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In Oman, many coastal sites dated to the Neolithic have yielded material culture related to ornament manufacture. These sites are the remnants of fishermen occupations, developing an economy mainly based on maritime and mangrove resources. The Omani islands of Maṣīrah and Al‐Ḥallāniyah are both situated in the Arabian Sea. Today, Maṣīrah is located about 20 km from the continent, while Al‐Ḥallāniyah is part of the Khurīyā Murīyā archipelago off the southern coast of Oman. On Maṣīrah, workshops have been discovered in Neolithic shell middens, revealing the work of stone and Spondylus sp. shells for bead production, using lithic tools. Separated by approximately 400 km from Maṣīrah, Al‐Ḥallāniyah yielded several Neolithic sites with similar evidence for shell bead production. The main lithic tools discovered are micro‐drills, pièces esquillées (splintered pieces) made of local chert, and multitasking tools made of stone, used as anvils, hammerstone and/or polishing stone. Most of the micro‐drills are made from bladelets either with sharped edges or with steep edges and testify to predetermined knapping operations. However, others created on undifferentiated flakes appear to be more opportunistic (or expedient). Micro‐drills of the Maṣīrah and Al‐Ḥallāniyah types seem to be quite new to the Neolithic toolkit of coastal Oman. Pièces esquillées demonstrate the use of bipolar flaking (performed on an anvil) but functional questions remain. These could be cores, but also chisels used between a hammer and a material (shell) placed on an anvil. Stone tools show marks that are characteristic of use as hammers, anvils and as tools used to polish the beads after perforation. [ABSTRACT FROM AUTHOR]

Chert is a sedimentary rock abundant and conspicuous throughout the geologic record. It serves as an essential geological archive and is vital for palaeogeographic reconstruction. The Chert Database Working Group is part of the OneSediment Working Groups of the Deep‐time Digital Earth (DDE) Big Science Program. To facilitate the sharing of chert information and promote chert research, we have compiled a summary of literature containing chert information worldwide and established the Global Chert Database (GCDB). The main body of the current database consists of seven data tables, each providing details on references, lithology, depositional age, geographic location, depositional environment and geochemical information for each sample. As of December 2023, the GCDB contains 8417 sample data from 617 pieces of literature, which can be downloaded from the 'DDE Data Publish & Repository'. [ABSTRACT FROM AUTHOR]

The Mamonia Mélange in the Ayia Varvara area (southwestern Cyprus) is characterized by a matrix supported mélange which is composed of tectonized siltstones and mudstones with numerous blocks that were derived from the Mamonia Allochthonous Complex (Petra tou Romiou Formation reefal limestones, Phasoula Formation volcanics, Kholetria Member pelagic limestones, Akamas Member sandstone, Parekklisha Member sandstone, Ayia Varvara Formation metamorphics and Episkopi Formation radiolarian cherts). Subordinate blocks were derived from the Troodos Ophiolite Complex: serpentinites, gabbro, pillow lavas and cherty umbers (Perapedhi Formation). Radiolarian assemblages from chert blocks display a broad spectrum in age, ranging from the Late Triassic (latest Carnian–early Norian) to the youngest Cenomanian. The composition of the mélange in the Ayia Varvara area differs from the one described in the Petra tou Romiou area (SW Cyprus), as various lithologies were recorded (like Akamas Member sandstone and Parekklisha Member sandstone) which were not detected previously. The Mamonia Mélange was formed during the Late Cretaceous, most probably after the end of deposition of the Perapedhi Formation (late Santonian–early Campanian). [ABSTRACT FROM AUTHOR]

Archaeological studies carried out in recent decades have demonstrated that the Pre‐Pyrenees, a mountain range in north‐east Iberia, were regularly frequented by several human groups during the Late Pleistocene. The Cova del Parco archaeological site is an example of this large‐scale and regular human presence. The site was discovered and first excavated in the 1970s, and since the 1980s, a team from the University of Barcelona has been conducting archaeological work. So far, we have found that the site was at least frequented from the Middle Magdalenian upon historical times. In this paper, we present the results of the archaeopetrological, geochemical and geographic information system (GIS) analyses of chert tools ascribed to the Middle Magdalenian sequence. The textural, micropalaeontological and geochemical analysis of the lithic artefacts has allowed us to identify several chert types from local, regional and long‐distance sources. Some of these cherts had their origin in the northern slopes of the Pyrenean chain, suggesting that this mountain chain was regularly crossed by Magdalenian groups. Next, we performed GIS analyses to determine the paths and connections that may have linked the archaeological site with the different chert outcrops, and to identify the best routes for crossing the Pyrenean Mountain range. Moreover, this study provides a larger vision of the mobility and the complex economic interactions between the different Magdalenian groups that settled Cova del Parco at the end of the Late Pleistocene. [ABSTRACT FROM AUTHOR]

Chert is abundant in Archean and Paleoproterozoic rocks and is commonly densely packed with authigenic Fe(II)-silicate nanoparticles such as greenalite, indicating a close relationship between iron and silica deposition. We investigate the relationship between Fe(II)-silicate minerals and dissolved silica during precipitation, settling, and diagenesis using anoxic synthesis, sorption, and heating experiments. Excess silica is associated with the solid during precipitation, resulting in high molar Si/Fe ratios (<1.52) that exceed that of stoichiometric greenalite (0.67). At pH 8–8.5, silica sorbs to the surface, reaching sorption densities of 0.68 mmol Si per mmol Fe(II)-silicate. Furthermore, excess Si is released upon heating as the Fe(II)-silicate gel crystallizes. We suggest that Fe(II)-silicate minerals acted as an effective Si shuttle between the water column and the sediments in Archean and Paleoproterozoic marine environments, providing sites for the growth of early diagenetic chert, consistent with observations from the sedimentary record. Our results explain the exceptional preservation of greenalite in early chert and indicate that these minerals could provide a robust archive of marine geochemical data. [ABSTRACT FROM AUTHOR]

Abstract Chert is a sedimentary rock abundant and conspicuous throughout the geologic record. It serves as an essential geological archive and is vital for palaeogeographic reconstruction. The Chert Database Working Group is part of the OneSediment Working Groups of the Deep‐time Digital Earth (DDE) Big Science Program. To facilitate the sharing of chert information and promote chert research, we have compiled a summary of literature containing chert information worldwide and established the Global Chert Database (GCDB). The main body of the current database consists of seven data tables, each providing details on references, lithology, depositional age, geographic location, depositional environment and geochemical information for each sample. As of December 2023, the GCDB contains 8417 sample data from 617 pieces of literature, which can be downloaded from the ‘DDE Data Publish & Repository’.

Abstract Radiolarians have been used to determine geological ages and have contributed markedly to our understanding of Earth’s history. Hydrofluoric acid (HF) has traditionally been used to extract radiolarian fossils from siliceous deposits (i.e., radiolarian cherts), but this acid is strictly regulated because of environmental and human health concerns. Here we report on the successful extraction of radiolarians from cherts using a low-concentration NaOH solution (1 mol/L NaOH) as an alternative to HF. The degree of chert dissolution in NaOH is strongly temperature-dependent and is limited at

During the third millennium cal BC, the Indus communities exploited great quantities of chert from the Rohri Hills mines in Upper Sindh for making different types of artifacts. This paper discusses the way chert was transported to the Indus Civilization centers and the problems related to the type, quantity, and quality of raw material and artifacts that were transported, including when, why, and where. This paper raises the question of land and water transport. Both these methods were probably used according to the landscape location of the Indus sites. Another problem concerns the landscape characteristics of the Indus Valley during the Bronze Age before the climate changes that took place around the end of the third millennium cal BC and the disappearance of the Hakra River, which was an important watercourse during the Indus phase. What do we know of the way the Indus communities exploited, transported, and circulated knappable chert? Why have the Indus settlements excavated around the Rohri Hills, the largest chert mines of the Indian Subcontinent, yielded little evidence of chert artifacts and nodules? What do we know of this important problem, which is strictly related to the everyday life of the Indus communities and their economy? Why this problem has been systematically neglected by most archaeologists despite its importance? [ABSTRACT FROM AUTHOR]

The Sichuan Basin in Southeastern China contains extensive bedded cherts dating back to the Late Ordovician–Early Silurian period. To investigate the origin and depositional environment of these cherts, we conducted a comprehensive study using field observations, thin sections microscopic, silicon isotope analysis, and major and trace element geochemistry of samples from three sections. Our results indicate that the cherts from Wufeng and Longmaxi formations are non-hydrothermal, normal biogenic seawater deposits mainly affected by terrigenous input and slightly associated with volcanic ash. Al2O3/(Al2O3 + Fe2O3T) and LaN/CeN ratios, δCe values and Fe2O3T/TiO2 − Al2O3/(Al2O3 + Fe2O3T), Fe2O3T/(100 − SiO2) − Al2O3/(100 − SiO2), 100 × (Fe2O3T/SiO2) – 100 × (Al2O3/SiO2), and LaN/CeN − Al2O3/(Al2O3 + Fe2O3T) discrimination diagrams indicated that the bedded cherts deposited in the continental margin environment. [ABSTRACT FROM AUTHOR]

Background: Gastroliths are stones of uncertain purpose that are commonly found inside the rib cages of plesiosaur fossils worldwide. Gastroliths from four Alberta (Canada) plesiosaurs were studied to determine both their shapes and masses, and their mass fractions relative to body mass. One animal's set of gastroliths was 100% complete and fully visible, but the others showed varying degrees of loss, damage or obscuration, so estimations of their original states were needed. Methods: The studied animals were: Albertonectes vanderveldei, Fluvionectes sloanae, Nichollssaura borealis and Wapuskanectes betsynichollsae. The animals come from three different palaeoenvironments: open marine, near shore marine, and fluvial. Gastrolith shapes were classified as either xiphoid, cylindrical, discoidal or spherical based on observed and/or estimated dimensions. Although not all methods could be applied in all cases, gastrolith shapes and masses were estimated four different ways: (1) direct measurement and weighing of a subset and predicting the properties of the remaining obscured and hidden stones; (2) measuring triaxial ellipsoid dimensions of free stones to calculate volumes and multiplying by the mass density of chert; (3) measuring two visible triaxial dimensions of embedded stones, estimating the hidden third dimension three different ways, and then determining volumes and masses by calculation; and (4) predicting the density and mass of a densely packed cluster of small gastroliths using geometrical arguments. Results: Total gastrolith mass never exceeded 0.2% of body mass in any plesiosaur, and is consistent with the idea that the amounts of gastroliths recovered with plesiosaurs would be ineffective as ballast. The largest plesiosaur in the sample had the largest single gastrolith and total gastrolith mass increases with body size. The shape characteristics of the gastroliths were different for different environments, but compositionally they are dominated by black cherts. A possible common source for the gastroliths was identified for the two geographically close and near-contemporanous Nichollssaura and Wapuskanectes. [ABSTRACT FROM AUTHOR]

Lithic raw material properties are often invoked to explain the presence, absence, form, or ontogeny of Paleolithic stone tools. Here, we explore whether the frequency of the Middle Paleolithic Nubian core form and core‐reduction systems co‐varies with toolstone quality in two neighboring regions in Oman: the southern region of Nejd, Dhofar, and the south‐central region of Duqm, Al Wusta. Specifically, we predicted that if raw material differences were influencing the distribution of Nubian cores, the chert would be of higher quality in the southern region, where Nubian cores were frequent, and of lower quality in the south‐central region, where they were scarce. We tested this prediction by collecting 124 chert samples from 22 outcrops and then quantitatively assessed two geochemical variables that are widely thought to influence knapping: impurity amount and silica content. We also examined the mineralogical composition, and the crystallite size and lattice strain for quartz (crystalline α‐SiO2) of representative chert samples. Our results suggest that the cherts in the two regions are similar, which is not consistent with the hypothesis that lithic raw material quality contributed to Nubian core spatial distribution in Oman. We discuss potential alternative hypotheses to explain Nubian core geographic patterning, and provisionally suggest that the scarcity of Nubian cores in south‐central Oman may be due to a concomitant scarcity of toolmakers, given a lack of water availability. [ABSTRACT FROM AUTHOR]

This study presents the results of a provenance study on Middle–Upper Paleolithic chert tools from North Bosnia. It is part of a larger geoarchaeological research dedicated to using interdisciplinary methodologies to collate and review the known Middle–Upper Paleolithic archaeological record of North Bosnia. Chert is a raw material commonly used in prehistory for tool crafting and this region is known to have abundant geological sources. However, there is a lack of detailed data, especially regarding the geochemical characteristics and composition of these sources. The Middle‐Upper Paleolithic lithic assemblages found in North Bosnia are dominated by chert and there is an untested theory suggesting the exploitation of local sources. The presented research uses macroscopic examination and laser ablation‐inductively coupled plasma mass spectrometry to distinguish the different chert varieties and identify groups with specific geochemical characteristics/signatures in the assemblages. The field‐ and lab‐based work suggests multiple sources but most importantly, presents strong evidence of chert tools having almost identical geochemical signatures with specific chert sources from North Bosnia. These are the first results confirming the exploitation of Indigenous chert sources and subsequently providing insights into hominan activity and raw‐material networks during the Middle–Upper Paleolithic in the region. [ABSTRACT FROM AUTHOR]

The evolution of the land plant alternation of generations has been an open question for the past 150 years. Two hypotheses have dominated the discussion: the antithetic hypothesis, which posits that the diploid sporophyte generation arose de novo and gradually increased in complexity, and the homologous hypothesis, which holds that land plant ancestors had independently living sporophytes and haploid gametophytes of similar complexity. Changes in ploidy levels were unknown to early researchers. The antithetic hypothesis is contradicted by generation cycles in Lower Devonian Rhynie chert plants, whose sporophytes and gametophytes have similar morphologies and by some Silurian sporophytes whose complexity exceeds that of Rhynie chert sporophytes. The oldest unambiguous bryophyte gametophytes (thalli) are from the upper Middle Devonian, with an unconnected sporophyte nearby. Based on the 2024 discovery that conjugate algae are paraphyletic to land plants, we present a new hypothesis for the evolution of the land plant generation cycle, focusing on labile ploidy levels and types of reproduction found in conjugate algae. Our 'sexual lability' hypothesis assumes a period of unstable generation cycles (as regards ploidy), likely with predominant clonal growth, as is common in conjugate algae, resulting in sporophytes and gametophytes of similar morphology. When sexual reproduction became stabilized, the timing of gamete fusion, meiosis, and resistant wall formation, which are heterochronic in some conjugate algae, became standardized, with wall formation permanently delayed. In our scenario, independently living adult sporophytes are the land plant ancestral condition, and life-long sporophyte retention on the gametophyte is a bryophyte apomorphy. All land plants cycle between a haploid generation that grows from spores and ends with the production of gametes and a diploid generation that grows from a zygote and ends with the production of spores. Renner and Sokoloff propose a new explanation for how this type of life cycle may have evolved from an algal ancestor. [ABSTRACT FROM AUTHOR]

Acid deposition is widespread in Japan, but acidification of stream water is rare in forest ecosystems. Bedrock‐derived cations, including those released into the soil by weathering of bedrock minerals, generally act to neutralize acid deposition and flow out into streams. Volcanic ash, which is widespread in Japan, may also release cations and neutralize acids, but the contribution of volcanic‐ash‐derived cations is currently poorly explored. To assess the importance of volcanic ash as a source of base cations, we examined strontium in two catchments underlain by chert bedrock at Mount Amamaki, Japan. Additionally, we obtained comparative data from two sandstone‐bedrock catchments in the same area. We measured 87Sr/86Sr ratios in samples of stream water, bulk precipitation, riverbed rock, and soil from the catchments. We used the 87Sr/86Sr data to analyze the relative contributions of atmospheric deposition, bedrock, and volcanic ash in soil as sources of Sr in the stream waters. We estimated volcanic ash in soil to contribute between 46% and 78% of stream‐water Sr for one chert‐bedrock catchment, and between 0% and 52% for the other. We conclude that volcanic ash in soil is an important source of Sr in stream water. Thus, volcanic ash can act as a source of base cations and hence contribute to the acid‐neutralizing capacity of soil in forest ecosystems in Japan. [ABSTRACT FROM AUTHOR]

This rapid communication describes a lithic blade that was recently recovered during excavations in the Velondriake Marine Protected Area in southwest Madagascar. This represents the only recorded archaeological lithic blade recovered from southwest Madagascar. The blade was recovered in situ at a depth of 1.66 m, a deposit dating to between 750 and 1200 BP at site G134, adjacent to the modern village of Antsaragnasoa. While similar in material choice (translucent-brown chert) and morphology (parallel-sided blade) to other lithics recovered at the northern sites of Ambohiposa and Lakaton'i Anja, it is significantly larger than other recorded lithics on Madagascar. More research is required but this finding suggests that lithic technology may have been more widespread on the island, particularly among coastal communities, than previously thought. [ABSTRACT FROM AUTHOR]

The Rhynie Chert (Lower Devonian, Scotland) hosts a remarkably well‐preserved early terrestrial ecosystem. Organisms including plants, fungi, arthropods, and bacteria were rapidly silicified due to inundation by silica‐rich hot spring fluids. Exceptional molecular preservation has been noted by many authors, including some of the oldest evidence of lignin in the fossil record. The evolution of lignin was a critical factor in the diversification of land plants, providing structural support and defense against herbivores and microbes. However, the timing of the evolution of lignin decay processes remains unclear. Studies placing this event near the end of the Carboniferous are contradicted by evidence for fungal pathogenesis in Devonian plant fossils, including from the Rhynie Chert. We conducted organic geochemical analyses on a Rhynie Chert sample, including hydropyrolysis (HyPy) of kerogen and high‐resolution mass spectrometric mapping of a thin section, to elucidate the relationship between lignin and the potential fungal marker perylene. HyPy of kerogen showed an increase in relative abundance of perylene supporting its entrapment within the silicate matrix of the chert. Lignin monomers were isolated through an alkaline oxidation process, showing a distribution dominated by H‐type monomers. G‐ and S‐type monomers were also detected, preserved by rapid silicification. Polycyclic aromatic hydrocarbons including perylene, a known marker for lignin‐degrading fungi, were also concentrated in the kerogen and found to be localized within silicified plant fragments. Our results strongly link perylene in the Rhynie Chert to the activity of phytopathogenic fungi, demonstrating the importance of fungal degradation processes as far back as the Early Devonian. [ABSTRACT FROM AUTHOR]

Radiolarian biochronology of radiolarites associated with ophiolitic lavas in northern Armenia provides important age constraints for the geodynamic reconstruction of Tethys in an area that makes the link between the Lesser Caucasus and the Eastern Pontides. We present results obtained from a moderately well-preserved radiolarian assemblage extracted from radiolarian cherts that crop out in the Bazoum Horst (between Stepanavan and Amasia). The age of these radiolarites may be restricted to the late Valangingian-Hauterivian based on the co-occurrence of the radiolarian species Archaeodictyomitra pseudoscalaris (Tan), Crolanium bipodium (Parona), Pseudodictyomitra suyarii Dumitrica and Tethysetta ovoidala Dumitrica. The dated radiolarites lie stratigraphically ca. 7-8 m above basaltic lavas that have a subduction-related geochemical signature. In combination with results from the Amasia ophiolite, this indicates the presence of a subduction-related island arc at the scale of the Amasia-Stepanavan oceanic realm that was active during Valanginian to Barremian times. [ABSTRACT FROM AUTHOR]

Accretionary complexes in the Japanese Islands preserve material from parts of the oceanic plates of Panthalassa that have subducted and are now lost. The age of the oceanic plate that is incorporated into the Jurassic accretionary complex of Japan has been previously estimated from scant data on Carboniferous bedded chert. In this study, we investigated a Carboniferous to Permian basalt-chert sequence in the Jurassic accretionary complex of the North Kitakami-Oshima belt in Northeast Japan. The sequence is composed of basaltic rocks, red bedded chert and grey bedded chert in ascending order. The basaltic rocks at the base contain red cherty nodules that yielded conodonts indicating the Bashkiran to early Moscovian, the latter age being more likely (late Carboniferous). The red bedded chert yielded middle Sakmarian (early Permian) radiolarians. The grey bedded chert yielded conodonts indicating the latest Kungurian to earliest Roadian. Thus, our study section demonstrates a formation of the oceanic plate in the late Carboniferous and a following deposition of pelagic siliceous sediments. This is the first time that basaltic rocks within the Jurassic accretionary complex of Japan are directly dated. While previous data need careful reviewing, our results demonstrate that the oldest part of the oceanic plate within the Jurassic accretionary complex is Serpukhovian or older and the youngest part may be as young as the Sakmarian. [ABSTRACT FROM AUTHOR]

Capitanian (late Guadalupian, Middle Permian) and Changhsingian (late Lopingian, Late Permian) radiolarians were obtained from chert blocks within the conglomerates of the Kamiaso Complex of the Mino Belt in Awano, Gifu Prefecture, central Japan. The former contains 15 species assigned to 10 genera with 4 undetermined species, and the latter contains 5 species assigned to 11 genera with 9 undetermined species. The chert blocks were presumably derived from an accretionary complex prior to accretion on the oceanic plate. [ABSTRACT FROM AUTHOR]

Radiolarians have been used to determine geological ages and have contributed markedly to our understanding of Earth's history. Hydrofluoric acid (HF) has traditionally been used to extract radiolarian fossils from siliceous deposits (i.e., radiolarian cherts), but this acid is strictly regulated because of environmental and human health concerns. Here we report on the successful extraction of radiolarians from cherts using a low-concentration NaOH solution (1 mol/L NaOH) as an alternative to HF. The degree of chert dissolution in NaOH is strongly temperature-dependent and is limited at < 80 °C. However, even a 1 mol/L NaOH solution is sufficient to dissolve chert at 100 °C. Our new NaOH method yields better-preserved radiolarian fossils compared with the conventional HF method. The 1 mol/L NaOH solution is less hazardous, easier to handle, and has fewer effects on the environment and human health than HF. Therefore, this method can be widely used for research and teaching purposes in studies of radiolarian fossils, even in institutions where HF cannot be used owing to chemical restrictions. [ABSTRACT FROM AUTHOR]

The Ediacaran-Cambrian (E-C) transition period witnessed one of the most important environmental changes in Earth’s history. The western margin of the South China Block (SCB), a shallow-water environment, shows a complete sedimentary record of the E-C transition. Section surveys revealed that dolostone, microbial carbonate, chert, and phosphorite predominantly compose the lithologies of the western margin of the SCB during the E-C transition. Petrological analysis indicates that microbial carbonates in this region exhibit stromatolitic, thrombolytic, cavitated, and sporadic microbial structures. Microbial carbonates with stromatolitic, thrombolytic/cavitated, and sporadic structures correspond to strong, moderate, and weak hydrodynamic conditions, respectively. Microcrystalline dolomites crystallize during the syngenesis stage, while meso- to macrocrystalline and sparry dolomites develop during the burial diagenesis stage. Analysis of major elements and rare earth elements anomalies (δCe: 0.580 ~ 0.753; δEu: 1.234 ~ 1.433) suggests that the siliceous component originates from hot-water sources and is transported into shallow-water environments by upwelling. The absence of a δEu anomaly and the morphology of peloids indicate that the phosphatic component is primarily influenced by biological activity and upwelling. During the Tongwan Movement (545–535 Ma) in the E-C transition period, cyclical upwelling transported increased amounts of deep-source materials into shallow platform waters, leading to higher concentrations of siliceous components and widespread microbial mortality. Following the widespread microbial mortality, the phosphatic component became enriched in deep-water environments. Subsequently, the upwelling transported siliceous- and phosphatic-rich fluids back into the shallow-water environments. The phosphatic component was ultimately assimilated by small shelly fauna and deposited in the phosphatic-rich strata of the early Cambrian period. This study elucidates the origins of complex lithological compositions and the sedimentary evolution model in shallow water environments of the E-C transition period in western SCB, offering evidence for global environmental changes during this period. [ABSTRACT FROM AUTHOR]

The paper presents new data on the age of Triassic–Jurassic cherts replaced up section by siliceous mudstones, then by mudstones, which together with basalts form thin (up to hundreds of meters) plates and lenses that wedge out along strike at different levels of the multikilometer terrigenous section of the Ulban terrane (zone). These deposits in the Nimelen subzone (Albazino gold deposit area) formed in the Norian–Early Toarcian; host terrigenous deposits formed in the Pliensbachian–Bathonian. The age of cherts and siliceous–clayey rocks in the Mewachan subzone is Middle Triassic–Callovian, and that of host terrigenous rocks is Middle–Late Jurassic (including the Tithonian). Comparison of deposits of the Ulban terrane with well-studied deposits of the Samarka terrane similar in age and composition allows us to consider the Ulban terrane (zone) as part of the Jurassic accretionary complex of the Sikhote-Alin orogenic belt. There are also sufficient signs to consider that its structural features are consistent with the subduction model. This idea is based on the fact that Triassic–Jurassic cherts and siliceous–clayey rocks, which accumulated over about 45 Ma at a rate of about 1.8 m/Ma, are considered the sedimentary cover of the oceanic plate. At the same time, a gradual transition from cherts to mudstones is evidence of movement of the oceanic plate into the subduction zone. The occurrence of its fragments in the terrigenous section is the result of their detachment in the trench and under the overhanging slab. Tectonostratigraphic columns of the subzones of the Ulban terrane and a zonal scheme of the Jurassic accretionary wedge, including four structural-age levels, have been compiled. [ABSTRACT FROM AUTHOR]

Cherts originating from carbonate lacustrine environments have been widely exploited by Upper Palaeolithic hunter‐gatherers in the south of the Pyrenees. Archaeo‐petrographic sourcing studies have identified different potential sources but were unable to distinguish them. This study conducted geochemical characterisation of geological and archaeological lacustrine chert samples using laser‐induced breakdown spectroscopy (LIBS), and applied the supervised classification model partial least squares–discriminant analysis to LIBS spectra. The model was able to discriminate geological sources and provide predictions for the origin of a selection of chert artefacts recovered at the Middle Magdalenian level from Cova del Parco (Lleida, Spain). [ABSTRACT FROM AUTHOR]

[Objective] The organic-enriched black bedded cherts in the Kuhfeng Formation were deposited in the Lower Yangtze during the Middle Permian. The hydrothermal cherts may be the key part for the relationship analysis between chert deposits and the extra-ordinarily high organic matter enrichment. This would be the basic theories for the shale gas exploration in this area. [Methods] This work uses major, minor, and rare-earth elements, combined with the petrology, to analyze the origin of chert and their tectonic setting for the Kuhfeng Formation in the Yeshan of Tongling and Pingdingshan of Chaohu, Anhui province. [Results] The black bedded cherts in the Chaohu area contain abundant siliceous sponge spicules and radiolarians. The cinerous cherts in the Kuhfeng Formation in the Tongling area contain extremely rare siliceous fossils and consist of micro-quartz. Hydrothermal proxies, such as Al/(Al+Fe+Mn), Eu/Eu*, Al-Fe-Mn diagram, and LuN/LaN, indicate a hydrothermal and biotic origin for the chert in the Kuhfeng Formation in the Tongling and Chaohu areas, respectively. The La-Th-Sc diagram and crossplot between La/Sc and Ti/Zr indicate oceanic island arc and active continental margin origins for the Tongling and Chaohu areas. [Conclusions] The chert in the Kuhfeng Formation in the Tongling area was primary deposited by hydrothermal activity. The silicic acid was brought by a hydrothermal vent near the slope environments. The black bedded cherts in the Lower Yangtze area are biotic in origin, but the source of silicon was related to the hydrothermal activity. The organic matter enrichment in the Kuhfeng Formation in the Lower Yangtze area may be related to the phytoplankton flourishment induced by the nutrient element input from hydrothermal activity. [ABSTRACT FROM AUTHOR]

The Belson site is located on an outwash plain draining the Early Algonquin stage of the central Great Lakes (coinciding with the Older Dryas stadial period around 14,000 Cal B.P) southwest across Lower Michigan into the Ohio tributaries. By 13,000 Cal B.P the St. Joseph River had incised multiple channels into this plain. On a terrace just north of a now-abandoned channel, a detailed surface study by Talbot from 2005–2018 showed several flake clusters largely of Attica chert, procured about 235 km southwest of Belson. A study of the surface sample was published by the authors in 2021 and indicated that the points were made with the Clovis technological pattern. Excavations in 2020–21 revealed hundreds of buried flakes and multiple tools in the lower, less-disturbed terrace sediment. Plotting of this material indicates successive occupations below the ploughed deposit and covering more than 30 m2. The buried assemblages are similar to the published surface assemblage with the addition of more small scrapers and manufacturing debris. Several of the buried tools have traces of proteins from a range of mammals, suggesting a broad-spectrum subsistence strategy. The documentation of a succession of little disturbed deposits with precisely recorded micro-debris will allow for testing of models describing settlement choice and developing dynamics of internal site organization. Initial analysis of recovered data provides support for an 'outcrop centered' model where high-quality chert outcrops serve as central places on the landscape. Samples of sediment and charcoal for identification and dating await study. [ABSTRACT FROM AUTHOR]

We reinvestigated the distinctive pentalocular fruits known as Sahniocarpon from the latest Cretaceous (late Maastrichtian) Deccan Intertrappean beds of central India, whose familial affinities within the angiosperms have previously been elusive. Using micro–computed tomography scanning to produce digital sections and surface renderings of the fruits and the contained seeds, supplementing the traditional thin section and peel methods, we discovered new characters useful in establishing affinities with the Burseraceae. The fruit is pedicellate with a hypogynous perianth, and each of the five locules contains a single-seeded pyrene, which bears narrow lateral wings similar to those of extant Boswellia (frankincense). Sahniocarpon fruits opened by the shedding of five septifragal valves, in the manner of dehiscent drupes in the Burseraceae. Co-occurring fruits, previously known as Cremocarpon deccanii Karanjekar, show a similar organization but differ by their smaller size. We consider the larger- and smaller-fruited species to represent two members of the same genus: S. harrisii Chitaley & Patil and S. deccanensis (Karanjekar) Manch., Kapgate & Judd comb. nov. These fruits, together with those of Bursericarpum indica Kumar et al. and others as yet undescribed, indicate that the Burseraceae were well represented in the vegetation of central India near the end of the Cretaceous and in the early Cenozoic. [ABSTRACT FROM AUTHOR]

Chert, a by-product rock of sand quarrying, has historically posed economic challenges for aggregate production, resulting in significant "waste" accumulation in quarries. Our study investigates the effect of microwave irradiation on the mechanical properties of chert gravel, a mineralogically homogenous material composed of fine quartz grains. The results, which demonstrate that increased irradiation time leads to a substantial decrease in chert gravel strength (by a factor of 4–6 for 2.5 min of irradiation), underscore the potential impact of this research on comminution processes. With quenching altering the fractional content of the samples after the crushing test, reducing the Gravel-to-Sand ratio, this study is driven by the promising potential of crushed chert gravel as a pivotal aggregate within the concrete and asphalt industries, offering a practical solution to their material needs. The urgent need to rehabilitate previously utilized quarry areas, offering an environmentally beneficial solution for which we all should be responsible, motivated the present study. [ABSTRACT FROM AUTHOR]

ABSTRACT The Barra Velha Formation and other Aptian pre‐salt deposits record the history of the proto‐Atlantic basin and the rifting of Gondwana. Studies have sought to characterize the depositional environment of the basin with a focus on carbonate fabrics and magnesium silicate clays. However, the water chemistry and fluid sources in the basin, the silica cycle, and how the basin evolved over time are not fully constrained. Additionally, current understanding of the microbiota that inhabited this basin is incomplete because microfossils have rarely been identified in pre‐salt deposits, especially on the Brazilian margin. This study describes authigenic chert in the Barra Velha Formation that preserves distinct, organic‐rich structures and textures. The petrographic relationships between the chert and carbonate suggest that both formed as authigenic phases, but their formation was temporally decoupled. These relationships and δ30Si and δ18O data suggest that chert post‐dates the formation and subsequent dissolution of the carbonates, and may have formed from a different fluid. By characterizing the chert–carbonate paragenesis and mechanism of chert formation, this study provides new insights into the fluid sources and complexity of the basin. Together, the results of this research suggest that the chert precipitated as primary, authigenic phases after karstification of the carbonate from a newly introduced, low temperature, freshwater fluid that was chemically distinct from the lake water. The chert preserves organic matter that is compositionally and texturally distinct from the void‐filling bitumen associated with the classically studied carbonate facies. Based on the composition and morphologies of organic structures, this is likely primary organic matter and a morphologically diverse microfossil assemblage preserved in place at the time of chert formation. Thus, this early chert provides new insights into the water chemistry, fluid sources and silica cycle in the basin, and represents a unique taphonomic window that helps us characterize the pre‐salt basin microbiota. [ABSTRACT FROM AUTHOR]

Seventy-one pumping tests were carried out in various dolomites, revealing two of the less-studied hydrogeological parameters related to double-porosity flow: the interporosity flow coefficient λ and the ratio between storage in the fractures and storage in the whole system (ω). Conceptually, they are both tied to the flow properties of the fractures and matrix and define the communication between these two hydrogeological domains. Five different groups of dolomites were included in this study, with different diagenesis types, crystal sizes, bed thicknesses, fracture intensities and chert contents represented. The results of both parameters reflect variations in the sedimentological and resulting hydrogeological properties of dolomites. The largest values of the interporosity flow coefficient λ (6.53 × 10−1) are found in dolomites formed by late diagenesis, exhibiting the highest degree of fracturing, resulting in fast responses in fractures and large λ values. The values of the storage ratio ω also vary (the range of most values is from 3.32 × 10−4 to 2.14 × 10−1), with the overall range almost completely filling all the theoretical limits from zero to one. The greatest values of ω are found in dolomites with the largest storage, due to the large number of small fractures, and silica diagenesis probably reduces the matrix storage. The correlations among the parameters show some significant relationships, especially between λ and Km, λ and Sf, ω and Sf, and ω and Sm. [ABSTRACT FROM AUTHOR]

Alkali–silica reaction (ASR) occurs when alkali oxides coming from the cement composition in concrete come together with reactive silica and moisture coming from the aggregate. Additional maintenance and repair costs caused by the development of ASR in concrete cause the cost to increase. However, thanks to the measures taken against ASR in the early period, it contributes to the creation of sustainable and durable concrete structures. The article investigated the usability of cherts with eight different chemical compositions as aggregates in ready-mixed concrete plants in Gümüşhane. Cherts have been investigated for alkaline reactivity and are intended to be used largely as a source for concrete plants. ASR length changes of the samples prepared according to ASTM C1260 standard were determined after 3, 7, 14, and 28 days of the curing period. Microstructural examination, ultrasonic P-wave velocity, and bending and compressive strength experiments supporting ASR were carried out. The obtained test results were compared between the reference (limestone) sample and each other, as well as with the values specified in the standards. The compressive and bending strength values of the samples increase depending on their ASR. It was observed that the crack structures and types increased depending on the increase in the crack values. [ABSTRACT FROM AUTHOR]

Cross-borehole electrical resistivity tomography (CHERT) technology has been implemented in field-scale CCS/CCUS (carbon capture and storage/carbon capture, utilization and storage) projects. It is highly desirable to investigate how to optimize the design of the ERT electrode arrays and corresponding working schemes for both laboratory experiments and field applications. A CHERT system was developed for laboratory experiments of CO2 geological storage applications. An optimization method was established for optimizing the structure of electrode arrays and corresponding working schemes. The developed CHERT system was calibrated systematically to determine the measurement range and accuracy of electrical impedance. Laboratory experiments were designed and implemented to validate the performance of the developed CHERT system. It has been illustrated that: (1) It is an essential step to optimize the structure of electrode arrays and corresponding working schemes of CHERT according to the real application background. The optimization method based on finite-element modelling provides an effective means for designing a field-scale CHERT system. (2) The quality of the images inverted from the CHERT data is highly dependent on the working schemes and specific modes, which is closely related to the size of the data sets used for the inversion. The AM-BN scheme is recommended due to the better uniformity of the resultant sensitivity field and application to larger borehole spacing. (3) Based on the calibration, the measurement range of the developed CHERT system can be determined as 100 Ω to 4.5 kΩ with an error limit of 1.5%. The maximum relative errors of the impedance magnitude and phase angle are 5.0% and 7.0%, respectively. Based on the test results the location of the CO2-bearing objects can be identified accurately. The shapes of the tested objects present distortion to some extent, but this can be alleviated by selecting working modes with a larger size of data set. [ABSTRACT FROM AUTHOR]

This study describes an assemblage of Dzieduszyckia brachiopods preserved in sedimentary barite deposits from the Famennian, Upper Devonian of Nevada, USA. The brachiopods lived in a methane-seep environment like those described from Sonora, Mexico, and the Western Meseta, Morocco. Although the original carbonate fabrics are not preserved, pockets of limestone within the brachiopod barite are depleted in with δ13C values ranging from -31.1 to -27.3‰ VPDB. The fossils are preserved as internal and external molds only but record enough detail to demonstrate key internal features of Dzieduszyckia such as a pronounced dorsal septum, septalium, and vertical dental plates. The lack of common bifurcation or trifurcation of the costae as well as larger size of the shells recommends against inclusion within D. sonora as previously published. Based on the number of costae per width of shell, it is possible that there are two distinct species in Nevada, like other localities in Morocco, the Urals, and South China. These new data expand the body of knowledge of these earliest dimerelloids and it is hypothesized that this seep-dwelling macrofauna arose from depauperate-successful lineages between the Famennian biotic crises. As nearly all global Dzieduszyckia deposits are associated with active tectonic margins, it is also suggested that tectonically-driven methane expulsion in low nutrient waters spurred the evolution of dimerelloids. [ABSTRACT FROM AUTHOR]

We report the first discovery of vase-shaped microfossils (VSMs) and possible multichambered foraminifera from the Ediacaran rocks of Saudi Arabia. The Ediacaran successions of Saudi Arabia are well exposed in the northwestern and central part of the Arabian plate but are relatively understudied due to the lack of economic potential. The exposures can be found in different small sedimentary basins distributed along the flanks of Najd Fault system of the western Arabian Plate. The Dhaiqa sub-basin located near the historic city of Al-Ula contains some of the best exposures of Ediacaran Mattar and Dhaiqa Formations with collective exposure almost 400 m thick. These formations (especially the Dhaiqa Formation) were investigated to describe sedimentary facies, depositional environment, and possible microfossils. This study focuses on the identification of vase-shaped microfossils and possible trochamminid foraminifera of Ediacaran age that are herein recognized for the first time in Saudi Arabia. Outcrop samples were thin-sectioned and analyzed to reveal nine sedimentary facies belonging to four facies associations. The observed microfossils were found in a total of four samples from the cherty/siliceous carbonate and sandy microbialite facies. The microfossils are observed to be associated with diagenetic chert, which is abundant in these facies. The two facies contain a sparse microfossil assemblage with vase-shaped microfossils, which are single-chambered microfossils of uncertain taxonomic affinity, and possible multichambered agglutinated foraminifera that resemble trochamminids. [ABSTRACT FROM AUTHOR]

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This study characterizes the microstructure and mineralogy of 132 (ODP sample), 1000 and 1880 million‐year‐old chert samples. By using ultra‐small‐angle X‐ray scattering (USAXS), wide‐angle X‐ray scattering and other techniques, the preservation of organic matter (OM) in these samples is studied. The scarce microstructural data reported on chert contrast with many studies addressing porosity evolution in other sedimentary rocks. The aim of this work is to solve the distribution of OM and silica in chert by characterizing samples before and after combustion to pinpoint the OM distribution inside the porous silica matrix. The samples are predominantly composed of alpha quartz and show increasing crystallite sizes up to 33 ± 5 nm (1σ standard deviation or SD). In older samples, low water abundances (∼0.03%) suggest progressive dehydration. (U)SAXS data reveal a porous matrix that evolves over geological time, including, from younger to older samples, (1) a decreasing pore volume down to 1%, (2) greater pore sizes hosting OM, (3) decreasing specific surface area values from younger (9.3 ± 0.1 m2 g−1) to older samples (0.63 ± 0.07 m2 g−1, 1σ SD) and (4) a lower background intensity correlated to decreasing hydrogen abundances. The pore‐volume distributions (PVDs) show that pores ranging from 4 to 100 nm accumulate the greater volume fraction of OM. Raman data show aromatic organic clusters up to 20 nm in older samples. Raman and PVD data suggest that OM is located mostly in mesopores. Observed structural changes, silica–OM interactions and the hydrophobicity of the OM could explain the OM preservation in chert. [ABSTRACT FROM AUTHOR]

Fungi are integral to well-functioning ecosystems, and their broader impact on Earth systems is widely acknowledged. Fossil evidence from the Rhynie Chert (Scotland, UK) shows that Fungi were already diverse in terrestrial ecosystems over 407-million-years-ago, yet evidence for the occurrence of Dikarya (the subkingdom of Fungi that includes the phyla Ascomycota and Basidiomycota) in this site is scant. Here we describe a particularly well-preserved asexual fungus from the Rhynie Chert which we examined using brightfield and confocal microscopy. We document Potteromyces asteroxylicola gen. et sp. nov. that we attribute to Ascomycota incertae sedis (Dikarya). The fungus forms a stroma-like structure with conidiophores arising in tufts outside the cuticle on aerial axes and leaf-like appendages of the lycopsid plant Asteroxylon mackiei. It causes a reaction in the plant that gives rise to dome-shaped surface projections. This suite of features in the fungus together with the plant reaction tissues provides evidence of it being a plant pathogenic fungus. The fungus evidently belongs to an extinct lineage of ascomycetes that could serve as a minimum node age calibration point for the Ascomycota as a whole, or even the Dikarya crown group, along with some other Ascomycota previously documented in the Rhynie Chert. Here, the authors describe a pathogenic fungus from a 400-million-year-old fossil plant from the Devonian Rhynie Chert in Scotland. They use advanced imaging methods to determine that the fungus belongs to the sac fungi, the most diverse group of Fungi today. [ABSTRACT FROM AUTHOR]

The Sichuan Basin in Southeastern China contains extensive bedded cherts dating back to the Late Ordovician–Early Silurian period. To investigate the origin and depositional environment of these cherts, we conducted a comprehensive study using field observations, thin sections microscopic, silicon isotope analysis, and major and trace element geochemistry of samples from three sections. Our results indicate that the cherts from Wufeng and Longmaxi formations are non-hydrothermal, normal biogenic seawater deposits mainly affected by terrigenous input and slightly associated with volcanic ash. Al2O3/(Al2O3 + Fe2O3T) and LaN/CeN ratios, δCe values and Fe2O3T/TiO2 − Al2O3/(Al2O3 + Fe2O3T), Fe2O3T/(100 − SiO2) − Al2O3/(100 − SiO2), 100 × (Fe2O3T/SiO2) – 100 × (Al2O3/SiO2), and LaN/CeN − Al2O3/(Al2O3 + Fe2O3T) discrimination diagrams indicated that the bedded cherts deposited in the continental margin environment.

Southwestern Iberia has played a key role in characterizing Late Pleistocene human ecodynamics. Among other aspects of human behavior, chert procurement and management studies in this region have received increasing attention in the past two decades, especially focusing on the sites showing repeated human occupation, such as the case of Vale Boi (Southern Portugal). However, these studies have been very limited in their geographical scope, and mostly focused on brief macroscopic descriptions of the raw materials. To further our knowledge of the relationship between regional availability of raw materials and its impact on human adaptations and mobility, a more detailed approach to characterizing geological sources is needed. This paper characterizes chert raw materials location, diversity, and availability in a geologically well-defined region of southern Portugal ‐ the Algarve. Through macroscopic and petrographic approaches, we provide a detailed characterization of geological chert sources to build a frame of reference for chert exploitation in the region. Our results show that there are four main chert formations in Algarve, and that despite the within-source variability, sufficient differences at macroscopic and petrographic levels are present to allow clear source attribution. These results provide a baseline for raw material studies in archaeological assemblages across southwestern Iberia, that will be essential to further characterize the dynamics of human behavior in some of the most important eco-cultural niches. [ABSTRACT FROM AUTHOR]

New data are presented for the rare-metal bearing A-type granitoids of the Al-Ghurayyah stock in the northwestern segment of the Arabian Shield, a composite pluton intruding metamorphosed volcano-sedimentary successions of the Silasia Formation. Metals in the granitoids are variably enriched, with up to 1 990 µg/g Zn, 7 680 µg/g Zr, 2 316 µg/g Nb, 232 µg/g Ta, 485 µg/g Hf, 670 µg/g Th, 137 µg/g U and 1 647 µg/g total rare earth elements (REE). The silexite is highly mineralized and yields higher maximum concentrations of several metals than the granitoids, including up to 1 860 µg/g Y, 9 400 µg/g Zr, 878 µg/g Hf, 1 000 µg/g Th, and 2 029 µg/g total REE. The Al-Ghurayyah stock has been assigned to an intraplate setting. Lithospheric delamination led to generation of mantle melts that supplied heat to melt the juvenile crust of the ANS. The fluorine and rare-metal enriched parental magma evolved by fractional crystallization. The quartz-rich silexite, distinct in character from ordinary hydrothermal vein quartz, is inferred to be co-genetic with the granitoids on the basis of their similar REE patterns; it is interpreted as a small volume of residual magma enriched in SiO2, volatiles, and trace metals. Mineralization took place both at the magmatic stage and later during a hydrothermal stage that concentrated these elements to economic grades. [ABSTRACT FROM AUTHOR]

The early Aptian Selli Oceanic Anoxic Event 1a (ca 120 Ma) is a major Mesozoic episode of biotic, climatic, environmental and geochemical perturbations associated with the extensive burial of organic matter. Based on the new sedimentological, biostratigraphic and carbon‐isotope data from the Kazhdumi Intrashelf Basin, this study tracks the Oceanic Anoxic Event 1a‐associated perturbations along the north‐eastern margin of the Arabian Plate. The studied succession has five complete third‐order sequences with three facies associations: (i) deep open‐marine and intrashelf basin; (ii) shallow open‐marine mid‐ramp; and (iii) inner ramp. The Oceanic Anoxic Event 1a‐equivalent deposits include the former two facies associations – (i) and (ii) – and are 25 to 31 m thick, which corresponds to the accumulation rates of ca 1.9 to 3.1 cm kyr−1 (uncorrected for compaction) based on the 1.0 to 1.3 Myr duration of the event. The interval retained a high‐resolution record of carbon‐isotope and sea‐level fluctuations, which enables correlation across the Arabian Plate and Tethys. The Oceanic Anoxic Event 1a onset is marked by a biotic change from ostreid‐dominated shallow‐marine limestone with abundant foraminifera (Palorbitolina lenticularis and Choffatella decipiens) to dark grey deep‐water planktonic foraminifera‐rich and radiolaria‐rich limestone with chert and organic‐rich shale (Radiolarian Flood Zone). The upper oceanic anoxic event part of 1a is characterized by the shallowing‐upward, backstepping facies marking the return to a shallow open‐marine setting, albeit without recovery of the Palorbitolina–Choffatella association. Deep open‐marine deposition (Kazhdumi Tongue) was restored early during the Oceanic Anoxic Event 1a recovery in the latest early Aptian. A return to shallow open‐marine environments with Mesorbitolina‐rich limestone marks the beginning of the late Aptian, followed by a major sea‐level fall and karstification. This study resolves some of the uncertainties related to the order and timing of the events influencing the environmental disturbances across the eastern Arabian Plate during Oceanic Anoxic Event 1a and stresses the importance of shallow carbonate‐dominated intrashelf basins as faithful recorders of carbon‐isotope and sea‐level oscillations and palaeoenvironmental changes during global oceanic perturbations. [ABSTRACT FROM AUTHOR]