Late Devonian carbonate magnetostratigraphy from the Oscar and Horse Spring Ranges, Lennard Shelf, Canning Basin, Western Australia

• Published in: Earth and Planetary Science Letters
• Main Authors: Hansma, J., Tohver, E., Yan, M., Trinajstic, Katherine, Roelofs, Brett, Peek, S., Slotznick, S., Kirschvink, J., Playton, T., Haines, P., Hocking, R.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier Science BV 2015
• Subjects: Lennard Shelf; Devonian; biostratigraphy; magnetostratigraphy; Canning Basin; Napier; Geomagnetic Pole
• Online Access: https://hdl.handle.net/20.500.11937/35043; https://doi.org/10.1016/j.epsl.2014.10.054

The Late Devonian was a time of major evolutionary change encompassing the fifth largest mass extinction, the Frasnian–Famennian event. In order to establish a chronological framework for global correlation before, during, and following the Frasnian–Famennian mass extinction, we carried out a coupled magnetostratigraphic and biostratigraphic study of two stratigraphic sections in the Upper Devonian carbonate reef complexes of the Lennard Shelf, in the Canning Basin, Western Australia. Magnetostratigraphy from these rocks provides the first high-resolution definition of the Late Devonian magnetic polarity timescale. A 581-m-reference section and an 82-m overlapping section through the marginal slope facies (Napier Formation) of the Oscar Range as well as a 117-m section at Horse Spring (Virgin Hills Formation) were sampled at decimeter to meter scale for magnetostratigraphy. Conodont biostratigraphy was used to correlate both sections, and link magnetostratigraphic polarity zones to a globally established biostratigraphy. A stable, Characteristic Remanent Magnetization (ChRM) with dual polarities (NE, shallowly upward and SW, shallowly downward) is recovered from ∼60%∼60% of all samples, with magnetite inferred to be the chief magnetic carrier from thermal demagnetization characteristics. These directions define a geomagnetic pole at 49.5°S/285.8°E and α95=2.4α95=2.4 (n=501n=501), placing the Canning Basin at 9.9°S during the Late Devonian, consistent with carbonate reef development at this time.A conservative interpretation of the magnetostratigraphy shows the recovery of multiple reversals from both sections, not including possible cryptochrons and short duration magnetozones. Field tests for primary remanence include positive reversal tests and matching magnetozones from an overlapping section in the Oscar Range. A strong correlation was found between magnetic polarity stratigraphies of the Oscar Range and Horse Spring sections, and we correlate 12 magnetostratigraphic packages. The relative stratigraphic ...