T313 Paleoecological Patterns, Ecological Processes, Modeled Scenarios: Crossing Temporal Scales to Understand an Uncertain Future (Posters)

Wednesday, 4 November 2015
9:00 AM - 6:30 PM
Exhibit Hall

FROM ARAGONITE TO CALCITE: IMPACTS OF RECRYSTALLIZATION ON STABLE ISOTOPE (δ18O & δ13C) COMPOSITION OF THE BIVALVE BIO-ARCHIVE ARCTICA ISLANDICA

Paper number: T313-3
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

  • Lars Beierlein Presenting Author
    Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven
  • Gernot Nehrke
    Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven
  • Bernd R. Schöne
    University of Mainz, Mainz
  • Torsten Bickert
    University of Bremen, Bremen
  • Andreas Mackensen
    Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven
  • Thomas Brey
    Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven

Abstract

Shells of the bivalve Arctica islandica serve as high-resolution archive of past environmental conditions. Stable oxygen isotopes (δ18O) values from well-preserved A. islandica shells are frequently used as a proxy for water temperature (and salinity). Hence, this species may improve distinctly our understanding of seasonal temperature dynamics in the past.

We present the first stable isotope (δ18O & δ13C) analysis on a fossil semi-recrystallized A. islandica shell from the Tjörnes Beds of Iceland (Pliocene). Confocal Raman microscopy is used to identify areas of pristine aragonite and recrystallized calcite shell, which were then sampled by high-resolution micro-milling. We compare paleo-water temperatures inferred from stable oxygen isotope ratios of both recrystallized and non-recrystallized portions of the shell to highlight and discuss the impacts of taphonomic alterations on a micro-scale and its implications for paleo-environmental reconstructions. Our findings emphasize the need for careful interpretation of carbonate-based water temperature reconstructions, because small-scale diagenesis can significantly modify the original stable oxygen isotope signature and substantially distort the paleoclimatic or paleoenvironmental signals inferred thereof.