The infralittoral prograding wedge: a new large-scale progradational sedimentary body in shallow marine environments

A progradational sedimentary body, the infralittoral prograding wedge (IPW), has been developing from the mean fair-weather wave-base level to the storm wave-base level between the onshore (beach) and the offshore (inner continental shelf) depositional zones along the Spanish coast during the Late Holocene. The main sedimentary body is composed of large inclined master beds which prograde seawards parallel to the shoreline, formed by sediments swept offshore by waves from shallow-water littoral environments. The inclined beds downlap onto finer-grained offshore sediments and, in turn, are overlain by shoreface deposits. The IPW is generated by downwelling storm currents and associated seaward transport of sediment. It represents a new depositional model for clastic wave-dominated coasts, and its identification requires a new subdivision of the nearshore environment.