Interaction between proximal foreland basin sedimentation and the structural evolution of the Catalan Coastal Range, near Gandesa, Catalunya, Spain

The Horta-Gandesa alluvial system in northeastern Spain is an Eocene-Oligocene age proximal foreland basin sequence that documents the structural evolution of the adjacent Catalan Coastal Range thrust belt, from its inception to its demise.; Between the towns of Gandesa and Horta de Sant Joan, the {dollar}sim{dollar}945 m thick stratigraphic section is divided into five mappable sequences based on the distribution and the internal characteristics of the stratigraphy (including grain size, composition, and palaeotransport). The stratigraphy chronicles the initiation, propagation and maturation of the adjacent thrust belt during five tectonic stages. Stages 1-3 resulted in the overall progradation of gravel into the foreland basin, while Stages 4 and 5 heralded the progressive segregation of gravel deposition in the foreland basin into separate depocentres.; Regional subsidence and sediment supply, resulting from the uplift, loading and erosion of the Pyrenees, Iberian and Catalan fold-and-thrust belts, exerted a first-order control on the geometry of the Ebro foreland basin and its fill. However, the detailed internal development of the proximal foreland-basin stratigraphy was controlled by local variation in the balance between the rates of subsidence and sediment supply, resulting from along-strike temporal and spatial variation in the structural evolution of the thrust front. Significant variation in gravel distribution and palaeotransport was documented along the foreland basin over short distances (as little as a few hundreds of metres), emphasizing the complexity of the three-dimensional relationship between deformation and sedimentation.; The timing and location of tectonic activity in the thrust belt is indicated within the proximal foreland-basin stratigraphy by changes in gravel composition. Thrusting is associated with a retraction in gravel distribution relative to the thrust front, and the deposition of fine grained sediment in the foreland basin, as predicted by recent models where variations in subsidence rates control the distribution of gravel in the foreland basin. However, in contrast to these models, the retraction in gravel distribution is attributed to a decrease in the supply of sediment associated with structural partitioning of the foreland basin, rather than to a significant increase in subsidence associated with loading.