Diferenciación de facies relictas y actuales en los sedimentos recientes de los fondos de la bahía de Cádiz

Abstract

In subtidal littoral zones and inner continental shelf, recent sea level changes force to coexist relict sediment sdeposits, formed when sea level was lower than nowadays, with more recent sediments which are in equilibrium with hydrodynamic agents. Cadiz bay sea bottom sediments has been studied in order to classify and to map fades, determine depositional conditions and to establish differentiation criteria between present and relicts sediments.

The sea bottom Cadiz bay displays several sediment types: external bay, with silty-sand; inner bay (SacoJ with clayed-mud, and littoral zone formed by beachs, cliffs, river mouhts and tidal creek and salt marsh edges. Sediments are mainly composed by quartz, followed by calcite and phylosilicates. Classifying criteria have been established from Modo-Q Factor Analysis. Criteria for reworked level were established from quartz grain exoscopic analysis. Four types representative of different environments and deposicional conditions have been differentiated, ones presents day and others relict. In the external bay dominate silty-sand while in the inner bay clayed-mud is preodominant. The first one is a good relict facies example, whose sediments have a high level of reworking textural madurity and sorting