Sedimentación durante una etapa regresiva de corta duración en el Aptiense (Miembro Arenas y arcillas del Burgal), en la Cordillera Ibérica suroccidental

Abstract

The Aptian El Burgal Mb. up to 85 m in thickness crops out in the SE Iberian Ranges (Central Spain). It is mainly comprised of fine to coarse-grained', white and ochre sandstones (arkoses)with intercalated levels of medium-sized, rounded quartzite pebbles, fine red sediments and local coal (lignite) horizons. Detailed study o f isopachs, 15 logs and 6 facies associations indicate that the El Burgal Mb. was deposited within different environments of sandy fluvial systems and fluvialwave-tidal interaction environments, commonly truncated by tidal channels from northern to southern zones respectively. The fluvial environments are represented by bedload, deposited as bars that till channels of mainly low but also of high sinuosity. Crevasse splays are frequent, showing long complex sheet-sandstone bodies interspersed with the channel fill in the northern area. The fluvio-marine transitional zone is located in the central area, where sandy fluvial meandering deposits cut soil horizons and coal seams in flood plain areas. Fluvial-wave-tide interaction deltas vertically alternate with shallow water marine sediments of Urgonian carbonate facies in the southern zone. Dispersion of the sediments are clearly controlled by the NW-SE tectonic alignment of Lower Cretaceous rift development that represented the Iberian Basin, with an interaction o f both extrabasinal and intrabasinal tectonics resulting in a regression within a long term transgressive episode.