Network‐based biostratigraphy for the late Permian to mid‐Triassic Beaufort Group (Karoo Supergroup) in South Africa enhances biozone applicability and stratigraphic correlation

Abstract

The Permo‐Triassic vertebrate assemblage zones (AZs) of South Africa's Karoo Basin are a standard for local and global correlations. However, temporal, geographical and methodological limitations challenge the AZs reliability. We analyse a unique fossil dataset comprising 1408 occurrences of 115 species grouped into 19 stratigraphic bin intervals from the Cistecephalus, Daptocephalus, Lystrosaurus declivis and Cynognathus AZs. Using network science tools we compare six frameworks: Broom, Rubidge, Viglietti, Member, Formation, and one suggesting diachroneity of the Daptocephalus/Lystrosaurus AZ boundary (Gastaldo). Our results demonstrate that historical frameworks (Broom, Rubidge) still identify the Karoo AZs. No scheme supports the Cistecephalus AZ, and it probably comprises two discrete communities. The Lystrosaurus declivis AZ is traced across all frameworks, despite many shared species with the underlying Daptocephalus AZ, suggesting that the extinction event across this interval is not a statistical artefact. A community shift at the upper Katberg to lower Burgersdorp formations may indicate a depositional hiatus which has important implications for regional correlations, and Mesozoic ecosystem evolution. The Gastaldo model still identifies a Lystrosaurus and Daptocephalus AZ community shift, does not significantly improve recent AZ models (Viglietti), and highlights important issues with some AZ studies. Localized bed‐scale lithostratigraphy (sandstone datums), and singleton fossils cannot be used to reject the patterns shown by hundreds of fossils, and regional chronostratigraphic markers of the Karoo foreland basin. Metre‐level occurrence data suggests that 20–50 m sampling intervals capture Karoo AZs, unifying the use of metre‐level placements of singleton fossils to delineate biozone boundaries and make regional correlations.

Mercury evidence from southern Pangea terrestrial sections for end-Permian global volcanic effects

“…This level represents the upper part of the extinction interval (i.e., third extinction wave) proposed by Smith and Botha-Brink 43 , and it coincided with the nadir of the carbon isotope excursion 47 as well as with the rapid faunal turnover phase of the protracted extinction interval proposed by Viglietti et al 46 . Evidence is mounting that the LPME was not a single bioevent but multiple extinction episodes over an interval of 10 4 –10 5 years in both marine 48 and terrestrial ecosystems 43 , 49 .

Fig.

…”

A natural history of networks: Modeling higher-order interactions in geohistorical data

“…When comparing unipartite, bipartite, and multilayer representations of this benchmark data, the multilayer network achieves the shortest codelength and the best compression (Table 1). 3), arbitrary temporal bins (Pilotto et al 2022), and biostratigraphic frameworks (Viglietti et al 2022). Interlayer dynamics in multilayer networks are often modeled based on the intralayer information (Eriksson et al 2022).…”

“…In addition, we delineate future research directions for current challenges in network paleobiology. We focus on the Map Equation framework and its applications in paleobiology research because it is an increasingly popular alternative to the standard statistical approaches currently used in paleobiology research (Kocsis et al 2021; Rojas et al 2021; Pilotto et al 2022; Viglietti et al 2022). The associated software called Infomap for finding community structure in standard and higher-order networks is also widely used in natural and social sciences (Law et al 2022; Lazaridis et al 2022; Martins et al 2022).…”

“…In the Map Equation framework, multilayer networks can be used to model temporal and non-temporal data. Temporal constraints in real geohistorical systems include ordered geological stages (Rojas et al 2021)(Figure 3), arbitrary temporal bins (Pilotto et al 2022), and biostratigraphic frameworks (Viglietti et al 2022). Interlayer dynamics in multilayer networks are often modeled based on the intralayer information (Eriksson et al 2022).…”

“…In the paleobiology literature, alluvial diagrams have been used primarily to compare alternative partitions obtained from bootstrapping (Rojas et al 2021) and sensitivity analysis (Pilotto et al 2022). Recently, alluvial diagrams have been used to compare solutions representing alternative biostratigraphy models for the late Permian-mid Triassic Beaufort Group in South Africa (Viglietti et al 2022). Because it is impractical and typically unnecessary to represent all individual nodes, an alluvial diagram highlights changes in the most important nodes’ module assignment across partitions.…”