A new Late Triassic age for the Puesto Viejo Group (San Rafael depocenter, Argentina): SHRIMP U–Pb zircon dating and biostratigraphic correlations across southern Gondwana

Ottone, Eduardo G.; Monti, Mariana; Marsicano, Claudia Alicia; Fuente, Marcelo S. de la; Naipauer, Maximiliano; Armstrong, Richard; Mancuso, Adriana Cecilia

doi:10.1016/j.jsames.2014.08.008

Cited by 103 publications

(71 citation statements)

References 44 publications

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“…Our proposed explanation brings together data considered thus far puzzling and contradictory, and is compatible with recent observations in other long-lived arc to postorogenic systems that show protracted zircon recycling (Pereira et al 2014). Our observations support recent evidence from South America that the absolute ages assigned to Gondwanan biozones may be erroneously old (Ottone et al 2014). Our new data are in agreement with all recently published ages (Fildani et al 2007(Fildani et al , 2009Lanci et al 2013;Rubidge et al 2013) and demonstrate the importance of considering the magmatic history of a volcanic source when interpreting U-Pb zircon datasets from tuffs to estimate maximum depositional ages.…”

Section: Discussionsupporting

confidence: 90%

“…While this age range could be due to mixing of different age domains within individual zircon grains during analysis, analytical uncertainty, or Pb-loss (Castiñeiras et al 2010), magma system evolution is complex and commonly recycles older zircon into later eruption/emplacement events and some individual plutons have been resolved to be emplaced over a period of >10 Ma (Coleman et al 2004;Miller et al 2007;Schwartz et al 2014). The suspected volcanic sources, the Choiyoi and Puesto Viejo igneous suites, are known to have large populations of recycled zircon (Spalletti et al 2008;Domeier et al 2011;Ottone et al 2014). We therefore interpret this range to represent mixing of the zircon age population based on (1) high MSWD (1.6-17) of the weighted mean for Permian/Permo-Triassic zircon populations (Miller et al 2007;Compston and Gallagher 2012); (2) lack of inherited cores interpreted from catholuminescence images; (3) the reproducibility of ages between several grains (s ≥ 3); (4) concordance of the analyses; and (5) known history of the volcanic system.…”

Section: U-pb Results and Interpretationmentioning

confidence: 99%

“…Two successive magmatic suites in South America, the Permian Choiyoi Group and Triassic Puesto Viejo Group, record the same volcanism responsible for tuffs in the Karoo Supergroup. The Permian Choiyoi Group yields well-defined U-Pb zircon age peaks between 280 and 253 Ma ( Figure 6D-F Spalletti et al 2008; from the Potrerillos Fm, a coeval, stratigraphic equivalent of the Puesto Viejo Group [Ottone et al 2014] Domeier et al (2011) to suggest that these volcanics were dominated by recycled, xenocrystic zircon. These observations were further used to propose that the Puesto Viejo magma chamber was volumetrically too small to generate new zircon grains (Domeier et al 2011).…”

Section: Maximum Depositional Ages From U-pb Zircon Analysesmentioning

confidence: 96%

“…The Triassic Puesto Viejo Group is dominated by recycled Permian (>260 Ma) zircon with few co-eruptive zircons (Spalletti et al 2008;Domeier et al 2011), interpreted to be due to assimilation of Permian country rocks during Triassic magmatic assent (Domeier et al 2011). Weighted mean U-Pb ages for the Puesto Viejo Group range from~260 Ma tõ 230 Ma (Spalletti et al 2008;Domeier et al 2011;Ottone et al 2014), even though it is generally accepted that Puesto Viejo magmatism occurred between 241 and 230 Ma (Kleiman and Japas 2009;Domeier et al 2011).…”

Section: Geologic Backgroundmentioning

confidence: 99%

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U-PB zircon tuff geochronology from the Karoo Basin, South Africa: implications of zircon recycling on stratigraphic age controls

McKay

Weislogel

Fildani³

et al. 2015

International Geology Review

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Along the >650 km long southern margin of the Karoo Basin in South Africa, we traversed four evenly spaced stratigraphic transects and collected 22 samples of volcanic, air-fall tuffs thought to be distal deposits derived from the Permian-Triassic Southern Gondwanan volcanic arc. We present 469 new U-Pb zircon ages determined by sensitive high-resolution ion microprobe reverse geometry (SHRIMP-RG) at the Stanford-USGS Microanalytical Center in order to constrain the maximum depositional ages for the southern Karoo Basin strata. Weighted means of these youngest coherent zircon populations were selected to maximize the number of analyses while minimizing the mean square weighted deviation (MSWD) to increase the robustness and decrease the influence of Pb-loss and inheritance in determining the maximum depositional age. Maximum depositional ages for the marine Ecca Group range from 250 to 274 Ma, whereas in the conformably overlying terrestrial Beaufort Group maximum depositional ages ranged from 257 to 452 Ma. Across the southern Karoo Basin, the Ecca Group tuffs produce maximum depositional ages that young upward; however, the Beaufort Group tuffs yield maximum depositional ages that are geochronologically out of sequence. Furthermore, maximum depositional ages of the Beaufort Group tuffs are consistently older than ash ages within the underlying marine strata. Our results are supported by previously published U-Pb tuff zircon geochronology in the Karoo Basin and demonstrate that the presence of out-of-sequence, older tuff ages are repeatable in Beaufort Group tuffs along the southern margin of the basin. We propose that tuffs in the Karoo Basin are correlative with tuffs in southern South America, and that the age spectra of these tuffs were influenced by magmatic crustal recycling. We use these data to highlight the complexity of U-Pb zircon datasets from tuffs, address the use of U-Pb zircon ages to provide absolute age controls, and discuss the implications of these new age controls on the Permian-Triassic Karoo strata.

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Section: Discussionsupporting

confidence: 90%

Section: U-pb Results and Interpretationmentioning

confidence: 99%

Section: Maximum Depositional Ages From U-pb Zircon Analysesmentioning

confidence: 96%

Section: Geologic Backgroundmentioning

confidence: 99%

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U-PB zircon tuff geochronology from the Karoo Basin, South Africa: implications of zircon recycling on stratigraphic age controls

McKay

Weislogel

Fildani³

et al. 2015

International Geology Review

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“…Cynognathus crateronotus and Diademodon tetragonus have been widely-utilized in biostratigraphic correlations, since they achieved a broad Gondwanan distribution (Argentina, South Africa, Namibia, Zambia, Antarctica) during the Triassic and are relatively abundant in the fossil record [8, 10, 109, 110, 112]. Based upon the new radiometric dating from San Rafael Group and the traditionally older inferred age of the Cynognathus AZ of the Karoo (although see [113]), Ottone et al [106] suggested two possible scenarios: (a) that the classical Cynognathus AZ of South Africa is much younger than previously thought or (b) that the biochron of Cynognathus and Diademodon is longer than previously thought, and thus their records in Argentina reflect the persistence of this fauna for nearly 20 million years. Both of these scenarios are highly problematic for Triassic faunal correlation (Fig 19).…”

Section: Discussionmentioning

confidence: 99%

The African cynodont Aleodon (Cynodontia, Probainognathia) in the Triassic of southern Brazil and its biostratigraphic significance

et al. 2017

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In this contribution we report the first occurrence of the enigmatic African probainognathian genus Aleodon in the Middle-early Late Triassic of several localities from the state of Rio Grande do Sul in southern Brazil. Aleodon is unusual among early probainognathians in having transversely-expanded postcanine teeth, similar to those of gomphodont cynognathians. This genus was previously known from the Manda Beds of Tanzania and the upper Omingonde Formation of Namibia. The Brazilian record of this genus is based upon multiple specimens representing different ontogenetic stages, including three that were previously referred to the sectorial-toothed probainognathian Chiniquodon theotonicus. We propose a new species of Aleodon (A. cromptoni sp. nov.) based on the specimens from Brazil. Additionally, we tentatively refer one specimen from the upper Omingonde Formation of Namibia to this new taxon, strengthening biostratigraphic correlations between these strata. Inclusion of A. cromptoni in a phylogenetic analysis of eucynodonts recovers it as the sister-taxon of A. brachyrhamphus within the family Chiniquodontidae. The discovery of numerous specimens of Aleodon among the supposedly monospecific Chiniquodon samples of Brazil raises concerns about chiniquodontid alpha taxonomy, particularly given the extremely broad geographic distribution of Chiniquodon. The discovery of Brazilian Aleodon and new records of the traversodontid Luangwa supports the hypothesis that at least two subzones can be recognized in the Dinodontosaurus Assemblage Zone.

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Skull anatomy and paleoneurology of a new traversodontid from the Middle‐Late Triassic of Brazil

Kerber,

Roese‐Miron,

Medina

et al. 2024

The Anatomical Record

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Traversodontidae, a clade of gomphodont cynodonts, thrived during the Middle and Late Triassic, displaying a wide geographical distribution. During fieldwork in 2009, a new specimen was discovered in Ladinian/early Carnian stratigraphic layers in southern Brazil. Here, we describe this specimen and propose a new taxon closely related to Traversodon stahleckeri (Traversodontinae) but displaying a unique combination of traits (e.g., presence of a poorly developed suborbital process, mesiodistal length of the paracanine fossa similar to the length of the canine, short diastema between the fourth incisor and the upper canine, and coronoid process not entirely covering the distalmost lower postcanine). Furthermore, the endocranial anatomy of the new taxon was examined. The reconstruction of the cranial endocast revealed paleoneurological features consistent with non‐Gomphodontosuchinae traversodontids. These features include the presence of a pineal body (but the absence of an open parietal foramen). These recent findings contribute significantly to our understanding of the evolutionary history and cranial anatomy of Middle‐Late Triassic traversodontids, shedding light on the diversity and adaptations of non‐mammaliaform cynodonts.

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A new Late Triassic age for the Puesto Viejo Group (San Rafael depocenter, Argentina): SHRIMP U–Pb zircon dating and biostratigraphic correlations across southern Gondwana

Cited by 103 publications

References 44 publications

U-PB zircon tuff geochronology from the Karoo Basin, South Africa: implications of zircon recycling on stratigraphic age controls

U-PB zircon tuff geochronology from the Karoo Basin, South Africa: implications of zircon recycling on stratigraphic age controls

The African cynodont Aleodon (Cynodontia, Probainognathia) in the Triassic of southern Brazil and its biostratigraphic significance

Skull anatomy and paleoneurology of a new traversodontid from the Middle‐Late Triassic of Brazil

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