The Pacoota Sandstone, Amadeus Basin, Northern Territory: stratigraphy and palaeontology

The Pacoota Sandstone is a thick (up to 850 m) deposit of siliciclastic rocks straddling the Cambrian- Ordovician boundary in the Amadeus Basin of central Australia. It is economically the most important hydrocarbon reservoir of the basin, contains a potentially significant reserve of phosphorite, and may be an important aquifer. The internal stratigraphy of the Pacoota Sandstone, not previously documented in detail on a basin-wide scale, is based here on a sequence of four informally defined sedimentary packages, separated by unconformity or disconformity. The age and stratigraphic distribution of these sequences is measured against a preliminary and equally informal biostratigraphic scheme, which involves body-fossil and ichnofossil assemblages. Although a late Cambrian-early Ordovician age has long been known, it is now possible to date the sequences, at least to stage-level of resolution. Sequence 1, characterised by channel-fill sediments at several localities, is Payntonian to early Datsonian (latest Cambrian). It overlies earlier Upper Cambrian (Mindyallan) formations with regional unconformity, and it, in turn, is overlain unconformably by Sequence 2. The latter is a tidal and storm-dominated sequence with concentrations of the Skolithos ichnocoenosis, but lacking age-diagnostic body fossils. It is separated by a further major unconformity from Sequence 3, comprising predominantly phosphatic and glauconitic clastic sediments of latest Warendian (late Tremadoc) age, which thus indirectly date Sequence 2 also. Sequence 4, which may be disconformable, at least in part on Sequence 3, again has storm and tidally dominated sandstones rich in ichnofossils, but impoverished in body fossils. The limited fauna that does occur dates this sequence at the Tremadoc/Arenig transition. The Pacoota Sandstone is in places unconformably overlain by the Horn Valley Siltstone, of early Arenig age.

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Date (Publication)
1991-01-01T00:00:00
Date (Revision)
2019-04-08T05:50:25
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Geoscience Australia Persistent Identifier/https://pid.geoscience.gov.au/dataset/ga/34

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Bureau of Mineral Resources, Geology and Geophysics

 Canberra
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Shergold, J.H.

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Bulletin

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237

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Commonwealth of Australia (Geoscience Australia)
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  • palaeontology

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2018-11-01T00:00:00
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English
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Download the Bulletin (pdf)

Download the Bulletin (pdf)

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Australian Government Security ClassificationSystem

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2018-11-01T00:00:00
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https://www.protectivesecurity.gov.au/Pages/default.aspx

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Unclassified

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English
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Commonwealth of Australia (Geoscience Australia)

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Legacy AGSO BMR Bulletins

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eCatId/34

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2018-04-20T06:04:30
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1996-10-29T00:00:00

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AU/NZS ISO 19115-1:2014

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ISO 19115-1:2014

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ISO 19115-3

Title

Geoscience Australia Community Metadata Profile of ISO 19115-1:2014

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Version 2.0, September 2018

Citation identifier
https://pid.geoscience.gov.au/dataset/ga/122551

 
 

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palaeontology stratigraphy

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