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Abstract: The properties of seven ferruginous paleosols, formed in alluvial continental deposits of Upper Cretaceous-Paleocene age in central-southern Sardinia (Italy), were examined to understand their genesis. Particular attention has been addressed to their paleoenvironmental and paleogeographic significance, also in comparison with similar paleosols in southern France, and to their potential to represent good pedostratigraphic markers for a larger area. The paleosols are characterized by petroplinthic, pisoplinthic, plinthic or pisolithic horizons. Their genesis started under a warm and humid tropical climate, with distinct wet and dry seasons, of the Latest Maastrichtian-Lower Paleocene and continued, under increasingly dry conditions, during the Middle to Upper Paleocene. The major differences that occur among the paleosols can be related to differences in geomorphic position, parent material characteristics and drainage conditions. The pisolithic paleosols of central-southern Sardinia show a structure and composition comparable to those of the coeval ones in southern France, which were formed under similar climatic conditions. On the basis of the constant stratigraphic position, the large geographic extent and the supposed former lateral continuity, the studied ferruginous paleosols can be considered to be a good pedostratigraphic marker in central-southern Sardinia and in southern France and are informally named as the “Monte Maraconis geosol”. This allows extensive chronostratigraphic correlations as well as regional-scale morphostratigraphic correlations and represents, with its typical pedofacies, a pedostratigraphic unit worthy of consideration in future regional geological mapping. [Copyright &y& Elsevier]

Abstract: Soils are characterized by an intrinsic variability through time and space at different scales of observation and are often affected by morphodynamic processes strictly interacting with pedogenesis, under changing (paleo)environmental/climatic conditions. We focus on exploring this interplay in modern soils and paleosols of southeast Sardinia (Italy), integrating two innovative techniques to a traditional pedological study: (i) laser ablation ICP-MS spot analyses applied to detect microscale distribution of trace elements in discrete soil features of organic-mineral (A) and argillic (Bt) horizons in thin sections, and (ii) radioactive disequilibria as tracers and chronometers of pedogenetic alteration and geomorphic dynamics. The Pleistocene paleosols developed mainly during interglacial periods, with important clay illuviation and rubification. The other soils are essentially characterized by organic matter incorporation into the profiles. Field discontinuities described within soil profiles, related to phases of sediment aggradation and/or surface erosion, are often supported by laboratory results, mainly micromorphological and geochemical data. LA-ICP-MS data show an overall trend of increase of most trace elements (REEs included) from skeletal rock fragments to both clayey and organic-rich soil matrix to clay coatings. This pathway is clearly controlled by the degree of weathering of primary minerals and by pedogenetic processes, where element adsorption onto reactive sites of organic matter and clay particles and clay illuviation play prominent roles. Recent trends of the studied soils/paleosols in terms of geomorphic stability (equilibrium) or morphodynamic processes (erosion/accumulation rates) are estimated using radionuclide disequilibria in the order of 1cm/a or lower. [Copyright &y& Elsevier]

Field soil pore water monitoring was applied in a highly heavy-metal contaminated area in SW Sardinia, Italy, as a direct, realistic measure of heavy metal mobility. The main chemistry of pore waters well reflects the local characteristics of soils, ranging from Ca–SO 4 to (Ca)Mg–HCO 3 to Ca(Na)–SO 4 (Cl), with a wide range of conductivity. The mobility of Zn and Pb is apparently controlled by equilibrium with minerals such as hydrozincite or smithsonite, and cerussite, respectively. These results allow a correct estimate of the actual environmental risk associated with the presence of heavy metals in soils, and may serve as a supporting tool for phytoremediation planning. [ABSTRACT FROM AUTHOR]

Abstract: Some of the weathering deposits that formed during the emersive phase, which in Sardinia lasted from Late Cretaceous to Palaeocene–Early Eocene, consist today of ferruginous palaeosols (ferricretes), sometimes overlain by palustrine limestones. In this article, the two outcrops at Nuxis and Guardia Pisano, containing a ferricrete composed of subspherical goethitic-hematitic concretions, are studied in detail. The main components are Fe, Al, Si, along with Ba, which is very abundant in the Nuxis outcrop. With the exception of the barite, the pisolithic ferricretes of Sardinia can be compared, for their chemical and mineralogical composition, with the pisoplinthites that form in modern tropical soils. They are also comparable with the pisolithic ferricretes cropping out in southern France, that formed around the K/T boundary. The pisolithic ferricretes of southern France and Sardinia can be interpreted as the weathering product of identical warm and humid climatic conditions and, reasonably, of the same climatic event. Therefore, they provide further evidence that Sardinia and southern France formed part of the same palaeogeographic province. A tropical environment is, on the other hand, consistent with the barite leaching from the Palaeozoic substratum and with its reprecipitation into the iron pisoliths. Micro- and nanostructures, observed using SEM analysis within and between the concentric layers of the pisoliths, are consistent with biological processes involving bacteria during their deposition. [Copyright &y& Elsevier]