The contents and the distribution of clay minerals in modern sediments of the Cadiz bay and the continental shelf have been studied aiming to establish the sedimentary exchange model and the pathways followed by the clay fraction between the bay and the adjoining continental shelf. The most abundant clay minerals in the muddy sediments consist mainly of illite, smectite, interstratified illite-smectite, kaolinite and chlorite. The application of factor analysis method (PCA) to clay minerals data are considered to be useful in the determination of sedimentary transport patterns. The data from clay mineral assemblages, and their distribution map, make possible to establish the fine sediments transport paths in the study area using clay mineral as natural tracers. This model of transport takes in consideration the facies distribution, the supplies sources and the way of fine sediments are incorporated to the marine environment Two flows paths have been established: the outflows coming from Cadiz bay and the littoral zones; and the inflows coming from external marine zones of the bay. These flows are controlled by tidal currents and the morphology of the coast. The action of surge and the marine currents, specially the Atlantic Surface Water flow, are also important in the transport of fine sediments coming from sources located to the north of the study zone.

Abstract--The kaolinite crystallization by homogeneous precipitation with previous hydrolysis of the feldspars added has been followed by pH and potassium concentration measurements. The synthesized products were studied by X-ray powder diffraction and electron microscopy and consist of kaolinite and mica, accompanied occasionally by traces of smectite. The relative quantities of the synthesized minerals depend fundamentally on the supply rate of the alkaline ions.

A B S T RA C T: The distribution of clay minerals in recent sediments on the continental shelf and in the Bay of C~idiz has been analysed as part of a wider study of sedimentary exchange between the continent and the continental margin. The clay minerals included in the muddy sediments consist mainly of illite, kaolinite, smectite, randomly mixed-layered illite-smectite, chlorite, vermiculite and randomly mixed-layered illite-chlorite. Distribution of the minerals indicates that inheritance from the adjacent continental areas is the most important process involved.The relations between the clay minerals were established by Q-mode and R-mode factor analysis. The main clay mineral associations are: (1) illite-kaolinite, (2) smectite-random mixed-layered illitesmectite, and (3) kaolinite-random mixed-layered illite-smectite-vermiculite. The main sources of sediment supply to the continental shelf are the Guadalquivir and Guadiana rivers. Sediment from these rivers and from the rivers flowing into the Bay of Cfidiz (mainly the Guadalete) is transported to the part of the shelf outside the bay by ebb-tide currents. The path of this outflow to the continental shelf, where the sediment is partially deposited, is influenced by the morphology of the coast and by hydrodynamic processes.

El seguimiento morfológico de más de 60 barras intermareales del tipo "swash bar" en el sector Chipiona-Rota (litoral de Cádiz), efectuado a diferentes escalas temporales, ha permitido determinar sus principales características morfométricas y morfodinámicas, evidenciando las diferencias de comportamiento respecto a las barras "ridge and runnel". Las barras asociadas a playas disipativas son de escasa altura y sin una cara de avalancha bien definida; las barras asociadas a playas intermediasreflectivas presentan morfologías más abruptas, mientras que las barras asociadas a playas con plataforma rocosa presentan morfologías parecidas a las observadas en playas intermedias-reflectivas. Se han estudiado también la estructura interna y la dinámica de las barras asociadas a playas disipativas. Éstas se encuentran compuestas por láminas paralelas a la superficie y, cuando la barra se ubica en la parte alta del estrán, la cara de avalancha presenta láminas de foreset nítidas. En cuanto a su morfodinámica, se ha visto que ésta está controlada por diferentes procesos que dependen de las características del oleaje, de la morfología de la barra y de las variaciones del nivel del mar a lo largo de un ciclo mareal. Finalmente, en cuanto a su distribución temporal, las barras presentan una mayor frecuencia en la época primaveral, con un máximo secundario en otoño.

RESUMENSe ha seleccionado el Sector Central de la Depresión del Ebro para tratar de conocer la incidencia que la diagénesis tiene sobre la asociación mineralógica primaria, considerada fundamentalmente compuesta por minerales heredados. En este contexto, se han estudiado cuatro perfiles, desarrollados en abanicos aluviales, en los que se han analizado separadamente los niveles de areniscas y de margas lutíticas.El estudio por SEM y EDAX confirma la composición mineralógica ya conocida, así como la composición bimodal de las ilitas (moscovita y fengitas). Por otra parte, se observa que las esmectitas presentes son, más bien, interestratificados al azar ilita (fengita)-esmectita (beidellita-nontronita).Este estudio confirma que la herencia es el mecanismo de depósito principal y que los procesos posteriores se limitan a una etapa de diagénesis precoz, representada por la presencia de interestratificados por degradación de ilitas y por la cementación carbonatada de las areniscas, junto con la precipitación de sulfatos y, ocasionalmente, algún cloruro. Palabras clave: Diagenesis, minerales de la arcilla, depresión del Ebro. ABSTRACTFour profiles built of sandstones, lutites and marls, dated Upper Oligocene-Lower Miocene, and located at the southern central sector of the Ebro basin have been studied, in order to know the postdepositional changes undergone by the original deposits, and the possible use of the inherited clay minerals as paleogeographic and paleoclimatic indicators for this basin.The mineralogical study concludes that illite is the main clay mineral along randon interstratified I-Sm clay minerals. The SEM study confirms that the main process in the deposil of these materials was the inheritance. The postdepositional processes are limited to early diagenesis represented by the development of interstratified I-Sm minerals in degradative processes and by carbonatic cementation of sandstones, in which the effect oí several stages of dissolution and reprecipitation oí carbonates and crystallization oí sulfates and chlorides can be observed.