Publication: Indicadores paleoambientales durante la crisis Smithiense-Spathiense (Triásico inferior) en medios continentales del oeste del Peri-Tethys
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2017-12-12
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Universidad Complutense de Madrid
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Abstract
El objetivo principal de esta tesis es abordar desde un punto de vista multidisciplinar, y por primera vez en el oeste de Europa, la crisis ambiental ocurrida durante el final del Smithiense y principios del Spathiense (Olenekiense, Triásico Inferior). Dicha crisis ha sido observada tanto en medios continentales como marinos en todo el planeta, pero hasta fechas recientes había quedado enmascarada por una crisis anterior más severa acaecida durante el límite Pérmico-Triásico (P-T), de la cual está separada por sólo por 3 m.a. Ambas crisis están interconectadas, ya que la del P-T estuvo desencadenada por una intensa actividad volcánica de las Trampas Siberianas, y la del Smithiense-Spathiense (S-S) se relaciona con un repunte del mismo vulcanismo. Aunque dicha crisis causó una menor mortalidad en las especies en continentes y océanos que la sucedida en el P-T, provocó una interrupción en la tendencia de recuperación de esta última, retardando con ello la aparición de la nueva fauna y flora tras la crisis P-T. El estudio detallado en esta memoria se ha realizado en medios continentales, concretamente en la Cordillera Ibérica, extendiéndose posteriormente a la Cordillera Costero Catalana y a las islas de Menorca y Cerdeña, con el fin de conocer si las alteraciones ambientales fueron similares en otras cuencas. La forma de afrontarlo ha sido desde diferentes disciplinas, donde se incluyen estudios de mineralogía, sedimentología, paleosuelos, bioturbación, paleoflora y climas. El método seguido ha consistido en proporcionar un marco paleoambiental y, posteriormente, canalizar los cambios principales de éste mediante el estudio de las variaciones mineralógicas, concretamente en la concentración de minerales fosfato-sulfatos alumínicos (minerales APS) ricos en estroncio, que potencialmente pueden servir como indicadores del pH existente en el momento de su precipitación, ya que para ello requieren unas condiciones ácidas. Los datos texturales obtenidos en la zona de estudio indican que las fases minerales se formaron durante la diagénesis temprana, antes de la compactación de los sedimentos, lo que ha permitido inferir que precipitaron en contacto con aguas meteóricas ácidas, y por tanto, que las variaciones en su concentración pueden utilizarse para conocer la duración e intensidad de las condiciones de acidez en el medio...
The main objective of this PhD thesis is to approach from a multidisciplinary point of view, and for the first time in western Europe, the environmental crisis that occurred during the late Smithian and early Spathian (Olenekian, Early Triassic). This crisis has been observed both in continental and marine environments throughout the planet, but until recently it had been masked by a more severe previous crisis, which occurred during the Permian-Triassic (P-T) boundary, some 3 m.y. before. Both crises are interrelated because the P-T was triggered by intense, volcanic activity in the Siberian Traps, while the S-S was possibly related to a rebound of the same volcanism. Although the S-S crisis represented a lower mortality in the species than the one occurred in the P-T, it represented an interruption in the recovery trend of the latter. The study has been carried out in continental environments, specifically in the Iberian Ranges, extending later to the Catalan Coastal Ranges and the islands of Minorca and Sardinia in order to know whether the environmental variations were similar in other basins. The approach has been carried out from different disciplines, including studies of mineralogy, sedimentology, palaeosols, bioturbation, palaeoflora and climates. Methodologically, a palaeoenvironmental framework has been established, and the changes to this framework have been compared with mineralogical variations, specifically in the concentration of strontium-rich aluminium phosphate-sulphate minerals (APS minerals). These minerals can potentially be indicators of pH in the precipitation moment, since they require acidic conditions. The textural data obtained indicate that the mineral phases in the study area were formed during early diagenesis, before sediment compaction, which allowed inferring that they precipitated in contact with acidic meteoric waters. Therefore, the variations in their concentration can be used to determine the duration and intensity of the acidic conditions in the environment...
The main objective of this PhD thesis is to approach from a multidisciplinary point of view, and for the first time in western Europe, the environmental crisis that occurred during the late Smithian and early Spathian (Olenekian, Early Triassic). This crisis has been observed both in continental and marine environments throughout the planet, but until recently it had been masked by a more severe previous crisis, which occurred during the Permian-Triassic (P-T) boundary, some 3 m.y. before. Both crises are interrelated because the P-T was triggered by intense, volcanic activity in the Siberian Traps, while the S-S was possibly related to a rebound of the same volcanism. Although the S-S crisis represented a lower mortality in the species than the one occurred in the P-T, it represented an interruption in the recovery trend of the latter. The study has been carried out in continental environments, specifically in the Iberian Ranges, extending later to the Catalan Coastal Ranges and the islands of Minorca and Sardinia in order to know whether the environmental variations were similar in other basins. The approach has been carried out from different disciplines, including studies of mineralogy, sedimentology, palaeosols, bioturbation, palaeoflora and climates. Methodologically, a palaeoenvironmental framework has been established, and the changes to this framework have been compared with mineralogical variations, specifically in the concentration of strontium-rich aluminium phosphate-sulphate minerals (APS minerals). These minerals can potentially be indicators of pH in the precipitation moment, since they require acidic conditions. The textural data obtained indicate that the mineral phases in the study area were formed during early diagenesis, before sediment compaction, which allowed inferring that they precipitated in contact with acidic meteoric waters. Therefore, the variations in their concentration can be used to determine the duration and intensity of the acidic conditions in the environment...
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Tesis presentada en la Universidad Complutense de Madrid, Facultad de Ciencias Geológicas, leída el 04-07-2017