Carbon isotope composition in modern brachiopod calcite: A case of equilibrium with seawater?

Autor(en)

Uwe Brand, K. Azmy, E. Griesshaber, M.A. Bitner, Alan Logan, Martin Zuschin, E. Ruggiero, P.L. Colin

Abstrakt

We examined a large number of modern, shallow-water articulated brachiopods representing the orders
Terebratulida, Rhynchonellida, Thecideida and one inarticulated brachiopod of the order Craniida from polar to
tropical regions for their carbon isotope compositions. Based on our detailed investigation, we recommend
avoiding fast growth areas such as the youngest shell increments; in addition, the primary layer and transition
zone calcites of brachiopods must be avoided because they are in carbon and oxygen isotope disequilibrium
with ambient seawater. After adjusting isotope compositions for the Mg effect,we observed no significant difference
(p N 0.05) in δ13C values between dorsal and ventral valves of our articulated brachiopods.
Using the calcite-bicarbonate enrichment factor (ε) inconjunctionwithδ13C values of dissolved inorganic carbon
of habitat seawater, we conclude that modern shallow-water articulated and some inarticulated brachiopods incorporate
oxygen (Brand et al., 2013) and carbon isotopes into shell calcite of secondary and/or tertiary layers in
apparent equilibriumwith ambient seawater. Within the general concept of equilibriumincorporation,with seawater,
shell δ13C values are an excellent recorder of local/global seawater environments and water mass circulation.
Thus, application of theMg-effect permits brachiopods to be an extremely powerful archive, and δ13C values
more precise proxy and tracer of past changes in marine productivity, evolution of seawater carbon chemistry
and variation in the global carbon cycle.

Organisation(en)

Institut für Paläontologie

Externe Organisation(en)

University of New Brunswick (UNB), Brock University, Memorial University of Newfoundland, Ludwig-Maximilians-Universität München, Polish Academy of Sciences (PAS), Università degli studi di Napoli Federico II, Coral Reef Research Foundation

Journal

Chemical Geology

Band

411

Seiten

81-96

Anzahl der Seiten

16

ISSN

0009-2541

DOI

https://doi.org/10.1016/j.chemgeo.2015.06.021

Publikationsdatum

09-2015

Peer-reviewed

Ja

ÖFOS 2012

105118 Paläontologie

Schlagwörter

ASJC Scopus Sachgebiete

Geochemistry and Petrology, Geology

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/carbon-isotope-composition-in-modern-brachiopod-calcite-a-case-of-equilibrium-with-seawater(21c73d1d-1e33-40d3-9fe9-2ccddc2cd18e).html