Publication: Historia tectonotermal Mesozoica y Cenozoica del NO peninsular establecida mediante termocronología de huellas de fisión en apatito
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Publication Date
2008
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Sociedad Geológica de España.
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Abstract
La modelización de datos de huellas de fisión en apatitos aporta nueva información sobre la evolución tectonotermal del NO peninsular. Se han muestreado los tres bloques morfotectónicos más destacados del NO (Cordillera Cantábrica-Ancares, Montes Galaico-Leoneses, y Rías Bajas-llanuras de Terra Chá). La historia tectonotermal de la región comenzaría con la intrusión de los granitos Variscos y su enfriamiento en niveles superiores corticales. Posteriormente, se observa un primer periodo de calentamiento que tiene lugar en el Jurásico Superior y Cretácico Inferior en relación con la evolución del margen pasivo gallego. El segundo periodo de calentamiento, sólo se refleja en las rocas situadas más al Norte, y se interpreta en relación con el comienzo de la colisión Europa-Iberia que tiene lugar durante el Cretácico Superior y el Paleógeno. Por ultimo, la evolución de las muestras varía, de forma que el enfriamiento durante el Paleógeno se produce lenta y progresivamente en las muestras situadas fuera de los relieves (llanuras de Terra Chá), y bruscamente en los relieves. En las muestras situadas dentro de los relieves de los Montes Galaico-Leoneses, el enfriamiento comienza en el Mioceno medio y superior, mientras que para la muestra situada en Ancares este enfriamiento comienza antes (Oligoceno). Todo ello indicaría un levantamiento posterior de los Montes Galaico-Leoneses con respecto a los Ancares.
Modelling of the apatite fission-track data contributes to new information about the tectonothermal evolution of the NW Iberian Peninsula. We have sampled the three main morphotectonic blocks (Cantabrian Range-Ancares, Galaico-Leoneses Mountains and Rías Bajas-Terra Chá Plains). The tectonothermal history observed in the AFT models begins with the intrusion of the late Variscan granites cooling in the upper crustal levels. After this initial event, an important heating took place during the Upper Jurassic and Earlier Cretaceous. This episode can be related to the evolution of the Atlantic passive margin. The second heating episode, which is only registered in the Northern samples, can be connected to the beginning of the Europe-Africa collision during the Upper Cretaceous and Earlier Palaeogene. Finally, a variation in the samples evolution is observed. Thus, slower cooling episode is observed during the Palaeogene in the samples of the Terra Chá Plains than those in the ranges. In the samples of Galaico-Leoneses Mountains cooling started in the Middle and Upper Miocene whereas the sample of Ancares the cooling started before, in the Oligocene. These data point to a later exhumation of the Galaico-Leoneses Mountains than in Ancares area.
Modelling of the apatite fission-track data contributes to new information about the tectonothermal evolution of the NW Iberian Peninsula. We have sampled the three main morphotectonic blocks (Cantabrian Range-Ancares, Galaico-Leoneses Mountains and Rías Bajas-Terra Chá Plains). The tectonothermal history observed in the AFT models begins with the intrusion of the late Variscan granites cooling in the upper crustal levels. After this initial event, an important heating took place during the Upper Jurassic and Earlier Cretaceous. This episode can be related to the evolution of the Atlantic passive margin. The second heating episode, which is only registered in the Northern samples, can be connected to the beginning of the Europe-Africa collision during the Upper Cretaceous and Earlier Palaeogene. Finally, a variation in the samples evolution is observed. Thus, slower cooling episode is observed during the Palaeogene in the samples of the Terra Chá Plains than those in the ranges. In the samples of Galaico-Leoneses Mountains cooling started in the Middle and Upper Miocene whereas the sample of Ancares the cooling started before, in the Oligocene. These data point to a later exhumation of the Galaico-Leoneses Mountains than in Ancares area.