Evolución sedimentaria y paleogeográfica cenozoica de la Cuenca Quebrada Del Profeta, norte de Chile
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2016
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Sociedad Geológica de España.
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Abstract
El antearco andino del norte de Chile alberga diversas cuencas cenozoicas continentales cuyo relleno sedimentario responde a la erosión y denudación de la Precordillera Andina. La Cuenca Quebrada Del Profeta es una de estas cuencas intramontañosas situada a ~200 km al SE de Antofagasta. En este trabajo se describe una secuencia sedimentaria de ~145 m de potencia, donde se distinguen dos tramos (TI y TII) separados por una discordancia. El TI, compuesto por paraconglomerados, arenas, limos y niveles de calizas, se interpreta como un sistema fluvio-aluvial y lacustre. El TII, compuesto por brechas masivas y por niveles de brechas cementadas por yeso, se interpreta como un sistema aluvial dominado por flujos de tipo debris flow. El análisis de facies y las variaciones laterales de estas, sumado a la medida de paleocorrientes y procedencia de clastos, indica que en el TI (Eoceno Superior), predominaba un sentido de transporte NO-SE, mientras que en el TII (Mioceno), el sentido de transporte era E-O. Este cambio implica una importante reorganización paleogeográfica en el límite Paleógeno – Neógeno en esta zona.
The Andean forearc in northern Chile contains several cenozoic continental basins filled up with deposits coming from the erosion of the Andean Precordillera. The Quebrada Del Profeta Basin is one of this intramontane basins located ~200 km SE of Antofagasta. In this study we describe a ~145 m thick sedimentary sequence, where two sections, separated by a discordance, are distinguished: TI and TII. The TI is composed by paraconglomerates, sandstones, siltstones and limestones and is interpreted as a fluvio-alluvial and lacustrine system. The TII is composed by massive breccias and levels of breccias cemented by gypsum and is interpreted as an alluvial system dominated by debris flows. Facies analysis and lateral variations of these, added to paleocurrent data and studies of clasts provenance, indicate that in the TI (Late Eocene) prevailed a NW-SE sediment transport direction, whereas in the TII (Miocene) prevailed an E-W sediment main transport. This change implies an important palaeogeographic redistribution during the Paleogene – Neogene boundary in this region.
The Andean forearc in northern Chile contains several cenozoic continental basins filled up with deposits coming from the erosion of the Andean Precordillera. The Quebrada Del Profeta Basin is one of this intramontane basins located ~200 km SE of Antofagasta. In this study we describe a ~145 m thick sedimentary sequence, where two sections, separated by a discordance, are distinguished: TI and TII. The TI is composed by paraconglomerates, sandstones, siltstones and limestones and is interpreted as a fluvio-alluvial and lacustrine system. The TII is composed by massive breccias and levels of breccias cemented by gypsum and is interpreted as an alluvial system dominated by debris flows. Facies analysis and lateral variations of these, added to paleocurrent data and studies of clasts provenance, indicate that in the TI (Late Eocene) prevailed a NW-SE sediment transport direction, whereas in the TII (Miocene) prevailed an E-W sediment main transport. This change implies an important palaeogeographic redistribution during the Paleogene – Neogene boundary in this region.