X-ray nanotomography and electron backscatter diffraction demonstrate the crystalline, heterogeneous and impermeable nature of conodont white matter

Ayse Ozdemir*, A D Warren, Peter George Martin, Manuel Guizar-Sicairos, Mirko Holler, Federica Marone, Carlos Martínez-Pérez*, Philip C J Donoghue *

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

2 Citations (Scopus)
43 Downloads (Pure)

Abstract

Conodont elements, microfossil remains of extinct primitive vertebrates, are commonly exploited as mineral archives of ocean chemistry, yielding fundamental insights into the palaeotemperature and chemical composition of past oceans. Geochemical assays have been traditionally focused on the so-called lamellar and white matter crown tissues, however, the porosity and crystallographic nature of the white matter and its inferred permeability is disputed, raising concerns over its suitability as a geochemical archive. Here we constrain the characteristics of this tissue and address conflicting interpretations using Ptychographic X-ray Computed Tomography (PXCT), Pore Network analysis and Electron Back-Scatter Diffraction (EBSD). PXCT and Pore Network analyses based on these data reveal that while white matter is extremely porous, the pores are unconnected, rendering this tissue closed to postmortem fluid percolation. EBSD analyses demonstrate that white matter is crystalline and comprised of a single crystal typically tens of microns in dimensions. Combined with evidence that conodont elements grew episodically, these data suggest that white matter, which comprises the denticles of conodont elements, grew syntactically, indicating that individual crystals are time heterogeneous. Together these data provide support for the interpretation of conodont white matter as a closed geochemical system and, therefore, its utility of the conodont fossil record as a historical archive of Palaeozoic and early Mesozoic ocean chemistry.
Original languageEnglish
Article number202013
Number of pages10
JournalRoyal Society Open Science
Volume8
Issue number8
DOIs
Publication statusPublished - 4 Aug 2021

Bibliographical note

Funding Information:
Data accessibility. The original tomographic raw data, as well as the Avizo projects with the segmented information and the Pore Network Analysis (see readme file) are hosted at the data.bris Research Data Repository (doi:10.5523/bris. 3rjh9x2tbviqs2j6sbuuren8l1). Authors’ contributions. A.A.-O., C.M.P. and P.C.J.D. designed the study. A.A.-O., X.W. and P.G.M. carried out the EBSD analysis; M.G.-S., M.H. and C.M.P. scanned the specimens at the cSAXS, and F.M. scanned the samples at the TOMCAT, both at the Paul Scherrer Institute; A.A.-O., C.M.P. and P.C.J.D. wrote the manuscript, with critical revision from all authors. All the authors gave final approval for submission. Competing interests. We declare that we have no competing interests. Funding. C.M.P. and P.C.J.D. were supported by Paul Scherrer Institute to conduct the cSAXS experiments and by the Ministry of Science and Innovation of Spain, Research Project PID2020-117373GA-I00. Acknowledgements. We acknowledge the Paul Scherrer Institute, Villigen, Switzerland for provision of synchrotron radiation beamtime at the TOMCAT and cSAXS beamline of the SLS. We thank Robert S. Nicoll for donating the samples of Teridontus nakamurai used in this analysis; Sarawuth Wantha (thermofisher) for his technical support to develop the Pore Network Analysis; and three anonymous reviewers whose comments improved the final version of the manuscript.

Publisher Copyright:
© 2021 The Authors.

Keywords

  • conodont white matter
  • cSAXS
  • EBSD
  • X-ray tomography
  • ptychographic nanotomography

Fingerprint

Dive into the research topics of 'X-ray nanotomography and electron backscatter diffraction demonstrate the crystalline, heterogeneous and impermeable nature of conodont white matter'. Together they form a unique fingerprint.

Cite this