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  13 C chemostratigraphy (and corresponding  18 O data) from the lower Cambrian 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 δ 13 C 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 3 CA-TIMS zircon dates from the upper Hawker Group and Billy Creek Formation provide 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 multi-proxy methods for global correlation of regional biostratigraphic schemes, facilitating robust global correlation of lower Cambrian successions from South Australia with coeval terranes on other Cambrian palaeocontinents, including South and North China, Siberia, Laurentia, Avalonia and West Gondwana.

Brachiopods from the Byrd Group (Cambrian Series 2, Stage 4) Central Transantarctic Mountains, East Antarctica: biostratigraphy, phylogeny and systematics

“…, ) has been closely integrated with detailed chemostratigraphy (from the same fossil‐bearing horizons) to develop a robust chronostratigraphic framework for the lower Cambrian successions in South and central Australia (Betts et al . ). This new framework provides a more secure and reliable means of regional, provincial and intercontinental correlation.…”

A comprehensive Cambrian correlation chart

“…Yet, it appears that their true stratigraphic position is still not generally accepted. In addition, the correlation of the oldest/lowest Parabadiella huoi assemblage (concerning the incorrectly assumed synonymy of Parabadiella with Abadiella see Geyer, in press) from the platform facies belt of South China with a fauna in South Australia, from which the same trilobite species is identified, led to an erroneously much too early estimation of the age of the oldest trilobites in Australia as well (e.g., Betts et al, 2018;Paterson et al, 2019). A similarly incorrect assessment affects the age of the Schmidtiellus mickwitzi Zone in Baltica, which is triggered by its cooccurrence with the Skiagia ornata-Fimbriaglomerella membranacea acritarch assemblage (Moczydlowska, 1998;Schoenemann et al, 2017).…”

(Re)proposal of three Cambrian Subsystems and their Geochronology

“…The latter approach that uses informal Cambrian divisions is widespread and includes studies on all of the Cambrian paleocontinents. These include West and East Gondwana (e.g., Compston et al, 2008;Álvaro et al, 2014;Betts et al, 2016Betts et al, , 2018, Laurentia (e.g., Knight et al, 2017), Baltica (e.g., Nielsen and Schovsbo, 2011), Avalonia (e.g., Landing, 1996;Fletcher, 2006), the South China Platform (e.g., Dong and Zhang, 2017), Siberian Platform (Kouchinsky et al, 2008;Zhuravlev et al, 2015;Zhuravlev and Wood, 2018), and also in global summaries (e.g., He et al, 2019).…”