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| Locality map and stratigraphic column of the Ediacaran-Early Cambrian Corumbá Group: composite section compiled from logs in the CorumbáLadário region, Mato Grosso do Sul State, Brazil. a,b, Locality map (a) and stratigraphic column (b). Dates are derived from this study. White stars indicate localities from which samples for geochronology were obtained. Black stars indicate ichnofossil localities described in this study: Laginha Mine (Guaicurus Formation) 19° 07′ 09.8′ ′ S, 057° 38′ 40.4′ ′ W; Ladário (Tamengo Formation) 19° 0′ 04.0′ ′ S, 57° 36′ 00.7′ ′ W. Carbon isotope stratigraphy comes from the Laginha Mine section 52. Age uncertainties are expressed as MSWD.
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The evolutionary events during the Ediacaran–Cambrian transition (~541 Myr ago) are unparalleled in Earth history. The fossil record suggests that most extant animal phyla appeared in a geologically brief interval, with the oldest unequivocal bilaterian body fossils found in the Early Cambrian. Molecular clocks and biomarkers provide independent es...
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... we report a new assemblage of meiofaunal ichnofossils from siltstones of the Ediacaran-Cambrian Tamengo and Guaicurus for- mations, Corumbá Group, central western Brazil (Fig. 1). The age of the assemblage is constrained by U-Pb (zircon) isotope dilution ther- mal ionization mass spectrometry (ID-TIMS) dating of inter-stratified ash beds. The dates indicate that the Tamengo Formation specimens are late Ediacaran in age, and those in the Guaicurus Formation lie close to the Ediacaran-Cambrian boundary. Our ...
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... Corumbá Group, part of the Southern Paraguay Belt, is a ~600-m-thick sedimentary unit comprising carbonate and silici- clastic facies deposited on a stable continental margin following a late Neoproterozoic rift event 30,31 (Fig. 1). The lowermost units of the Corumbá Group are the terrigenous Cadieus and Cerradinho formations, which are probably contemporaneous with the Puga Formation of the Amazon Craton 30 (and thus possibly Marinoan- equivalent). Stromatolitic dolostones and phosphorites of the Bocaina Formation lie above those siliciclastic units. The lower ...
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... Craton 30 (and thus possibly Marinoan- equivalent). Stromatolitic dolostones and phosphorites of the Bocaina Formation lie above those siliciclastic units. The lower Corumbá Group is unconformably overlain by the fossiliferous dark organic-rich marls and limestones of the Tamengo Formation, and laminated siltstones of the Guaicurus Formation 31 (Fig. 1). A breccia horizon marks the base of the Tamengo Formation in several sec- tions, and is concordantly overlain by interbedded mudstones and grainstones deposited in a shallow platform setting. The laminated calcareous siltstones of the Guaicurus Formation indicate deposi- tion in a setting with low hydrodynamic energy, probably below ...
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... energy, probably below fair-weather wave base. The sedimentary succession has previously yielded macroscopic body fossils including the scyphozoan-like Corumbella werneri and Paraconularia 4 , along with Cloudina lucia- noi, in the upper Tamengo Formation, and possible vendotaenid algae (Eoholynia) in the lowermost Guaicurus Formation 31 (Fig. ...
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... geochronology. Three volcanic tuff horizons were sampled within the Corumbá Group ( Fig. 1) and zircons from these tuffs were dated using U-Pb chemical abrasion ID-TIMS (CA-ID-TIMS) methods (see Methods for full methodology). An ash bed from the top of the Bocaina Formation (from Porto Morrinhos; Fig. 1) yielded a weighted mean 206 Pb/ 238 U date of 555.18 ± 0.30/0.34/0.70 Ma (mean square weighted deviation (MSWD) = 1.6, n = ...
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... geochronology. Three volcanic tuff horizons were sampled within the Corumbá Group ( Fig. 1) and zircons from these tuffs were dated using U-Pb chemical abrasion ID-TIMS (CA-ID-TIMS) methods (see Methods for full methodology). An ash bed from the top of the Bocaina Formation (from Porto Morrinhos; Fig. 1) yielded a weighted mean 206 Pb/ 238 U date of 555.18 ± 0.30/0.34/0.70 Ma (mean square weighted deviation (MSWD) = 1.6, n = 8 out of 8) (Supplementary Fig. 6; Supplementary Tables 3 and 4), which we consider to approximate the age of the sample. This date provides a maximum age for the overlying Tamengo Formation. Two fur- ther ash ...
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... fossils of the Guaicurus and Tamengo formations. Three- dimensionally mineralized fossils were collected from approxi- mately 30-40 m above the base of the Tamengo Formation at two levels in the Ladário section ( Fig. 1), and from a single horizon and loose material ~7 m above the base of the Guaicurus Formation from the Laginha Mine section (Fig. 1). The latter horizon is < 542.0 Ma in age based on the U-Pb CA-ID-TIMS data presented ...
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... fossils of the Guaicurus and Tamengo formations. Three- dimensionally mineralized fossils were collected from approxi- mately 30-40 m above the base of the Tamengo Formation at two levels in the Ladário section ( Fig. 1), and from a single horizon and loose material ~7 m above the base of the Guaicurus Formation from the Laginha Mine section (Fig. 1). The latter horizon is < 542.0 Ma in age based on the U-Pb CA-ID-TIMS data presented ...
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... Supplementary Fig. 1). The presence of calcite and framboids throughout the infill suggests that the framboids and calcite formed at a similar time. ...
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... zons in finely laminated sediments rather than crossing multiple horizons. Some Ediacaran body fossils, such as the simple conical Conotubus, can grow through sedimentary laminae if felled 34 . In contrast, the branching ichnofossils of the Guaicurus Formation are ~0.5 mm wide and cross up to ~7 mm of stratigraphic thickness. The contemporaneous (Fig. 1) vendotaenid alga Eoholynia corum- bensis is superficially similar in size and morphology to the ichno- fossils described herein 31 . Two factors make algal origins for the fossils we describe unlikely: mode of preservation, and morphology. First, in contrast to these authigenically mineralized trace fossils, Eoholynia specimens in the ...
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... Finally, depositional ages for the Bocaina Fm are loosely constrained by its lower erosive contact with Early Ediacaran cap carbonates of the Cerradinho Fm (cf. Hippertt et al., 2023) and its upper age limit dated at 555 ± 0.3 Ma (Parry et al., 2017) (See details below). Therefore, depositional ages for the unit are bracketed between the early-mid Ediacaran and the mid-upper Ediacaran (>555 Ma). ...
... Depositional ages for the upper phosphatic interval are constrained at 555 0.3 Ma as the interval has been associated via lithostratigraphy and sequence stratigraphy (Hippertt et al., 2023) with the Porto Morrinhos section, which presents a U-Pb TIMS depositional age of 555 0.3 Ma (Parry et al., 2017). Unfortunately, the Lower phosphatic interval has poorly constrained depositional ages bracketed between the early/ mid Ediacaran basal age limits of the unit and the Mid-Ediacaran (555 0.3 Ma) depositional ages of the upper phosphatic interval (Fig. 3). ...
... However, the later interpretation has to be taken cautiously, as the lack of precise geochronological constraints in lower Bocaina Fm strata limits the assertiveness of those biostratigraphic correlations. Alternatively, considering the upper-mid Ediacaran ages reported for both Khesen and Bocaina Fms (Parry et al., 2017;Anderson et al., 2017Anderson et al., , 2019, the lower DPK taxonomic diversity observed in those units may be related to the well known late-Ediacaran decline in DPK diversity, as observed in acritarch assemblages in South China (Ye et al., 2023;Zhang et al., 2023;) and elsewhere (Huntley et al., 2006;Cohen & Macdonald, 2015). ...
The Neoproterozoic phosphogenic event records biotic and biogeochemical changes that seem to indicate intrinsic relationships between phosphogenesis and phosphatic fossil preservation. However, chemo-litho and biostratigraphic correlations conducted on fossiliferous, phosphatic successions of the Doushantuo Formation, South China, evidence a highly heterogeneous record, featuring diachronic depositional ages, variable taxonomic diversity and inconsistent, "noisy" δ 13 C records. Similar detailed chemo-litho and biostratigraphic correlations targeted in high-grade phosphorite strata have not been performed along Ediacaran units elsewhere. Considering the significance and scarcity of Ediacaran high-grade phosphorite strata, establishing a comprehensive correlation framework within and between those units is fundamental to understanding Ediacaran biogeochemical and biotic evolution. This work aims to integrate new δ 13 C isotope stratigraphy, and existing Doushantuo-Pertatataka acritarch assemblages and geochronological records from Bocaina (Brazil), Khesen (Mongolia) and Doushantuo (China) Formations. Phosphate rich strata in those units feature inconsistent δ 13 C signatures characterized by negative values showing large bed-to-bed variations, possibly reflecting local modification of original marine signals by phosphogenesis, suggesting caution against the use in global/regional chemostrati-graphic correlation. The record of phosphatized acritarch assemblages shows contrastive taxonomic diversities, and a small number of common taxa including Megasphaera. Whereas the presence of biozonal Doushantuo Formation taxa on Khsesen Fm, resonates with growing views of strong environmental resilience and large temporal ranges of acanthomorph acritarchs throughout the Ediacaran-early Cambrian, the scarcity of similar taxa in the Bocaina Fm may question the reliability of Doushantuo Fm acritarch biozones in other paleogeo-graphic or paleoenvironmental scenarios. Alternatively, the low taxonomic diversity recorded in Bocaina and Khesen Fms may also reflect the effects of the late Ediacaran decline in acritarch diversity. Further, combined evidence of selective paleoenvironmental phosphatization, local geochemical signals, narrow time spans and heterogeneous taxonomic diversity found in phosphatized DPK acanthomorph assemblages indicate the local nature of Ediacaran phosphatic fossil preservation events. Finally, evidence for diachronic preservation between high-grade phosphatic strata and phosphatized microfossils show non-causal relationships between Ediacaran phosphogenesis and phosphatic fossil preservation, highlighting the punctuated, intrinsic local nature of those events.
... Regarding age constraints, the Tamengo Formation is well positioned in the late Ediacaran interval by high-precision U-Pb ages from zircon grains extracted from volcanic ash layers: depositional ages of 542.27 ± 0.38 Ma and 541.85 ± 0.75 Ma were set from volcanic tuffs at the upper part of the unit, whereas the lower age limit is 550 ± 0.3 Ma, obtained from volcanic ashes interbedded in dolostones of the underlying Bocaina Formation (Parry et al., 2017). A rich fossil record is documented within the Tamengo Formation and in accordance with radiometric data, with remarkable occurrences of shell-beds containing the skeletal metazoan Cloudina lucianoi (Gaucher et al., 2003;Adorno et al., 2017), and the scyphozoan cnidarian Corumbella werneri well-preserved within pelitic intercalations (Babcock et al., 2005;Pacheco et al., 2015). ...
... A) Stratigraphy of the southern paraguay belt (afterBoggiani et al., 2010;Freitas et al., 2011). Geochronological ages from U-Pb dating in zircon grains from volcanic ash beds (yellow stars) fromParry et al. (2017) and the maximum depositional age for the Puga Formation provided by U-Pb ages from detrital zircon grains (yellow triangle) from McGee et al. (2018). b) Stratigraphic chart from the Bambuí Group (after Reis et al., 2016). ...
The late Ediacaran record encompasses frequent occurrences of 34 S-enriched pyrites, which can surpass the coexisting sulfate isotope values. Deciphering what controls this marine isotope record is important to understand its biogeochemical implications, especially considering the early metazoan evolution. We present here multiple sulfur isotope compositions from pyrites of two distinct geotectonic settings within the late Ediacaran-early Cambrian West Gondwana, allowing to constraint spatial and temporal distribution of 34 S-enrichments. The Tamengo Formation represents a carbonate-siliciclastic ramp at Gondwana's continental margin, whereas the Bambuí Group records an epeiric sea within the core of this supercon-tinent. Both units display positive d 34 S py excursions matching regressive trends (d 34 S py up to 51 ‰), with a drop in d 34 S py values associated with transgressions. A scenario of sulfate-distillation events throughout regressions is supported by the multiple sulfur isotope data, after transgressive events that episodically recharged sulfate in these environments. However, in the epicontinental Bambuí sea, d 34 S py, D 33 S py and D 36 S py values suggest almost quantitative conversion of the initial sulfate into sulfide at the end of regressive stage, forced by enhanced stratification and inefficient circulation within continental areas. In this case, widespread toxic euxinic conditions were developed in inland seas, accompanied by methanogenesis, which resulted in highly 13 C-enriched DIC due to methanogenic CO 2 , as recorded in the Bambuí Group. In the Tamengo ramp, on the other hand, sulfate levels would have not been completely consumed due to more frequent and efficient mixing with open waters, preventing perturbations in the carbon cycling and representing more favorable conditions to metazoan colonization, considering the abundant metazoan fossil record in this unit. The studied basins illustrate how 1 st-order tectonic cycles may have been the major player over remarkable 34 S-enrichments in pyrite for specific time intervals of the sedimentary record, through supercontinent assembly and expansion of restricted settings more prone to sulfate distillation. Ó
... Here, we present the first iron speciation data, along with novel trace element measurements, total organic carbon (TOC) contents and both inorganic and organic carbon isotopes, of mudstone, marl and carbonate samples of the Corumbá Group (Almeida, 1965) in western Brazil (Figs. 1 and 2). The two uppermost units of this group, the Tamengo and Guaicurus formations, contain fragments of late Ediacaran index biomineralizing fossils such as Cloudina lucianoi (Beurlen and Sommer, 1957) and Corumbella werneri (Hahn et al., 1982) and meiofaunal bilaterian burrows (Parry et al., 2017). All this evidence indicates a complex ecological behavior throughout this section, which spans one of the most important intervals of biological innovation, the Ediacaran/Cambrian transition. ...
... Samples with ichnofossils interpreted as meiofaunal bilaterian burrows were recovered ca. 7 m above the base of the Guaicurus Formation in the Laginha quarry, and elsewhere at the top of the Tamengo Formation (Parry et al., 2017). Synsedimentary structures such as slumps and load structures are interpreted in local places (Fazio et al., 2019), but these have not been related to a possible sedimentary setting such as a slope. ...
... The presence of index fossils such as Cloudina lucianoi and Cloudina carinata (Cortijo et al., 2010) and chemostratigraphic correlations of the C and Sr isotope curves ( 87 Sr/ 86 Sr ratios around 0.7084) assign a terminal Ediacaran age for the Tamengo Formation (Gaucher et al., 2003;Boggiani et al., 2010;Adôrno et al., 2019b). Meiofaunal bilaterian burrows were found in the Guaicurus Formation and in the topmost mudstones interleaved with carbonates of the Tamengo Formation (Parry et al., 2017), indicating that the transition between the two units might span the Ediacaran/Cambrian boundary. This is also supported by organicwalled microfossils (Adôrno et al., 2019a). ...
... The Tagatiya Guazú Formation is essentially a carbonate unit whose fossil content, as well as the geochemical signatures and geochronological data, allow it to be positioned in the Ediacaran-Cambrian transition (Warren et al., , 2017(Warren et al., , 2023. Similarly, the Tamengo Formation corresponds to a mixed siliciclastic-carbonate unit, whose typical skeletal fossil assemblage, geochemical and geochronological data allow positioning it in the terminal Ediacaran Parry et al., 2017;Amorim et al., 2020;Ramos et al., 2022). However, a detailed correlation between their sedimentological, paleontological, and geochemical records is still lacking. ...
... However, a detailed correlation between their sedimentological, paleontological, and geochemical records is still lacking. Recent detailed data have been presented for the Tamengo Spangenberg et al., 2014;Walde et al., 2015;Adorno et al., 2017;Parry et al., 2017;Oliveira et al., 2019;Amorim et al., 2020;Diniz et al., 2021;Fernandes et al., 2022;Ramos et al., 2022) and Tagatiya Guazú formations (Warren et al., , 2017(Warren et al., , 2023, reinforcing the need for a detailed and critical comparison of these successions. Considering this scenario, the goal of this study is to assess and refine the correlation between these units based on new and previously published data, aiming at a better understanding of their coevolution and paleoenvironmental context within the Western Gondwana margin. ...
... The Corumbá Group crops out in western Brazil, covering the rocks of the Rio Apa Block crystalline basement, diamictite of the Puga Formation, or sedimentary successions of the BIF-bearing Jacadigo Group. The upper part of the Corumbá Group is dominated by Ediacaran mixed carbonate-siliciclastic successions comprising, from base to top, Bocaina, Tamengo, and Guaicurus formations (Table and Fig. 1; Boggiani, 1998;Gaucher et al., 2003;Alvarenga et al., 2009;Boggiani et al., 2010;Freitas et al., 2011Freitas et al., , 2021Parry et al., 2017;Amorim et al., 2020). ...
The Tagatiya Guazú (PY) and Tamengo (BR) formations are South-American Ediacaran-Cambrian carbonate units that share striking similarities between their sedimentological, paleontological, and geochemical records. The Tagatiya Guazú Formation is mainly composed of grainstone and abundant microbial facies, bearing a diverse fossil content represented by autochthonous to parautochthonous remains of late Ediacaran tubular skeletal taxa, such as Cloudina, Corumbella, and Namacalathus, in addition to complex trace fossils indicative of the Ediacaran-Cambrian transition. The Tagatiya Guazú Formation is interpreted as deposited in a protected inner ramp setting. The Tamengo Formation is constituted by grainstone, packstone, wackestone, mudstone, marl, shale, and microbialite facies, also containing Cloudina and Corumbella as allochthonous and parautochthonous remains, respectively. The possible recognition of hummocky and swaley cross-stratification in the Brazilian unit, led to the interpretation of deposition in a storm-dominated middle to outer ramp setting in slightly deeper conditions than the Tagatiya Guazu Formation. Both units display the characteristic late Ediacaran Positive Carbon Isotope Plateau (EPIP) detected in terminal Ediacaran successions worldwide, commonly interpreted as a result of an intensely redox-stratified ocean, which is probably responsible for a decreasing δ13C trend from inner to outer ramp settings. The existence of this gradient can be inferred between the Tagatiya Guazú Formation and its lateral correlate, the Camba Jhopo Formation. On the other hand, the Tamengo Formation shows an unexpected opposite pattern (i.e., increasing δ13C values from inner to outer ramp settings). The limited size of the putative hummocky and swaley cross-stratifications, together with the problematic occurrence of parautochthonous skeletal fossils in deep (and probably anoxic) waters and the inverse δ13C isotopic gradient, suggest some inconsistencies in the Tamengo Formation depositional model. The reinterpretation of these deep-water facies as deposited in a shallower setting would solve (or reduce) the isotopic gradient problem and provide a better fit between the Tamengo Formation redox model and the ones interpreted for other units worldwide. Finally, multiple lines of evidence indicate that both the Tagatiya Guazú and Tamengo formations represent coeval successions (with the former being slightly younger) deposited in similar, shallow water depths in carbonate ramps opened to the Clymene Ocean.
... The Nama Group of southern Namibia and northwest South Africa is one of the most important successions for the calibration of terminal Ediacaran to lower Cambrian chronostratigraphy (Figs. 2, S2, S3;Kaufman et al., 1991;Grotzinger et al., 1995;Saylor et al., 1995Saylor et al., , 1998Bowring et al., 2007;Wood et al., 2015;Linnemann et al., 2019;Nelson et al., 2022). Here, mixed carbonate and siliciclastic deposits of the lower Kuibis Subgroup stratigraphically underlie an ash bed dated at 547.36 ± 0.23 Ma (Bowring et al., 2007 et al., 1998;Boggiani et al., 2010;Wood et al., 2015;Parry et al., 2017;Yang et al., 2021;Bowyer et al., 2022). The lowermost Nama Group therefore occupies an interval that may overlap with, or immediately postdate the transition between the White Sea and Nama assemblage biozones, as well as recording the oldest occurrence of animal biomineralization (Figs. 1, S1; Germs, 1972;Yang et al., 2021). ...
We present new stratigraphic and fossil occurrence information from a previously undescribed section of the Nama Group that outcrops in the Namib Desert of southwest Namibia. This section records the oldest confirmed regional occurrence of tubular skeletal metazoan fossils of the Nama assemblage. We also present an updated and revised global age model that shows the current understanding of global biostratigraphic information for the mid-late Ediacaran and lower Cambrian.
... Importantly, recent palaeontological evidence indicates that these sediments are highly fossiliferous, providing diversified acritarchs, including putative metazoan embryos associated with the Doushantuo-Pertatataka biota (Morais et al., 2021). Available depositional ages are constrained by U-Pb TIMS -555 AE 0.3 Ma age obtained from a volcanic ash layer sampled from an outcrop of the Bocaina Formation in Porto Morrinhos section (Parry et al., 2017;see Figs 2 and 4). The Bocaina Formation is overlain by fossiliferous limestones with subordinate shale levels of the Tamengo Formation, which were deposited in a mixed carbonate-siliciclastic ramp setting (Almeida, 1965;Boggiani, 1998;Gaucher et al., 2003;Boggiani et al., 2010;Parry et al., 2017;Amorim et al., 2020), featuring the occurrence of important Ediacaran metazoan fossils Cloudina (Zaine & Fairchild, 1985;Zaine, 1991;Adorno et al., 2017;Becker-Kerber et al., 2017, Corumbella (Gaucher et al., 2003;Pacheco et al., 2015;Amorim et al., 2020) and Paraconularia (Van Iten et al., 2014;Leme et al., 2022). ...
... Available depositional ages are constrained by U-Pb TIMS -555 AE 0.3 Ma age obtained from a volcanic ash layer sampled from an outcrop of the Bocaina Formation in Porto Morrinhos section (Parry et al., 2017;see Figs 2 and 4). The Bocaina Formation is overlain by fossiliferous limestones with subordinate shale levels of the Tamengo Formation, which were deposited in a mixed carbonate-siliciclastic ramp setting (Almeida, 1965;Boggiani, 1998;Gaucher et al., 2003;Boggiani et al., 2010;Parry et al., 2017;Amorim et al., 2020), featuring the occurrence of important Ediacaran metazoan fossils Cloudina (Zaine & Fairchild, 1985;Zaine, 1991;Adorno et al., 2017;Becker-Kerber et al., 2017, Corumbella (Gaucher et al., 2003;Pacheco et al., 2015;Amorim et al., 2020) and Paraconularia (Van Iten et al., 2014;Leme et al., 2022). Terminal Ediacaran depositional ages are confirmed by a 543 AE 2 Ma U-Pb SHRIMP dating age (Babinski et al., 2008) and by 541.85 AE 0.75 Ma and 542.27 ...
... Terminal Ediacaran depositional ages are confirmed by a 543 AE 2 Ma U-Pb SHRIMP dating age (Babinski et al., 2008) and by 541.85 AE 0.75 Ma and 542.27 AE 0.38 Ma (Parry et al., 2017), obtained in interbedded volcanic ash layers of upper Tamengo. The contact between these units is marked by a regional erosional surface, commonly associated with the occurrence of an overlying polymictic breccia level (Boggiani, 1998;Trompette et al., 1998;Gaucher et al., 2003;Boggiani et al., 2010;Fernandes et al., 2022), separating platform deposits of the Bocaina and Tamengo formations (Trompette et al., 1998;D'el-Rey et al., 2016;Fernandes et al., 2022 -Fig. ...
Extensive phosphorite deposition is observed in the Neoproterozoic after a prolonged hiatus during most of the Mesoproterozoic era. This event is thought to represent an important record of major palaeoenvironmental, palaeoceanographic and biotic changes that shaped Neoproterozoic ecosystems, suggesting close relationships between phosphogenesis and the preservation of key Ediacaran biotas. However, high-grade Ediacaran phosphorite deposits are relatively uncommon, diminishing the opportunity to test current phosphate mineralization-deposition models and their implications for Neoproterozoic research. In this scenario, widespread Ediacaran phosphorite–dolomite–shale successions of Bocaina Formation (Corumbá Group – Central Brazil) are poorly explored in international literature. Nevertheless, recent advances in phosphate exploration gave access to continuous drill core sections and freshly opened mine pits, revealing an unprecedented record of complex phosphatic successions featuring the occurrence of Ediacaran microfossils assigned to the Doushantuo–Pertatataka assemblages. This work seeks to constrain main lithofacies, sequence stratigraphy and depositional settings from these phosphatic successions in order to analyze the sedimentary evolution of the unit under the current Neoproterozoic phosphorite research framework. These results indicate that Bocaina Formation records secular sustained phosphate deposition. These deposits are related to unprecedented, microbialite reef rim phosphorites deposited during a lower accretionary rimmed platform stage, followed by the deposition of Doushantuo-like, whole platform phosphorites associated with a later, drowned platform stage, therefore, reinforcing the evidence for the operation of strong allogeneic controls on phosphate mineralization-concentration. In addition, this study concludes that fossiliferous Ediacaran phosphatic deposits such as the Bocaina Formation are important to understanding Neoproterozoic phosphogenic events, because they may record the transition from a Precambrian to Phanerozoic-like phosphogenesis associated with the instauration of the Ediacaran–Cambrian phosphatic taphonomic window. This evidence hints that the growing dataset from the Bocaina Formation may bring new, exciting perspectives for Neoproterozoic research as a whole.
... They are distributed worldwide in almost all habitats and play key roles in ecosystems by linking soil food webs, influencing plant growth and facilitating nutrient cycling (Yeates et al., 2009;van den Hoogen et al., 2019;Zhang et al., 2020). The earliest known definite nematode fossil occurs in the Lower Devonian Rhynie Chert inside the cortex cells of an early land plant and has been considered to be a plant parasite , but unconfirmed nematode-like fossils and trace fossils may date back to the Precambrian (Poinar, 1979;Parry et al., 2017; ...
Mermithid nematodes are obligate invertebrate parasites dating back to the Early Cretaceous. Their fossil record is sparse, especially before the Cenozoic, thus little is known about their early host associations. This study reports 16 new mermithids associated with their insect hosts from mid-Cretaceous Kachin amber, 12 of which include previously unknown hosts. These fossils indicate that mermithid parasitism of invertebrates was already widespread and played an important role in the mid-Cretaceous terrestrial ecosystem. Remarkably, three hosts (bristletails, barklice, and perforissid planthoppers) were previously unknown to be parasitized by mermithids both past and present. Furthermore, our study shows that in contrast to their Cenozoic counterparts, Cretaceous nematodes including mermithids are more abundant in non-holometabolous insects. This result suggests that nematodes had not completely exploited the dominant Holometabola as their hosts until the Cenozoic. This study reveals what appears to be a vanished history of nematodes that parasitized Cretaceous insects.
... They are distributed worldwide in almost all habitats and play key roles in ecosystems by linking soil food webs, influencing plant growth and facilitating nutrient cycling (Yeates et al., 2009;van den Hoogen et al., 2019;Zhang et al., 2020). The earliest known definite nematode fossil occurs in the Lower Devonian Rhynie Chert inside the cortex cells of an early land plant and has been considered to be a plant parasite , but unconfirmed nematode-like fossils and trace fossils may date back to the Precambrian (Poinar, 1979;Parry et al., 2017; ...
Mermithid nematodes are obligate invertebrate parasites dating back to the Early Cretaceous. Their fossil record is sparse, especially before the Cenozoic, thus little is known about their early host associations. This study reports 16 new mermithids associated with their insect hosts from mid-Cretaceous Kachin amber, 12 of which include previously unknown hosts. These fossils indicate that mermithid parasitism of invertebrates was already widespread and played an important role in the mid-Cretaceous terrestrial ecosystem. Remarkably, three hosts (bristletails, barklice, and perforissid planthoppers) were previously unknown to be parasitized by mermithids both past and present. Furthermore, our study shows that in contrast to their Cenozoic counterparts, Cretaceous nematodes including mermithids are more abundant in non-holometabolous insects. This result suggests that nematodes had not completely exploited the dominant Holometabola as their hosts until the Cenozoic. This study reveals what appears to be a vanished history of nematodes that parasitized Cretaceous insects.
... They are distributed worldwide in almost all habitats and play key roles in ecosystems by linking soil food webs, influencing plant growth and facilitating nutrient cycling (Yeates et al., 2009;van den Hoogen et al., 2019;Zhang et al., 2020). The earliest known definite nematode fossil occurs in the Lower Devonian Rhynie Chert inside the cortex cells of an early land plant and has been considered to be a plant parasite , but unconfirmed nematode-like fossils and trace fossils may date back to the Precambrian (Poinar, 1979;Parry et al., 2017; ...
Mermithid nematodes are obligate invertebrate parasites dating back to the Early Cretaceous. Their fossil record is sparse, especially before the Cenozoic, thus little is known about their early host associations. This study reports 16 new mermithids associated with their insect hosts from mid-Cretaceous Kachin amber, 12 of which include previously unknown hosts. These fossils indicate that mermithid parasitism of invertebrates was already widespread and played an important role in the mid-Cretaceous terrestrial ecosystem. Remarkably, three hosts (bristletails, barklice, and perforissid planthoppers) were previously unknown to be parasitized by mermithids both past and present. Furthermore, our study shows that in contrast to their Cenozoic counterparts, Cretaceous nematodes including mermithids are more abundant in non-holometabolous insects. This result suggests that nematodes had not completely exploited the dominant Holometabola as their hosts until the Cenozoic. This study reveals what appears to be a vanished history of nematodes that parasitized Cretaceous insects.
... Not only do bioturbating animals have powerful effects on resource flows and in modifying the physical environment (Rhoads et al., 1978;Jones et al., 1994;Rosenberg et al., 2001;Meysman et al., 2006), but they are also a record of ecosystem engineering that is relatively easy to preserve as fossils (Marenco and Bottjer, 2007). A detailed search through Nama-aged sediments in several localities worldwide has uncovered a remarkable diversity of Ediacaran ichnotaxa (e.g., Parry et al., 2017;Buatois et al., 2018;Turk et al., 2022), while other studies have shown that the impacts of these behaviors potentially reach Cambrian levels millions of years before the E-C boundary (e.g., Cribb et al., 2019). When set alongside the apparent low genus diversity of Nama-aged Ediacara biota (Laflamme et al., 2013;Darroch et al., 2015;2018a,b), this would seem to lend strong support for the 'biotic replacement' modelat least over the White Sea-Nama transition (i.e., the first extinction pulse). ...
Since the 1980s, the existence of one or more extinction events in the late Ediacaran has been the subject of debate. Discussion surrounding these events has intensified in the last decade, in concert with efforts to understand drivers of global change over the Ediacaran–Cambrian transition and the appearance of the more modern-looking Phanerozoic biosphere. In this paper we review the history of thought and work surrounding late Ediacaran extinctions, with a particular focus on the last 5 years of paleontological, geochemical, and geochronological research. We consider the extent to which key questions have been answered, and pose new questions which will help to characterize drivers of environmental and biotic change. A key challenge for future work will be the calculation of extinction intensities that account for limited sampling, the duration of Ediacaran ‘assemblage’ zones, and the preponderance of taxa restricted to a single ‘assemblage’; without these data, the extent to which Ediacaran bioevents represent genuine mass extinctions comparable to the ‘Big 5’ extinctions of the Phanerozoic remains to be rigorously tested. Lastly, we propose a revised model for drivers of late Ediacaran extinction pulses that builds off recent data and growing consensus within the field. This model is speculative, but does frame testable hypotheses that can be targeted in the next decade of work.
