Identification of the Cambrian Series 2 – Miaolingian boundary, western Stansbury Basin, South Australia using multiproxy chronostratigraphy

2024

Birksmith, Courtney

Betts, Marissa J

Holmes, James D

Castle-Jones, Jack

Hall, Philip A

Klaebe, Robert M

Zhang, Zhiliang

Brock, Glenn A

Journal Article

en

Publication

Australasian Palaeontologists

Australia

une:1959.11/70857

The Global Boundary Stratotype Section and Point (GSSP) of the Series 2–Miaolingian Series boundary has been ratified in South China based on the first appearance of the trilobite Oryctocephalus indicus (Reed 1910) coincident with a major negative δ¹³C excursion, the Redlichiid–Olenellid Extinction Carbon isotope Excursion (ROECE). Unfortunately, O. indicus does not occur in Australian–Antarctic Cambrian successions impeding recognition of the Series 2 – Miaolingian boundary in East Gondwana. New multiproxy data integrating δ¹³C and δ¹⁸O chemostratigraphy and shelly fossil biostratigraphy from subsurface cores in the western Stansbury Basin, South Australia, is presented. A sharp -5.3 ‰ δ¹³C peak in the Stansbury Limestone in core Cur D 9 and a -2.7 ‰ δ¹³C peak in the same unit in core Port Julia 1A are interpreted to be synchronous and represent the global ROECE event and the Series 2 – Miaolingian boundary in this basin. Mirroring the GSSP, the last occurrence of Redlichia sp. occurs below the ROECE level and the range of the guide taxon Pagetia straddles the interpreted ROECE event. The biostratigraphic utility of the scalidophoran ecdysozoans Chalasiocranos exquisitum Brock & Cooper 1993 and Kaimenella sp. aff. K. reticulata Märss 1988 to define a potential new late Stage 4 zone/subzone in South Australia is discussed. A distinctive -2.0 ‰ δ¹³C peak in the Ramsay Limestone captured in two cores in the western Stansbury Basin is correlated with an identical amplitude peak in the middle part of the Wirrealpa Limestone in the Arrowie Basin, just below the last occurrence of archaeocyaths in South Australia. This event in upper Stage 4 may represent the Archaeocyathid Extinction Carbon isotope Excursion (AECE).

link

Australasian Palaeontological Memoirs, v.57, p. 21-47

2205-8877

21

47