

The Cenozoic sedimentary cover of the Malaguide Complex (Internal Betic Cordillera, Spain), in the Almería and Málaga areas, consists of a suite of sedimentary successions from continental and shallow-marine to deep-marine environments. Structural and stratigraphic relations, and petrological and geochemical signatures reveal the sedimentary evolution of the Cenozoic Malaguide Complex (CMC) from pre-orogenic (Palocene-Eocene) to syn-orogenic (Oligocene-Early Miocene) stages. Sandstones detrital modes of the overall succession are heterogeneous testifying to a multi-source area, marked by exhumation of the Malaguide basement terranes and of the Internal Betic Zone (Alpujárride Complex) in lower position. Pre-orogenic and syn-orogenic strata consist of four main depositional sequences: the Mula Group (Paleocene), the Xiquena Group (Eocene) for the preorogenic successions; and Ciudad Granada Group (Oligocene-Aquitanian) and Viñuela Group (Burdigalian) for the synorogenic successions. Pre-orogenic strata evolve from intra-arenite to hybrid arenites to progressive increase of sandstones in abundance of detrital supply from sedimentary cover of the internal Betic units. The unroofing history of the internal Betic Units, predominantly in the Malaguide Complex, is clearly testified in strata of the synorogenic clastic units, where detrital supply is coming from the Malaguide Complex. Sedimentary lithic fragments were derived from the Mesozoic strata of the Malaguide Complex while metamorphic detritus is related to the Internal Betic Zone basement that was exhumed starting from the Oligocene. Pre-orogenic mudrocks mainly show abundance of calcite and dolomite over quartz and phyllosilicates. Syn-orogenic mudrocks, record an abrupt decrease in calcite and dolomite and an increase of phyllosilicate, quartz and feldspars mainly in the Malaga section. The geochemical signatures attest to a compositional variation of the samples from pre-to-synorogenic successions, with palaeoweathering indices showing moderate values and a weak up-section decrease. The Cenozoic Malaguide Complex played a key role in the geodynamic evolution of the Betic Cordillera, representing the key tectonic element of the western Mesomediterranean domains.

Petrology, geochemistry and origin of the sierra de baza ophiolites (Betic cordillera, Spain)

In this work we present for the first time a petrological-geochemical and genetic study of the Sierra de Baza ophiolites, which represent one of theophiolitic occurrences of the Betic Cordillera (Southern Spain). They are composed of ultramafic, mafic and sedimentary rocks, largely affected bothby ocean floor and polyphasic metamorphism during the Alpine orogeny. Ultramafic rocks are serpentinized lherzolites and harzburgites, whereas themetabasites are meta-gabbros and meta-basalts. On the whole, Sierra de Baza ophiolites show striking geochemical similarities with those from otherBetic occurrences, as well as with other Tethyan ophiolites of the Western Mediterranean (Calabria, Internal and External Ligurides, Platta, Corsica andWestern Alps). In particular, metabasites show petrological and geochemical features similar to the E-MORB magmatism of the Atlantic Ridge between45 and 63oN generated under ultra-slow spreading ridge conditions. This process originated a strip of few hundreds km of ocean floor at the western endof the Tethys, located SE of the Iberian-European margin during the Mesozoic. The inversion of the stress regime in the European-Iberian and Africangeodynamics, starting from the Late-Middle Cretaceous, caused subduction and metamorphism in the eclogite facies of oceanic slices that were partiallyexhumed on the continental margin, forming the Betic Ophiolites. These ophiolites were disarticulated and dismembered as a result of the shift towardsSW of the Alboran continental block, progressively separated from the AlKaPeCa (Alboran, Kabilias, Peloritani, Calabria) microplate, finally occupyingtheir current position in the Betic Internal Zones.

Linking Palaeozoic palaeogeography of the Betic Cordillera to the Variscan Iberian Massif: new insight through the first conodonts of the Nevado-Filábride Complex

Graphite-rich metamorphic limestones included within low-grade black schists of the lowest Nevado-Filabride tectonic unit in the Sierra de Baza (Bodurria Unit) provided the first conodonts found in this complex (Declinognathodus bernesgae, D. inaequalis. D. cf. praenoduliferus, and Idioprioniodus sp.). This demonstrates the early Bashkirian age of the sedimentary protoliths, and their deposition in open marine anoxic environments of a continental margin that opened towards the E and that was related to the Palaeotethys. This breakthrough offers strong support for the hypothesis that the lower Nevado-Filabride units show stratigraphic and palaeogeographic affinities with the external domains of the Iberian Massif (Palentian Domain of the Cantabrian Zone in particular). Consequently, this part of the Betic Internal Zones must be related to the basement of the South-Iberian Palaeomargin and excluded from the Alboran Domain tectonostratigraphic terrane.

Unravelling hinterland and offshore palaeogeography from pre-to-syn-orogenic clastic sequences of the Betic Cordillera (Sierra Espuña), Spain

The Malaguide Complex (Betic Cordillera) occurs in the Sierra Espuña area (SE Spain) providing a favorable setting to study a sedimentary successions from continental and shallow-marine to deep-marine environments using structural and stratigraphic relations, and petrological and geochemical signatures. The aim of this work is to outline the sedimentary evolution of the Malaguide Complex and the El Niño Fm. This succession is arranged into pre-orogenic (Paleocene-Early Oligocene) and syn-orogenic (Late Oligocene-Early Miocene) stages. The detrital modes of sandstones of the overall succession are heterogeneous and indicate a multi-source area, marked by exhumation till an unknown Malaguide basement and probably lower units of the Internal Betic Zone (e.g. Alpujarride Complex) in the case of the El Niño Fm. Pre-orogenic deposits are mainly carbonate with abundant skeletons of intrabasinal to extra-basinal larger foraminifera, calcareous lithic fragments and quartz grains, and metamorphic lithic fragments. Minor metamorphic lithic fragments occur in the Eocene deposits (i.e. Espuña Fm). Calcareous lithic fragments and extra-basinal fossils (lithoclastic bioclasts) are mostly present in the Early Oligocene pre-orogenic formations (i.e. As Fm) and were derived from the Paleocene-Eocene sedimentary successions of the Malaguide Complex. Syn-orogenic sandstones are quartzolithic with abundant metamorphic and sedimentary lithic fragments (slate, phyllite, fine-grained schist, ooidal grainstone, mudrock and quartz-rich siltstone fragments). Sedimentary lithic fragments were derived from the Mesozoic successions of the Malaguide Complex while metamorphic detritus is related to the Malaguide basement (probably also Alpujarride from Burdigalian on) that was exhumed starting from the Late Oligocene. Mudrocks of the syn-orogenic clastics, record an increase of phyllosilicate, quartz and feldspars and an abrupt decrease in calcite and dolomite. The abundance of calcite and dolomite, and traces of hematite occur dominantly in the pre-orogenic mudrocks. The geochemical signatures suggest a provenance mostly derived from felsic source rocks with a minor supply from mafic metavolcanic rocks in some samples of the syn-orogenic stage. The syn-orogenic formations (i.e. Rio Pliego Fm and El Niño Fm) are characterized by higher Cr/V values than the pre-orogenic formations suggesting a mafic supply for the syn-orogenic samples. In particular, the contents of Cr (average=85ppm) and Ni (average=48ppm) for the samples of the Rio Pliego and El Niño Formations are higher than those samples (Cr average=20ppm; Ni average=14ppm) of the pre-orogenic formations. Palaeoweathering indices suggest low to moderate weathering conditions for the source area(s). The Cenozoic studied succession played a key role in the geodynamic evolution of the Betic Cordillera, representing the key tectonic element of the western Mesomediterranean domains.

The nevado-filábride complex in the western part of Sierra de los Filabres (Betic Internal Zone), structure and lithologic succession

In the western part of Sierra de los Filabres (in the Nevado-Filábride Complex, within the Betic Internal Zone) several tectonic units have been described, in varying numbers depending on the author describing them. However, new cartographical data show that the limits of these units pass through the lithological formations without displacing them. Moreover, the rocks belonging to some units that are supposedly situated in a lower tectonic position really belong to higher formations. From bottom to top, these lithological formations are the following: (1) dark schists and quartzites; (2) quartzites, sandstones, sands, lutites, schists, and mica schists; (3) schists; (4) marbles, schists, and mica schists. High-angle reverse faults are associated with the great E-W anticline of Sierra de los Filabres. The existence of sands and apparent lutites visibly interlayered between rocks, such as schists and mica schists with garnets, poses a metamorphic problem that has not as yet been addressed.

Compositional signatures of the Cenozoic sedimentary successions of the Malaguide Complex (Betic Cordillera, Spain)

The studied Cenozoic sedimentary successions consist of deposits from continental/shallow-water to deep-marine environments of the Malaguide Complex (Betic Cordillera) outcropping in the Sierra Espuna area (SE Spain). The aim of this study is to characterize the composition, source area(s) provenance and weathering processes of these sedimentary successions from the pre-orogenic (Paleocene-Early Oligocene) to the syn-orogenic (Late Oligocene-Early Miocene) stage using petrological and geochemical methodologies. The studied sandstones are mainly quartzolithic with abundant metamorphic and sedimentary lithic fragments. In particular, the composition of samples from the pre-orogenic cycle is mainly carbonate with important siliciclastic components that occur within the medium to fine grained arenites. The composition of samples from the syn-orogenic cycle is characterized by a sharp change from carbonate to siliciclastic terms. Thus, the composition of the overall sandstone samples is very heterogeneous and suggests a source area mainly characterized by the Malaguide basement and lower units of the Internal Betic Zone, that partially compose the Mesomediterranean Microplate. The geochemical proxies suggest a provenance mainly from felsic source area with a minor supply from mafic rocks in some samples of the syn-orogenic stage. Furthermore, palaeoweathering indices indicate low to moderate weathering conditions for the sources. The Cenozoic sedimentary successions of the Malaguide Complex played an important role in the geodynamic evolution of the Betic Cordillera that represents the key tectonic element of the western domains of the Mesomediterranean Microplate.

The Zafarraya Polje (Betic Cordillera, Granada, Spain), a basin open by lateral displacement and bending

The Zafarraya Polje is situated in the Subbetic (Betic External Zone), near the contact with the Betic Internal Zone. This is a small tectonic basin delimited by faults of which the main component is normal, but located among folds and reverse and dextral-reverse faults formed in a compressive context. One N–S fault marks the western border of the basin and shows major dextral displacements in its southern part (at the SW of the basin but directly outside the basin) and major normal movements in the northern part (on the west side of the basin). This fault took on great importance in the formation of the basin, and its movements are not compatible with the stress ellipsoids existing during the Neotectonic period. The basin appeared just at the end of the formation process of the compressive structures, probably at the beginning of the late Tortonian, as the result of the westward push of the Internal Zone in the southernmost part of the Subbetic in this area. This resulted in an intense local compression on the present southern border of the basin, causing a southward bending of this border and the dextral displacements of the N–S fault. Simultaneously, this movement created tension in the interior of the basin, forming different normal faults within the basin. The whole structure constitutes a basin formed by lateral displacement and bending. Nevertheless, the sinking process of the basin has continued until the present owing to the later radial extension in the region.

Amphibole-derived evidence of medium P/T metamorphic ratio in Alpujárride and Federico “HP” units (Western Betic-Northern Rif, Spain and Morocco): possible interpretations

The significance of zoned Ca-amphibole found in metapelites, quartzites, and synfolial veins of the Internal Zone of the Betic-Rif range (Federico units from Northern Rif and Alpujarride units from Western Betic) in the Alpine tectono-metamorphic evolution of these units is discussed for first time. Typical Al-rich metapelites from both areas show assemblages consisting of white mica and chlorite, with sporadic kyanite and chloritoid. Nevertheless, in the Rif zone, phyllites and synfolial veins of Permo-Triassic units show the assemblage pumpellyite + epidote + actinolite. In the Jubrique area (Betic zone), Ca-rich phyllites, fine-grained quartzites, and quartz veins show assemblages consisting of Ca-amphibole, plagioclase, epidote, titanite, chlorite, and quartz. The Al-in-amphibole thermobarometer defines clockwise pressure–temperature paths with a range of prograde temperatures and pressures between 272°C-1.2 kbar and 484°C-3.2 kbar for the Federico unit and between 274°C-1.1 kbar and 620°C-6.1 kbar in the Jubrique unit. Amphiboles from both areas define prograde pressure–temperature paths typical of Barrovian-type metamorphism. This finding contrasts with previous estimates, which deduced high-pressure conditions in both areas. The described amphiboles indicate metamorphic conditions similar to those found in the tectonically deepest complex (Veleta complex) of the Betic Internal Zone and suggest formation during a medium P/T Alpine event, which has not been previously identified in the Alpujarride complex.

A new tectonic discontinuity in the Betic Cordillera deduced from active tectonics and seismicity in the Tabernas Basin

In the Tabernas Desert, a Neogene basin situated in SE Spain, major E-W folds coexist with large E-W dextral faults and abundant NNW-SSE faults. These faults affect the Plio-Quaternary sediments. The palaeostress ellipsoids indicate a roughly constant tension (σ3 axe) in the ENE-WSW direction, coexisting with a changeable direction of the main compression (σ1 axe) from the vertical to the NW-SE direction. The numerous NNW-SSE faults in southern areas, directly to the east of the city of Almería, tend to propagate northwards, forming a tectonic discontinuity of the Betic Internal Zone. The 2002 seismic swarm of the Gergal earthquake occurred in this NNW-SSE fault zone. In this setting, the E-W fractures act as transfer faults.

Estructura de los mármoles alpujárrides situados entre Calahonda y Castell de Ferro (Cordillera Bética, provincia de Granada)

The marbles of the Calahonda-Castell de Ferro area present two systems of folds: the first one has a N70°E to E-W direction and the second, according to the observed superposed structures, is N-S. Both systems were deformed under plastic conditions. The strike of the first system is common in the Betic Internal Zone, linked to compression and nappe structuring. The second one, less represented, could be related with the westward drifting of the cited zone. A great number of faults and joints formed in later stages of deformation. The first ones correspond to the continuation of the westward translation of the Internal Zone. The rest of the deformations occurred during the middle Miocene and, particularly, from the Late Miocene onwards.

Triassic continental rifting of Pangaea: direct evidence from the Alpujarride carbonates, Betic Cordillera, SE Spain

Abstract: Evidence is presented for Triassic rift-related palaeo-structures from the Alpujarride Complex carbonates of the Betic Cordillera, SE Spain. Direct evidence of synsedimentary extensional tectonics is provided by macro- to meso-scale normal faults overstepped by younger strata. Most faults define domino-like horst and graben structures. The faults are associated with an expanded synrift sedimentary prism in which soft-sediment deformation, gravity-flow deposits and unconformities are widely developed. Syntectonic mafic igneous intrusions also occur. The age of this phase of extension is constrained as Ladinian–Carnian ( c . 237–216 Ma). From a palaeogeographical standpoint, the thick Triassic carbonates of the Betic Internal Zone, together with comparable successions in Northern Calabria (Southern Apennines), occupied a belt with elevated subsidence connecting the Neo-Tethys to the east with the eastern North American intracontinental rift system to the west. Their carbonate facies, intermediate between classical Alpine- and Germanic-type Triassic facies, recorded the main episodes of rifting affecting Central Pangaea.

Unidades tectónicas y estructura general de la Sierra de Gádor y zonas adyacentes (Cordillera Bética, provincia de Almería): implicaciones paleogeográficas

In the Sierra de Gador (Almeria province) terrains belonging to the Internal Betic Zone crop out. According to stratigraphic, structural and petrologic features we have recognised five tectonic units. These units are called, from bottom to top, Gador-Turon, Laujar, Murtas, Felix and Chiran unit. The lower fourth are ascribed to the Alpujarride Complex, whilst the last one is ascribed to the Malaguide Complex. We also discuss if the Felix unit may be included in the Intermediate Units. The Felix unit represents the Triassic palaeogeographic transition between the Alpujarride and the Malaguide, and it was located between both complexes during the alpine tectono-metamorphic evolution of the Betic Cordillera.

Geometry and kinematics of an antiformal stack deduced from brittle structures. Example of the Internal Betic Zone in the Sierra Espuña (province of Murcia, Spain)

In this work, we present a detailed analysis of brittle and brittle–ductile structures related to the contacts of a stack of tectonic units cropping out in the Sierra Espuña (Betic Cordillera, southern Spain). These data show two superposition stages with opposing transport directions: first, a top-to-the-north (according to current coordinates) stage (Oligocene in age), and a second stage from the Middle Oligocene–Aquitanian, with a top-to-the-north sense of transport. In the Burdigalian, the Internal Betic Zone units of the Sierra Espuña sector could rotate near 180° because of the oblique collision against the External Zones, and therefore the previous stacking directions went in the contrary direction with respect to that measured nowadays. The reconstruction of movements shows that the Malaguide Complex was situated to the south of the Alpujarride prior to the Alpine tectonics, which is in good agreement with previous palaeogeographic reconstructions.

Paleogene tectono-sedimentary evolution of the Alicante Trough (External Betic Zone, SE Spain) and its bearing on the timing of the deformation of the South-Iberian Margin

The Paleogene Alicante Trough of the South-Iberian Margin (External Betic Zone) consists of a narrow sedimentary basin that has active margins located to the north-northwest (active mainly during the Eocene) and to the south-southeast (active during the Oligocene). Both margins, consisting of shallow unstable platforms, were the source areas for the external-platform slope (in the opposite margins) and deepbasin (in the middle) depositional realms. The southern margin, lost under the Mediterranean Sea, is recognized only by the reconstructed Oligocene slope sediments. The eight successions studied, on opposites external-platform-slope margins and the deep within the central part of the basin, lead us to divide the basin into two depositional realms: the subsident Western Depositional Area (WDA) and the not subsident Eastern Depositional Area (EDA). This study has also enabled us to divide the infilling of the basin into two depositional sequences: Eocene p.p. (EDS) and Oligocene p.p. (ODS) in age, respectively, bound by two sequence boundaries (unconformities) at the Early Eocene (P6 zone) and Early Oligocene (P19 zone). The EDS and ODS are comprised of turbiditic and olisthostromic deposits and frequently slumps, evidencing an active tectonic in the margin-basin system. The correlation of the Paleogene sedimentary reconstructed in the Alicante Trough with other four synthetic successions throughout the External (three in the Subbetic Domain) and one in the Internal Betic Zone indicate a Paleogene generalised deformational framework. In addition, this evolution is contemporaneous to the Pyrenean, Iberian and the Nevado-Filabride Alpine deformation. The Paleogene tectonic recognised in the External Betic Zone is younger since the main orogenic deformation took place in the late Burdigalian to early Tortonian. The origin of these early tectonics is discussed in relation to the Nevado-Filabride Alpine deformation.