Stratigraphic and tectonosedimentary development of the Eocene Sant Llorenç del Munt and Montserrat fan-delta complexes (Southeast Ebro basin margin, Northeast Spain)

Abstract

The depositional environment, climatic conditions, structural evolution, age, catchment area characteristics, and sequence stratigraphic arrangement along an early Cenozoic forelandhinterland boundary in northeastern Spain were determined from sedimentologic, palynologic, stratigraphic, structural, and paleomagnetic data. As the transpressional Catalan Coastal Ranges (characterized by NNW-verging folds and thrusts) rose during the Paleogene, two fan-deltas prograded into the Ebro basin. The syntectonic condition of the Paleogene deposits is evidenced by facies and geometries directly related to the growth of specific structures and tectonic activity in the catchment area. A tectonosedimentary evolution was deduced along the basin margin, clearly indicating a NE to SW migration of the deformation. In the present study, the effects of high rates of subsidence and sediment supply, associated with orogenic uplift and loading, on the sequence-stratigraphic organization of two fandelta clastic wedges are highlighted. Specific topics addressed are the relevance of different key stratigraphic surfaces to the development of basic depositional cycles; the stacking pattern of high-order sequences, and the formation of lower-order composite sequences; the time span and periodicity recorded by the sequence hierarchy; the traceability of coastal sequences into the alluvial realm; and the relative importance of accommodation vs. sediment supply changes in controlling sequence hierarchy.