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Timing of Deposition and Geochemistry of Source Rocks in the Georgina Basin, Australia

  • Author / Creator
    Miles, Naomi E
  • This study characterized two organic-rich source rock formations from three
    different sub-basins of the Georgina Basin, Central Australia, using the 187Re – 187Os
    isotope system and a suite of major, minor, and trace elements. The major organic-rich
    source rock in the Georgina Basin, the lower section of the middle to late Cambrian
    Arthur Creek Formation, overlies two minor source rocks, the middle Cambrian Hay
    River and Thorntonia Limestone Formations. Two major sub-basins, the Toko Syncline
    and the Dulcie Syncline in the southern Georgina Basin, controlled many aspects of
    sedimentation, organic matter accumulation and hydrocarbon generation. The Arthur
    Creek Formation was deposited in both sub-basins, but at different times, according to
    the trilobite record. The ages of the Arthur Creek and Thorntonia Limestone Formations
    are currently defined based on specific trilobite species from the Central Australian
    Trilobite Zonation. Biostratigraphy in the Georgina Basin tied to the Central Australian
    Trilobite Zonation identified specific species of trilobites that are similar to globally
    recognized trilobites with isotopically defined ages. In the Dulcie Syncline, the Arthur
    Creek Formation was deposited between ~509 and 501 Ma, whereas in the Toko Syncline
    the ages were from ~503 to 498 Ma based on ages from the biostratigraphic record.
    Farther to the north, in the Undilla sub-basin, the Thorntonia Limestone deposited
    synchronously with the Dulcie Syncline Arthur Creek Formation between ~508 and 505
    Ma.
    Based on the 187Re – 187Os isotopic ages determined in this study, the ages of the
    Arthur Creek Formation in both sub-basins are younger than the biostratigraphically
    determined ages. In the Dulcie Syncline, the Arthur Creek Formation Re-Os age is 481 ±
    ii
    10 Ma. The Toko Syncline Arthur Creek Formation is 477.5 ± 9.5 Ma. The trace element
    suites were able to characterize specific paleoenvironments, controlled by basin
    geometry, during deposition of the Arthur Creek and Thorntonia Limestone Formation.
    In the Dulcie Syncline, the trace element profiles indicate deposition in a heavily
    restricted basin.
    Trace element abundances in the Arthur Creek Formation of the Toko Syncline
    show a progression from severe restriction towards a better-circulated sub-basin.
    Towards the top of the Arthur Creek Formation, marginal regions of the Toko Syncline
    experienced regular oxidation but deeper regions of the basin did not experience any
    oxidation. The Thorntonia Limestone Formation showed signs of regular oxidation,
    possibly seasonally related. Rock-eval data for both formations indicated that the Arthur
    Creek and Thorntonia Limestone Formations reached the oil window.

  • Subjects / Keywords
  • Graduation date
    Fall 2015
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/R34J0B322
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.