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Published January 1, 2017 | Published
Book Section - Chapter Open

Using elemental chemostratigraphy on Mid-Late Frasnian platform-top successions from the Lennard Shelf outcrops, Canning Basin, Western Australia


High-resolution chronostratigraphic correlation using elemental chemostratigraphy in platform carbonates is typically difficult to achieve. Here, elemental chemostratigraphy is used to correlate between two platform-top, carbonate-dominated field sections from the narrow Lennard Shelf that existed on the NE margin of the Canning Basin, Western Australia, during the mid-late Frasnian. The correlation, constrained by magnetic polarity reversals and physical ground truthing, is based on recognition of distinctive cyclical "stacking patterns" defined by changes in concentrations of the trace element zirconium (Zr). Zr concentrations are controlled by the amount of the heavy mineral zircon in the sediments, which is derived from a terrigenous source and is diagenetically very stable. The stacking patterns in the lower part of the study sections display gradually upward-increasing values of Zr to a maximum, followed by an almost immediate fall to a minimum. In the upper part of the study interval, the cycles are more symmetrical, with both gradually increasing and decreasing portions. The point at which the change in Zr stacking pattern occurs in the two sections is synchronous and occurs in association with a supersequence maximum flooding surface. The correlation based on maximum and minimum Zr values throughout the two sections is demonstrated to be chronostratigraphic by comparison with correlations based upon paleomagnetism and physical ground truthing. When element ratios commonly used as provenance and paleoclimate proxies are plotted, the variations between closely spaced samples are greater than any systematic variations throughout the study intervals. Therefore, no isochemical chemozones can be defined, implying that during deposition of the study intervals, there were no long-lived changes in sediment provenance or paleoclimate that the elemental chemistry can detect. The work presented here shows that the standard approach of defining isochemical chemozones for chemostratigraphic correlation is not always appropriate. However, an approach using cyclical changes in elemental variables for chemostratigraphic correlation between two closely spaced sections is chronostratigraphically valid. The greater challenge is in application of the same approach to more widely spaced sections, potentially in different facies of a carbonate setting.

Additional Information

© 2016 SEPM. Published: January 01, 2017. We especially thank the Aboriginal tribes of the Bunaba and Gooniyandi (Kuniandi) people, who allowed us to conduct this research on their sacred lands. Thanks go to Paul Montgomery and Peter Cawood for the integrated chronostratigraphic vision, and to Phil Playford for introduction to the outcrop belt. Funding was supplied by the Australian Research Council Linkage Program (grant LP0883812), ARC-QEII Grant Program, ARC-DORA–3 Grant Program, Minerals Research Institute of Western Australia (MERIWA), Western Australian Energy Research Alliance (WAERA), Commonwealth Scientific and Industrial Research Organization (CSIRO), Buru, Chevron Australian Business Unit, Chevron Energy Technology Company, the University of Greenwich, and Chemostrat, Ltd. Field support and safety were provided by Wundargoodie Aboriginal Safaris (Colin and Maria Morgan and family and crew), the Geological Survey of Western Australia, Chevron Australian Business Unit, and Steve Meyer, Sean O'Connell, and Bill Robinson of Chevron. Thanks go to Windjana Gorge National Park, Napier Downs, the Mimbi Community, Mount Pierre Station, Fossil Downs Station, Brooking Downs Station, the Pillara Mine, and the Cadjebut Mine for field area access and resources. Thanks also go to R. Addenbrooke, H. Allen, A. Duffy, G. Beacher, M. Diamond, M. Ducea, K. Grice, J. Hansma, K. Hillbun, T. Holland, J. Hsieh, D. Katz, J. Klemm, L. Lanci, K. Liebe, E. Maslen, L. McEvoy, F. Pardini, S. Pisarevsky, T. Raub, B. Roelofs, S. Shoepfer, U. Singh, S. Slotznick, S. Tulipani, M. Thorp, K. Trinajstic, T. Tobin, A. Vonk, F. Wellmann, P. Ward, and K. Williford for field assistance and project-related contributions beyond the scope of this paper. Roger Hocking and Peter Haines publish with the permission of the executive director of the Geological Survey of Western Australia. The Chemostrat authors would like to thank Chemostrat for allowing them time to publish this work. The authors are also grateful to the two referees, both of whom made invaluable suggestions that improved the publication.

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