| 1. |
- Betts, Marissa J., et al.
(författare)
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First multi-proxy chronostratigraphy of the lower Cambrian Byrd Group, Transantarctic Mountains and correlation within East Gondwana
- 2024
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Ingår i: Gondwana Research. - : Elsevier. - 1342-937X .- 1878-0571.
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Tidskriftsartikel (refereegranskat)abstract
- Antarctica and Australia were sutured together at the equator during the major pulse of animal biodiversification associated with the Cambrian radiation. However, the lack of detailed systematic chemostratigraphic and biostratigraphic sampling of lower Cambrian sedimentary successions from Antarctica has significantly impeded precise age determination and correlation with Cambrian strata on other palaeocontinents. This study is the first to present integrated, simultaneously sampled biostratigraphic and chemostratigraphic (δ13C isotopes) data from the same measured stratigraphic sections through the lower Cambrian Byrd Group in the Transantarctic Mountains. Shelly fossil assemblages (brachiopods, tommotiids, molluscs, bradoriids, trilobites) from the Holyoake Range and Churchill Mountains facilitate direct correlation with the Dailyatia odyssei Zone of South Australia (Cambrian Stages 3–4), and trilobites provide strong correlation between the Starshot Formation and the Cymbric Vale Formation in western New South Wales. A new ID-TIMS radiometric date of 514.96 ± 0.16 Ma from a tuff in the lower Cymbric Vale Formation is similar to dates from tuff beds in the Third Plain Creek Member of the Mernmerna Formation in the Flinders Ranges, providing an important absolute-age tie point between these lower Cambrian successions. Chemostratigraphic data from the upper Shackleton Limestone in the Holyoake Range capture a negative δ13C excursion that correlates closely with the global Sinsk event. This excursion occurs between positive δ13C values that likely represent lower parts of the MICE (cycles V–VIII in Siberia). Integrated faunal and chemostratigraphic data indicate a Cambrian Stages 3–4 age, giving robust chronostratigraphic context for the upper Shackleton Limestone–Holyoake Formation–Starshot Formation succession for the first time, permitting reconstruction of the depositional history of the lower Cambrian of Antarctica and global correlation of Byrd Group strata.
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| 2. |
- 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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| 3. |
- Claybourn, Thomas M., 1989-, et al.
(författare)
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BRACHIOPODS FROM THE BYRD GROUP (CAMBRIAN SERIES 2, STAGE 4) CENTRAL TRANSANTARCTIC MOUNTAINS, EAST ANTARCTICA: BIOSTRATIGRAPHY, PHYLOGENY AND SYSTEMATICS
- 2020
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Ingår i: Papers in Palaeontology. - : Wiley. - 2056-2799 .- 2056-2802. ; 6:3, s. 349-383
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Tidskriftsartikel (refereegranskat)abstract
- Brachiopods from Cambrian Series 2, Stage 4 carbonate strata of the Byrd Group in the Central Transantarctic Mountains, East Antarctica, are described for the first time. These include six lingulate, one paterinate, and one rhynchonelliform taxa, including the new lingulate brachiopod Plicarmus wildi gen. et sp. nov. The biostratigraphy correlates closely to the brachiopods recently reported from the Xinji Formation (Shuiyu section) in North China, as well as brachiopods recovered from the Dailyatia odyssei Zone across the Arrowie Basin of South Australia. These findings also support the previously identified close palaeobiogeography of these regions. The first unambiguous example of the acrotretid brachiopod Eohadrotreta zhenbaensis Li and Holmer outside South China is also identified in the context of its ontogenetic stages. Well preserved specimens of the acrotheloid Schizopholis yorkensis (Holmer and Ushatinskaya in Gravestock et al.) facilitates a new reconstruction of its musculature and visceral region. This data is synthesised into a new cladistic analysis that resolves Acrotheloidea as a well-supported monophyletic clade and supports previous hypotheses of a morphocline in acrotheloid evolution.
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| 4. |
- Popov, Leonid E., et al.
(författare)
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Himalayan Cambrian brachiopods
- 2015
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Ingår i: Papers in Palaeontology. - : Wiley. - 2056-2799 .- 2056-2802. ; 1:4, s. 345-399
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Tidskriftsartikel (refereegranskat)abstract
- A synoptic analysis of previously published material and new finds reveals that Himalayan Cambrian brachiopods can be referred to 18 genera, of which 17 are considered herein. These contain 20 taxa assigned to species, of which five are new: Eohadrotreta haydeni, Aphelotreta khemangarensis, Hadrotreta timchristiorum, Prototreta? sumnaensis and Amictocracens? brocki. Well-preserved topotype material from the classic Parahio Valley section is described for three species that have not previously been illustrated photographically. A biostratigraphical scheme based on Cambrian brachiopod occurrence is integrated with that recently proposed for trilobites. Regional correlations based on shared taxa within and across Himalayan lithotectonic belts demonstrate that erosion of Cambrian rocks in the Kurgiakh orogeny in the Parahio Valley removed little of the Parahio Formation and that all of the fossil-bearing lithotectonic zones share similar late early Cambrian brachiopods, suggesting regional faunal continuity at the time. Palaeobiogeographical analysis of the Cambrian brachiopod faunas from the Himalaya shows that they occupied a marginal position of the Australasian segment of Gondwana.
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