Tectonic and geomorphic controls on the fluvial styles of the Eslida Formation, Middle Triassic, Eastern Spain

Abstract

The Eslida Fm is an alluvial unit of the Buntsandstein Facies of the Iberian Ranges deposited in a half-graben basin over a period of 2–2.5 Ma during the lower Anisian (Middle Triassic). It can be subdivided into six cycles that can be correlated along the basin. The overall architecture and cyclicity were controlled by the episodic activity of the basin boundary fault. Two proximal source areas of minor importance and a distal one of major importance are identified. The petrological composition of the sandstones is arkosic to subgrauwackic, indicating source areas containing both low-metamorphic rocks and gneiss, and granitic rocks. Alluvial fans, very common in rift basins, were not developed because of slow fault scarp retreat and the lack of large antecedent rivers cutting across the rift shoulders. Paleocurrents point to the SE, except for a zone in the middle part of the basin where interference with a NE–SW fault system deflected the channels to the S. The infilling of the basin is asymmetric in a transverse section, with channel facies near the basin boundary fault to the NE and overbank facies in the distal SW part.