The sequence stratigraphic framework of carbonate diagenesis within transgressive fan-delta deposits: Sant Llorenc del Munt fan-delta complex, SE Ebro Basin, NE Spain

The Eocene (Bartonian-Priabonian) Sant Llorenc del Munt fan-delta complex f ormed at the front of the Catalan Coastal Range as a result of Alpine defor mation. Alluvial fan and fan-delta progradation into the Ebro Basin was arr ested by repeated transgressive episodes, thus producing a hierarchy of tra nsgressive-regressive sequences. This study focuses on the two transgressiv e-regressive fundamental sequences that comprise the El Marcet Unit, a succ ession of predominantly elastic deposits of shallow-marine and coastal plai n origin. Sandstones and conglomerates within the EI Marcet Unit are cement ed by calcite. Under cathodoluminescence these cements display varying degr ees of luminosity. On the basis of differences in luminosity and stable iso topic composition, temporal relationships between the various cements have been established. Cementation commenced in the soil zone with the local for mation of calcretes. Early burial cements precipitated in the vadose zone f rom waters of meteoric origin, and later cements in the shallow phreatic zo ne. Stable isotopic evidence suggests that all cements probably precipitate d from pore waters of essentially the same origin, but at varying burial de pths and with varying contents of organically derived carbon. Calcite cements formed by the remobilisation of biogenic and elastic carbon ate, and from pedogenic CO2. The formation of early cements was facies-depe ndent and principally controlled by the distribution of shell material. Var iations in cement distribution related to the observed cyclicity of the uni t are also apparent. The abundance of early cements increases towards the t op of progradational sequences, and early cements dominate the upper sequen ce, while late cements dominate the lower sequence. (C) 2000 Elsevier Scien ce B.V. All rights reserved.