Carboniferous subduction complex in the South Portuguesa zone Coeval with basement reactivation and uplift in the Iberian Massif

[Resumen] Para la formación de potentes series de tipo flysch es necesaria la existencia de áreas marinas estrechas, Ia denudación activa de los continentes que las rodean y subsidencia generalizada en las márgenes. Estas condiciones se cumplen en las tasas iniciales y finales del ciclo de Wilson. En este sentido, el flysch precámbrico superior del Macizo Ibérico corresponde a la fase inicial de apertura, mientras el Culm de la zona Surportuguesa está relacionado con un proceso de subducción que permaneció activo después de la colisión de las placas ibérica y norteamericana. La zona de colisión corresponde al área madre de los depósitos del Culm, los cuales se acumularon en un área oceánica residual situada en el borde no suturado de la placa ibérica. Este modelo de formación de flysch sinorogénico ha sido utilizado anteriormente para otras áreas con similar disposición de placas. Por otra parte, este modelo permite explicar la diferencia de las estructuras y el magmatismo de la zona Ossa-Morena (situada junto a una margen activa) frente a las estructuras y el magmatismo del resto del Macizo (zona de reactivación cortical). Además este modelo parece favorecer la hipótesis de un origen primario para el Arco[Abstract] The formation of thick piles of flysch-like sediments needs the existence of narrowed seas, active denouement of neighbouring continents and generaHzedmarginal subsidence. These conditions are present during the initial and final stages of Wilson's perceptive cycle. In this context, the Late Precalmbrian flysch of the Iberian Massif must be related to the initial rifting, whilst theCulm of southwestern Iberia was accumulated during an episode of Upper Palaeozoic subduction that remained active after impingement of Iberia against North America. Culm sediment shed from the uplifted collision zone and fed into a remnant ocean that remained at the nonsutured southern border of Iberia. This ·model of synorogenic flysch formation has been described elsewhere for similar plate arrangements. On other grounds this model provides a framework that explains the different structural and mag'matic trends of the Ossa-Morena Zone (near the a'ctive margin) in the context ,of the rest of the Massif (basement reactivation). In addition to this, it seems to support a partly primary origin for the Iberian arc versus a secondary origi

Formación de cuencas cenozoicas de pequeño y mediano tamaño drenadas por el Río Tajo (Portugal y España). Ejemplo de cuencas sedimentarias formadas por plegamiento a escala cortical

The Tagus river drains several small- to medium-sized Cenozoic sedimentary basins located along a tectonic depressed area which is flanked by two basement highs. These basins were created during the onset of the Cenozoic compressive event that underwent the interior of the Iberian Peninsula in the wake of the Africa-Eurasia convergence. They show the distinctive characteristics of compressional sedimentary basins (flanked by thrusts and reverse faults) whose mechanism of formation can be ascribed to crustal-scale folds. They constitute a good, and perhaps exceptional, example of compressional sedimentary basins formed by this type tectonic mechanismEl Río Tajo drena varias cuencas sedimentarias cenozoicas de tamaños pequeño y mediano, localizadas en un área tectónicamente deprimida y flanqueada por elevaciones de basamento. Estas cuencas fueron creadas al inicio del evento compresivo cenozoico que afectó al interior de la Península Ibérica por la convergencia entre África y Eurasia. Muestran unas características distintivas de cuencas sedimentarias compresivas (flanqueadas por cabalgamientos y fallas inversas), cuyo mecanismo de formación se puede atribuir a un plegamiento a escala cortical. Constituyen un buen, y quizás excepcional, ejemplo de cuencas sedimentarias compresivas formadas por este tipo de mecanismo tectónic

Modelo tectónico para el evento extensional del Triásico final-Jurásico temprano en y alrededor de la Península Ibérica

An array of 200-Ma-old (Lower Jurassic) dolerite dikes in both the eastern and western sides of the Atlantic records an episode of SE directed extension which occurred in and around the Iberian Peninsula. This extensional regime episode is responsible for the formation of the main structures in the Iberian Peninsula and neighboring areas at the beginning of the JurassicUna serie de diques básicos de edad Jurásico Inferior (200 Ma), tanto en las zonas orientales como occidentales del dominio Atlántico, permite definir un episodio de extensión con dirección SE que afectó a la Península Ibérica y a las regiones vecinas. Este episodio de régimen extensional es responsable de la formación de las principales estructuras de la Península Ibérica y áreas próximas al comienzo del Jurásic

Palaeomagnetic results from Upper Miocene and Pliocene rocks from the Internal Zone of the eastern Betic Cordilleras (southern Spain)

Palaeomagnetic and rock-magnetic studies were carried out on samples from thirteen volcanic and nine sedimentary sites of Late Miocene to Pliocene age from the Internal Zone of the eastern Betic Cordilleras. After comparing palaeomagnetic results with the expected Pliocene/Miocene direction, rotated and unrotated areas can be recognized, rotations being clockwise and counter-clockwise. Some rotations are of great magnitude. Unlike deformation in the External Betics, Late Miocene to Present block rotations in the Internal Betic Zone are non-systematic, and related to the movement of faults as local responses to the Late Miocene-Present regional stress field, due to the N140 convergence of Africa and the Iberian Peninsula

Seismic and tectonic interpretation of the ESCI-Béticas and ESCI-Alborán deep seismic reflection profiles: structure of the crust and geodynamic implications

The seismic and tectonic interpretation of the ESCI-Béticas and ESCI-Alborán deep seismic reflection profiles provides an overall image of the crust on the northern flank of the Betic-Rif orogenic system. In these interpretations, previous wide-angle refraction-reflection and MCS industrial profiles were used in order to identify the sequence of collisional-extensional events that built up the crust in this escape-type orogenic area. A model of convergence between the Iberian crust and the Alborán domain, including coeval extension due to lateral escape, is consistent with the data presented in this paper

Tectonic model for the latest Triassic-Early Jurassic extensional event in and around the Iberian Peninsula

An array of 200-Ma-old (Lower Jurassic) dolerite dikes in both the eastern and western sides of the Atlantic records an episode of SE directed extension which occurred in and around the Iberian Peninsula. This extensional regime episode is responsible for the formation of the main structures in the Iberian Peninsula and neighboring areas at the beginning of the Jurassic

Seismic crustal structure in the southwest of the Iberian Peninsula and the Gulf of Cadiz

The crust under the southwestern Iberian Peninsula and the Gulf of Cadiz has been sampled by 1200 km of deep seismic refraction=wide-angle reflection profiles, together with many seismic reflection lines and bore-holes. Wide-angle seismic data were collected during the last three decades. Commercial multichannel data provide a detailed image of the uppermost crust, improving the confidence about the models of the deeper structures. P-wave velocities within the thick column of sediments in the Gulf of Cadiz range from 2.0 to 3.8 km=s, while the Algarve and the Sines areas have higher velocities of 4.3 to 4.8 km=s. The top of the Palaeozoic basement rises to the northwest, outcropping in the South Portuguese zone of the Iberian Massif, and is characterized by P-wave velocities of 5.7–5.9 km=s. High velocities of 6.4 km=s have been found at shallow depths of 7 to 10 km in the South Portuguese zone, that could be related to the mafic and ultramafic rocks in the Beja-Acebuches zone. Lower crustal velocities are in the range of 6.7–6.9 km=s. The crustal thickness shows important lateral changes from 29 km beneath the Guadalquivir Basin=Iberian Massif contact to 35 km in the southeastern part of the South Portuguese zone. From the interpretation of these seismic data, a geodynamic model of the evolution of the crust in Southwestern Iberia and the Gulf of Cadiz is proposed. The Guadalquivir Basin, and its continuation at sea, the Gulf of Cadiz, is a flexure area of the crust that could be related to the overloading due to the overthrusting of the Alboran Domain over the Iberian plate