Integrated biostratigraphy, chemostratigraphy and geochronology of the lower Cambrian succession in the western Stansbury Basin, South Australia

Integration of multiproxy time-series data including biostratigraphy, chemostratigraphy and geochronology is presented for lower Cambrian sedimentary packages in the western Stansbury Basin, South Australia. Systematic sampling of shelly fossils and δ¹³C and δ¹⁸O stable isotope values from the same stratigraphic layers in the Kulpara Formation and overlying Parara Limestone (including Koolywurtie Limestone Member) intersected by the Minlaton 1 and SYC 101 drill cores are supplemented by sampling from the ‘classic’ locality at Horse Gully, Yorke Peninsula. The <i>Kulparina rostrata</i>, <i>Micrina etheridgei</i> and <i>Dailyatia odyssei</i> shelly fossil zones along with the partially overlapping <i>Parabadiella huoi</i> and <i>Pararaia bunyerooensis</i> trilobite zones are identified and correlated. The positive δ¹³C Cambrian Arthropod Radiation Excursion (CARE) is reinterpreted to occur in the upper Kulpara Formation within the <i>Kulparina rostrata</i> Zone (at Horse Gully) below the lowest occurrence of trilobites of the <i>Parabadiella huoi</i> Zone, which contains a CA-TIMS dated tuff in SYC 101 of 517.53 ± 0.20 Ma providing, for the first time, an absolute calibration point for the oldest trilobite biozone in Australia. A second positive δ¹³C excursion in the Parara Limestone (lower <i>D. odyssei</i> Zone) represents the lower peak of the Mingxinsi Carbon Isotope Excursion (MICE). In SYC 101, this excursion is sandwiched between the 517.53 ± 0.20 Ma tuff and a 515.22 ± 0.19 Ma dated tuff occurring in the lower <i>P. bunyerooensis</i> Zone, aligning closely with previous CA-TIMS U–Pb dates in the <i>P. bunyerooensis</i> Zone in the Arrowie Basin. The onset of archaeocyath-microbialite bioherm development (<i>Syringocnema favus</i> archaeocyath Zone) in the Koolywurtie Limestone Member can be precisely calibrated based on its occurrence immediately above a 514.78 ± 0.22 Ma CA-TIMS U–Pb dated tuff layer in SYC 101. This multiproxy integration of faunal, isotopic and radiometric data creates a new chronostratigraphic scheme for the western Stansbury Basin and provides important new calibration points for the early Cambrian time-scale. The previously defined <i>Kulparina rostrata</i>, <i>Micrina etheridgei</i> and <i>Dailyatia odyssei</i> shelly fossil Zones are formally identified and recognised for the first time in the western Stansbury Basin. Three new CA-TIMS U–Pb absolute ages from zircon grains within tuff beds in the Parara Limestone are reported: 514.78 ± 0.22 Ma, 515.22 ± 0.19 and the oldest reported South Australian Cambrian date of 517.53 ± 0.20 Ma. Two positive δ¹³C excursions are identified in the western Stansbury Basin—the Cambrian Arthropod Radiation Excursion (CARE) in the upper Kulpara Formation and the lower peak of the Mingxinsi Carbon Isotope Excursion (MICE) in the Parara Limestone. Detailed chronostratigraphic data reported herein reveal the western Stansbury Basin overlaps with the youngest part of the Normanville Group succession in the eastern Stansbury Basin.