Environmental conditions and microbial community structure during the Great Ordovician Biodiversification Event; a multi-disciplinary study from the Canning Basin, Western Australia
The Ordovician is an important period in Earth’s history with exceptionally high sea levels that facilitated the Great Ordovician Biodiversification Event. This crucial biological event is regarded as the second most significant evolutionary event in the history of Paleozoic life, after the Cambrian radiation. The present study integrates palynological, petrographic, molecular and stable isotopic (δ13C of biomarkers) analyses of cores from five boreholes that intersected the Goldwyer Formation, Canning Basin, Western Australia, to determine depositional environments and microbial diversity within a Middle Ordovician epicontinental, tropical sea.
A major transgression was detected in the laminated shales of the lower Goldwyer Formation (Units 1+2) which were deposited in anoxic bottom waters, as confirmed by low (<1) Pristane/Phytane ratios, and elevated dibenzothiophene and gammacerane indices. A second, less extensive, flooding event is recorded by shallow marine sediments of the upper Goldwyer Formation (Unit 4). Cores of these sediments, from two wells (Solanum-1 and Santalum-1A) are bioturbated and biomarkers indicate relatively oxygenated conditions, as well as the presence of methanotrophic bacteria, as determined from the high 3-methylhopane indices.
Typical Ordovician marine organisms including acritarchs, chitinozoans, conodonts and graptolites were present in the lower and upper Goldwyer Formation, whereas the enigmatic organism Gloeocapsomorpha prisca (G. prisca) was only detected in Unit 4. The presence of G. prisca was based on microfossils and specific biosignatures presenting an odd-over-even predominance in the C15 to C19 n-alkane range.
Cryptospores were identified in Unit 4 in the Theia-1 well and are most likely derived from bryophytes, making this is the oldest record of land plants in Australian Middle Ordovician strata. Biomarkers in some samples from Unit 4 that also support derivation from terrestrial organic matter include retene, benzonaphthofurans and δ13C-depleted mid-chain n-alkanes.
This research contributes to understanding Ordovician marine environments from a molecular perspective since few biomarker studies have been undertaken on age-equivalent sections. Furthermore, the identification of the oldest cryptospores in Australia and their corresponding terrestrial biomarkers contributes to understanding the geographical evolution of early land plants.
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- Date (Creation)
- 2017-05-17T00:00:00
- Date (Publication)
- 2017-11-21T04:29:06
- Citation identifier
- Geoscience Australia Persistent Identifier/http://pid.geoscience.gov.au/dataset/110783
- Cited responsible party
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Role Organisation / Individual Name Details Author Spaak, G.
Co-author Edwards, D.S.
Co-author Foster, C.B.
Co-author Pagès, A.
Co-author Summons, R.E.
Co-author Sherwood, N.
Co-author Grice, K.
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Manuscript submitted to Global and Planetary Change
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Product data repository: Various Formats
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Ordovician
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Canning Basin
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Gloeocapsomorpha prisca
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cryptospores
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- Australian and New Zealand Standard Research Classification: Fields of Research
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Earth Sciences
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Published_External
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Creative Commons Attribution 4.0 International Licence
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4.0
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- 2018-11-01T00:00:00
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html
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Link to Journal Article (50 download limit)
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html
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Australian Government Security ClassificationSystem
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- 2018-11-01T00:00:00
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- Unclassified
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urn:uuid/6f202a8b-f40a-4bf8-8086-46573b580dcf
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GeoNetwork UUID
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- English
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Role Organisation / Individual Name Details Point of contact Edwards, D.S.
Commonwealth of Australia (Geoscience Australia)
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- Date info (Creation)
- 2017-05-16T02:17:07
- Date info (Revision)
- 2018-04-20T05:51:32
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AU/NZS ISO 19115-1:2014
Metadata standard
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ISO 19115-1:2014
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ISO 19115-3
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Geoscience Australia Community Metadata Profile of ISO 19115-1:2014
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Version 2.0, September 2018
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- https://pid.geoscience.gov.au/dataset/ga/122551