El sistema de terrazas del valle bajo del Guadalquivir y su relación con la Formación Arcillas de Marismas

The aim of this study is to set-up the geometric and temporal relationships between the Marismas Clay Formation and the fluvial terraces system of the lower Guadalquivir valley. In order to establish this correlation, the data provided by the geological - geomorpho-logical maps of the area have been combined with the data of the lithological sections of boreholes. The gravels of terrace T13 (Middle to Upper Pleistocene) were buried by the Holocene fine grain allu-vials as a consequence of the Flandrian transgression at the city of Seville. These gravels have continuity below the recent alluvials un-til near Coria del Rio. This Pleistocene gravel alluvial level must be equivalent to the main alluvial intercalation existing in the Marismas Clay Formation in the Lebrija hydrogeological borehole, both being of the same age. The lower section of the Marismas Clay Formation (Middle Pleistocene) in the Lebrija borehole, which would have been formed in conditions of high sea level (MIS 6-7), would be related to the T12 or T11 terraces.