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Garnet Reference Materials for In Situ Lu‐Hf Geochronology
No full textIn situ garnet Lu-Hf geochronology has the potential to revolutionise the chronology of petrological and tectonic processes, yet there is a paucity of well-characterised reference materials to account for laser-induced matrix-dependant elemental fractionation. Here, we characterise two reference garnets GWA-1 (Lu ~ 7.0 μg g−1) and GWA-2 (Lu ~ 8.5 μg g−1) for in situ garnet Lu-Hf geochronology. Isochron ages from isotope dilution Lu-Hf analyses yield crystallisation ages of 1267.0 ± 3.0 Ma with initial 176Hf/177Hfi of 0.281415 ± 0.000012 (GWA-1), and 934.7 ± 1.4 Ma with 176Hf/177Hfi of 0.281386 ± 0.000013 (GWA-2). In situ Lu-Hf analyses yield inverse isochron ages up to 10% older than the known crystallisation age due to matrix effects between garnet and reference glass (NIST SRM 610) under different instrument tuning conditions. This apparent age offset is reproducible for both materials within the same session and can be readily corrected to obtain accurate ages. Our results demonstrate that GWA-1 and GWA-2 are robust reference materials that can be used to correct for matrix-analytical effects and also to assess the accuracy of in situ Lu-Hf garnet analyses across a range of commonly encountered garnet compositions.Research funders and strategic development areas: Natural Sciences and Engineering Research Council of Canada 10.13039/501100000038</p
Evolution and diversity of biomineralized columnar architecture in early Cambrian phosphatic-shelled brachiopods
No full textBiologically-controlled mineralization producing organic-inorganic composites (hard skeletons) by metazoan biomineralizers has been an evolutionary innovation since the earliest Cambrian. Among them, linguliform brachiopods are one of the key invertebrates that secrete calcium phosphate minerals to build their shells. One of the most distinct shell structures is the organo-phosphatic cylindrical column exclusive to phosphatic-shelled brachiopods, including both crown and stem groups. However, the complexity, diversity, and biomineralization processes of these microscopic columns are far from clear in brachiopod ancestors. Here, exquisitely well-preserved columnar shell ultrastructures are reported for the first time in the earliest eoobolids Latusobolus xiaoyangbaensis gen. et sp. nov. and Eoobolus acutulus sp. nov. from the Cambrian Series 2 Shuijingtuo Formation of South China. The hierarchical shell architectures, epithelial cell moulds, and the shape and size of cylindrical columns are scrutinised in these new species. Their calcium phosphate-based biomineralized shells are mainly composed of stacked sandwich columnar units. The secretion and construction of the stacked sandwich model of columnar architecture, which played a significant role in the evolution of linguliforms, is highly biologically controlled and organic-matrix mediated. Furthermore, a continuous transformation of anatomic features resulting from the growth of diverse columnar shells is revealed between Eoobolidae, Lingulellotretidae, and Acrotretida, shedding new light on the evolutionary growth and adaptive innovation of biomineralized columnar architecture among early phosphatic-shelled brachiopods during the Cambrian explosion
Manual for collection, preparation and storage of blue mussels for the Swedish National Monitoring Program for Contaminants in Marine Biota
No full textPlant-insect interactions across the Triassic–Jurassic boundary in the Sichuan Basin, South China
No full textPlants and insects are the most diverse and ecologically important organisms in the terrestrial biosphere. Their interactions are also among the richest biotic relationships, and offer significant insights into the evolution of terrestrial ecosystem complexity through the geological record. This investigation of the late Rhaetian Xujiahe and the earliest Jurassic Zhenzhuchong floral assemblages provides the first data on foliar herbivory generated by terrestrial arthropods across the Triassic–Jurassic transition in the eastern Tethys (East Asia) region. The damage types from two fossil assemblages are collectively attributed to seven functional feeding and egg-laying categories (i.e., hole feeding, margin feeding, surface feeding, skeletonization, piercing and sucking, oviposition, and galling). Most feeding strategies are spread across the major plant groups and persist through the Triassic–Jurassic boundary, with the exception of skeletonization (a category of external foliage feeding), which was restricted to the latest Triassic within dipteridacean ferns. The survey reveals that the respective frequency and diversity of interactions between plants and insects prior to and following the end-Triassic mass extinction event are almost the same, despite a substantial turnover of floral components. This suggest that insect herbivores were largely able to transfer to alternative (but commonly related) plant groups during the dramatic floristic turnover and environmental changes at the end of the Triassic. Sporadic occurrences of foliar modifications, such as marginal cusps on pinnules of Pterophyllum and prominent ridges on the rachises of some ferns and bennettites are interpreted as adaptations for defense against insect herbivores. A few differences in taxonomic composition and herbivory representation between the latest Triassic Xujiahe flora and the earliest Jurassic Zhenzhuchong flora are more likely to be related to collection and preservational biases rather than reflecting palaeoecological changes. We encourage further investigations exploring the distribution of insect damage in fossil floras from other palaeolatitudinal zones and spanning other major extinction events to develop a better understanding of terrestrial ecosystem responses to major crises in Earth’s history.The author(s) declare financial support was received for theresearch, authorship, and/or publication of this article. This study isfinancially supported by the National Natural Science Foundation of China (grant numbers 42330208, 42072009, 41972120, 42172129, 42202020), the Stratigraphic Priority Program (B) ofthe Chinese Academy of Sciences (grant number XDB 2610302), the Programs from State Key Lab of Palaeobiology and Stratigraphy (20191103, 173131, 213112), and CSC (grant number 202204910396). SM is funded by grants from the Swedish ResearchCouncil (VR grant numbers 2018-04527 and 2022-03920).</p
A new Rhaetian plant assemblage from Zilanba, the northern Sichuan Basin, South China
No full textTriassic and Jurassic strata are thick and widely distributed in the Sichuan Basin, South China. In particular, the continental Upper Triassic Xujiahe Formation is well-exposed in this region, yielding rich assemblages of fossil plants. Here, a new Rhaetian fossil assemblage is reported from Zilanba in the Guangyuan area, northern Sichuan Basin. In this locality, 29 species of fossil plants belonging to 17 genera have been newly collected and identified within Member III of the Xujiahe Formation. Based on the floral assemblages and previous magnetostratigraphic and palynostratigraphic studies, the host strata are considered Rhaetian in age. This flora in the Guangyuan area is dominated by Cycadales and Bennettitales but also contains abundant ferns and less common sphenopsids, conifers and other gymnosperms. The occurrence of some climate diagnostic plants, such as Dipteridaceae, Anthrophyopsis and Ptilozamites, indicate that this area experienced a humid and warm tropical or subtropical climate during the Rhaetian.This study is financially supported by the National NaturalScience Foundation of China (grant numbers 42330208, 42072009,41972120, 42172129), the Stratigraphic Priority Program (B) of the Chinese Academy of Sciences (grant number XDB 2610302), the Programs from State Key Lab of Palaeobiology and Stratigraphy (20191103, 173131, 213112), and CSC (grant number 202204910396). S.M. is supported by grants from the Swedish Research Council (VRgrant numbers 2018-04527 and 2022-03920).</p
Comprehensive survey of Early to Middle Triassic Gondwanan floras reveals under-representation of plant–arthropod interactions
No full textPlants and arthropods are primary drivers of terrestrial ecosystem function. Trace fossils of plant–arthropod interactions (PAIs) provide a unique window into assessing terrestrial ecosystem states through geological time and evaluating changes in herbivorous arthropod feeding guilds in the wake of global biotic crises. The end-Permian event (EPE; c. 252 Ma) resulted in the loss of keystone plant species from humid tropical and high-latitude ecosystems and the extinction of several major insect groups. The subsequent Early to Middle Triassic evinced diminished terrestrial productivity, punctuated by a series of second-order biotic crises that hindered recovery. Here, we survey records of Gondwanan Early to Middle Triassic floral assemblages for evidence of PAIs as an indication of ecosystem recovery following the EPE. We compiled a comprehensive dataset of fossil plant taxa and PAIs for lower Mesozoic strata of Gondwana, revealing an increase in specific and generic floral diversity from the Early to Middle Triassic. We noted a lack of PAIs reported from many localities with abundant fossil leaves, which might be interpreted to be a consequence of a post-EPE delay in the recovery of arthropod feeding guilds compared to the flora. However, by comparing floral assemblages between regions of Gondwana, our results also partly attribute the absence of PAIs to the relative paucity of palaeoichnological and palaeobotanical studies of this interval. To test for potential under-reporting of PAIs in the Triassic, we present a case study of the well-described Australian Middle Triassic Benolong Flora. In contrast to existing Australian Early to Middle Triassic PAI reports on only three plant specimens, this systematic investigation revealed 44 PAI traces comparable to published examples, hosted by 40 fossil plant fragments (7.77% of fragments assessed; N = 591). Margin-feeding traces constituted the dominant Functional Feeding Group (FFG) identified (23 examples: 3.72% of fragments assessed). Our review highlights several Early and Middle Triassic Gondwanan plant fossil-rich successions and existing collections that require further examination. We predict that investigations of these assemblages will greatly elucidate the relationships between rapidly changing environments during the Early and Middle Triassic and their effects on the plant and arthropod communities in the Southern Hemisphere.The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This project was supported by an Irish Research Council Government of Ireland Postgraduate Scholarship awarded to H-AT (GOIPG/2022/2071), a Swedish Research Council (VR) grant (2022-03920) awarded to SM, and research grant 13/RC/2092_P2 from Science Foundation Ireland’s Research Centre in Applied Geosciences (13/RC/2092_P2) awarded to CM.</p
Predictive Models for Detrital Titanite Provenance With Application to the Nanga Parbat—Haramosh Syntaxial Massif, Western Himalaya
No full textParallel evolution of angiosperm‐like venation in Peltaspermales: a reinvestigation of Furcula
No full textLeaf venation is a pivotal trait in the success of vascular plants. Whereas gymnosperms have single or sparsely branched parallel veins, angiosperms developed a hierarchical structure of veins that form a complex reticulum. Its physiological consequences are considered to have enabled angiosperms to dominate terrestrial ecosystems in the Late Cretaceous and Cenozoic. Although a hierarchical-reticulate venation also occurs in some groups of extinct seed plants, it is unclear whether these are stem relatives of angiosperms or have evolved these traits in parallel. Here, we re-examine the morphology of the enigmatic foliage taxon Furcula, a potential early Mesozoic angiosperm relative, and argue that its hierarchical vein network represents convergent evolution (in the Late Triassic) with flowering plants (which developed in the Early Cretaceous) based on details of vein architecture and the absence of angiosperm-like stomata and guard cells. We suggest that its nearest relatives are Peltaspermales similar to Scytophyllum and Vittaephyllum, the latter being a genus that originated during the Late Triassic (Carnian) and shares a hierarchical vein system with Furcula. We further suggest that the evolution of hierarchical venation systems in the early Permian, the Late Triassic, and the Early Cretaceous represent ‘natural experiments’ that might help resolve the selective pressures enabling this trait to evolve
Five centuries of consanguinity, isolation, health, and conflict in Las Gobas: A Northern Medieval Iberian necropolis
No full textAnatomy of a fumarole field: drone remote-sensing and petrological approaches reveal the degassing and alteration structure at La Fossa cone, Vulcano, Italy
No full textHydrothermal alteration and mineralization processes can affect the physical and chemical properties of volcanic rocks. Aggressive acidic degassing and fluid flow often also lead to changes in the appearance of a rock, such as changes in surface coloration or intense bleaching. Although hydrothermal alteration can have far-reaching consequences for rock stability and permeability, limited knowledge exists on the detailed structures, extent, and dynamic changes that take place near the surface of hydrothermal venting systems. By integrating drone-based photogrammetry with mineralogical and chemical analyses of rock samples and surface gas flux, we investigate the structure of the evolving volcanic degassing and alteration system at the La Fossa cone on the island of Vulcano, Italy. Our image analysis combines principal component analysis (PCA) with image classification and thermal analysis through which we identify an area of approximately 70 000 m2 that outlines the maximum extent of hydrothermal alteration effects at the surface, represented by a shift in rock color from reddish to gray. Within this area, we identify distinct gradients of surface coloration and temperature that indicate a local variability in the degassing and alteration intensity and define several structural units within the fumarole field. At least seven such larger units of increased activity could be constrained. Through mineralogical and geochemical analysis of samples from the different alteration units, we define a relationship between surface appearance in drone imagery and the mineralogical and chemical composition. Gradients in surface color from reddish to gray correlate with a reduction in Fe2O3 from up to 3.2 % in the unaltered regime to 0.3 % in the altered regime, and the latter coincides with the area of increased diffuse acid gas flux. As the pixel brightness increases towards higher alteration gradients, we note a loss of the initial (igneous) mineral fraction and a change in the bulk chemical composition with a concomitant increase in sulfur content from close to 0 % in the unaltered samples to up to 60 % in samples from the altered domains. Using this approach of combined remote-sensing and in situ analyses, we define and spatially constrain several alteration units and compare them to the present-day thermally active surface and degassing pattern over the main crater area. The combined results permit us to present a detailed anatomy of the La Fossa fumarole field, including high-temperature fumaroles and seven larger units of increased alteration intensity, surface temperature, and variably intense surface degassing. Importantly, we also identify apparently sealed surface domains that prevent degassing, likely as a consequence of mineral precipitation from degassing and alteration processes. By assessing the thermal energy release of the identified spatial units quantitatively, we show that thermal radiation of high-temperature fumaroles accounts for < 50 % of the total thermal energy release only and that the larger part is emitted by diffuse degassing units. The integrated use of methods presented here has proven to be a useful combination for a detailed characterization of alteration and activity patterns of volcanic degassing sites and has the potential for application in alteration research and for the monitoring of volcanic degassing systems