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- Betts, Marissa J, et al.
(författare)
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Integrated chronostratigraphy of the lower Cambrian Byrd Group, Transantarctic Mountains
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Antarctica and Australia were sutured together straddling the equator during the major pulse of animal biodiversification associated with the Cambrian radiation. However, lack of detailed systematic sampling of lower Cambrian sedimentary packages from Antarctica has significantly impeded precise age determination and correlation with other Cambrian paleocontinents, especially with other parts of East Gondwana. Here were present new, integrated biostratigraphic and chemostratigraphic (δ13C isotopes) data from three stratigraphic sections measured through autochthonous shallow water carbonates (including archaeocyath-microbial bioherms) from the lower Cambrian Byrd Group in the Transantarctic Mountains. Recovered shelly fossil assemblages (brachiopods, tommotiids, molluscs, trilobites) from the Holyoake and Churchill Ranges include conspecific taxa previously described from Hawker Group rocks in the Arrowie Basin of South Australia facilitating direct correlation with the upper Dailyatia odyssei biozone. Synchronous chemostratigraphic data capture a distinctive positive ?13C excursion in the Churchill Range interpreted as the global Mingxinsi Carbon Isotope Excursion (MICE) peak. A succeeding gradual negative ?13C excursion captured in the Churchill and Holyoake sections is interpreted as the global Archaeocyathid Extinction Carbon Isotope Excursion (AECE) event. There is no chemostratigraphic evidence for the large Redlichiid-Olenellid Extinction Carbon Isotope Excursion (ROECE) negative event that straddles and defines the Cambrian Stage 4 – Miaolingian boundary. Hence, the integrated faunal and new chemostratigraphic data presented herein strongly support a Cambrian Stage 4 age for the upper Shackleton Limestone – Holyoake Formation – Starshot Formation succession of the Byrd Group.
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| 2. |
- Claybourn, Thomas M, et al.
(författare)
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Cambrian Series 2, Stage 3–4 micromolluscs from the Shackleton Limestone, Central Transantarctic Mountains, East Antarctica
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- An assemblage of lower Cambrian (Series 2, Stages 3–4) molluscan fossils from the Shackleton Limestone, Transantarctic Mountains, East Antarctica is formally described and illustrated. The assemblage is composed of one bivalve and ten helcionelloid molluscs, including the first discovery of the genus Xinjispira outside North China. The new fauna shows some similarity to previously described micromollusc assemblages from lower Cambrian glacial erratics from the Antarctic Peninsula. The fauna of the Shackleton Limestone is mainly composed of steinkerns, and of relatively low diversity, but the presence of key taxa, including the molluscs Mackinnonia rostrata and Pojetaia runnegari and the tommotiid Dailyatia odyssei strengthens correlation to the newly defined Dailyatia oddysei Zone of South Australia
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