Chemostratigraphy and palaeo-environmental characterisation of the Cambrian stratigraphy in the Amadeus Basin, Australia

The sedimentary succession of the central Australian Amadeus Basin consists of Neoproterozoic to Carboniferous sedimentary rocks and contains shallow marine, subtidal carbonates of Middle to Late (Series 2 to Furongian) Cambrian age. A combination of sequence stratigraphy, geochemistry and mineralogy shows a transgressive 2nd order cyclicity deposited between ~ 511-490 Ma and a change from arid, low energy to humid, high energy depositional environments. This is reflected in an initially evaporitic sequence with upward decreasing halite and anhydrite abundance and transition from oxygenated to anoxic conditions, reflected by the Fe mineral species change from hematite to pyrite during transgression. Sequence boundaries of several 3rd order cycles consisting of HST carbonate rocks and LST siltstones, correlate with globally recognised sequence boundaries linked to the inferred eustatic sea level record for the upper two series of the Cambrian System. The carbon isotope record for this ~ 1400 m thick succession in combination with biostratigraphic age correlation allowed the identification of the globally recognised Steptoean Positive Carbon Isotope Excursion (SPICE), Drumian Carbon Isotope Excursion (DICE) and Redlichiid-Olenellid Extinction Carbon Isotope Excursion (ROECE).