Patterns of variability in ostracode species and communities from the late Cretaceous carbonate platforms: a report for ecozonal modelling and the study of ambient conditions

Previous palaeoecological and sedimentological analyses have demonstrated the marked variability of ostracode faunas in late Cretaceous environments. Such organisms are generally strongly related to their biotopes but deeply affected by fluctuations, even slight, of ambient conditions. Therefore, variations of both taxonomic units and communities may be used for a better knowledge and characterization of the main carbonate platform domains. An interesting method of investigation is provided by the study of anatomical and/or morphological variations within well defined taxonomic units, especially ornate species living in the more internal zones of platforms. They reflect with accuracy and reliability the impact of both ecological parameters and palaeogeographic settings. This is also the case for some genera and even families. ode type-assemblages have been recently erected in the Tethyan Upper Cretaceous. Microfaunas develop characteristic features such as richness, diversity, morphological trends, according to their position on the carbonate platform system and sedimentary facies patterns. Furthermore, without any consideration of the stratigraphical position of carbonate formations, certain morphological variations concerning analogous taxa may be used for palaeogeographical interpretations. c structures of ostracode communities versus nutrient flux are identifiable. Major changes occur through the sequences in the abundance, specific composition and quantitative ratio between two main sedimentological formations: carbonates (especially rudist limestones and calcareous marls with benthic foraminifers) and proximal terrigenous (siliciclastic, argillaceous) areas. y, this paper may be also considered as a useful attempt to synthesize present knowledge of late Cretaceous carbonate platform ostracodes, particularly intended for non-ostracodologists who are perhaps unaware of the potential contribution of these organisms for palaeoenvironmental reconstructions.