Stable isotope data of selected gastropod genera as proxies for seawater chemistry of the Central Paratethys
Abstract
Geodynamic processes influenced the complex evolution of the Paratethys, an extended marginal sea, which is characterised by intermittently open and closed marine seaways with its surrounding oceans. Especially in the Miocene, this led to substantial changes in marine environments and ecosystems by changing basin geometries, water circulation, water depth, water chemistry, climate etc. Investigations of stable isotopes of fossil carbonate shells provide information about paleoenvironmental parameters of the ancient seawater. Oxygen and carbon isotope data of selected gastropod genera, mainly Turritellidae, are used to reconstruct paleoenvironmental parameters of different time slices of the Miocene of Austrian Neogene basins. Recent Turritellidae live in a wide range of environments, mainly shallow infaunal or epifaunal, but prefer fully marine conditions. Stable isotope investigations of recent specimens support their usefulness as isotopic indicators for environmental parameters. For detecting diagenetic alterations of the aragonitic gastropod shells, samples were analysed for their shell mineralogy and microstructures with X-ray diffraction analyses and scanning electron microscopy prior to stable isotope analyses. Several microsamples for isotope analyses of each shell were taken to test the intrashell variability. Oxygen and carbon isotopes for Karpatian and Badenian turritellids from the Vienna Basin and the Korneuburg Basin show slightly lighter oxygen and carbon isotope values for the Karpatian. In addition to turritellids, two other gastropod genera (Ocenebra and Granulolabium), both preferring an intertidal habitat and tolerating some salinity fluctuations, were investigated, yielding information about mixing of seawater with freshwater. So parameters for different environments can be obtained, and also comparisons of different gastropod genera are possible. The study was supported by the Austrian Science Foundation (FWF), project "Stable isotopes and changing Miocene palaeoenvironments in the East Alpine region" (P-14366 BIO), and project "Evolution Versus Migration: Changes in Austrian Marine Miocene Molluscan Paleocommunities" (P-13745 BIO).
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....5596L