During the past decades, volume calculation of extant calcareous nannoplankton has been performed in order to convert coccolith fluxes data into carbonate export productivity. The most useful and relative recent method to estimate the volume of coccoliths is described by Young & Ziveri (2000). Several studies on estimates of recent coccolithophore carbonate contribution have been published and this methodology has also been successfully applied to Mesozoic sediments (Tremolada & Young, 2002), thus providing a new promising proxy to be used in paleoceanographic reconstructions. Based on these fruitful practices, we have decided to test these methodologies on Paleocene sediments from several DSDP/ODP Sites. The study areas are located at different latitudes both in the Atlantic (401, 690, 1051, 1260 and 1263) and Pacific (ODP Site 1209) Oceans with the intention of giving a global perspective. We have investigated well-preserved deep-sea sediments in order to determine the average dimensions and calculate the volume of the most abundant Paleocene nannofossils, which include Coccolithus, Toweius, Sphenolithus, Fasciculithus, Discoaster and Zygrhablithus. For each taxon, we have measured at least 250 specimens to obtain accurate size estimates; furthermore, we have analyzed 30 specimens of each species to calculate shape constant (Ks), which, in turn, is used to obtain calcareous nannofossil volumes. This approach permits to evaluate the total amount of CaCO3 produced by coccoliths and could be used to provide an important tool for palaeoecological and biogeochemical interpretations. However, the present work represents the first attempt to investigate the significance of volume variation within Paleocene nannofloras.
|Titolo:||Volume calculation of Paleocene calcareous nannofossils|
DE BERNARDI, BIANCA (Primo)
|Data di pubblicazione:||set-2008|
|Appare nelle tipologie:||01 - Articolo su periodico|