Middle Jurassic volcanism in a magmatic-rich passive margin linked to the Caudiel Fault Zone (Iberian Range, East of Spain): biostratigraphical dating

Abstract

During the Early and Middle Jurassic, the Iberian Basin (East of Spain) recorded the transition from a generally magma-poor passive margin, which operated during the latest Triassic and most of Early Jurassic, to a magma-rich passive margin, developed from Pliensbaextensional fault zones. One of these zones of weakness, from which the volcanic deposits were expelled to the sea bottom, was the Caudiel -formations. So far, the accurate age of these volcanisms, critical in the knowledge of the palaeogeographical and geodynamical evolution of the Iberian Basin, has remained uncertain. The ammonite content of the carbonate successions, with which these rocks are interbedded, allows precise biostratigraphical dating at the chronozone scale. For this purpose, 9 sections have been measured and 360 specimens of ammonites were collected and determined. The obtained data indicate that the Middle Jurassic volcanic deposits that are linked to the Caudiel Fault Zone and included into the El Pedregal Formation show a slight diachrony. They were deposited around the boundary between the Late Aalenian Concavum and the Early Bajocian Discites chronozones. However, in very restricted areas of the Caudiel Fault Zone, an older intra-Murchisonae volcanism was recorded.Keywords: Volcanism, Biochronostratigraphy, Ammonites, Middle Jurassic, Iberian Range ResumenDurante el Jurásico Inferior y Medio, la Cuenca Ibérica (Este de España) registró la transición de un margen pasivo pobre en magmatismo, que operó durante el Triásico terminal y la mayor parte del Jurásico Inferior, a un margen pasivo rico en actividad magmática, que se desarrolló desde el Pliensbachiense hasta el comienzo del Jurásico Medio. El volcanismo submarino, fundamentalmente piroclástico y con volcánicas que tuvieron lugar a lo largo del Jurásico Medio en relación con esta línea de debilidad. La fase principal se manifestó mientras y geodinámica de la Cuenca Ibérica, ha permanecido incierta. El contenido en ammonites de las sucesiones de carbonatos, entre los que del Jurásico Medio que están asociados a la Zona de Falla de Caudiel e incluidos en la Formación El Pedregal muestran una sincronía casi perfecta. Se depositaron hacia el límite entre la Cronozona Concavum del Aaleniense Superior y la Cronozona Discites del Bajociense Inferior. Con anterioridad, un volcanismo de edad intra-Murchisonae quedó registrado en áreas muy localizadas de la Zona de Falla de Caudiel.

Middle-Upper Triassic stratigraphy and structure in the Alt Palància region (eastern Iberian Chain): A multidisciplinary approach

“…Striking differences in depositional thickness and facies were also recorded by Gómez (1979) in the Jurassic successions of the northern part of the Alt Palància due to NW-SE-oriented faults ('Fault Zone of Caudiel'). Moreover, igneous rocks appear in this area assigned to the Late Triassic (ophitic dolerites) and the Early-to-Middle Jurassic (basalts and trachybasalt flows and pyroclastic deposits; see Ortí and Vaquer, 1980), as documented in several studies near Caudiel (Cortés and Gómez, 2016;Cortés, 2018;Gómez and Goy, 1977). The Espina-Espadà Fault can be related to the 'Molina-Teruel-Espadà' fault of López- Gómez and Arche (1994) and of Arche and López-Gómez (1996).…”

Dating metasomatic events in the lithospheric mantle beneath the Calatrava volcanic field (central Spain)

“…Their trace-element compositions combined with Sr-Nd isotopic signatures, close to CHUR values, suggest derivation from a metasomatized lithospheric source (Mata et al, 2015). A unique alkaline basaltic outcrop at the Languedoc volcanic field (SE France) yielded 161 Ma (Dautria et al, 2010), but slightly older Middle Jurassic alkaline volcanism (~176-165 Ma) has been described in the Iberian Range, also considered to be related to passive margin settings (Lago et al, 2004;Cortés and Gómez, 2016).…”

Interacción entre vulcanismo, tectónica y sedimentación en una plataforma carbonatada somera: Ejemplo en el Tethys occidental (Jurásico Medio, sureste de la Cordillera Ibérica)

“…2A) includes two volcanic phases, the most recent being the subject of this study. It coincides in time with the Concavum-Discites chronozonal boundary (Cortés & Gómez, 2016;Cortés, 2018), and corresponds to the 12 th position of the total (Cortés, 2018) (Fig. 2B).…”

“…Based on 500 ammonite specimens extracted from the carbonate strata, taxonomic and taphonomic analyses were carried out by Professors Fernández-López and Ureta (Departamento de Geodinámica, Estratigrafía y Paleontología, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid) in order to date the pre-volcanic sediments, the volcanic phase and the post-volcanic carbonate sediments that interact with the volcanic level. All the taxonomic and taphonomic data are available in Cortés (2018), Cortés et al (2009) and Cortés & Gómez (2016). Following Fernández-López (1984a,b), resedimented and reelaborated specimens have been distinguished according to their state of preservation.…”

“…This assemblage could be indicating both the top of the Concavum Chronozone (late Aalenian) and the base of the Discites Chronozone (early Bajocian). Given that the uppermost pre-volcanic sediments are Aalenian (Concavum Chronozone) in age, the time of the volcanic event is constrained to the Aalenian-Bajocian boundary or, preferably, to the latest Aalenian (Cortés & Gómez, 2016;Cortés, 2018), since none of the typically indicative forms of the Discites Chronozone has made the first appearance yet. From this conclusion, it can be inferred that the deposition of carbonate layers interbedded around the pinching-out zones of both volcanic flanks took place shortly after the accumulation of volcanic matter.…”