The Guadiana Basin is an E-W intraplate Cenozoic basin located in SW of the Iberian Peninsula, covering an area close to 6000 km2. NE-SW Alpine faults divide the basin into two subbasins: the Vegas Altas (VA) to the E...The Guadiana Basin is an E-W intraplate Cenozoic basin located in SW of the Iberian Peninsula, covering an area close to 6000 km2. NE-SW Alpine faults divide the basin into two subbasins: the Vegas Altas (VA) to the East, and the Vegas Bajas (VB) to the West. Sedimentary record consists of <200 m thick of sediments, arranged in two main depositional sequences, DS1 and DS2. Petrographic analysis of sediment sandy-fraction combined with geochemical analysis of <2 mm fraction permit to infer provenance and factors controlling sediment composition. Petrographic analysis of sandy-fraction reveals provenance from basin margins lithologies. In VA subbasin, quartzolithic petrofacies characterized eastern subbasin infill related to the erosion of Neoproterozoic and Palaeozoic metasediments. To the West quartzofeldspathic petrofacies predominates, associated with the erosion of coarse-grained plutonites and short distance transport of their products. Intermediate petrofacies characterizes clastic deposits from the VB. Chemical analysis of clastic deposits corroborates a main felsic origin of sediments with a composition that fits well with the upper crust compositional norm and with the Neoproterozoic Iberian Average Shale (NIBAS). In addition, minor contributions from mafic sources can be identified in DS1 from VB, manifested by anomalies in the content of Co, Ni, Cr, V and Sc. Different stages of weathering (from intermediate to intense) can be deduced by the analysis of both, sandy-fraction petrography and bulk sediment geochemistry. This fact is related to the great hiatus at the base of the Cenozoicbasin infill. Transport-limited denudation regimes can be inferred by the presence of high and intermediate weathered and texturalyinmature sediments. In addition, trace element ratios suggest local enrichment in dense minerals, attributable to recycling processes from metasediments. Finally, the sedimentary record of the Guadiana Basin is constituted by immature sediments formed by limited transsport processes of very variable weathered products from recycled metasedimentary and first-order sediments from granitoids.展开更多
文摘The Guadiana Basin is an E-W intraplate Cenozoic basin located in SW of the Iberian Peninsula, covering an area close to 6000 km2. NE-SW Alpine faults divide the basin into two subbasins: the Vegas Altas (VA) to the East, and the Vegas Bajas (VB) to the West. Sedimentary record consists of <200 m thick of sediments, arranged in two main depositional sequences, DS1 and DS2. Petrographic analysis of sediment sandy-fraction combined with geochemical analysis of <2 mm fraction permit to infer provenance and factors controlling sediment composition. Petrographic analysis of sandy-fraction reveals provenance from basin margins lithologies. In VA subbasin, quartzolithic petrofacies characterized eastern subbasin infill related to the erosion of Neoproterozoic and Palaeozoic metasediments. To the West quartzofeldspathic petrofacies predominates, associated with the erosion of coarse-grained plutonites and short distance transport of their products. Intermediate petrofacies characterizes clastic deposits from the VB. Chemical analysis of clastic deposits corroborates a main felsic origin of sediments with a composition that fits well with the upper crust compositional norm and with the Neoproterozoic Iberian Average Shale (NIBAS). In addition, minor contributions from mafic sources can be identified in DS1 from VB, manifested by anomalies in the content of Co, Ni, Cr, V and Sc. Different stages of weathering (from intermediate to intense) can be deduced by the analysis of both, sandy-fraction petrography and bulk sediment geochemistry. This fact is related to the great hiatus at the base of the Cenozoicbasin infill. Transport-limited denudation regimes can be inferred by the presence of high and intermediate weathered and texturalyinmature sediments. In addition, trace element ratios suggest local enrichment in dense minerals, attributable to recycling processes from metasediments. Finally, the sedimentary record of the Guadiana Basin is constituted by immature sediments formed by limited transsport processes of very variable weathered products from recycled metasedimentary and first-order sediments from granitoids.
