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Ediacaran acritarch biota from the Giles 1 drillhole, Officer Basin, Australia, and its potential for biostratigraphic correlation
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
2008 (English)In: Precambrian Research, ISSN 0301-9268, Vol. 162, no 3-4, 498-530 p.Article, review/survey (Refereed) Published
Abstract [en]

The remarkable diversification of single-celled photosynthesising biota of algal and other as yet unknown affinities (acritarchs), followed by the diversification of metazoans, occurred during the Ediacaran Period, which is marked by extreme climatic and environmental changes. Here we describe a taxonomically diverse acritarch association from the Ediacaran part of the Giles 1 drillcore in the Officer Basin, South Australia, which documents further the Ediacaran phytoplankton radiation. The studied palynoflora comprises 21 known acritarch species belonging to 15 genera. One new monospecific genus is described (Calyxia xandaros sp. nov.) as well as one new species of Tanarium (Tanarium anozos sp. nov.). We also propose the genus Knollisphaeridium to replace the preoccupied genus Echinosphaeridium. Three stratigraphically successive assemblages that match previously observed patterns of acritarch replacement are distinguished. The present record is from slightly older strata than in previous records, thus extending the ranges of certain acanthomorphic species. The lower boundaries of three stratigraphically higher assemblage zones among the four formerly established zones, are identified by the occurrence of the index species Tanarium conoideum, Tanarium irregulare and Apodastoides verobturatus, respectively. The substantial morphological disparity of acritarchs in the Giles 1 succession suggests that they may represent a great diversity of microorganisms, not only as biological species but also representing perhaps vegetative and encysted stages in their life cycle. The reconstructed palaeogeographic distribution of several species between Australia, Siberia, Baltica (the East European Platform), and to South China, shows that acritarchs are suitable for both intra- and inter-regional correlation.

Place, publisher, year, edition, pages
2008. Vol. 162, no 3-4, 498-530 p.
Keyword [en]
Neoproterozoic, Ediacaran, Acritarchs, Biostratigraphy, Palaeogeography, Officer Basin
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-97148DOI: 10.1016/j.precamres.2007.10.010ISI: 000255849000009OAI: oai:DiVA.org:uu-97148DiVA: diva2:171958
Available from: 2008-04-15 Created: 2008-04-15 Last updated: 2011-01-13Bibliographically approved
In thesis
1. The Ediacaran Diversification of Organic-walled Microbiota: Ocean Life 600 Million Years Ago
Open this publication in new window or tab >>The Ediacaran Diversification of Organic-walled Microbiota: Ocean Life 600 Million Years Ago
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The only direct evidence of past life is provided by fossils. Fossils tell us about the evolution of life on Earth and they give us clues concerning ancient environments. The Ediacaran Period (roughly 635-542 million years ago) is characterised by the appearance and diversification of various microbiota and also the diversification of metazoans. Well-preserved organic-walled microfossils referred to as acritarchs occur abundantly in Ediacaran sedimentary successions in the Officer Basin in South Australia. Acritarch assemblages from the Giles 1 and Murnaroo 1 drillcores show a wide morphological disparity and are taxonomically diverse. Assemblages change over short stratigraphic intervals which enables the recognition of different biozones. The presence of taxa common between Australia, Siberia, Baltica and China provides a means for global correlation of the Ediacaran System. Examination of the wall ultrastructure of several acritarch specimens by use of transmission electron microscopy reveals a complexity in the cell wall that is not seen in prokaryotes but is indicative in some cases of particular clades of microalgae. Wall ultrastructures range from single-layered to three- and four-layered and from homogeneous to porous. The wall ultrastructure can be used to assess biological affinities and the affinities of the studied taxa in relation to green algae, dinoflagellates and metazoans are discussed. However, before taxonomic interpretations can be made with confidence, an understanding of taphonomic degradation of microorganisms is required. With focus on illustrated specimens, one part of this thesis explains what happens to an acritarch as it undergoes various types of degradation and why an understanding of these processes is important for taxonomic identification. A meteorite impact in South Australia spread an ejecta layer over a 550 km radius area. This ejecta layer is recognised in subsurface drillcores and provides an independent stratigraphic marker horizon that supports an acritarch-based correlation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 33 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 428
Earth sciences, acritarchs, Ediacaran, Australia, biostratigraphy, microfossils, Geovetenskap
urn:nbn:se:uu:diva-8684 (URN)978-91-554-7185-9 (ISBN)
Public defence
2008-05-16, Axel Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00
Available from: 2008-04-15 Created: 2008-04-15 Last updated: 2011-07-08Bibliographically approved

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