The Upper Eocene south pyrenean coastal deposits (Liedena Sandstone, Navarre): Sedimentary facies, benthic foraminifera and avian ichnology

During the 1960's and the 1970's the Liedena Sandstone was a type deposit f or "flysch-like facies" (sandstone and lutite alternations) of coastal sedi mentary systems. However, the depositional system of these beds was never a ccurately defined. The sedimentological analysis along 100 km of outcrops i n the western part of the South Pyrenean Zone (Navarre) allows these peculi ar facies to be assigned to a mixed intertidal flat. Furthermore, sandy bea ch facies, different types of heterolithic, backbarrier deposits and conglo meratic, fluviatile facies have been recognized associated with these intri guing deposits. Generally, a northwestward-facing barrier-island system or wave-dominated delta was the likely depositional environment. The benthic foraminiferal assemblage in the intertidal deposits exhibits th e typical characteristics of a marginal marine environment: extremely high dominance of one species (Pararotalia inermis), low species diversity, and a hyaline dominance with discrete amounts of miliolids. Furthermore, the mo st abundant species indicates that the Liedena Sandstone was deposited duri ng the Late Eocene. Abundant footprints of aquatic birds are known in the tidal flat deposits. Six morphotypes have been distinguished: two (types 1 and 2) are ciconiifor me-like; type 1 is here assigned to a new ichnotaxon, Leptoptilostipus pyre naicus and is one of the oldest occurrences of Ciconiiforme-like ichnites i n the fossil record. Two other morphotypes (5 and 6) are similar to those o f the Charadriiformes and are referred to as Charadriipeda. Finally, the af finities of the two remainder morphotypes (3 and 4) are unclear; they could have been made by Charadriiformes. Synsedimentary tectonic activity controlled the evolution of the deposition al system, as the area of deposition of the Liedena Sandstone was progressi vely incorporated into the active thrust sheets of the Pyrenean Orogen duri ng the Late Eocene. The structural uplift and the large amount of sediments derived from the adjacent highlands induced progradation of the deposition al system and the definitive retreat of the sea from the South Pyrenean Zon e.