ASINGULAR MIOCENE PALEOBOTANIC RECORD IN DELTAIC SEQUENCES OF NORD-BETIC CORRIDOR (GUADALQUIVIR BASIN, SOUTH OF SPAIN) M.Abad 1 , F. Ruiz 1 , C. Martin-Closas 2 , J. Tosquella 1 ,A.Toscano 1 , M.L. González-Regalado 1 1 Departamento de Geodinámica y Paleontología, Universidad de Huelva, 21071- Huelva, Spain. e-mail: manuel.abad@dgyp.uhu.es 2 Departamento de Estratigrafía, Paleontología y Geociencias Marinas, Universidad de Barcelona, 08028-Barcelona, Spain In the central and western sectors of the Guadalquivir basin, the scarce paleobotanical record can be justified by the restricted presence of coastal and continental facies de- posited under subaerial conditions. Previous researches highlight its presence in Early Pliocene units (Muñiz et al., 1999; Barrón et al., 2003) indicating high temperatures and subtropical palaeoclimatic conditions although not previous works have described macroflora fossils of Tortonian age. Along the northern margin the sedimentary fill includes very different facies grouped into the Tortonian Basal Transgressive Complex, or BTC (Abad, 2007). The BTC is com- posed of several internal sequences linked to 4 th order cycles of sea-level change and provides a clear example of stacked high-frequency cycles of mixed carbonates and siliciclastics. Siliciclastic sedimentation took place in deltas, beaches and shallow marine zones. Deltaic systems migrated basinwards during stillstand phases whereas transgressive pulses provided better conditions for the production and accumulation of biogenic carbonates. Facies association of deltaic plain has been described in the central sector of this foreland margin (Arroyo Parroso section, Sevilla province). Facies are constituted mainly by con- glomerates and gravely deposits, although sandy deposits are also common. They show massive to crudely horizontally stratified and lenticular channelized forms interpreted as migration of subaqueous dunes and infilling of scours inside mobile channel belts in a braided fluvial system (Hein and Walker, 1977). Gravel and pebbles bedload transport occurred under high flow regime. Subordinate muddy facies were deposited during lower flow regime although high proportions of fine sediments were winnowed out in suspension as turbidity plumes from plain delta to delta front and neighbouring shallow marine zones. These facies are yellowish, laminated silts and grey, massive clays and show tabular and lenticular geometry. Microfaunistic record is very poor but some specimens of benthic foraminifera (Ammonia beccari, A. inflata, Elphidium crispum and Nonion boueanum) have been 54 Climate changes, bioevents and geochronology in the Atlantic and Mediterranean over the last 23 Myr Joint RCMNS - RCANS Interim Colloquium, Salamanca. September 21 st to 23 rd , 2011