Early Cambrian chronostratigraphy and geochronology of South Australia

Abstract

The most successful chronostratigraphic correlation methods enlist multiple proxies such as biostratigraphy and chemostratigraphy to constrain the timing of globally important bio- and geo-events. Here we present the first regional, high-resolution shelly fossil biostratigraphy integrated with δ¹³C chemostratigraphy (and corresponding δ¹⁸O data) from the traditional lower Cambrian (Terreneuvian and provisional Cambrian Series 2) of South Australia. The global ZHUCE, SHICE, positive excursions II and III and the CARE are captured in lower Cambrian successions from the Arrowie and Stansbury basins. The South Australian shelly fossil biostratigraphy has a consistent relationship with the δ¹³C results, bolstering interpretation, identification and correlation of the excursions. Positive excursion II straddles the boundary between the Kulparina rostrata and Micrina etheridgei zones, and the CARE straddles the boundary between the M. etheridgei and Dailyatia odyssei zones, peaking in the lower parts of the latter zone. New CA-TIMS zircon dates from the upper Hawker Group and Billy Creek Formation provide geochronologic calibration points for the upper D. odyssei Zone and corresponding chemostratigraphic curve, embedding the lower Cambrian successions from South Australia into a global chronostratigraphic context. This multi-proxy investigation demonstrates the power of integrated methods for developing regional biostratigraphic schemes and facilitating robust global correlation of lower Cambrian successions from South Australia (part of East Gondwana) with coeval terranes on other Cambrian palaeocontinents, including South and North China, Siberia, Laurentia, Avalonia and West Gondwana.