Timing of mammal-like reptile extinctions across the Permian-Triassic boundary in South Africa

MacLeod, Kenneth G.; Smith, Roger M. H.; Koch, Paul L.; Ward, Peter D.

doi:10.1130/0091-7613(2000)028<0227:tomlre>2.3.co;2

Cited by 45 publications

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“…This paleontological placement of the extinction at Lootsberg Pass is unlikely to be wrong, due to the long history of vertebrate fossil collecting in this area. It is also a possibility that there initially was an additional reverse polarity interval present in the Permian-Triassic boundary interval in the southern main Karoo Basin, but the reported overlap (Smith, 1995;MacLeod et al, 2000;Ward et al, 2000) between the occurrences of Dicynodon and Lystrosaurus during the latest Permian argues for continuous sedimentation across this boundary interval. It follows that for the global marine extinction to take place during an interval of reverse polarity it may either precede (placed within the R1 reverse interval) or follow (placed in the R2 reverse interval) the terrestrial extinction as observed in the main Karoo Basin.…”

Section: Discussionmentioning

confidence: 99%

“…Within the Karoo Basin the commencement of noisy isotopic signatures roughly corresponds to the interval of overlap between the Lystrosaurus and the Dicynodon assemblage zones (MacLeod et al, 2000). The limitations of their (MacLeod et al, 2000) data set should, however, be kept in mind, most important of which is possibly the sporadic stratigraphic occurrence of carbonate concretions (especially within green mudstone). From marine successions it is clear that the marine extinction event and as such the PT boundary senso stricto coincides with a large negative anomaly in carbon isotopic values and as such occurs during a time of a noisy isotopic signature as well as within a period of reverse magnetic polarity.…”

Section: Discussionmentioning

confidence: 99%

“…5). Within the Karoo Basin the commencement of noisy isotopic signatures roughly corresponds to the interval of overlap between the Lystrosaurus and the Dicynodon assemblage zones (MacLeod et al, 2000). The limitations of their (MacLeod et al, 2000) data set should, however, be kept in mind, most important of which is possibly the sporadic stratigraphic occurrence of carbonate concretions (especially within green mudstone).…”

Section: Discussionmentioning

confidence: 99%

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Paleomagnetic Constraints on the Permian-Triassic Boundary in Terrestrial Strata of the Karoo Supergroup, South Africa: Implications for Causes of the End-Permian Extinction Event

Kock¹,

Kirschvink

2004

Gondwana Research

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The closure of the Palaeozoic witnessed the greatest biotic crisis in earth history. Surprisingly little is known about the effects and timing of the terrestrial counterpart of the well-described End-Permian mass extinction from known marine successions worldwide. In the present study, reliable paleomagnetic results were obtained from a PT boundary section in the terrestrial Karoo Basin of South Africa. Permo-Triassic aged mudstones from a locality in the Eastern Cape Province yielded two magnetic chrons, reverse followed by normal (with the boundary possibly close to the reversal). This extends to results from a previous study: thereby jointly identifying a R/N/R polarity pattern for this boundary interval. The PTB interval is constrained below the red mudstones of the Beaufort Group at the present locality and within reverse-magnetised green mudstone, implying a diachronic relation between the marine and terrestrial End-Permian mass extinction events.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Paleomagnetic Constraints on the Permian-Triassic Boundary in Terrestrial Strata of the Karoo Supergroup, South Africa: Implications for Causes of the End-Permian Extinction Event

Kock¹,

Kirschvink

2004

Gondwana Research

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“…9; Kohut, Muehlenbacks & Dudas, 1995). In addition, Upper Permian-Lower Triassic palaeosols record dramatic fluctuations in both the δ 18 O and δ 13 C values of precipitated carbonate (MacLeod et al 2000;Ward et al 2005;Coney et al 2007), reflecting isotopic changes in the atmosphere (Retallack et al 2006). Given that the South Urals dataset comprises palaeosol nodules from 156 different stratigraphic horizons through the Permian-Triassic interval, the ranges of the calcite and dolomite fields would be expected to be far greater than in the modern and overlapping fields.…”

Section: C Pedogenic Originmentioning

confidence: 99%

“…Palaeosol nodules with an unusual mineralogy have been recorded at, or very close to, the latest Permian mass extinction horizon in Antarctica, reflecting the specific atmospheric and climatic conditions associated with the biotic crisis (Sheldon & Retallack, 2002). Palaeosol morphology and composition vary across the Permian-Triassic boundary, which may be a response to changes in climate and atmosphere (Retallack & Krull, 1999;Krull & Retallack, 2000;Macleod et al 2000;Ward et al 2005;Tabor et al 2007;de la Horra et al 2008;Gastaldo & Rolerson, 2008).…”

Section: Introductionmentioning

confidence: 99%

The origin and significance of pedogenic dolomite from the Upper Permian of the South Urals of Russia

2011

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-Pedogenic carbonate nodules from six sections spanning the continental Permian-Triassic boundary in the South Urals, Russia, were analysed. Morphological, petrographic, SEM and XRD analyses have demonstrated that many of the latest Permian palaeosols are dolomitic. This dolomite forms the microcrystalline (5-16 μm) groundmass of the nodules. Later diagenetic phases, represented by coarser crystalline textures, were identified as calcite. Isotopic analysis of the microcrystalline dolomite has revealed it to be similar in isotopic composition to authigenic dolomite forming today in saline soils in Alberta, Canada. These data indicate that the dolomite found in these nodules is pedogenic, and formed in equilibrium with the atmosphere. Upper Permian pedogenic dolocretes in the studied sections are most frequent in (a) palaeosols that formed on palaeo-highs and (b) in the latest Permian period (Changhsingian), which may indicate that there was an increase in seasonality and evaporation in the South Urals region at this time. The presence of only calcitic palaeosols in the earliest Triassic may reflect a subsequent dramatic change in the basin conditions, possibly relating to the Permian-Triassic mass extinction, which stopped the conditions that are necessary for dolomite formation.

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Calcium and calcium isotope changes during carbon cycle perturbations at the end-Permian

Komar

Zeebe

2016

Paleoceanography

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Negative carbon and calcium isotope excursions, as well as climate shifts, took place during the most severe mass extinction event in Earth's history, the end-Permian (∼252 Ma). Investigating the connection between carbon and calcium cycles during transient carbon cycle perturbation events, such as the end-Permian, may help resolve the intricacies between the coupled calcium-carbon cycles, as well as provide a tool for constraining the causes of mass extinction. Here we identify the deficiencies of a simplified calcium model employed in several previous studies, and we demonstrate the importance of a fully coupled carbon cycle model when investigating the dynamics of carbon and calcium cycling. Simulations with a modified version of the Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir model, which includes a fully coupled carbon-calcium cycle, indicate that increased weathering rates and ocean acidification (potentially caused by Siberian Trap volcanism) are not capable of producing trends observed in the record, as previously claimed. Our model results suggest that combined effects of carbon input via Siberian Trap volcanism (12,000 Pg C), the cessation of biological carbon export, and variable calcium isotope fractionation (due to a change in the seawater carbonate ion concentration) represents a more plausible scenario. This scenario successfully reconciles 13 C and 44 Ca trends observed in the sediment record, as well as the proposed warming of >6 ∘ C.

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Timing of mammal-like reptile extinctions across the Permian-Triassic boundary in South Africa

Cited by 45 publications

References 0 publications

Paleomagnetic Constraints on the Permian-Triassic Boundary in Terrestrial Strata of the Karoo Supergroup, South Africa: Implications for Causes of the End-Permian Extinction Event

Paleomagnetic Constraints on the Permian-Triassic Boundary in Terrestrial Strata of the Karoo Supergroup, South Africa: Implications for Causes of the End-Permian Extinction Event

The origin and significance of pedogenic dolomite from the Upper Permian of the South Urals of Russia

Calcium and calcium isotope changes during carbon cycle perturbations at the end-Permian

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