Pangea break-up

At mid-ocean ridges, the mantle temperature and composition, and the lithosphere thickness control the melting conditions, which influence the feeding and structure of the neo-volcanic areas. We present a study of the eastern intersection between the Romanche transform fault (TF) and the adjacent southward segments of the Mid-Atlantic Ridge (MAR). A strong thermal gradient is expected along the axis. We focus on the construction of the axial domain and on the spatial and temporal volcano-tectonic interplays. The geological mapping of the intersection shows a progressive variation in the orientation of the normal faults from about 30°t o 90°oblique to the spreading direction with increasing distance from the TF. This attests to the decrease of the transform-related shear stress component and the thinning of the axial lithosphere southward. Contextually, the coupled thermal edge effect influences the effusion rate and magma supply which in this area are low compared to other MAR segments. However, recent volcanic activity along the axis starts about 10 km south of the ridgetransform intersection. Rather than a progressive increase of the magma supply with the distance from the TF, the volcanic activity seems to increase abruptly about 30 km south of the intersection. The segment RC2, from ∼30 to 55 km from the Romanche TF, displays more numerous and larger seamounts than the segment RC3 located ∼80 km from the TF, an observation which we interpret to result from the increased thickness of the lithosphere under RC2, due to its proximity with the ridge-transform intersection.

A multiple basic to intermediate sill is reported for the fi rst time in the south-eastern Iberian Ranges. It is composed of several tabular to irregular levels intercalated within the fl uvial sediments of the Alcotas Formation (Middle-Upper Permian). The sill could represent the youngest Paleozoic subvolcanic intrusion in the Iberian Ranges. The igneous rocks are classifi ed as basaltic andesites. They show a subophitic microstructure constituted by plagioclase (An62 -An6), augite (En48Wo44Fs7 -En46Wo39Fs15), pseudomorphosed olivine, minor amounts of oxides (magnetite and ilmenite) and accessory F-apatite. According to the mineralogy and whole-rock composition, their geochemical affi nity is transitional from subalkaline to alkaline. Radiometric dating of the sill is not feasible due to its signifi cant alteration. Field criteria, however, suggest an emplacement coeval to the deposition of the Alcotas Formation (Middle-Upper Permian). This hypothesis is supported by the transitional affi nity of these rocks, similar to other Middle-Upper Permian magmatisms in the western Tethys, e.g., from the Pyrenees. Taking into account their isotopic signature (ε Sr : -6.8 to -9.2; ε Nd : +1.7 to +8.3), an enriched mantle source with the involvement of a HIMU component has been identifi ed. This interpretation is supported by the trace element contents.

Magma-rich passive margins are characterized by mafic intrusions and lavas, making their density comparable to that of the adjoining oceanic crust. As a result, these margins may sink along with the oceanic crust when subduction begins. This possibility warrants further investigation in the geologic record. A fitting example can be found in the Sanandaj-Sirjan Zone (SaSZ), north of the Neotethyan Zagros suture in Iran, where amphibolite to eclogite-facies metabasites are exposed in the Zayanderud high-pressure metamorphic complex. We present U-Pb zircon ages, whole rock elemental analyses, and Sr-Nd-Hf isotope data to constrain the ages, chemical and isotopic composition, as well as the tectonic setting of the metabasite protoliths. Ion microprobe U-Pb zircon geochronology on petrographic thin sections reveals Early-Middle Permian protolith ages for small (≤10 μm in diameter) zircon crystals that have been metamorphically overgrown in the eclogite. The elemental and Sr-Nd-Hf isotopic compositions of eclogites and amphibolites indicate a continental flood basalt affinity. Trace element and isotopic signatures closely resemble those of widespread Permian flood basalts erupted during breakup of Pangea and the opening of the Neotethys Ocean, with well-studied examples from Oman, the Himalayas, and the Asian Large Igneous Provinces in Tarim, Tianshan, and Emeishan. Earlier investigations suggested that the eclogitization occurred in the Early-Middle Jurassic. Our findings support a scenario where a magma-rich passive margin was established during the Permian and subsequently sank into the mantle at the onset of Jurassic subduction along this segment of the Neotethys. This studied example advocates a poorly explored possibility of the deep sinking of magma-rich passive margins at the beginning of subduction.

A multiple basic to intermediate sill is reported for the fi rst time in the south-eastern Iberian Ranges. It is composed of several tabular to irregular levels intercalated within the fl uvial sediments of the Alcotas Formation (Middle-Upper Permian). The sill could represent the youngest Paleozoic subvolcanic intrusion in the Iberian Ranges. The igneous rocks are classifi ed as basaltic andesites. They show a subophitic microstructure constituted by plagioclase (An62 -An6), augite (En48Wo44Fs7 -En46Wo39Fs15), pseudomorphosed olivine, minor amounts of oxides (magnetite and ilmenite) and accessory F-apatite. According to the mineralogy and whole-rock composition, their geochemical affi nity is transitional from subalkaline to alkaline. Radiometric dating of the sill is not feasible due to its signifi cant alteration. Field criteria, however, suggest an emplacement coeval to the deposition of the Alcotas Formation (Middle-Upper Permian). This hypothesis is supported by the transitional affi nity of these rocks, similar to other Middle-Upper Permian magmatisms in the western Tethys, e.g., from the Pyrenees. Taking into account their isotopic signature (ε Sr : -6.8 to -9.2; ε Nd : +1.7 to +8.3), an enriched mantle source with the involvement of a HIMU component has been identifi ed. This interpretation is supported by the trace element contents.

The 2-10-km-thick, mainly carbonate cap of the 14,000 km 2 Bahamas carbonate platform (BCP) has impeded imaging of its underlying crustal structure. The deeper structure of the BCP records both its Mesozoic rift and hotspot history and its later deformation related to its Paleogene collision with the Great Arc of the Caribbean (GAC). We use regional gravity data to model the crustal structure, type, and deformational processes of the BCP by: (a) integrating publicly available seismic data; (b) inverting the Moho along 2D regional gravity transects across the collisional zone; (c) modeling flexural uplift of a forebulge that reflects the attempted subduction of the BCP beneath the GAC; and (d) using downhole temperatures and radiogenic heat production in 1D basin models to differentiate crustal types related to the Mesozoic rift history. We interpret three crustal domains underlying the BCP: (a) 27-12-km-thick, rifted, and thinned continental crust of the northern Bahamas between the Blake Plateau and Exuma Sound; (b) 24-12-km-thick, volcanically-thickened oceanic crust related to the Triassic-Jurassic Bahamas hotspot in the central Bahamas southeast of Long Island; and (c) 20-12-km-thick, thickened oceanic crust north of Hispaniola. We propose that these crustal types reflect northwest-southeastward, Triassic-Jurassic rifting of the Bahamas region during the breakup of Pangea and accompanying magmatic activity related to the Triassic-Jurassic Bahamas hotspot and early oceanic spreading. Growth of the BCP during the Cretaceous in this area was followed by Late Cretaceous-Paleogene subductionrelated flexure and terminal Paleogene collision between the GAC and the BCP. Plain Language Summary We investigate the thickly-sedimented and difficult-to-image Bahamas carbonate platform (BCP) by generating different gravity-based models of its sub-surface crustal structure. These models help us better understand the crustal types extended and formed during Mesozoic rifting and hotspot activity and the later deformation of these crustal types during the Paleogene collision between the Cuban island arc and the BCP.

Stephano-permian basins are found in several rather small places in and around the present-day French Variscan basement. They are mostly considered as intramontane post-orogenic (Variscan) basins, developing in close relationships with crustal to lithospheric geological events (such as extensive strike-slip, exhumation of metamorphic rocks, and widespread magmatism). On the other hand, little is known about their occurrences under their post depositional sedimentary covers. This is for instance the case in the Paris Basin, where significant but scarce studies aimed to find their location under the Mesozoic sedimentary cover. There, the questions of their extension, thickness, sedimentary filling, internal geometry and structural control still remain open. In the same way, their differential conservation compared with the basins known in the field, or the possible structural decoupling between the pre-Mesozoic and Mesozoic units, has still to be debated. Our study addresses the Steph...

The Celtic Sea, offshore southern Ireland, is underlain by several discrete rift basins, which are part of a larger set of such basins that developed marginal to the North Atlantic within the tectonic framework of Pangaean break-up and episodic opening of the North Atlantic Ocean. This paper documents the development of depositional systems within a rift basin setting by analysis of the sequence stratigraphic evolution of the North Celtic Sea Basin, the largest basin in the area, with particular emphasis on the influence of pre-existing structural fabric on that evolution. The Caledonian and Variscan orogenies each imprinted distinct structural grains on this area, and the intersecting pattern of their respective tectonic trends provided the structural framework which influenced subsequent Triassic, Late Jurassic and Early Cretaceous phases of rifting. Detailed analysis of an extensive well and seismic database indicates that the mode of reactivation of pre-existing lines of structural weakness depended on the orientation of the principal extensional stress direction relative to these lineaments. Triassic and Late Jurassic northwest-southeast orientated extensional stress reactivated Caledonian lineaments as half-graben boundary faults and Variscan lineaments as accommodation zones and lateral transfer faults which offset the basin margin faults. In contrast, during the Early Cretaceous, extensional stress was orientated approximately north-south, oblique to the Caledonian trend. This resulted in transtensional pull-apart basin geometries dominated by reactivation of Variscan structures. The intrinsic relationship between plate tectonic setting, pre-existing structural fabric and the resulting structural style provides insight into the influence of tectonism on depositional system development in an evolving rift basin. During Late Jurassic and Early Cretaceous rifting, depositional system development was predominantly controlled by tectonism and partly conforms to empirically derived tectono-stratigraphic models of sequence development in non-marine rifts. Depositional environments changed from fluvialdominant to lacustrine-dominant as each rifting episode evolved through its early to active rift stages. During post-rift subsidence, marine transgressions dominated depositional system development, overriding the influence of local tectonism. Spatially, pre-existing structural fabric and the style of structural deformation are the dominant influences on sediment input and drainage systems within the evolving rift basin. Recognition of the intrinsic structural fabric of a rift basin is one of the key factors in understanding and predicting stratigraphic distributions within this type of basin.

The Valdemeca Conglomerates unit is here described as the basal part of the Late Permian-Early Triassic sedimentary cycle in the central-eastern part of the Iberian Ranges, equivalent to the upper part of the Hoz de Gallo Conglomerates Formation of the classic Molina de Aragon area. It is interpreted as braided river deposits with paleocurrents parallel to the basin axis. The identification in this new area represents the expand of the sedimentation realm of this cycle to the SE of the Iberian Ranges.

Recent studies have confirmed the important role played by magmatism during the Late Carboniferous-Permian transition. In this report, we describe the characteristics of this magmatism in the Central Iberian realm (Iberian Ranges and eastern Spanish Central System) and discuss its palaeoenvironmental impact. In the studied area, the late-Variscan transtensional to extensional tectonic regime favoured the emplacement of a calc-alkaline magmatism during the Late Stephanian-Permian. This magmatism is expressed both as pyroclastic rocks filling small half-graben basins and hypabyssal intrusions (sills and dykes). Pyroxenic-and amphibolic-andesites are the main rock compositions, while basalt, dacite and rhyolite are less represented. The available K/Ar isotopic data suggests a Lower Permian age for this magmatism, also supported by its complete macro-and microflora content and by features related to its emplacement (hypabyssal intrusions crosscut Stephanian rocks and are in turn overlain by late Permian-Triassic sediments). Frequent xenoliths of middle and lower crustal levels indicate considerable magma-crust interaction. This interaction may have led to substantial crustal assimilation during the first emplacement stages in conditions of a low extension rate. Crustal contamination barely affected the final magmatic products emplaced under conditions of greater extension. The palaeoecological effects of explosive manifestations of this volcanism are expressed in the varied macroflora record in volcaniclastic basins. The number and volume of hypabyssal intrusions suggest that the original geological record of explosive activity in these basins was much greater and was reduced by subsequent erosion processes.

This study presents new U-Pb analyses using a sensitive high-resolution ion microproble (SHRIMP) on zircons from a basic dyke intruded in Devonian slates and limestones from the Axial Zone of the Central Pyrenees. The zircon grains exhibit euhedral shapes with clear magmatic characteristics as oscillatory or sector zoning without recrystallized rims. Zircons yield a concordant age of 259 ± 3.2 (2σ) Ma, that we interpret as the intrusion age of the dyke. The petrological features of the dyke points to a close relationship with the post-Variscan volcanism recognized in the area, an interpretation that is consistent with the Permian age of the dyke. This magmatism developed under late-to post-orogenic conditions and is related to the formation of the Stephanian-Permian basins disseminated along the Pyrenees. The new obtained age broadens the time span of the Permian magmatism in the Pyrenees.

This study presents new U-Pb analyses using a sensitive high-resolution ion microproble (SHRIMP) on zircons from a basic dyke intruded in Devonian slates and limestones from the Axial Zone of the Central Pyrenees. The zircon grains exhibit euhedral shapes with clear magmatic characteristics as oscillatory or sector zoning without recrystallized rims. Zircons yield a concordant age of 259 ± 3.2 (2σ) Ma, that we interpret as the intrusion age of the dyke. The petrological features of the dyke points to a close relationship with the post-Variscan volcanism recognized in the area, an interpretation that is consistent with the Permian age of the dyke. This magmatism developed under late-to post-orogenic conditions and is related to the formation of the Stephanian-Permian basins disseminated along the Pyrenees. The new obtained age broadens the time span of the Permian magmatism in the Pyrenees.

This study presents new U-Pb analyses using a sensitive high-resolution ion microproble (SHRIMP) on zircons from a basic dyke intruded in Devonian slates and limestones from the Axial Zone of the Central Pyrenees. The zircon grains exhibit euhedral shapes with clear magmatic characteristics as oscillatory or sector zoning without recrystallized rims. Zircons yield a concordant age of 259 ± 3.2 (2σ) Ma, that we interpret as the intrusion age of the dyke. The petrological features of the dyke points to a close relationship with the post-Variscan volcanism recognized in the area, an interpretation that is consistent with the Permian age of the dyke. This magmatism developed under late-to post-orogenic conditions and is related to the formation of the Stephanian-Permian basins disseminated along the Pyrenees. The new obtained age broadens the time span of the Permian magmatism in the Pyrenees.

This study is focused on the investigation of four lithostratigraphic units (two potential reservoir rocks and two potential seal rocks) for geological storage of CO 2 in the Mesozoic Asturian basin (NW Spain). Two systems reservoir-seal are studied both in the Jurassic (Liassic limestones and dolostones of the Gijón formation as reservoir rock and Sinemurian-Bajocian marly limestones of Rodiles formation as seal rock) and Cretaceous (Aptian greywackes and sandstones of the Pola de Siero formation as reservoir rock and Albian grainstone-type limestones with argillaceous horizons as seal rock) sequences. Detailed information of the mineralogical distribution and texture, geochemical composition, porosity and pore size distribution is provided for each rock. Compared to the Cretaceous system, the Jurassic reservoir shows a better net thickness and pore size distribution and the Jurassic seal has an already demonstrated low permeability. The Cretaceous reservoir presents better porosity values (7.96% against a 0.5% of the Gijón formation), but the seal permeability is yet to be proven as low.

During the Triassic the Iberian Peninsula was placed at the western part of the Tethys Sea. The Middle-Late Triassic (Anisian Norian) rocks of the Iberian, Catalonian and External Betic (Prebetic and Subbetic) Ranges, contain three main intervals inter preted as prograding carbonate ramps: lower Muschelkalk (Anisian), upper Muschelkalk (Ladinian) and Imon Dolomites For mation (Norian); some carbonatic levels appear in the Subbetic (Carnian). The fossil record is f r equently scarce and bad preserved. During one century (1853-1954), spanish paleontologicaJ works on the Muschelkalk dealt with several punctual aspects and showed taxonomical confusion. In this paper the results of the last ten years of paleontological research on trias sic bivalves f r om Spain have been updated. At the moment, one Anisian, three Ladinian, two Ladinian-Carnian, one Carnian and one Norian bivalve assemblages have been identified. The record appears in sediments from protected areas of shallow carbonatic ramps. The bivalve species have not biostratigraphical meaning but its assemblages characterize each carbonatic intercalation. The most of the taxa are common in the Tethys realm.

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En el Triásico del sector central de la Cordillera Bética se pueden diferenciar, a grandes rasgos, tres tipos de facies litológicas: carbonatos (facies Muschelkalk), terrígenos (facies Keuper), evaporitas (facies Keuper). El estudio de varios afloramientos en este área ha supuesto un mayor conocimiento de los aspectos paleoecológicos del Trías, y ha permitido la revisión bioestratigráfica de las series. En el tramo carbonatado, el registro fósil está constituido en su mayoría por moluscos y braquiópodos. La asociación de bivalvos encontrada puede atribuirse al Ladiniense medio-superior, por la presencia de Coslatoria goldfussi y Enantiostreon flabellum, formas características de los tramos terminales del Ladiniense en el sector occidental del Dominio Sefardí. En conjunto, el registro es muy escaso y la preservación de los fósiles es, en general, deficiente. La mayor parte de la fauna se encuentra en las capas terminales del Muschelkalk, en niveles de calizas-margosas con intercalaci...

This study is focused on the investigation of four lithostratigraphic units (two potential reservoir rocks and two potential seal rocks) for geological storage of CO 2 in the Mesozoic Asturian basin (NW Spain). Two systems reservoir-seal are studied both in the Jurassic (Liassic limestones and dolostones of the Gijón formation as reservoir rock and Sinemurian-Bajocian marly limestones of Rodiles formation as seal rock) and Cretaceous (Aptian greywackes and sandstones of the Pola de Siero formation as reservoir rock and Albian grainstone-type limestones with argillaceous horizons as seal rock) sequences. Detailed information of the mineralogical distribution and texture, geochemical composition, porosity and pore size distribution is provided for each rock. Compared to the Cretaceous system, the Jurassic reservoir shows a better net thickness and pore size distribution and the Jurassic seal has an already demonstrated low permeability. The Cretaceous reservoir presents better porosity values (7.96% against a 0.5% of the Gijón formation), but the seal permeability is yet to be proven as low.

The Permian-Triassic rifting represents the first of the two Mesozoic rifting stages recorded in the Iberian Peninsula. Its first phases of development started during the Early Permian, and were linked to the beginning of the break-up of Pangea, the large, unique and rheologically unstable supercontinent that mainly resulted from the collision of Gondwana and Laurussia. This chapter analyzes this first rifting stage in Iberia in two separate phases, an initial or tectonic phase, and a later mature phase. This analysis focuses on the main Permian-Triassic basins of the Iberian Peninsula: the Pyrenean, Iberian, Catalan, Ebro and Betic basins, as well as the basins located in the present-day Balearic Islands. In order to achieve a better understanding of the analyses of these basins, a multidisciplinary approach has been carried out by 48 researchers, including studies of tectonics, sedimentology, magmatism, mineralogy, geochemistry and paleontology.

The Caspe structure was formed by the convergence of the Iberian Range and the Catalonian Coastal Range, during the Tertiary compression. Traditionally, the Caspe structure has been interpreted from seismic profiles without considering surface structural data. Therefore, several models were obtained with different results. The aim of this study is to build a 3D geological model taking into account the structural data from the geological map, stress fields and lineaments from satellite imagery. Four surfaces have been modelled: Buntsandstein Top, Muschelkalk-I Top, Muschelkalk-II Top and Cenozoic Bottom. The presented 3D geometrical model shows two major thrusts of WSWENE direction with northward and southward vergence. In the major thrust sheet there is a large NW–SE trending anticline bounded by the two thrusts with small, associated reverse faults. The geometrical model is consistent with a transpressive, push-up structure that could be associated with the lateral continuation of ...

Recent studies have confirmed the important role played by magmatism during the Late Carboniferous-Permian transition. In this report, we describe the characteristics of this magmatism in the Central Iberian realm (Iberian Ranges and eastern Spanish Central System) and discuss its palaeoenvironmental impact. In the studied area, the late-Variscan transtensional to extensional tectonic regime favoured the emplacement of a calc-alkaline magmatism during the Late Stephanian-Permian. This magmatism is expressed both as pyroclastic rocks filling small half-graben basins and hypabyssal intrusions (sills and dykes). Pyroxenic-and amphibolic-andesites are the main rock compositions, while basalt, dacite and rhyolite are less represented. The available K/Ar isotopic data suggests a Lower Permian age for this magmatism, also supported by its complete macro-and microflora content and by features related to its emplacement (hypabyssal intrusions crosscut Stephanian rocks and are in turn overlain by late Permian-Triassic sediments). Frequent xenoliths of middle and lower crustal levels indicate considerable magma-crust interaction. This interaction may have led to substantial crustal assimilation during the first emplacement stages in conditions of a low extension rate. Crustal contamination barely affected the final magmatic products emplaced under conditions of greater extension. The palaeoecological effects of explosive manifestations of this volcanism are expressed in the varied macroflora record in volcaniclastic basins. The number and volume of hypabyssal intrusions suggest that the original geological record of explosive activity in these basins was much greater and was reduced by subsequent erosion processes.

The lo w er Perm ian (A u tu n ian) has not been id entified up to n o w in the subsurface o f the Tertiary Ebro Basin because o f the scarcity o f borehole samples availab le a n d the system atic attribution to the C arboniferous w ithout an y p aleo n to lo g ical data, o f the siliciclastic sediments found at the base o f som e o f them, w e ll above the hercynian basem ent an d unm etam orfosed G re y a n d black shales reco vered from cores preserved in the R E P S O L archives o f the Caspe-1 o il w e ll b etw een meters 1.437 an d I .449 have yie ld e d a p a lyn o g ica l assem blage com posed b y Vittatina cf. costabilis, Potonieisporites novices-bhardw aji, N uskoisporites sp. a n d other forms not so w e ll preserved. This association has a Low er Perm ian (A u tu n ian) age an d com pares w e ll with other findings in the Iberian Ranges, the Pyrenees an d other areas in Iberia, shading a n e w light on the early stages o f evolution o f the cen tral an d N E parts o f Iberia ju st after the H ercyn ian orogeny.

The Valdemeca Conglomerates unit is here described as the basal part of the Late Permian-Early Triassic sedimentary cycle in the central-eastern part of the Iberian Ranges, equivalent to the upper part of the Hoz de Gallo Conglomerates Formation of the classic Molina de Aragon area. It is interpreted as braided river deposits with paleocurrents parallel to the basin axis. The identification in this new area represents the expand of the sedimentation realm of this cycle to the SE of the Iberian Ranges.

La estructura geológica de Caspe se formó durante la convergencia de las Cordilleras Ibérica y Costero-Catalana. Las interpretaciones precedentes de los perfiles sísmicos que la atraviesan han obtenido morfologías de la estructura muy diferentes puesto que no consideran los datos geológicos superficiales. El objetivo de este trabajo es mostrar un modelo geológico 3D de la estructura de Caspe obtenido de una nueva interpretación de los perfiles sísmicos ajustándose a los datos geológicos: cartografía geológica, el campo de esfuerzos y los lineamientos. Se han modelado 4 superficies: techo de Buntsandstein, techo del Muschelkalk-I, techo del Muschelkalk-II y base del Cenozoico. El modelo obtenido muestra dos cabalgamientos OSO-ENE principales con vergencias contrarias. En la lámina cabalgante principal hay un anticlinal de dirección NO-SE limitado por pequeños cabalgamientos y fallas inversas asociados. El modelo geométrico es consistente con una estructura transpresiva tipo push-up q...

A multiple basic to intermediate sill is reported for the fi rst time in the south-eastern Iberian Ranges. It is composed of several tabular to irregular levels intercalated within the fl uvial sediments of the Alcotas Formation (Middle-Upper Permian). The sill could represent the youngest Paleozoic subvolcanic intrusion in the Iberian Ranges. The igneous rocks are classifi ed as basaltic andesites. They show a subophitic microstructure constituted by plagioclase (An62 -An6), augite (En48Wo44Fs7 -En46Wo39Fs15), pseudomorphosed olivine, minor amounts of oxides (magnetite and ilmenite) and accessory F-apatite. According to the mineralogy and whole-rock composition, their geochemical affi nity is transitional from subalkaline to alkaline. Radiometric dating of the sill is not feasible due to its signifi cant alteration. Field criteria, however, suggest an emplacement coeval to the deposition of the Alcotas Formation (Middle-Upper Permian). This hypothesis is supported by the transitional affi nity of these rocks, similar to other Middle-Upper Permian magmatisms in the western Tethys, e.g., from the Pyrenees. Taking into account their isotopic signature (ε Sr : -6.8 to -9.2; ε Nd : +1.7 to +8.3), an enriched mantle source with the involvement of a HIMU component has been identifi ed. This interpretation is supported by the trace element contents.

This study presents new U-Pb analyses using a sensitive high-resolution ion microproble (SHRIMP) on zircons from a basic dyke intruded in Devonian slates and limestones from the Axial Zone of the Central Pyrenees. The zircon grains exhibit euhedral shapes with clear magmatic characteristics as oscillatory or sector zoning without recrystallized rims. Zircons yield a concordant age of 259 ± 3.2 (2σ) Ma, that we interpret as the intrusion age of the dyke. The petrological features of the dyke points to a close relationship with the post-Variscan volcanism recognized in the area, an interpretation that is consistent with the Permian age of the dyke. This magmatism developed under late-to post-orogenic conditions and is related to the formation of the Stephanian-Permian basins disseminated along the Pyrenees. The new obtained age broadens the time span of the Permian magmatism in the Pyrenees.

During the Carboniferousdic elongatedSouth EuropePlate was bounded by two fold beltswhich migratedaway from a centralcontinentalridge, pointing to two subductionzonesalong the NW and SE ma¿rginsof South Europe retreatingocean-wards.Due to releaseof abondantwater during subduetion, dehydrationand probablepartial melting of former oceaniccrust at the two subductionzones,one or severalupper mantle diapirs formed. Ríse of this hot upper mantle material causedwidespreadpartial melting in the lower crust of SouthEuropeandhigh temperature-lowpressuremetamorphism,and is believed to have reducedthe thickness and rigidity of the South Europe Plate considerably. Subductionof the Mid-Europeanoceancrust northwestof South Europe finally lcd to collision with North America-Europeand subduction of the Tethys oceancrust lcd to collision of South Europewith Africa in the southwest. Both collisions terminatedthe orogenicactivity at the sites of the fold bites. Approaching North Amcrica-EuropeandAfrica...

The Iberian Basin was an intracratonic rift basin in central-eastern Spain developed since Early Permian times. The basin boundary faults were normal, listric faults controlling an asymmetric extension propagating northeast with time. Hercynian or older lineaments controlled the orientation of the Iberian Basin and extension was accommodated basically in the hanging wall block by the formation of secondary grabens and a central high. The basin was related with the coeval Ebro, Catalan and Cuenca-Mancha Basins and their connections are discussed. Subsidence curves show that the Early Permian-Early Jurassic period of extension can be subdivided into three rifting episodes and a flexural one. Extension factor increases from 1.17 in the northwest to 1.29 near the Mediterranean coast. The increasing extension rate was accommodated by transfer faults trending NNE-SSW, more important in the Levante area. The rift evolution is intermittent and seems to reflect distinct stress fields. The collapse of the late Hercynian orogen and related increased heat flux, extension and rifting is the most probable origin of the Iberian Basin and related basins. The origin of the Catalan and the Valencia-Prebetic Basins is related to the southwards migration of the Hesse-Burgundy Rift along the eastern margin of the Iberian Microplate.

The Eslida Fm is an alluvial unit of the Buntsandstein Facies of the Iberian Ranges deposited in a half-graben basin over a period of 2-2.5 Ma during the lower Anisian (Middle Triassic). It can be subdivided into six cycles that can be correlated along the basin. The overall architecture and cyclicity were controlled by the episodic activity of the basin boundary fault. Two proximal source areas of minor importance and a distal one of major importance are identified. The petrological composition of the sandstones is arkosic to subgrauwackic, indicating source areas containing both low-metamorphic rocks and gneiss, and granitic rocks. Alluvial fans, very common in rift basins, were not developed because of slow fault scarp retreat and the lack of large antecedent rivers cutting across the rift shoulders. Paleocurrents point to the SE, except for a zone in the middle part of the basin where interference with a NE-SW fault system deflected the channels to the S. The infilling of the basin is asymmetric in a transverse section, with channel facies near the basin boundary fault to the NE and overbank facies in the distal SW part.

The Eslida Fm is an alluvial unit of the Buntsandstein Facies of the Iberian Ranges deposited in a half-graben basin over a period of 2–2.5 Ma during the lower Anisian (Middle Triassic). It can be subdivided into six cycles that can be correlated along the basin. The ...

A multiple basic to intermediate sill is reported for the fi rst time in the south-eastern Iberian Ranges. It is composed of several tabular to irregular levels intercalated within the fl uvial sediments of the Alcotas Formation (Middle-Upper Permian). The sill could represent the youngest Paleozoic subvolcanic intrusion in the Iberian Ranges. The igneous rocks are classifi ed as basaltic andesites. They show a subophitic microstructure constituted by plagioclase (An62 -An6), augite (En48Wo44Fs7 -En46Wo39Fs15), pseudomorphosed olivine, minor amounts of oxides (magnetite and ilmenite) and accessory F-apatite. According to the mineralogy and whole-rock composition, their geochemical affi nity is transitional from subalkaline to alkaline. Radiometric dating of the sill is not feasible due to its signifi cant alteration. Field criteria, however, suggest an emplacement coeval to the deposition of the Alcotas Formation (Middle-Upper Permian). This hypothesis is supported by the transitional affi nity of these rocks, similar to other Middle-Upper Permian magmatisms in the western Tethys, e.g., from the Pyrenees. Taking into account their isotopic signature (ε Sr : -6.8 to -9.2; ε Nd : +1.7 to +8.3), an enriched mantle source with the involvement of a HIMU component has been identifi ed. This interpretation is supported by the trace element contents.

The tiny outcrop of the mining area of Minas de Henarejos is unique among the early post-Variscan basins of the Iberian Ranges, Central Spain, for several reasons: Its age, considered up now to be Late Carboniferous (Stephanian B-C), its syn-sedimentary compressional structures and the thick coal beds in the upper part of the section. A re-assesment of the biostratigraphic range of its macrofl ora shows that it is representative of the hygrophytic assemblage that ranges from the Late Carboniferous to the Early Permian, coeval with the so-called "Autunian" assemblages. Nothing prevents this basin to be considered coeval with other continental basins of Early Permian age in the Iberian Ranges. Compressional structures can be related to a right restraining bend in the sinistral N-S Teruel strike-slip fault system that created a synformal basin in the underthrust block.

The Iberian Basin was an intracratonic rift basin in central-eastern Spain developed since Early Permian times. The basin boundary faults were normal, listric faults controlling an asymmetric extension propagating northeast with time. Hercynian or older lineaments controlled the orientation of the Iberian Basin and extension was accommodated basically in the hanging wall block by the formation of secondary grabens and a central high. The basin was related with the coeval Ebro, Catalan and Cuenca-Mancha Basins and their connections are discussed. Subsidence curves show that the Early Permian-Early Jurassic period of extension can be subdivided into three rifting episodes and a flexural one. Extension factor increases from 1.17 in the northwest to 1.29 near the Mediterranean coast. The increasing extension rate was accommodated by transfer faults trending NNE-SSW, more important in the Levante area. The rift evolution is intermittent and seems to reflect distinct stress fields. The collapse of the late Hercynian orogen and related increased heat flux, extension and rifting is the most probable origin of the Iberian Basin and related basins. The origin of the Catalan and the Valencia-Prebetic Basins is related to the southwards migration of the Hesse-Burgundy Rift along the eastern margin of the Iberian Microplate.

The goal of this project is to study the crustal and upper mantle structures under the Betic mountain ranges and their variations between the different geological domains. We deployed 50 broadband and short period seismic stations during 18 months following two profiles. We collect teleseismic events to perform a high-resolution P-to-S and Sto-P receiver function analysis. The main profile (TranSCorBe), of 160 km length, starts near the coast in Mazarron (Murcia) and follows a NW-SE direction, crossing the Cazorla mountain range. It probes, from south to north, the Alboran domain (metamorphic rocks), the External zones (sedimentary rocks) and the Variscan terrains of the Iberian Massif. The spacing between stations is around 3-4 km. This inter-station distance allows us mapping with high accuracy the variations of the crust and upper mantle discontinuities in the Betic Range and their transition to the Iberian Massif. A second profile (HiRe II) with a larger spacing between seismic ...

The Caspe structure was formed by the convergence of the Iberian Range and the Catalonian Coastal Range, during the Tertiary compression. Traditionally, the Caspe structure has been interpreted from seismic profiles without considering surface structural data. Therefore, several models were obtained with different results. The aim of this study is to build a 3D geological model taking into account the structural data from the geological map, stress fields and lineaments from satellite imagery. Four surfaces have been modelled: Buntsandstein Top, Muschelkalk-I Top, Muschelkalk-II Top and Cenozoic Bottom. The presented 3D geometrical model shows two major thrusts of WSWENE direction with northward and southward vergence. In the major thrust sheet there is a large NW–SE trending anticline bounded by the two thrusts with small, associated reverse faults. The geometrical model is consistent with a transpressive, push-up structure that could be associated with the lateral continuation of ...

A multiple basic to intermediate sill is reported for the fi rst time in the southeastern Iberian Ranges. It is composed of several tabular to irregular levels intercalated within the fl uvial sediments of the Alcotas Formation (Middle-Upper Permian). The sill could represent the youngest Paleozoic subvolcanic intrusion in the Iberian Ranges. The igneous rocks are classifi ed as basaltic andesites. They show a subophitic microstructure constituted by plagioclase (An62-An6), augite (En48Wo44Fs7-En46Wo39Fs15), pseudomorphosed olivine, minor amounts of oxides (magnetite and ilmenite) and accessory F-apatite. According to the mineralogy and whole-rock composition, their geochemical affi nity is transitional from subalkaline to alkaline. Radiometric dating of the sill is not feasible due to its signifi cant alteration. Field criteria, however, suggest an emplacement coeval to the deposition of the Alcotas Formation (Middle-Upper Permian). This hypothesis is supported by the transitional affi nity of these rocks, similar to other Middle-Upper Permian magmatisms in the western Tethys, e.g., from the Pyrenees. Taking into account their isotopic signature (ε Sr :-6.8 to-9.2; ε Nd : +1.7 to +8.3), an enriched mantle source with the involvement of a HIMU component has been identifi ed. This interpretation is supported by the trace element contents.

En este trabajo se estudian, de forma sintética y actualizada, las manifestaciones (hipovolcánicas y volcanoclásticas) calco-alcalinas que, con carácter epizonal, pluriepisódico y edad Stephaniense-Pérmico, afloran en la Cadena Ibérica. El estudio del magmatismo en la cuenca de Sauquillo de Alcázar (Soria) permite identificar la geometría y la modalidad de este magmatismo con mayor precisi6n, respecto a lo obtenido en los cuatro afloramientos volcano-clásticos seleccionados. Los resultados obtenidos facilitan realizar consideraciones sobre el estudio espacio-temporal de este magmatismo.

In Atienza area (W part of Iberian Chain) a set of Lower Permian andesitic hypovolcanic and volcanic outcrops occur. The hypovolcanic outcrops belong to a single sill of kilometer-scale and very variable thickness (up to several hundred meters), emplaced over the Lower Permian discontinuity. Their emplacement is related to the activity of the Bornova fault; a large NE-SW late-variscan fault. The volcanic deposits show a more reduced lateral and vertical extension and postdate the hypovolcanic ones. All the studied andesites show a very similar petrological composition. The structure and texture of these materials and the presence of fossils and volcanic clasts are key features to distinguish between volcanic and hypovolcanic rocks.

The stratigraphic and petrological study of basaltic outcrops in the Baix Ebre volcanic region (Tarragona, Spain) indicates the development of a pluriepisodic alkaline volcanism during the Late Triassic. Two magmatic stages can be recognised based on the main eruptive style: an initial hidromagmatic stage emplaced within the basal Keuper and a strombolian stage emplaced into the upper Keuper, always below the Imón Fm. (Rhaetian). In this last stage massive igneous bodies (sills) carried xenoliths, which are more abundant in the western part of the studied sector. We thimk that the magmatic centre was probably situated close to Prat de Compte, given that in this area there is a greater modal abundance of xenoliths, showing the maximum diameter.

Recent studies have confirmed the important role played by magmatism during the Late Carboniferous-Permian transition. In this report, we describe the characteristics of this magmatism in the Central Iberian realm (Iberian Ranges and eastern Spanish Central System) and discuss its palaeoenvironmental impact. In the studied area, the late-Variscan transtensional to extensional tectonic regime favoured the emplacement of a calc-alkaline magmatism during the Late Stephanian-Permian. This magmatism is expressed both as pyroclastic rocks filling small half-graben basins and hypabyssal intrusions (sills and dykes). Pyroxenic-and amphibolic-andesites are the main rock compositions, while basalt, dacite and rhyolite are less represented. The available K/Ar isotopic data suggests a Lower Permian age for this magmatism, also supported by its complete macro-and microflora content and by features related to its emplacement (hypabyssal intrusions crosscut Stephanian rocks and are in turn overlain by late Permian-Triassic sediments). Frequent xenoliths of middle and lower crustal levels indicate considerable magma-crust interaction. This interaction may have led to substantial crustal assimilation during the first emplacement stages in conditions of a low extension rate. Crustal contamination barely affected the final magmatic products emplaced under conditions of greater extension. The palaeoecological effects of explosive manifestations of this volcanism are expressed in the varied macroflora record in volcaniclastic basins. The number and volume of hypabyssal intrusions suggest that the original geological record of explosive activity in these basins was much greater and was reduced by subsequent erosion processes.