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[EN] The intraplate Cameros rift basin in the north of Spain was formed came into being between the Tithonian and the Early Albian and contains 9 000 m of mostly continental sediments. This basin is a good example of cyclicity of different depositional sequences (DSs) in sedimentary environments, which show clear repetition in their sandstone composition (petrofacies) and diagenetic patterns. The DSs are arranged in two megasequences (MSs) separated by a tectonic unconformity. A similar vertical sandstone compositional evolution, subdivided into two stages that repeat cyclically, has been recognised in both MSs: the first comprises quartzo-sedimentolithic petrofacies and the second is made up of several quartzo-feldspathic petrofacies. This was caused by a progression from the recycling of the pre-rift sedimentary cover to the erosion of the mainly plutonic and metamorphic crystalline basement. These changes in the erosion of the different source areas were conditioned by the tectonics of the basin. Furthermore, the original sandstone framework composition conditioned the diagenetic pattern of the two stages: quartzo-sedimentolithic sandstones containing large amounts of very pervasive carbonate cement that reduce their original porosity considerably, and quartzo-feldspathic petrofacies with a rigid framework that maintained the original pores during burial diagenesis. This compositional and diagenetic pattern is probably applicable to other non-volcanic rifted basins, depending upon the original amount of carbonate rock fragments present., [ES] La cuenca intraplaca de rift de Cameros se localiza al norte de España. Se desarrolló entre el Titónico y el Albiense Inferior, depositándose 9000 m de sedimentos fundamentalmente continentales. La cuenca es un buen ejemplo de ciclicidad en los medios sedimentarios en las diferentes Secuencias Deposicionales (SD), lo que genera una clara repetición de la composición de las areniscas (petrofacies) y de las pautas diagenéticas. Las SD están organizadas en dos megasecuencias (MS) separadas por una discordancia de carácter tectónico. Ambas MS presentan una evolución vertical similar en la composición de las areniscas, generando una repetición de dos estadios: (1º) constituido por una petrofacies cuarzosedimentolítica y (2º) formado por varias petrofacies cuarzofeldespáticas. Este hecho viene motivado por el cambio desde la erosión de una cobertera sedimentaria pre-rift a la erosión del basamento cristalino, principalmente constituido por áreas fuente plutónicas y metamórficas. Estos cambios en la erosión de distintas áreas fuente están controlados por la tectónica de la cuenca. Además, la composición original del esqueleto de las areniscas condiciona el tipo de diagénesis para los dos estadios anteriormente descritos: las areniscas cuarzosedimentolíticas contienen abundante cemento de carbonato, que reduce su porosidad inicial drásticamente. Sin embargo, las areniscas cuarzofeldespáticas presentan un esqueleto más rígido que mantiene los poros originales durante la diagénesis de enterramiento. Este patrón composicional y diagenético es probablemente aplicable a otras cuencas de rift intraplaca no volcánicas, dependiendo de la cantidad inicial de fragmentos de roca carbonática.

Three key sand petrofacies (fluvial and marine), derived from the Betic mountain belt, reflect the main clastic contribution of known source rocks, and the complex factors operating during pedogenesis, erosion, transport, deposition (first order parameters). These first order parameters are not independent but influenced by tectonics and climate.

Chemical weathering is the main sand producer within the regolithic environment in northern Calabria. In addition, rapid erosion resulting from steep slopes remove weathered products, and rapid and short transport leads to minimal sediment maturation.

The effects of weathering in a Mediterranean climate on the mineralogy and microfabric of Paleozoic gneiss of the Sila Massif have been studied. The determination of quantitative micropetrographic indices provides a measure of the various stages of weathering.

This study proposes an integrated methodology which includes pedological, petrographic, mineralogical and geochemical analyses of transparent heavy-minerals, to reconstruct the weathering patterns and pedogenetic processes in a transport-limited erosion regime. Three representative soil profiles developed on crystalline bedrocks, located in Calabria, southern Italy, were studied in detail including the complete weathering profile along the transect bedrock/grus/soil. Differences in the amounts of heavy minerals in each soil profile appear to be controlled by the nature of the local bedrocks. The addition of allochthonous parent material and a varying extent of chemical weathering, likely influenced by topography and duration of pedogenesis. The heavy mineral shapes and surface microtextures, together with the vertical distribution of major and trace elements, the values of the chemical index of alteration and the relative abundance of the clay mineral types along the profiles highlight the different weathering degrees among the profiles. These features are consistent with iron/manganese oxy-hydroxides and clay neogenesis observed on femic heavy minerals. Moreover, they mark a lithological discontinuity between the bedrock and the upper soil horizons, which led to rejuvenation by erosive and colluvial processes along the slopes and/or aeolian deposition of allochthonous material, presumably including a Late Pleistocene to Holocene pyroclastic input. Chemical weathering affecting the majority of heavy minerals is consistent with high rainfall rates, soil moisture availability and acidic pH conditions likely favored by organic acids, prone to chemical reactions and leaching processes. The clay coatings and iron/manganese segregations in the Bt horizons of all the profiles studied suggest that they developed in a warmer humid climate during the interglacial stages of the Pleistocene.