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Abstract

Middle to Upper Pleistocene fluvial sediments of the Cádiz Bay occur fifling partly two disconnected sub-basins excavated into shallow marine deposits of Pliocene to Lower Pleistocene age, and are buried under fluvial and estuarine Hofocene deposits. Subsurface, drill cores, and surface informatio indicate that the area of the Bay was occupied by a more or less continuous basin during the Late Pliocene-Lower Pleistocene, but the pattern changed during Middle to Late Pleistocene as revealed by facies analysis and palaeogeographical reconstruction of the fluvial environments. Fluvial deposits are laterally discontinuous, with variable rhickness and elongated troughs occupied by the coarsest sediments available. Our paleogeographical reconstruction for this periad shows a landscape with two subaerial sub-basins that acted as Fluvial valleys during glacially-forced lowstands, with two main Fluvial systems flowing constrained by topographical highs. This configurarion records the coincidence of very low sea level (regressive conditions) during glacial periods and active neotectonics. The valleys were flooded during the postglacial Holocene transgression and sea level surpassed the elevations separating the former valleys leading to the apparently simple configuration of the bay.