The Pliocene and Quaternary formations of El Abalario, in the Huelva province littoral (Spain)

The study of new and ancient boreholes in El Abalario area (Lower Guadalquivir basin) permitted to identify four main plio-quaternary formations above the Miocene marls, namely: Huelva Sands, Bonares Sands, Almonte Sands and Gravels, and El Abalario Sands. Respectively, they are interpreted as shallow marine, deltaic, alluvial and eolian sediments, together forming a marine to continental sequence that reaches a thickness of more than 250 metres. All sediments are arranged as a gentle dipping and thickening structure to the southeast. Only a few boreholes of the western border of El Abalario reach the top of the Miocene marls. In the rest of the Abalario area the Miocene marls are confined to an unknown level bellow the deepest boreholes. Upward, the marls grade to the Huelva sands, without any appreciable break in the sediments. To the north, the upper part of the Huelva formation grades to the Bonares sands, which is mainly developed outside the study area. Both formations are covered by the coarse clastic deposits of the Almonte formation. At the top, El Abalario sands recover all previous deposits and configure the current relief. This study improves the early existing geology profile and the connection with the surrounding areas (Author).