A possible chlorophycean affinity of some Neoproterozoic acritarchs

Khaled Arouri*, Paul F. Greenwood, Malcolm R. Walter

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    87 Citations (Scopus)

    Abstract

    Two taxa of Neoproterozoic acritarchs of unknown affinity, Multifronsphaeridium pelorium and Species A, are analysed by electron microscopic (SEM, TEM) and chemical (micro-FTIR, pyrolysis GC-MS, thermal desorption-MS) methods. Both acritarch species are characterised by multi-branched processes and a remnant trilaminar sheath (TLS) structure. The TLS-bearing wall structures in these acritarchs suggest a possible biological affinity to chlorophyte algaenan. The molecular data obtained from the two acritarchs were generally similar and also consistent with a chlorophycean affinity. A significant aliphatic moiety is evident in these acritarchs as a short-chain series of n-alkene/alkane pyrolysates and prominent aliphatic IR bands. The restricted molecular-weight range (<C20) of the n-alkene/alkane doublets and the lack of isoprenoid and other branched alkanes in the pyrolysates suggest a low degree of branching in the aliphatic component of these acritarch macromolecules. The significant methyl (CH3) IR signal was attributed to the terminal groups of short n-alkyl moieties. Alkylbenzenes, alkylphenols and alkylindoles were also significant pyrolysis products, indicating an aromatic component, although the latter two components may be attributed to artificially- and/or diagenetically-formed melanoidin moieties. The macromolecular structure of Multifronsphaeridium sp. and Species A consists of short n-alkylpolymethylenic chains, probably linked via ether/ester bonds, with possibly a small aromatic content. This study presents ultrastructural and molecular evidence of a genetic relationship between Neoproterozoic acritarchs and Chlorophyceae.

    Original languageEnglish
    Pages (from-to)1323-1337
    Number of pages15
    JournalOrganic Geochemistry
    Volume30
    Issue number10
    DOIs
    Publication statusPublished - Oct 1999

    Keywords

    • algaenan
    • chlorophyceae
    • electron microscopy
    • laser micropyrolysis GC-MS
    • micro-FT1R
    • neoproterozoic acritarchs
    • thermal desorption-MS
    • trilaminar sheath cell walls

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