An assessment of latest Cretaceous Pycnodonte vesicularis (Lamarck, 1806) shells as records for palaeoseasonality: A multi-proxy investigation

Niels J. De Winter*, Johan Vellekoop, Robin Vorsselmans, Asefeh Golreihan, Jeroen Soete, Sierra V. Petersen, Kyle W. Meyer, Silvio Casadio, Robert P. Speijer, Philippe Claeys

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

In order to assess the potential of the honeycomb oyster Pycnodonte vesicularis for the reconstruction of palaeoseasonality, several specimens recovered from late Maastrichtian strata in the Neuquén Basin (Argentina) were subject to a multi-proxy investigation, involving scanning techniques and trace element and isotopic analysis. Combined CT scanning and light microscopy reveals two calcite microstructures in P. vesicularis shells (vesicular and foliated calcite). Micro-XRF analysis and cathodoluminescence microscopy show that reducing pore fluids were able to migrate through the vesicular portions of the shells (aided by bore holes) and cause recrystallization of the vesicular calcite. This renders the vesicular portions not suitable for palaeoenvironmental reconstruction. In contrast, stable isotope and trace element compositions show that the original chemical composition of the foliated calcite is well-preserved and can be used for the reconstruction of palaeoenvironmental conditions. Stable oxygen and clumped isotope thermometry on carbonate from the dense hinge of the shell yield sea water temperatures of 11°C, while previous TEX86H palaeothermometry yielded much higher temperatures. The difference is ascribed to seasonal bias in the growth of P. vesicularis, causing warm seasons to be underrepresented from the record, while TEX86H palaeothermometry seems to be biased towards warmer surface water temperatures. The multi-proxy approach employed here enables us to differentiate between well-preserved and diagenetically altered portions of the shells and provides an improved methodology for reconstructing palaeoenvironmental conditions in deep time. While establishing a chronology for these shells was complicated by growth cessations and diagenesis, cyclicity in trace elements and stable isotopes allowed for a tentative interpretation of the seasonal cycle in late Maastrichtian palaeoenvironment of the Neuquén Basin. Attempts to independently verify the seasonality in sea water temperature by Mgĝ€ĝ•ĝ€Ca ratios of shell calcite are hampered by significant uncertainty due to the lack of proper transfer functions for pycnodontein oysters. Future studies of fossil ostreid bivalves should target dense, foliated calcite rather than sampling bulk or vesicular calcite. Successful application of clumped isotope thermometry on fossil bivalve calcite in this study indicates that temperature seasonality in fossil ostreid bivalves may be constrained by the sequential analysis of well-preserved foliated calcite samples using this method.

Original languageEnglish
Pages (from-to)725-749
Number of pages25
JournalClimate of the Past
Volume14
Issue number6
Early online date8 Jun 2018
DOIs
Publication statusPublished - 2018

Bibliographical note

Funding Information:
Acknowledgements. Niels J. de Winter is financed by a personal PhD fellowship from IWT Flanders (IWT700). This research was partly financed by the FOD40 Chicxulub grant obtained by Philippe Claeys and by Research Foundation Flanders (FWO) grant G.0B85.13 to Robert P. Speijer and Philippe Claeys. Johan Vellekoop is also funded by a personal research grant from FWO (grant 12Z6618N). Thanks go to the Hercules Foundation Flanders for acquisition of XRF instrumentation (grant HERC1309) and VUB Strategic Research Program for support of the AMGC research group. The authors thank Rudy Swennen from the KU Leuven for analytical support.

Publisher Copyright:
© 2018 Author(s).

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