Análisis de facies y de asociaciones fósiles en sedimentos del oxfordiense medo-superior localizados al sur de la provincia de Albacete

Resumen

The study of Oxfordian deposits in the Prebetic Zone of fue Betic Cordillera, conducted on the Pozo Cañada and Río Segura sections (south- em part of fue Albacete province), provides fue first step of an integrative research that combines palaeontologic and lithologic data in the area. The analysis of microfacies shows types and relative abundance of skeletals, especially in foraminifera. The combination of data about microfacies with macroscopic observations gives support for the differentiation of seven basic types of lithofacies: lumpy-oncolitic limestone, spongiolitic limestone, marl, lumpy liq¡estone, marl-limestone rhythmite, altemance of I spongiolitic marl and peloid limestone, and lumpy-oncolitic-condensed and bioclastic-rich limestone. A total around of 3700 specimens and fragments of macroinverte- J brates collected bed-by-bed have been identified on fue basis of a mini- j muro size of worked samples of 50 specimens per fossiliferous horizon. Arnmonoid are dominant (59%), while benthics are composed of brachiopods, bivalves, echinoids, crinoids, sponges and gastropods. Ammonite systematics and interpreted biostratigraphy result in the characterisation of the Bifurcatus, Bimarnrnatum and Planula Zones of the Upper Oxfordian, as well as in the probable existence of the Middle Oxfordian Transversarium Zone. Taphonomic observation and analyses have been focused on macro- fossils and centred on fue following features: state of preservation, specimen size, within-bed orientation, epibionts, abrassion, dissolution, bioero-SiDO, fragmentation, disarticulation, uncoupling, and plastic deforrnation. These show the slight incidence of post-mortero transportation and the absence, or rarity, of reworking (reelaboration). No cases of fue latter are known above fue level of biostratigraphic significance provided by ammonites.The stratigraphic variation in fue composition of macrofossil assemblages can be interpreted as related to fluctuation in fue relative sea leveI.. The data obtained and their interpretation allow to recognise fue combined influence of eustasy and tectonics in determining eco-sedimentary conditions throughout fue stratigraphlc interval studied.