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International audienceThe Eocene Hecho Group turbidite system of the Ainsa-Jaca foreland Basin (southcentral Pyrenees) provides an excellent opportunity to constrain compositional variations within the context of spatial and temporal distribution of source rocks during tectonostratigraphic evolution of foreland basins. The complex tectonic setting necessitated the use of petrographic, geochemical and multivariate statistical techniques to achieve this goal. The turbidite deposits comprise four unconformity-bounded tectonostratigraphic units (TSU), consisting of quartz-rich and feldspar-poor sandstones, calclithites rich in extrabasinal carbonates and hybrid arenites dominated by intrabasinal carbonates. The sandstones occur exclusively in TSU-2, whereas calclithites and hybrid arenites occur in the overlying TSU-3, TSU-4 and TSU-5. The calclithites were deposited at the base of each TSU and hybrid arenites in the uppermost parts. Extrabasinal carbonate sources were derived from the fold-and-thrust belt (mainly Cretaceous and Palaeocene limestones). Conversely, intrabasinal carbonate grains were sourced from foramol shelf carbonate factories. This compositional trend is attributed to alternating episodes of uplift and thrust propagation (siliciclastic and extrabasinal carbonates supplies) and subsequent episodes of development of carbonate platforms supplying intrabasinal detrital grains. The quartz-rich and feldspar-poor composition of the sandstones suggests derivation from intensely weathered cratonic basement rocks during the initial fill of the foreland basin. Successive sediments (calclithites and hybrid arenites) were derived from older uplifted basement rocks (feldspar-rich and, to some extent, rock fragments-rich sandstones), thrust-and-fold belt deposits and from coeval carbonate platforms developed at the basin margins. This study demonstrates that the integration of tectono-stratigraphy, petrology and geochemistry of arenites provides a powerful tool to constrain the spatial and temporal variation in provenance during the tectonic evolution of foreland basins

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The Middle Muschelkalk (Middle Triassic) of the Catalan Coastal Range (north‐east Spain) comprises sandstone, mudstone, anhydrite and minor carbonate layers. Interbedded sandstones and mudstones which are dominant in the north‐eastern parts of the basin are terminal alluvial fan deposits. South‐westward in the basin, the rocks become dominated by interbedded evaporites and mudstones deposited in sabkha/mudflat environments. The diagenetic and pore water evolution patterns of the Middle Muschelkalk suggest a strong facies control. During eodiagenesis, formation of microdolomite, anhydrite, baryte, magnesite, K‐feldspar and mixed‐layer chlorite/smectite was favoured within and adjacent to the sabkha/mudflat facies, whereas calcite, haematite, mixed‐layer illite/smectite and quartz formed mainly in the alluvial facies. Low δ18OSMOW values for microdolomite (+23.7 to +28.4%) and K‐feldspar overgrowths (+17.3 to +17.7%) suggest either low‐temperature, isotopic disequilibrium or precipitation from low‐18O porewaters. Low‐18O waters might have developed, at least in part, during low‐temperature alteration of volcanic rock fragments. During mesodiagenesis, precipitation of quartz overgrowths and coarse dolomite occurred in the alluvial sandstones, whereas recrystallization of microdolomite was dominant in the sabkha/mudflat facies. The isotopic compositions of these mesogenetic phases reflect increasing temperature during burial. Upon uplift and erosion, telogenetic calcite and trace haematite precipitated in fractures and replaced dolomite. The isotopic composition of the calcite (δ18OSMOW=+21.5 to +25.6%o; δ13C= 7.7 to ‐ 5.6%o) and presence of haematite indicate infiltration of meteoric waters.

Early diagenetic K‐feldspar in the Triassic Buntsandstein of the Iberian Range (Spain) occurs as pseudomorphs after detrital K‐feldspar (Or<93) and plagioclase (Ab<96). These pseudomorphs are chemically pure (Or>99), untwinned, commonly heavily clouded by vacuoles and tiny inclusions, dark‐luminescing and are composed of numerous fine euhedral crystals of K‐feldspar. The latter property suggests that the pseudomorphs form via dissolution of detrital K‐feldspar and plagioclase and precipitation of authigenic K‐feldspar. X‐ray diffraction analysis shows that the authigenic K‐feldspar is intermediate microcline.