Descripción de las facies presentes en el relleno holoceno del sector externo de la Bahía de Cádiz

Abstract

The Holocene sedimentary evolution in the continental margin of Cadiz Gulf is affected by different factors, which control the nature and distribution of the deposits. The physiography of coast and sea bottom linked to a hydrodynamic regime controlled by storms and tidal current system control the short term deposition. The aim of this paper is to study the sedimentary record in terms of facies and facies sequences, so as determine the sedimentary conditions of Cadiz Bay and their evolution during the Holocene. Drilling data were used to know the nature and distribution of the nonconsolidated recent sedimentary deposits. Thickness distribution shows significant variations related with the infilling of palaeochannels incised during the Late Pleistocene lowstand. The sedimentary record presents a succession of facies, having recognized 10 main sets of lithofacies, organized in sequences. According to the sedimentary record and to the prevalent dynamic process, the area has been divided in four different sectors. The first and second ones are respectively characterized by sequences of gravels (generated by storm relaxation currents) to muddy sand (deposited by tidal currents). The third sector is a rocky shoal with a thin gravel cover. A fourth sector is a zone partially protected from waves, due to the presence of the rocky shoal, and its sedimentary infill is constituted by sand and mud generated by the tidal currents, including some gravelly storm layers. The general decrease of energy shown by the sedimentary record is interpreted as a result of the decrease of tidal prism of the bay and the deviation of the main outlet currents to the southwest caused by the infilling