Clay minerals in recent sediments of the continental shelf and the Bay of Cádiz (SW Spain)

Abstract

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.

The use of clay minerals and microfossils in palaeoenvironmental reconstructions: The Holocene littoral strand of Las Nuevas (Doñana National Park) SW Spain

“…The variations of both contents and crystallochemical parameters of clay minerals could be due to the contribution of illite from marine deposits caused by the new, more important, marine input, that was established over the salt marsh deposits of zone B and which have been deduced from the palaeontological analysis. This hypothesis agrees with the composition of the sediments of the southeastern Gulf of Cádiz, rich in illite (Gutierrez Mas et al, 1997;López Galindo et al, 1999). Source mixing appears to be the main mechanism for explaining the distribution of clay minerals in zone C.…”

“…Clay minerals have been used over the last few decades in the interpretation of palaeoclimatic and palaeoenvironmental changes, e.g. to reconstruct palaeoclimatic conditions (Kuzvart & Konta, 1968;Vanderaveroet et al, 2000); to determine the palaeotopography in arid and semi-arid zones from the Cambrian up to the present (Callen, 1984); in the analysis of hydrodynamic processes in coastal environments (Gutierrez Mas et al, 1997); for palaeogeographic reconstructions (Ortega-Huertas et al , 1991;Deconinck & Chamley, 1995;Pletsch et al, 1996), and to determine sedimentological evolution in lacustrine (López Aguayo & González López, 1992Mayayo et al , 2000), alluvial (Tomadin & Varani, 1992, 1998 and marine (Delgado et al, 1992) environments.…”

Whole-rock and clay mineralogy as paleoenvironmental tracers during the Late Holocene sedimentary evolution of the Doñana National Park (SW Spain)

“…This group is formed by basal layers of cheniers with high proportions of bioclasts, which are illite-dominated in all cheniers studied (including core F). Cheniers are stabilized wave-built ridges (Otvos, 2005) and these high percentages of illite may be due to: (i) marine inputs, because illite is the most abundant clay mineral in the adjacent Atlantic shelf (Gutiérrez-Más et al, 1997;Achab et al, 2008); and (ii) an early deposition of illite, smectite remaining preferentially in suspension during flood and ebb tide. Smectites will accumulate on the basal coarse sediments (sand, bioclasts) during low hydrodynamic tidal conditions as a mud cream, which is partially removed during subsequent flood or ebb phase (Chamley, 1989).…”

Source-to-sink pathways of clay minerals in the cadiz contourite system over the last 25 kyrs: The segregational role of mediterranean outflow water

“…Some authors have investigated the mineralogy of clays from the middle slope of the Gulf of Cadiz (Grousset et al, 1988;Stumpf et al, 2011;Alonso et al, 2016), often with a low temporal resolution, but little attention has been paid to the spatial distribution of clay minerals among muddy-contourites of the CDS. By contrast, the pattern of clay mineral distribution on the shelf of the Gulf of Cadiz has been the subject of many studies and it is very well constrained (Fernández-Caliani et al, 1997;Gutiérrez-Mas et al, 1997;Gutiérrez-Mas et al, 2003;Gutiérrez-Mas et al, 2006;López-Galindo et al, 1999;Machado, 2005;Machado et al, 2007;Achab et al, 2008;Achab, 2011). The present study investigates clay mineralogy of sediments from three IODP sites and thirteen sediment cores collected across various sedimentary features of the Gulf of Cadiz in order to reconstruct the source-to-sink pathway of clay minerals from their sources (river/wind) to their deposition in the CDS of the Gulf of Cadiz.…”

“…Recent sedimentation in the Gulf of Cadiz is largely dominated by terrigenous material from the vicinity of the Iberian margin and North African continent (Milliman and Syvitski, 1992;Gutiérrez-Mas et al, 1997Achab et al, 2008;Achab, 2011). In this context, fine-grained detrital particles are supplied to the ocean by either (1) rivers (Grousset et al, 1988;Morales, 1997;López-Galindo et al, 1999) or (2) eolian transport (Moreno et al, 2002;Stuut et al, 2009;Bout-Roumazeilles et al, 2013;Stumpf et al, 2011), before being further advected or redistributed as suspended particulate matter (SPM) by (3) ocean currents and sedimentary processes (Pierce and Stanley, 1975;Grousset et al, 1988;Morales, 1997;Baringer and Price, 1999).…”