Sedimentary architecture of a prograding oolitic-siliciclastic wedge: Response to changes in wave-base oscillation (Kimmeridgian, Iberian Basin)

A detailed facies and sequential architectural analysis has been carried out along the wedge-shaped shallow marine cross-bedded oolitic-siliciclastic Ricla Member (Kimmeridgian, Northern Iberian Basin). The obtained results are based on fieldwork along the 4 × 1 km continuous outcrops with the use of high-resolution photomosaics and drone-made videos, which have led to a precise and extensive facies reconstruction. Three main facies that are laterally related (A to B to C) in down-dip direction have been differentiated, which correspond to the topset, foreset and bottomset parts of a sloping depositional surface. Sedimentation was controlled by sweeping drift and downwelling storm-induced currents causing avalanching processes, with the deep action of oscillatory currents. The sedimentary architecture consists in 5 successive units composed by several sub-units, arranged according to different stacking patterns, which reflect the sedimentary response to wave-base oscillations superimposed to the regressive part of a third-order transgressive-regressive cycle. The sedimentological features indicate that this unit, which has been previously interpreted as a dune complex fit with an infralittoral prograding wedge model, as it is observed in geographically close and stratigraphically similar units. The Ricla Member is therefore regarded as an example of a well-exposed grain-supported unit with broad potential application to other prograding grain-dominated lithosomes that do not conform to the traditional sand shoal model.