Person:
Fernández Barrenechea, José María

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First Name
José María
Last Name
Fernández Barrenechea
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Mineralogía y Petrología
Area
Cristalografía y Mineralogía
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Now showing 1 - 2 of 2
  • Publication
    Sources of Sr and S in Aluminum-Phosphate–Sulfate Minerals in Early–Middle Triassic Sandstones (Iberian Ranges, Spain) and Paleoenvironmental Implications for the West Tethys
    (SEPM (Society for Sedimentary Geology), 2013) Galán Abellán, Ana Belén; Alonso Azcárate, Jacinto; Newton, Robert J.; Bottrell, Simon H.; Fernández Barrenechea, José María; Benito Moreno, María Isabel; Horra del Barco, Raúl de la; López Gómez, José; Luque del Villar, Francisco Javier
    Aluminum-phosphate–sulfate (APS) minerals, formed during early diagenesis in relation to acid meteoric waters, are the main host of Sr and S in the Early–Middle Triassic continental sandstones of the Iberian Ranges (east of the Iberian Peninsula). The sources of these elements and the effects of paleoenvironmetal changes on these sources and on the formation of APS minerals during Early–Middle Triassic times, were established on the basis of Sr and S isotopic analyses. The S and Sr data (d34S V-CDT = +11 to +14% and 87Sr/86Sr = 0.7099–0.7247, respectively) can be interpreted as resulting from mixing of different sources. Strontium was sourced from the dissolution of pre-existing minerals like K-feldspar and clay minerals inherited from the source areas, causing high radiogenic values. However, the isotopic signal must also be influenced by other sources, such as marine or volcanic aerosol that decreased the total 87Sr/86Sr ratios. Marine and volcanic aerosols were also sources of sulfur, but the d34S was lowered by dissolution of pre-existing sulfides, mainly pyrite. Pyrite dissolution and volcanic aerosols would also trigger the acid conditions required for the precipitation of APS minerals. APS minerals in the study area are found mainly in the Cañizar Formation (Olenekian?–Aegian), which has the lowest 87Sr/86Sr ratios. The lower abundance of APS minerals in the Eslida Formation (Aegian–Pelsonian) may indicate change in the acidity of pore water towards more alkaline conditions, while the increased 87Sr/86Sr ratios imply decreased Sr input from volcanic activity and/or marine aerosol inputs during Anisian times. Therefore, the decrease in abundance of APS minerals from the Early to Middle Triassic and the variations in the sources of Sr and S are indicative of changes in paleoenvironmental conditions during the beginning of the Triassic Period. These changes from acid to more alkaline conditions are also coincident with the first appearance of carbonate paleosols, trace fossils, and plant fossils in the upper part of the Cañizar Formation (and more in the overlying Eslida Formation) and mark the beginning of biotic recovery in this area. The presence of APS minerals in other European basins of the Western Tethys (such as the German Basin, the Paris Basin and the southeastern France and Sardinia basins) could thus also indicate that unfavorable environmental conditions caused delay in biotic recovery in those areas. In general, the presence of APS minerals may be used as an indicator of arid, acidic conditions unfavorable to biotic colonization.
  • Publication
    Sedimentary evolution of the continental Early–Middle Triassic Cañizar Formation (Central Spain): Implications for life recovery after the Permian–Triassic crisis
    (Elsevier, 2012) López Gómez, José; Galán Abellán, Ana Belén; Horra del Barco, Raúl de la; Fernández Barrenechea, José María; Arche, Alfredo; Bourquin, Sylvie; Marzo Carpio, Mariano; Durand, Marc
    The Permian–Triassic transition (P–T) was marked by important geochemical perturbations and the largest known life crisis. Consequences of this event, as oxygen-depleted conditions and the unusual behavior of the carbon cycle, were prolonged during the Early Triassic interval delaying the recovery of life in both terrestrial and marine ecosystems. Studies on Lower Triassic sediments of continental origin, as in the case of Western Europe, are especially problematic due to the scarcity of fossils and absence of precise dating. The Cañizar Fm. is an Early–Middle Triassic unit of continental origin of the SE Iberian Ranges, E Spain. A detailed sedimentary study of this unit allows a shedding of light on some unresolved problems of the continental deposits of this age. The top of this unit is dated as early Anisian by means of a pollen association, while the age of its base is here estimated as late Smithian or Smithian–Spathian transition. Different facies associations and architectural elements have been defined in this unit. In the western and central parts of the basin, this unit shows sedimentary characteristics of fluvial deposits with locally intercalated aeolian sediments, while in the eastern part there is an alternation of both aeolian and fluvial deposits. Sedimentary structures also indicate changes in the climate conditions, mainly from arid to semiarid. Two marked arid periods when well-preserved aeolian sediments developed during early–middle Spathian and Spathian–Anisian transition. They alternated with two semiarid but more humid periods during the late Spathian and early Anisian. These conditions basically correspond with the general arid and very arid conditions described for central–western European plate during the same period of time. The Ateca–Montalbán High, in the northern border of the study basin, must have represented an important topographic barrier in the western Tethys separating aeolian dominated areas to the N and NE from fluvial dominated areas to the south. The Cañizar Fm. has been subdivided into six members (A–F) separated by seven (1–7) major bounding surfaces (MBS). These surfaces are well recognized laterally over hundred of km and they represent 104–105 My. MBS-5 is considered to be of late Spathian age and it is a clear indication of tectonic activity, represented by a mild unconformity. This event represents a change in the sedimentary characteristics (reactivation) of the unit and from here to the top of the unit are found the first signals of biotic recovery, represented by tetrapod footprints, plants, roots and bioturbation. All of these characteristics and the estimated age represented by the MBS-5 event permit this surface to be related to the coeval Hardegsen unconformity of Central–Western Europe. These first signals of biotic recovery can thus be related to an increased oxygen supply due to the new created paleogeographical corridors in the context of this tectonic activity. These biotic signals occurred 5 My after the Permian–Triassic limit crisis; a similar delay as occurred in other coeval and neighboring basins.