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1. Late Permian soil-forming paleoenvironments on Gondwana: A review

   https://doi.org/10.1016/j.palaeo.2021.110762  

   Gulbranson, Erik L.; Sheldon, Nathan D.; Montañez, Isabel P.; Tabor, Neil J.; McIntosh, Julia A. (January 2022, Palaeogeography, Palaeoclimatology, Palaeoecology)

   Paleosols represent fossil records of paleolandscape processes, paleobiotic interactions with the land surface, and paleoclimate. Paleosol-based reconstructions have figured prominently in the study of significant changes in global climate and terrestrial life, with one of the more highly studied examples being the end-Permian extinction (EPE). The EPE was once thought to consist of synchronous extinctions in the marine realm and the terrestrial realm, with the latter displaying a lower magnitude extinction of vertebrate, insect, and plant life. However, emerging stratigraphic records, anchored by high-precision U–Pb ages, and compilations of fossil taxa indicate that the terrestrial realm on Gondwana experienced an asynchronous extinction record with the marine realm; and, at the global-scale, possibly the lack of a true mass extinction for plant and vertebrate communities. Moreover, paleosol-based interpretations of the EPE on Gondwana typically focus on one depositional basin and extrapolate those finding to assess the potential for global paleoenvironmental/paleoclimatic change. This review compiles observations of paleosols, sedimentology, stratigraphy, and geochemical data across Gondwana during the Late Permian in order to critically assess these interpretations of global change in the lead up to the EPE. 

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2. Coupled stratigraphic and U-Pb zircon age constraints on the late Paleozoic icehouse-to-greenhouse turnover in south-central Gondwana

   https://doi.org/10.1130/G46740.1  

   Griffis, Neil Patrick; Montañez, Isabel Patricia; Mundil, Roland; Richey, Jon; Isbell, John; Fedorchuk, Nick; Linol, Bastien; Iannuzzi, Roberto; Vesely, Fernando; Mottin, Thammy; et al (October 2019, Geology)

   The demise of the Late Paleozoic Ice Age has been hypothesized as diachronous, occurring first in western South America and progressing eastward across Africa and culminating in Australia over an ~60 m.y. period, suggesting tectonic forcing mechanisms that operate on time scales of 106 yr or longer. We test this diachronous deglaciation hypothesis for southwestern and south-central Gondwana with new single crystal U-Pb zircon chemical abrasion thermal ionizing mass spectrometry (CA-TIMS) ages from volcaniclastic deposits in the Paraná (Brazil) and Karoo (South Africa) Basins that span the terminal deglaciation through the early postglacial period. Intrabasinal stratigraphic correlations permitted by the new high-resolution radioisotope ages indicate that deglaciation across the south to southeast Paraná Basin was synchronous, with glaciation constrained to the Carboniferous. Cross-basin correlation reveals two additional glacial-deglacial cycles in the Karoo Basin after the terminal deglaciation in the Paraná Basin. South African glaciations were penecontemporaneous (within U-Pb age uncertainties) with third-order sequence boundaries (i.e., inferred base-level falls) in the Paraná Basin. Synchroneity between early Permian glacial-deglacial events in southwestern to south-central Gondwana and pCO2 fluctuations suggest a primary CO2 control on ice thresholds. The occurrence of renewed glaciation in the Karoo Basin, after terminal deglaciation in the Paraná Basin, reflects the secondary influences of regional paleogeography, topography, and moisture sources. 

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3. Spatiotemporal variability of the late Paleozoic glacial-to-postglacial transition across eastern Paraná Basin, Brazil

   https://doi.org/10.1016/j.sedgeo.2023.106420  

   Mottin, T.E.; Vesely, F.F.; Iannuzzi, R.; Griffis, N.P.; Montañez, I.P. (July 2023, Sedimentary Geology)

   The late Paleozoic glacial-to-postglacial turnover evolved complexly across Gondwana. Successions bearing volcaniclastic material that can be radiometrically dated provide crucial information about the timing of those climate events. The southernmost part of the Paraná Basin, for instance, has a high-precision geochronological framework. The eastern sector of this basin (Paraná State and north of Santa Catarina State), however, lacks radiometric ages, but conversely, has a more complete stratigraphic record, and paleontological information still poorly explored for the purpose of biostratigraphic correlation. This work examines the glacial-to-postglacial interval in the Paraná State, represented by the upper Itararé Group (Taciba Formation; glacial) and lower–middle Rio Bonito Formation (postglacial). Sedimentological, paleontological and geochemical data from outcrops, cores and well logs were used to decipher the timing, paleoclimatic and paleogeographic scenarios of this transition. The examined succession comprises four stacked units (U1 to U4, from older to younger). Diamictite-dominated units (U1 and U3), here interpreted as consecutive glaciation–deglaciation events, are separated by non-glacial, continental to shallow marine deposits, commonly bearing fossil plants and coal seams (U2). An important transgression followed the first deglaciation,which is equivalent to the “Eurydesma transgression”, basedonthepresence of marine invertebrates of the homonymous fauna in the Passinho Shale. U2 holds elements of two different floras, i.e., Phyllotheca–Gangamopteris (P–G), predating the “Eurydesma transgression”, and Glossopteris Brasilodendron (G–B), above the transgression. Therefore, U2 is interpreted as an interglacial interval, once it records a climate improving before the last glacial episode of U3, which is further supported by relatively high values of the Chemical Index of Alteration (CIA). Deposits of U3, associated with a decrease in the value of the CIA, are unconformably overlain by U4. The occurrence of coal-bearing postglacial facies (U4) associated with the G–B Flora, coincides with an increase in the CIA values. Sediment transport was toward the SWin all units and in the same direction it is observed an overall thinning of U1 and U3 and thickening of U2. The interglacial P–G Flora of the study area correlates with postglacial southernmost floras, based on U–Pb CA-TIMS Asselian ages of tonsteins. Correlation of the Eurydesma fauna-containing Passinho Shale with equivalent successions with high-precision age control in southern Africa, allowed us to position both deglaciations of the Taciba Formation (U1 and U3) in the Asselian. These findings suggest that U1 and U3 record two early Permian glacial episodes, with the younger one (U3) disappearing southward. Accordingly, our results indicate that the glacial-to-postglacial turnoverwas diachronous along the eastern belt of the Paraná Basin, being progressively older southward, considering that interglacial fossil plant assemblages in the eastern margin correspond in time to postglacial assemblages farther south. 

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4. High-latitude ice and climate control on sediment supply across SW Gondwana during the late Carboniferous and early Permian

   https://doi.org/10.1130/B35852.1  

   Griffis, N.; Montañez, I.; Mundil, R.; Heron, D. Le; Dietrich, P.; Kettler, C.; Linol, B.; Mottin, T.; Vesely, F.; Iannuzzi, R.; et al (February 2021, GSA Bulletin)

   null (Ed.)

   Abstract The response of sediment routing to climatic changes across icehouse-to-greenhouse turnovers is not well documented in Earth's pre-Cenozoic sedimentary record. Southwest Gondwana hosts one of the thickest and most laterally extensive records of Earth's penultimate icehouse, the late Paleozoic ice age. We present the first high-resolution U-Pb zircon chemical abrasion–isotope dilution–thermal ionization mass spectrometry (CA-ID-TIMS) analysis of late Paleozoic ice age deposits in the Kalahari Basin of southern Africa, which, coupled with existing CA-ID-TIMS zircon records from the Paraná and Karoo Basins, we used to refine the late Paleozoic ice age glacial history of SW Gondwana. Key findings from this work suggest that subglacial evidence in the Kalahari region is restricted to the Carboniferous (older than 300 Ma), with glacially influenced deposits culminating in this region by the earliest Permian (296 Ma). The U-Pb detrital zircon geochronologic records from the Paraná Basin of South America, which was located downstream of the Kalahari Basin in the latest Carboniferous and Permian, indicate that large-scale changes in sediment supplied to the Paraná were contemporaneous with shifts in the SW Gondwana ice record. Gondwanan deglaciation events were associated with the delivery of far-field, African-sourced sediments into the Paraná Basin. In contrast, Gondwanan glacial periods were associated with the restriction of African-sourced sediments into the basin. We interpret the influx of far-field sediments into the Paraná Basin as an expansion of the catchment area for the Paraná Basin during the deglaciation events, which occurred in the latest Carboniferous (300–299 Ma), early Permian (296 Ma), and late early Permian (<284 Ma). The coupled ice and detrital zircon records for this region of Gondwana present opportunities to investigate climate feedbacks associated with changes in freshwater and nutrient delivery to late Paleozoic ocean basins across the turnover from icehouse to greenhouse conditions. 

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5. Origin of paleovalleys on the Rio Grande do Sul Shield (Brazil): Implications for the extent of late Paleozoic glaciation in west-central Gondwana

   Fedorchuk, N.D.; Isbell, J.L.; Griffis, N.P.; Montañez, I.P.; Vesely, F.F.; Iannuzzi, R.; Mundil, R.; Yin, Q.-Z.; Pauls, K.N.; Rosa, E.L.M (April 2018, Palaeogeography, palaeoclimatology, palaeoecology)

   The location, longevity, and geographic extent of late Paleozoic ice centers in west-central Gondwana remain ambiguous. Paleovalleys on the Rio Grande do Sul Shield of southernmost Brazil have previously been interpreted as fjords carved by outlet glaciers that originated in Africa and emptied into the Paraná Basin (Brazil). In this study, the sedimentology, stratigraphy, and provenance of sediments infilling two such paleovalleys (the Mariana Pimentel and Leão paleovalleys) were examined in order to test the hypothesis that an ice center over present day Namibia drained across southernmost Brazil during the Carboniferous and Permian. Contrary to previous findings, the facies assemblage from within the paleovalleys is inconsistent with a fjord setting and no clear evidence for glaciation was observed. The facies show a transition from a non-glacial lacustrine/estuarine environment, to a fluvial-dominated setting, and finally to a restricted marine/estuarine environment. Detrital zircon results present a single population of Neoproterozoic ages (c. 800–550 Ma) from the paleovalley fill that matches the ages of underlying igneous and metamorphic basement (Dom Feliciano Belt) and is incongruent with African sources that contain abundant older (Mesoproterozoic, Paleoproterozoic, and Archean) zircons. Furthermore, results suggest that the formation of the paleovalleys and the deposition of their fill were controlled by the reactivation of Neoproterozoic basement structures during the Carboniferous and Permian. The lack of evidence for glaciation in these paleovalleys highlights the need for detailed studies of supposed late Paleozoic glacial deposits. These results are supportive of the hypothesis that well-established glacial sediments on the Rio Grande do Sul Shield (southern margin of the Paraná Basin) may be the product of a separate lobe extending north across Uruguay, rather than a single, massive ice sheet draining west from Africa. 

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