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New insights into the ultrastructure, permeability, and integrity of conodont apatite determined by transmission electron microscopy

Trotter, Julie; Fitz Gerald, John; Kokkonen, Harri; Barnes, Christopher J

Description

New crystalline structures have been observed in argon ion-milled conodont elements from a diverse suite of Ordovician taxa ('Cordylodus robustus', Drepanoistodus suberectus, Panderodus gracilis, Plectodina? sp., Aphelognathus sp., Periodon aculeatus using transmission electron microscopy (TEM). Electron diffraction patterns of albid tissue reveal that the component crystals are extraordinarily large, in the order of hundred(s) of microns. These large albid crystals show typical cancellate...[Show more]

dc.contributor.authorTrotter, Julie
dc.contributor.authorFitz Gerald, John
dc.contributor.authorKokkonen, Harri
dc.contributor.authorBarnes, Christopher J
dc.date.accessioned2015-12-10T21:56:10Z
dc.identifier.issn0024-1164
dc.identifier.urihttp://hdl.handle.net/1885/39298
dc.description.abstractNew crystalline structures have been observed in argon ion-milled conodont elements from a diverse suite of Ordovician taxa ('Cordylodus robustus', Drepanoistodus suberectus, Panderodus gracilis, Plectodina? sp., Aphelognathus sp., Periodon aculeatus using transmission electron microscopy (TEM). Electron diffraction patterns of albid tissue reveal that the component crystals are extraordinarily large, in the order of hundred(s) of microns. These large albid crystals show typical cancellate porosity, although a distinctly lamellar structure has also been observed within a large albid crystal positioned between hyaline lamellar and cancellate albid tissues. There is a distinct absence of 'interlamellar space' within all hyaline tissues examined, which are characterized by a polycrystalline matrix of micron-scale elongate crystals that are both strongly aligned and tightly bound within a broader lamellar structure. Optical opacity, caused by light scattering within large (≥ 0.5 μm) pores, is also a feature of both albid and polycrystalline lamellar crown tissues. Accordingly, conodont hard tissues are differentiated by crystal size and shape, as well as inter- and intracrystalline porosity. These new observations highlight the structural complexities of conodont histologies and the need for more comprehensive investigations particularly of transitional crown tissues, which are not well defined by terms typically used in the literature. Their histological structures are interpreted to be a product of in vivo crystallization and thus provide new insights into the relative porosity, permeability, and inherent integrity of the tissues as well as their growth relationships. Accordingly, these data not only have implications for earlier histological and palaeobiological interpretations of conodont hard tissues but are also fundamental in determining their chemical integrity, which is crucial for characterizing palaeoseawater composition and palaeoenvironmental change. The potential for conodont apatite to retain primary chemical information depends on crystal size and permeability, so the large albid crystal domains are consistent with parallel geochemical studies that suggest that cancellate albid crown is more resistant to diagenetic modification.
dc.publisherWiley-Blackwell
dc.sourceLethaia; an international journal of palaeontology and stratigraphy
dc.subjectKeywords: apatite; conodont; crystal structure; diffraction; histology; Ordovician; permeability; porosity; seawater; taxonomy; transmission electron microscopy; ultrastructure; water chemistry; Cordylodus; Drepanoistodus suberectus; Panderodus gracilis; Periodon a Apatite; Conodont; Histology; Palaeoseawater chemistry; TEM; Transmission electron microscopy
dc.titleNew insights into the ultrastructure, permeability, and integrity of conodont apatite determined by transmission electron microscopy
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume40
dc.date.issued2007
local.identifier.absfor040306 - Mineralogy and Crystallography
local.identifier.absfor040203 - Isotope Geochemistry
local.identifier.absfor040308 - Palaeontology (incl. Palynology)
local.identifier.ariespublicationu9503261xPUB174
local.type.statusPublished Version
local.contributor.affiliationTrotter, Julie, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationFitz Gerald, John, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationKokkonen, Harri, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationBarnes, Christopher J, University of British Columbia
local.description.embargo2037-12-31
local.bibliographicCitation.startpage97
local.bibliographicCitation.lastpage110
local.identifier.doi10.1111/j.1502-3931.2007.00024.x
dc.date.updated2015-12-09T07:35:05Z
local.identifier.scopusID2-s2.0-34249672199
CollectionsANU Research Publications

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