HR: 14:25h
AN: PP13B-04 INVITED     [Abstracts]
TI: Calcareous Nannofossils and Orbitally Tuned Cyclostratigraphy in the Cenozoic
AU: * Raffi, I
EM: raffi@unich.it
AF: Dipartimento di Scienze della Terra, Universita' "G.d'Annunzio" di Chieti, Campus Universitario, via dei Vestini 31, Chieti Scalo, 66013 Italy
AB: The well known reputation of calcareous nannofossils as powerful biostratigraphic and dating tools has been improved in the last two decades, with a decisive advance towards consistently successful biostratigraphy. This has been obtained by improving the nannofossil database, following the pioneering paper of Backman and Shackleton (1983), with the application of a strategy that combines quantitative data-gathering techniques with high resolution sampling. The effort to optimize the analytical methodologies, in the study of an increasing numbers of suitable sedimentary successions, has generated excellent results for different intervals of geological time. The improvement of database is linked to improvements in the quality of sedimentary successions, as the high-quality sediment cores recovered by the Ocean Drilling Program (ODP). It has been proved that high-quality biostratigraphic data provide the potential for high resolution calibration between nannofossil biohorizons and the other records used for dating as, specifically, orbitally tuned cyclostratigraphy. In this way the accurate time resolution, which distinguishes this data sequence, is transferred to the biohorizons, and a precise biochronology is obtained. On the other hand, detailed nannofossil biostratigraphy can be used to provide preliminary control points for the astronomical tuning of cyclostratigraphic records. This rigorous approach in the study and use of calcareous nannofossils has been greatly stimulated by Nick Shackleton. The introduction of orbitally tuned time-scales has been crucial for the chronological precision of nannofossil biohorizons, and has provided an accurate chronologic framework which is continuously improved, in various intervals of the Cenozoic. Furthermore, an accurate database on ancient nannofossil communities provides informations useful for clarifying their possible paleoceanographic meanings and their paleoecological affinities, and for describing the evolutionary "behaviour" of nannofossils during prominent climatic episodes and climatic transitions.
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 3030 Micropaleontology
DE: 1035 Geochronology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting