Depositional sequence response to foreland deformation in the Upper Cretaceous of the Southern Pyrenees, Spain

During the initial stage of the evolution of the South Pyrenean foreland basin in the Late Cretaceous, foreland shortening resulted in the development of a major thrust sheet consisting of three main fold-thrust uplifts. As a consequence, the basin was segmented into uplift-bounded depocenters (minibasins) that were contemporaneously filled with basin-fill successions of pro-grading siliciclastics. A sequence-stratigraphic study has led to detailed regional correlations showing turbidite, deltaic, and fluvial facies transitions (Vallcarga, Aren, and Tremp formations, respectively). The deltaic deposits are grouped into four depositional sequences based on recognition and definition of sequence boundaries and systems tracts. The basinward migration of the depocenters was associated with uplifting and cyclic sedimentation. Turbiditic deposits accumulated on footwall syn-clines and onlapped onto growing anticlines during phases of active thrusting. Deltaic wedges prograded over deep-water sediments. Highstand shelves overlapped preexisting structural highs suggesting relative tectonic quiescence. The chronology of the shelves, based on planktonic foraminifera, provides new insight into the timing of deformation. Three hydrocarbon plays are found within low-stand systems tracts: delta front, canyon fill, and slope channel fill. These may prove helpful as models for more prolific hydrocarbon-bearing clastic basins. The depositional model may serve as an analog for intraslope minibasins on Atlantic margins.