INNOVATIVE APPLICATIONS OF GEOCHEMISTRY TO PROVENANCE, SOUTHERN EBRO BASIN, SPAIN

A complete Paleocene(?)-Oligocene terrestrial succession in the southwestern Catalán Coastal Ranges of northeastern Spain contains terrestrial strata characteristic of deposition in the forebulge, foredeep, and wedge-top depozones of recent foreland basin models. Whereas the appearance of conglomerate in the upper succession has been used to date the onset of orogenesis caused by uplift of the Pyrenean, Iberian and Catalán Coastal Ranges, pedogenic and fine-grained lithofacies preserved in the lower part of the study interval suggest that these strata may be the result of forebulge development. To constrain the onset and tempo of Catalán Coastal Range uplift, we have focused on the petrologic and geochemical makeup of the foreland units as compared to their source units, with the aim of determining the provenance of the foreland sandstones. To combat existing problems associated with calcarenite provenance, we complemented Gazzi-Dickinson point counts of foreland sandstones with stable isotope & ICP-AES geochemistry, and detrital-zircon He thermochronology, from both the foreland units and the Catalan Coastal Ranges source units. We have identified a marked change in the modal abundance of lithics in the foreland units upsection, reflecting changing areas of provenance and conditions of transport. A marked restriction in the range of stable isotope values in the foreland sandstones as compared to their source units may indicate the effects of chemical weathering, transport distance, and diagenesis via meteoric waters, but both stable isotope and elemental concentration trends suggest that foreland basin-fill provenance may be constrained by such methods. A more precise understanding of the provenance of the foreland basin sandstones should help evaluate competing tectonic models for the region.