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This study documents the mineralogical and geochemical record of a lateritic weathering event during the Pliocene in South-west Spain. The paleoweathering profile derived from arkosic sands and comprises a white sandy clayey saprolite, a red mottled clay zone overlain by a thick soft layer, and a ferruginous pisolitic hardcap partially dismantled by erosive processes. Kaolinite, quartz and degraded K-feldspars are the major minerals forming the saprolite, along with Al-goethite (mottled zone) as well as gibbsite and boehmite (soft layer), while the pisolitic duricrust is essentially composed of quartz grains embedded in a matrix of Fe oxy-hydroxides (hematite, goethite, and/or maghemite). Besides quartz, the phases most resistant to alteration were a variety of heavy minerals (mostly titanium oxides) that are present as minor impurities in the residual kaolin deposit. The dominant weathering process of kaolinization is geochemically characterized by striking losses of Na, K, Ca, Mg, and large-ion lithophile elements (Rb, Sr, Cs, Ba, and U), because of the almost entirely breakdown of primary minerals (mainly feldspars and 2:1 phyllosilicates). The Ti-normalized distribution patterns of trace elements also reveals remobilization and redistribution processes within the profile, involving high field strength elements classically regarded as immobile, like Zr and Hf. Iron showed a contrasted behaviour, with depletion in the saprolite zone and strong accumulation in the pisolitic duricrust. Various transition trace metals (Cr, V, Sc, Th, Nb, and Ta) remained relatively immobile during the weathering, and were residually concentrated in the duricrust linked to the Fe oxy-hydroxides. The geochemical and mineralogical evolution of the paleosol studied is consistent with a laterization process evolved under humid subtropical conditions, and driven by morphodynamic and hydrodynamic factors (gently sloping coastal area with fluctuating water table and rapid water percolation) favourable for the development of a deeply kaolinized paleosurface.

A multidisciplinary study of El Melah Lagoon (NE Tunisia) permits the analysis of the present scenario of this coastal environment. Salinity and pH values indicate a main marine origin for the permanent waters, which present locally high nutrient contents owing to the continuous flows coming from both the Slimene’s treatment station (STS) and the agricultural activities surrounding the southeastern margins of the lagoon. The heavy metal concentrations of the clayey-silty bottom sediments may be moderate to high near the STS’s effluent and close to a parapharmaceutical plant. Seven zones were distinguished in this limited area (200 ha), according to the physical–chemical parameters and nutrient contents of waters, the grain size and heavy metal contents of the bottom sediments and the distribution of ostracode assemblages (marine, high brackish and freshwater to low brackish). This analysis, together with the information provided by aerial photos (1948–1996), is the basis to hypothesize a future evolution of the system.

The Hercynian basement of the Iberian Peninsula was uplifted by the Alpine orogeny during the Tertiary. It gave rise to a set of block mountains and tectonic grabens, one of which is the Ciudad Rodrigo Basin. It is located in Western Spain and forms a westward extension of the great Tertiary Duero Basin. The sediments filling this graben are of continental origin, their ages ranging from Palaeogene to Quaternary. Morphologically, the southern part of this basin forms a set of piedmont surfaces (the “Rana” surfaces) appearing above the terrace system of the present rivers. This paper examines the weathering processes developed over these old piedmont surfaces using micromorphological, XR diffraction, scanning electron microscopy (SEM) and microporosity techniques. The Rana sediments are rich in quartzite pebbles and gravel within a clayey matrix. Once deposited, these materials underwent important in situ weathering processes under somewhat hydromorphic conditions, of which hydrolysis, ferrolysis and xerolysis were the most important. All these processes gave rise to: (1) transformation of most of the clasts of shists and slates into a matrix causing the destruction of the original sedimentary structures and a relative concentration of the resistant lithologies (quartzites and quartz); (2) important changes in the clay fraction, leading to a predominance of kaolinite in the upper levels of the profiles, (3) release of elements from primary minerals, Fe being one of the most important, and (4) redistribution of matter, mainly clay and Fe oxyhydroxides, within the profiles. The coexistence of seasonal periods with pF higher than 4.2 repeated over a long time, together with poor internal and external drainage conditions, are the cause of the special features displayed by Rana deposits.

Summary The Iberian Hercynian Massif occupies most of the western half of the Iberian Perninsula and forms the basement over which Mesozoic, Cenozoic and Quaternary materials rest unconformably. Over it can be found remains of weathering profiles that are fossilized by marine and/or continental sediments of different ages. On the southwestern border of the Tertiary basin of the Duero and below the series attributed to the lower Tertiary (Palaeocene), lies a weathering mantle that has been displaced by the effects of alpine tectonics. Accordingly, its remains may appear truncated and/or covered by other more recent deposits. The present work studies this ancient weathering mantle in the zones in which it appears developed over the slaty series of the basement in the province of Salamanca, central west Spain. The profiles chosen reveal the existence of a strong chemical weathering that involves the destruction of some primary materials (Fe-bearing chlorites and feldspars) and the formation of kaolinites and Fe-oxihydroxides. The start of the degradation of chlorite occurred during the first weathering phases; this evolved towards an expandible smectite-like mineral. This first phase reflects the disappearance of albite, and chemical analysis points to a pronounced loss of Na. In the most advanced stage the chlorites and smectites have disappeared, giving way to the presence of kaolinite, goethite and hematites. This weathering phase is associated with a strong loss of Mg. The main processes occurring in these profiles aremonosiallitisation andferruginisation.

In this paper, we present a multivariate approach (waters, sediments, microfauna) concerning the environmental state of the Nador Lagoon (NE Morocco). The normal water quality parameters (salinity, pH, nutrients) of the dominant marine flows are altered by local fecal water effluents, urban discharges, sewages derived from a water treatment station, and residues originated in a slaughterhouse. The geochemical analyses carried out in surficial sediment samples show very high concentrations of all metals studied near an old iron mine and moderate contents between Nador and its treatment station. Ostracods are good bioindicators of these environmental impacts, with the presence of a highly brackish assemblage in the quieter, more confined areas or the appearance of opportunistic species under hypoxic conditions. In addition, these microcrustaceans are absent in polluted bottom sediments or areas with high hydrodynamic gradients, whereas they decrease in both density and diversity if the subaerial exposure increases.