Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/120939
Type: Thesis
Title: Isotope constraints on paleo-depositional environments and intra-basin correlation in the Proterozoic McArthur Basin, Northern Territory, Australia
Author: Guiliano, W. C.
Issue Date: 2016
School/Discipline: School of Physical Sciences
Abstract: The Proterozoic McArthur Basin, Northern Territory, Australia, hosts some of the oldest proven hydrocarbon sources in the world including the organic rich black shale unit in the McArthur Group, the Barney Creek Formation. Stratigraphically positioned between dolomitic carbonate units, the depositional setting for the Barney Creek Formation has been in debate for at least three decades. Published literature supports both an anoxic coastal lagoon/lacustrine environment and also a relatively deep-marine low-energy deposition. Here we employ high-resolution records of stable isotope ratios (δ13C, δ18O,87Sr/86Sr) and elemental concentrations (Ba/Ca) in the carbonates rich sedimentary record of the McArthur Group (cores LV09001, McA5, Bj2, BCF 4) as proxies to constrain paleo-depositional environments. Using samples from the LV09001 core, we were able to create a high-resolution, geochemical and isotope ratio profile of the Glyde Package, McArthur Group, ranging from the Emmerugga Dolomite to the Donnegan Member. Acquired δ13C, 87Sr/86Sr and Ba/Ca stratigraphic trends indicate a changing paleo-environment at the time of sediment deposition and carbonate precipitation. In particular a systematic negative δ13C anomaly, magnitude around 2.5‰, is recorded in the Barney Creek Formation where Ba/Ca ratios are also anomalously high and a coeval 87Sr/86Sr trend indicates a ‘non-marine’ restricted environment. Observed light carbon (12C), and elevated barium concentrations (Ba/Ca ratios) are likely controlled by local cycling of organic matter in a redox-stratified restricted basin analogous to modern Black Sea. A restricted setting also aids in chemical and redox stratification, creating deep water anoxic and low energy conditions for the deposition of the Barney Creek Formation. Finally, our constraints from coupled C and Sr isotope data, collected from the most ‘marine’ carbonate intervals, suggest that the inferred δ13C and 87Sr/86Sr signatures of Proterozoic paleo-seawater (at about 1640 Ma) were close to -0.5 to 0 per mil, and 0.705 to 0.706, respectively.
Dissertation Note: Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2016
Where: McArthur Basin, Northern Territory
Keywords: Honours; Geology; isotopes; carbon; strontium; oxygen; carbonates; McArthur Basin; depositional environment; Proterozoic
Description: This item is only available electronically.
Provenance: This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the author of this thesis and do not wish it to be made publicly available, or you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals
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