THE MIDDLE-UPPER OXFORDIAN OF CENTRAL SIERRA-NORTE (MALLORCA, SPAIN),AND PROGRESSING ECOSTRATIGRAPHIC APPROACH IN WESTERN TETHYS

For the first time a detailed ammonite biostratigraphy is presented fo r the Oxfordian (Upper Jurassic) in the Central Sierra Norte in Mallor ca (Balearic archipelago, Spain). Three sections (Coll d'Es Cats, Cube r and Alfabia) have been studied on the basis of a continuous sampling of 10-20 cm thick samples in ammonitico rosso successions 2.3-5 m thi ck. Ammonite-rich but benthos-poor faunal assemblages enable us to ide ntify the Antecedens, Riazi (=Transversarium) and Bifurcatus Zones wit hin the Middle Oxfordian, and the Upper Oxfordian Bimammatum and Planu la Zones. No relationships were found between sedimentary changes and the main turnovers of ammonite assemblages which are of Mediterranean type. The evolution of relative abundance in macroinvertebrate assembl ages at the substage level (Middle and Upper-Oxfordian) correlates wel l with that known from the Subbetic Zone (southern Spain), indicating that the ecostratigraphic interpretation is related mainly to longterm eustasy. Taphonomic and ecostratigraphic interpretations are consiste nt with depositional shifts related to slight physiographic changes du ring Upper Oxfordian sea-level rises on the East Iberian margin. The c orrelation of the ammonites studied with those known from the Mediterr anean and Submediterranean areas is indicated. The possibility of corr elation far from Tethys (Chile, India, SE USA) is considered.