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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]

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]

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]

[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]

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]

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]

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]

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.

Microfossils are important components of sedimentary rocks used for palaeontological, biostratigraphic, palaeoenvironmental and palaeoclimatic investigations. They are usually extracted from rocks using an acid solution, which might vary depending on the embedding rock lithology. Here we propose a new method using common NaOH (sodium hydroxide; soda) to digest cherts (micro‐ and cryptocrystalline quartz) instead of the standard technique based on HF (hydrofluoric acid). This new method allows the collection of undamaged specimens of different kinds of microfossils, such as conodonts, radiolarians, teeth and dermal scales, the minerology of which is still preserved (e.g. biogenic apatite in conodonts). The use of soda is thus recommended, as it is less dangerous, less expensive, and it better preserves the extracted microfossils both in shape and mineralogy. [ABSTRACT FROM AUTHOR]

In this petrographic and geochemical study, we differentiated diverse quartz botryoids, including circular-concentric, twinned, columnar, wavy, and stromatolite-like structures versus synchronous biotic patterns of similar geometry and size dimensions (filamentous traits and stromatolites) in Precambrian cherts of Barberton, South Africa, and Gunflint, Canada. The botryoidal habits explored retained self-similar patterns of radially aligned acicular quartz with concentric laminae, which are not documented in biologically built stromatolites. These ancient fractals and their composition imitate those in chemically oscillating reactions, implying that the precipitation of botryoids was fueled by abiotic diagenetic degradation of organic matter and subsequently metamorphosed into chert. [ABSTRACT FROM AUTHOR]

The Upper Jurassic carbonates representing the microbial-sponge megafacies in the area of the Kraków- Częstochowa Upland (KCU) were locally silicified. In the reclaimed Lipówki Quarry, in Rudniki near Częstochowa (in the northern part of the Upland), macroscopically different silicification products were observed in blocks of Upper Jurassic limestones, deposited as mining waste. Two varieties were distinguished: (i) chert concretions representing the I silicification stage and (ii) light-brown, silicified limestones infilling the fractures in chert concretions or forming the cortices around the concretions or forming irregular bodies, all representing the II silicification stage. The diagnostic features are the following: (i) macroscopic development, (ii) the presence of moganite exclusively in chert concretions and (iii) significant differences in crystallinity index (CI) values, namely: 0.1-0.7 for chert concretions and 6.0-6.6 for silicified limestones. The formation of chert concretions was initiated as early as in unconsolidated sediment, whereas the II silicification stage followed the chemical compaction of the limestones. The results of geochemical analyses of the products of both silicification stages indicated that the probable source of silica were the low-temperature hydrothermal solutions. Two types of fractures were found in the chert concretions, generated during different tectonic events. The older, open fractures were formed during the extension of the Late Jurassic sedimentary basin, which formerly occupied the territory of the more recent KCU. These fractures were infilled with unconsolidated, fine-detrital carbonate sediment, in which the concretions were embedded and finally silicified in the II silicification stage. The younger, closed fractures, transversal to those filled by the products of II silicification stage, along which small displacements are evident, document the later tectonic deformations presumably related to Cenozoic faulting. [ABSTRACT FROM AUTHOR]

In this paper we present new data on the Jurassic radiolarian assemblages collected in seven sections of the sedimentary cover of the Mirdita ophiolites in Albania. These ophiolites form an outstanding NNW-SSE trending ophiolitic belt representing the remnants of the Mesozoic Neo-Tethyan oceanic lithosphere in the Mediterranean area. The studied sections were sampled in the sub-ophiolitic mélange of the Western Mirdita ophiolites (Rubik Complex) and in the Eastern Mirdita ophiolitic sequences. In the sub-ophiolitic mélange the oldest ages of radiolarians associated with the basalts are referable to the UAZ 4-5 (late Bajocian to latest Bajocian-early Bathonian) and UAZ 5 (latest Bajocian-early Bathonian). In the radiolarian cherts belonging to the Eastern Mirdita ophiolites similar ages were found: from UAZ 5 (latest Bajocian-early Bathonian) to UAZ 5-7 (latest Bajocian-early Bathonian to late Bathonian-early Callovian). These new biostratigraphic ages are consistent with the tectono-magmatic evolution of the Jurassic Neo-Tethys. In fact, the UAZ 4-5 and UAZ 5 correspond to the very early stages of subduction initiation, whereas the slightly younger UAZ 5 and UAZ 5-7 ages found in the Eastern Mirdita ophiolites could correspond to the subsequent mature stage of the subduction. [ABSTRACT FROM AUTHOR]

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Sedimentary and hydrothermal pyrites contained in selected Malaysian black shale and cherts have been analysed using laser ablation inductively coupled plasma (LA ICP-MS) and electron probe microanalysis (EPMA) at the University of Tasmania, Australia. This study shows that gold is concentrated in sedimentary and hydrothermal pyrite in the Middle Permian to Late Triassic black shales and Devonian cherts. According to LA ICP-MS analysis, gold contents in pyrite varied from 0.5 to 0.8 ppm Au in the Permo-Triassic black shale and between 0.2 and 0.8 ppm Au in the Devonian cherts. The lowest level of gold (0.3 ppm Au) was observed in the Permo-Triassic black shale that crops out at the Selinsing gold mine. In the Permo-Triassic period, the selenium contents display one peak (average range: 63.4–103.4 ppm Se) that is far from any gold deposit and one lowest point (average: 5.3 ppm Se) at the Selinsing gold deposit. In the Devonian period, the selenium content in sedimentary pyrite shows a peak (72.6–243.8 ppm Se) in the cherts. EPMA and LA ICP-MS data show consistent Se content variation in the Devonian and Permo-Triassic periods. Using selenium as a proxy for atmospheric oxygenation, the lowest level of Se content in the Permo-Triassic period is believed to decrease atmospheric oxygenation, as recorded in sedimentary pyrite found in black shale from the Selinsing gold deposit. The two peaks of selenium contents are interpreted as periods of increased atmospheric oxygenation. From an exploration perspective, the concentration of gold in sedimentary pyrites makes them sources for gold in the central sedimentary basin of Peninsular Malaysia. Therefore, the two maximum levels of Se and gold content during Permo-Triassic and Devonian times correspond to two stratigraphic levels of potential for orogenic gold mineralisation in the district. The EPMA data show significant values of Co over Ni in pyrite from the Gua Musang, Semantan, and Karak formation black shales, indicating a volcanic contribution of Co during the formation of sedimentary pyrite. Based on the current study's findings, gold exploration should not be restricted to areas in and around the Selinsing gold mine, Buffalo Reef, Penjom mine, Tersang mine, and Bukit Koman mine but can be extended to BRSZ Units 1 and 2, Gua Musang, and Karak formations in the central belt of Peninsular Malaysia. [ABSTRACT FROM AUTHOR]

Automatic techniques have not been applied in the geochemical discrimination of marine, terrestrial and hydrothermal cherts, which is critical to retrieving the paleoenvironmental information of ancient sedimentary basins. Here, we applied three supervised machine‐learning methods to analyse the labelled geochemical compositional data (32 major and trace elements) of cherts, including the support vector machine (SVM), sparse multinomial regression and linear discrimination analysis. Our results show that these machine‐learning methods can successfully discriminate different chert types, as the lowest classification score is 79%. Among the methods, the SVM is the most powerful approach (classification score 88%, on average), even though it is hard to be geochemically interpreted. Sparse multinomial regression and linear discrimination analysis are also efficient approaches (mean classification score 84%), which can be used to extract the important elements and the most representative sample for each chert type. Especially, the linear discrimination analysis can construct binary discrimination diagram superposed with biplot rays and posterior probability‐based decision boundaries, which could be quickly applied and explained by other researchers. Furthermore, the successful discrimination of different chert types indicates that cherts derived from different silica sources have different geochemical signatures, albeit mixing between different sources of silica during chert formation is common. Last, the general geochemical features of each chert type were summarised based on geochemical information extracted by machine‐learning methods and previous geochemical studies. [ABSTRACT FROM AUTHOR]

This archaeometric study aims at characterizing the archaeological finds belonging to the lithic industry from La Calvera rock shelter (Camaleño, Cantabria) and at hypothesizing the possible provenance of each material. The site, located in the mountainous area of Picos de Europa National Park (more than 1000 m a.s.l.) close to the megalithic complex of Peña Oviedo, is characterized by the presence of hearths and charcoal remains, ancient pottery, and a rich lithic assemblage composed of siliceous rocks dating back to >8000 BP and linked to the first Holocene occupations of the Cantabrian Mountains. For the study of the rock shelter's lithic assemblage, a multi-analytical approach was used: SEM-EDS and XRD analyses were performed to define the microtextural characteristics of samples and to identify the amorphous/crystalline phases; physical and mechanical tests were conducted to define the petrophysical properties (density, porosity, imbibition and saturation indexes, mechanical strength) of the samples. Preliminary data of chemical compositions, obtained by portable XRF, are also presented. The results show that the different siliceous materials (quartzite, cherts, hyaline quartz) can be distinguished through the basic analytical techniques used here. In addition, most of the archaeological samples have mineralogical and petrographic features similar to the natural samples coming from nearby outcrops, corroborating the hypothesis of a local material supply. The presence of local sources of useful raw materials could have favoured the site's occupation. Finally, the diverse compositional and textural feature of the analysed materials result in different mechanical properties (porosity, density, hardness, workability), so they likely had different uses and technical functions. [ABSTRACT FROM AUTHOR]

Rare earth element (REE) fluorocarbonate mineralization occurs in lacustrine shales in the Lower Devonian Rhynie chert, Aberdeenshire, UK, preserved by hot spring silicification. Mineralization follows a combination of first-cycle erosion of granite to yield detrital monazite grains, bioweathering of the monazite to liberate REEs, and interaction with fluorine-rich hot spring fluids in an alkaline sedimentary environment. The mineral composition of most of the fluorocarbonates is referable to synchysite. Mineralization occurs at the surface, and the host shales subsequently experience maximum temperatures of about 110 ℃. Most fluorocarbonate mineralization originates at much higher temperatures, but the Rhynie occurrence emphasizes that low-temperature deposits are possible when both fluorine and REEs are available from granite into the sedimentary environment. [ABSTRACT FROM AUTHOR]

The chert gravels are a by-product of sand mining in the south of Israel; the reserves amount to tens of millions of tons and continue to grow. The attempts of their comminution for the production of aggregates by conventional mechanical methods have not yet been successful due to the high abrasiveness, as well as the flaky form of their fracturing. This study was motivated by the need to find an alternative method to rock comminution that would ensure aggregate production in line with the requirements of the asphalt and concrete industry. This article deals with the first inevitable stage on the way to this goal, which consists of an extensive laboratory study of the physical and mechanical properties of the chert gravels, as well as the features of their chemical composition. The results show that the chert rock, consisting of quartz micro grains, contains calcium, sulfur, phosphorus, and barium impurities. The rock is characterized by extremely low porosity and water absorption (less than 1%) and high values of tensile strength (10.8 ± 3.3) and electrical resistivity (23.0 ± 11.9 kΩm). The cubic uniaxial compression strength of the rock is relatively not high (37.3 ± 10.4 MPa), which contradicts the assessment made based on the Schmidt hammer and Point Load studies (158 ± 30.4 MPa and 321 ± 118.5 MPa, respectively). [ABSTRACT FROM AUTHOR]

The Changning‐Menglian Belt in western Yunnan, China, is one of the key regions to decode the evolution of Palaeo‐Tethys. However, the work has been hampered considerably by the loose definition and composite nature of some stratigraphic units in the belt. These units normally have varied lithological components (slices of sequences), most of which yield scarce fossils. An example is the 'Middle‐Upper Devonian (D2‐3)' unit, which was established to accommodate a series of cherts, shales, siltstones and sandstones, occurring rather frequently in the central zone of the Belt. Its age assignment was mainly based on the Late Devonian conodonts from some siliceous shale intervals. However, the 'D2‐3' unit contains strata of ages other than Middle‐Late Devonian, as has been indicated by a few studies in the Chahe‐Manxin area. The Late Permian radiolarians have been obtained from bedded cherts of the 'D2‐3' in Paqiu area which provided the first solid evidence for the presence of Late Permian beds in the 'D2‐3' in this area. Radiolarians from two chert outcrops about 3 km apart can be assigned to two Wuchiapingian‐Changhsingian assemblages, namely, the Albaillella levis and Albaillella protolevis assemblages, respectively, with the former being slightly younger than the latter. Statistical analysis of Permian radiolarians from different localities in the Belt shows that Late Permian radiolarians are much commoner than Middle Permian radiolarians and Early Permian radiolarians. A review of the taxonomical composition of Late Permian radiolarians of the Belt shows that faunas from different localities can be classed into three groups, according to their contents of albaillellaians, latentifistularians, entactinarians and spumellarians, whose depositional environments correspond respectively to deep water (>500 m), intermediate water (200–500 m), and shallow water depths (<200 m). Such a composition indicates that the Late Permian radiolarian‐bearing siliceous rocks in the Changning‐Menglian Belt are slices from various palaeogeographic settings. [ABSTRACT FROM AUTHOR]

Cherts are used to reconstruct the evolution of seawater δ18O and temperature over geological time. However, given the influence of marine diagenesis, reconstructing seawater from the isotope composition of cherts is not straightforward, resulting in ambiguity of interpretation. Here, we present a detailed isotope and petrographic investigation of deep‐sea drilled 135–40 Ma cherts with focus on the effects of marine diagenesis. We combined triple O‐isotope data with in‐situ δ′18O‐16OH/16O measurements using secondary ion mass spectrometry (SIMS). We also provide electron microprobe maps, traditional δ′18O measurements from petrographically diverse domains, and δD and H2O wt.% values. The bulk δ′18O values range between 29‰ and 38‰ in our collection, while SIMS δ′18O data reveal significant intra‐sample heterogeneities up to 6‰ related to distinct petrographic features (e.g., filled radiolarian tests) and to micrometer‐scale variations in silica forms. Further, the δ′18O—Δ′17O values of these seafloor‐drilled cherts plot near and under equilibrium curve. Both triple‐O and SIMS δ′18O results reflect diagenesis in presence of marine pore waters at temperatures higher than ambient seawater, which is especially appreciable in cherts deposited on young oceanic crust. Despite the relatively constant δ18O seawater values over last 135 Ma, the marine silica spanning between 0 and 135 Ma occupies a wide compositional space in the δ′18O—Δ′17O rather than an equilibrium curve. The δ′18O values of cherts from modern‐seafloor positively correlate with the oceanic crustal age at the time of deposition, hinting at the importance of the heat flux in the diagenetic recrystallization of marine silica. Plain Language Summary: Chemical sediments extracted from seafloor represent an archive of ocean temperatures and solutes. Chemical resilience of siliceous sediments with composition of >90 wt.% SiO2 presents a promising avenue to constrain temperature of ancient oceans from distant geological epochs. However, such rocks termed cherts undergo complex recrystallization during compaction and lithification below the seafloor, preventing direct measurements of ocean temperatures. To isolate the effect of diagenesis, we carefully investigated several Mesozoic and Cenozoic seafloor‐drilled cherts. We used oxygen isotope ratios as a common proxy for temperature to test for the effects of recrystallization of these cherts that were buried at depths between 80 and 960 m. We combined two state‐of‐the‐art types of isotope measurements: (a) non‐destructive in‐situ measurements from microscopic domains and (b) bulk high‐precision triple O‐isotope ratios. We observe complex mineralogical and isotope compositions on the scale of 10–100 μm. The triple O‐isotope ratios depict the combined effects of original precipitation from seawater column and the thermal regime of recrystallization in subseafloor conditions. The compiled O‐isotope ratios of silica extracted from seafloor correlates with the age of oceanic crust. Since the age of oceanic crust and the heat flux are related, these observations hint at the importance of the sediment geothermal evolution during diagenesis. Key Points: Mesozoic and Cenozoic seafloor‐drilled cherts were measured for triple O‐isotope and in situ secondary ion mass spectrometry δ′18O‐16OH/16O valuesIn situ measurements display up to 6‰ range in the δ′18O values of seafloor‐drilled chertsThe δ′18O‐Δ′17O values of cherts plot near and under the silica‐seawater equilibrium curve (20°C–40°C). Together with the in‐situ variability, these data are best explained by a combination of original precipitation and recrystallization in sub‐seafloor conditions [ABSTRACT FROM AUTHOR]

Pelagic deep-sea siliceous successions in accretionary complexes preserve precious records of a vast deep seafloor that is now lost due to plate subduction. Microfossils are the key means of age assignment of these successions, but poor preservation due to tectonic deformation and metamorphism at the subduction zone hamper biostratigraphic records. X-ray computed microtomography, while not widely used in biostratigraphic studies until now, allows us to visualize fossils that are impossible or difficult to extract from host rocks due to poor preservation. In this study, we applied this method on conodonts from a pelagic chert–claystone succession in Okoshizawa, Iwaizumi Town, Northeast Japan, using a laboratory-based X-ray microscope. This work is a first close look at conodont biostratigraphy across the Carboniferous–Permian boundary in pelagic deep Panthalassa. We identified conodonts including ten species that are used as zonal markers in intensely studied areas such as around the East European Platform and Midcontinent United States. Based on the occurrence of conodonts, the studied section in Okoshizawa was correlated to the lower Moscovian to middle Artinskian. Confirmation of Moscovian to Artinskian age diagnostic conodonts from pelagic Panthalassa strengthens their role as global biostratigraphic indicators. By identifying more numerous specimens compared to the conventional hydrofluoric acid dissolution method, we were able to obtain information about conodont faunal characteristics around the Carboniferous–Permian boundary in pelagic deep areas of Panthalassa. The dominant taxa changed from Streptognathodus to Mesogondolella in the middle Asselian, probably reflecting an ecological takeover by the latter in the deep waters.

In this paper, and in previous works, quartzites within the Sable de Fontainebleau are clearly shown to occur only near outcrops in Plio-Pleistocene plateau landscapes and are related to groundwater flows. These arrangements, together with dating of encased calcites, led us to consider that silicification occurred during Plio-Pleistocene glacial stages. The precipitation of silica was most likely triggered by cooling of groundwaters as they approached cold zones in the regolith close to points of discharge. We describe the arrangement and morphologies of quartzites in Tertiary sand formations in the Paris Basin to demonstrate how cold climates could have influenced hydrologic regimes and promoted silicification. The coeval precipitation of calcite and silica in gypseous formations at the edges of plateaux-bordering valleys, along with the dissolution of gypsum, also points to interactions between silica-laden groundwater and carbonate host rocks during cold periods. In parallel, the distribution and micromorphology of silicifications in associated Tertiary limestone formations suggests that they formed during cold climates in the Quaternary. These are key pointers to the role of groundwater in regolith environments in controlling silicification processes. We detail a link to palaeosurfaces of the distinctive meulières facies in the Paris Basin. Geotropic structures and micromorphological organisations are the basis of new ideas about their origin in a combination of vadose and phreatic environments and proximity to impervious cold horizons. The active zone in a permafrost landscape is a good hydrological example. All silicifications in Tertiary formations in the Paris Basin can be linked to the hydrology of Quaternary periglacial environments in a single model. This could apply more widely to similar silicifications elsewhere and be tested using new analytical techniques that date silicifications and unravel the isotopic relationships between silicification, groundwater composition and the prevailing climate.

This study integrates provenance and statistical data, along with published sedimentological results, applied on the Lower Oligocene submarine‐fan deposits in Pindos foreland basin. Twelve outcrops were analysed using conglomerate clast composition, petrographic and statistical analysis and this integration suggests that the studied deposits were sourced by the Pindos Orogen. Conglomerate clast composition analysis suggests that the studied deposits contain mainly limestone clasts, followed by sandstone and chert clasts. This conclusion is further supported by the petrographic and cathodoluminescence analyses that have been conducted on the conglomerate matrix and, additionally, suggest the influence of a low‐grade metamorphic source. Potential source rock candidates in the Pindos Orogen that provided the detritus in the succession are represented by the Mesozoic carbonates (limestone and chert), the Cenozoic transitional (mixed carbonate and siliciclastic) and the Cenozoic clastic submarine‐fan deposits (sandstone). The rock units of Pelagonian zone likely represent the low‐grade metamorphic source rock. The principal component and cluster analysis of clast lithologies suggest the existence of three compositional clusters, with the first one being controlled by black chert clasts, the second one by sandstone clasts and the third one by limestone and red chert clasts. The upward increase of chert and lithic fragment abundances is ascribed to the progressive unroofing of the Pindos orogenic source regions. This study utilizes the Pindos foreland basin as an example to unravel the contribution of orogenic processes on sedimentary provenance of the adjacent pro‐foreland basins. Furthermore, this study highlights the advantage of implementing a multi‐faceted approach, including statistical treatment in sedimentary provenance. [ABSTRACT FROM AUTHOR]

The Ginosa archaeological storage reorganization, has made it possible to isolate and study the lithic set found at the rupestrian settlement of Rivolta, in the ravine of Ginosa (Taranto). In 2004 an archaeological research campaign in the settlement led to the stratigraphic excavation of a cistern (15th-18th century AD. For the filling action, this work proposes an episode contemporary or subsequent to the 18th century AD). The paper exposes how mechanical tinder flints can be recognized in comparison with prehistoric flints, describing the Techno-Functional aspects in a morphological-technological and traceological sense. In US 6, 11 lithic products have been documented: 9 between Paleolithic supports and cores made from the chert of the Fossa bradanica, divided into systemic categories Kombewa-Levallois, Levallois, Non-Levallois and bipolar on an anvil, as well as pièces esquillées; 2 tinder flint stones in nodular flint, for which one was also hypothesized to be used for manual rubbing, a hypothesis that in this article is revisited by means of new considerations of an experimental nature. The Techno-Functional approach of the tinder flint stones made it possible to identify them as such, by retracing the processes of realization of the production aims, supported by the functional analysis for the evaluation of actual use. [ABSTRACT FROM AUTHOR]

Acidophytic alpine mat-grass swards are rare in the alpine belt of the predominantly calcareous Southeastern Alps of Slovenia, mostly occurring where limestone is admixed with marlstone or chert. Those for which we were able to make phytosociological relevés can be classified mainly into two syntaxa: Carici curvulae-Nardetum strictae vaccinietosum gaultherioidis and Sieversio-Nardetum strictae vaccinietosum. At slightly lower elevations, in the forest zone of the subalpine plateau Pokljuka, we found similar swards occupying small areas in frost hollows with luvisol on limestone. They include character species of various subalpine-alpine sward and snow bed communities and are classified into the syntaxon Homogyno alpinae-Nardetum scorzoneroidetosum croceae. [ABSTRACT FROM AUTHOR]

The symbiotic partnership of plants and fungi was a critical means of nutrient uptake during colonization of the terrestrial surface. The Lower Devonian Rhynie Chert shows evidence for extensive phosphorus mobilization in plant debris that was pervasively colonized by fungi. Sandy sediment entrapped with fungi‐rich phytodebris contains grains of the phosphate mineral monazite which exhibit alteration to highly porous and leached surfaces. Mixed manganese‐iron oxide precipitates contain up to 2% P2O5. The mobilization of Mn, Fe, and P are all features of mycorrhizal nutrient concentration. However, the ecosystem was also exposed to toxic elements from hot spring hydrothermal activity. The oxide precipitates include titanium and iron‐titanium oxide which sequestered potentially toxic tungsten and antimony. Abundant pyrite framboids in the Rhynie Chert indicate that plant decomposition included microbial sulfate reduction. This caused the removal of some of the arsenic from the groundwaters into the pyrite, which reduced toxicity while leaving enough for putative arsenic metabolism. These relationships show the mineral component of the ecosystem modified the geochemistry of ambient waters. Plain Language Summary: The symbiotic partnership of plants and fungi was a critical means of nutrient uptake during colonization of the terrestrial surface. The Lower Devonian Rhynie Chert shows evidence for extensive phosphorus mobilization in plant debris that was pervasively colonized by fungi. Sandy sediment entrapped with fungi‐rich organic matter contains grains of the phosphate mineral monazite which exhibit alteration to highly porous and leached surfaces. The ecosystem was also exposed to toxic elements from hot springs. Precipitates of oxide minerals sequestered potentially toxic tungsten and antimony. Iron sulfide allowed the removal of excess arsenic from the groundwaters. These relationships show the mineral component of the ecosystem modified the geochemistry of ambient waters. Key Points: The plant‐bearing Rhynie Chert contains authigenic mineral phases, including pyrite, and manganese‐iron and titanium oxidesAuthigenic phases may be products of bacterial and fungal components and sequestered potentially toxic elements, including As, Sb, and WDetrital monazite was leached to supply phosphate, which was required by fungi in symbiosis with plants [ABSTRACT FROM AUTHOR]

Penelitian artefak litik Toalean yang semakin intensif masih belum banyak melakukan perbandingan teknologi pembuatan alat batu. Studi perbandingan perlu dilakukan untuk mengetahui kemungkinan adanya perbedaan strategi adaptasi teknologi berdasarkan aspek lingkungan. Tulisan ini membahas studi perbandingan artefak litik Toalean dari situs Leang Jarie yang ada di dataran rendah Maros-Pangkep dan situs Cappalombo 1 di dataran tinggi Bontocani. Metode yang digunakan adalah klasifikasi dan analisis temuan artefak litik, serta survei dan observasi sumber bahan baku di sekitar situs. Hasil studi perbandingan menunjukkan adanya strategi adaptasi terhadap kondisi bahan baku dan menghasilkan tren teknologi yang berbeda di kedua situs. Kualitas chert yang kurang baik di dataran tinggi Bontocani mendorong pembuatan alat batu di Cappalombo 1 menerapkan strategi pemanfaatan bahan baku yang beragam dan lebih sering menerapkan teknik bipolar untuk mereduksi dan meretus serpih. Sebaliknya, pemanfaatan bahan baku chert di Leang Jarie cenderung homogen dan lebih sering menerapkan teknik pukul langsung.

Although chert deposits are limited in geological distribution, their geological and geochemical characteristics can provide important information to reconstruct paleoenvironmental and diagenetic processes. For the Permian period, cherts are utilized to trace global silicon cycles and hydrothermal activities in relation to the Permian Chert Event. In Northwest China, Permian chert nodules have recently been discovered in both the southeastern and northwestern margins of the Junggar Basin. We conducted an analysis of the mineralogy, petrology and geochemistry of chert nodules of the Lucaogou Formation in the southeastern margin of the Junggar Basin to identify silicon sources and determine the precipitation mechanism of chert nodules. As evidenced by petrology, the chert nodules were mainly composed of crypto-microcrystalline silica (94.33% on average), with development of a soft-sediment deformation structure, indicating the synsedimentary deposition of silicon. Proven by trace elements, high Eu/Eu* ratios (average 2.14), low total rare earth element content (average 6.03 ppm), low LaN/YbN ratios (average 0.17) and low Y/Ho ratios (average 25.25) in chert nodules supports the hydrothermal source of silicon. The wide distribution of authigenic metal-bearing minerals and the significant positive Eu anomalies observed suggest that the chert depositions in the Lucaogou Formation intermittently received high-temperature (>250 °C) hydrothermal fluids, likely associated with the initiation of the Bogda Rift in the middle Permian. Following rapid cooling down and differential compaction, siliceous sediments dehydrated and deformed, finally forming chert nodules. [ABSTRACT FROM AUTHOR]

Sedimentary and hydrothermal pyrites contained in selected Malaysian black shale and cherts have been analysed using laser ablation inductively coupled plasma (LA ICP-MS) and electron probe microanalysis (EPMA) at the University of Tasmania, Australia. This study shows that gold is concentrated in sedimentary and hydrothermal pyrite in the Middle Permian to Late Triassic black shales and Devonian cherts. According to LA ICP-MS analysis, gold contents in pyrite varied from 0.5 to 0.8 ppm Au in the Permo-Triassic black shale and between 0.2 and 0.8 ppm Au in the Devonian cherts. The lowest level of gold (0.3 ppm Au) was observed in the Permo-Triassic black shale that crops out at the Selinsing gold mine. In the Permo-Triassic period, the selenium contents display one peak (average range: 63.4–103.4 ppm Se) that is far from any gold deposit and one lowest point (average: 5.3 ppm Se) at the Selinsing gold deposit. In the Devonian period, the selenium content in sedimentary pyrite shows a peak (72.6–243.8 ppm Se) in the cherts. EPMA and LA ICP-MS data show consistent Se content variation in the Devonian and Permo-Triassic periods. Using selenium as a proxy for atmospheric oxygenation, the lowest level of Se content in the Permo-Triassic period is believed to decrease atmospheric oxygenation, as recorded in sedimentary pyrite found in black shale from the Selinsing gold deposit. The two peaks of selenium contents are interpreted as periods of increased atmospheric oxygenation. From an exploration perspective, the concentration of gold in sedimentary pyrites makes them sources for gold in the central sedimentary basin of Peninsular Malaysia. Therefore, the two maximum levels of Se and gold content during Permo-Triassic and Devonian times correspond to two stratigraphic levels of potential for orogenic gold mineralisation in the district. The EPMA data show significant values of Co over Ni in pyrite from the Gua Musang, Semantan, and Karak formation black shales, indicating a volcanic contribution of Co during the formation of sedimentary pyrite. Based on the current study’s findings, gold exploration should not be restricted to areas in and around the Selinsing gold mine, Buffalo Reef, Penjom mine, Tersang mine, and Bukit Koman mine but can be extended to BRSZ Units 1 and 2, Gua Musang, and Karak formations in the central belt of Peninsular Malaysia.

The analyses of raw material provenance offers the possibility of tracing short and long-distance raw material transport. So far, most studies of raw material of flint and chert in Europe have been based on macroscopic analyses. We apply infrared spectroscopy to Aurignacian assemblages from Vogelherd cave and to the Magdalenian site Randecker Maar in southwestern Germany. We compare raw material samples from three chert-bearing areas in Germany with archaeological samples from Vogelherd. Our results show that infrared spectroscopy can distinguish between different raw materials. Our archaeological samples from Vogelherd correspond to the sampled geological cherts in terms of their spectral signature. Our comparison of reference samples and archaeological samples highlights problems in commonly used macroscopic identifications of chert raw materials. [ABSTRACT FROM AUTHOR]

The Cordillera of Canada and Alaska is a type example of an accretionary orogen, but the origin of some terranes remains contentious (e.g., Stikinia of British Columbia and Yukon, Canada). Presented herein are igneous and detrital zircon U/Pb-Hf and trace-element data, as well as the first radiolarian ages from the Asitka Group, the basement to eastern Stikinia. The data are used to evaluate the role of juvenile and ancient crust in the evolution of Stikinia and the tectonic environment of magmatism. Two rhyolites are dated by U-Pb zircon at 288.64 ± 0.21 Ma and 293.89 ± 0.31 Ma, with εHf(t) = +10. Red chert contains radiolarians that are correlated with P. scalprata m. rhombothoracata + Ruzhencevispongus uralicus assemblages (Artinskian-Kungurian). Detrital zircon U/Pb-Hf from a rare Asitka Group sandstone have a mode at ca. 320 Ma and εHf(t) +10 to +16; the detrital zircon suite includes five Paleoproterozoic zircons (~5% of the population). Detrital zircons from a stratigraphically overlying Hazelton Group (Telkwa Formation) volcanic sandstone indicate deposition at ca. 196 Ma with zircon εHf(t) that are on a crustal evolution line anchored from the Asitka Group. Zircon trace-element data indicate that the Carboniferous detrital zircons formed in an ocean arc environment. The Proterozoic detrital zircons were derived from a peripheral landmass, but there is no zircon εHf(t) evidence that such a landmass played any role in the magmatic evolution of eastern Stikinia. The data support that eastern Stikinia formed on Paleozoic ocean floor during the Carboniferous to early Permian. Consistent with previous fossil modeling, zircon statistical comparisons demonstrate that Stikinia and Wrangellia were related terranes during the Carboniferous to Permian, and they evolved separately from Yukon-Tanana terrane and cratonic North America. [ABSTRACT FROM AUTHOR]

The Jurassic‐Cretaceous chert of the Naga Hills Ophiolite (NHO) is tectonically juxtaposed with the mafics (mostly basalts) and ultramafics along the Indo‐Myanmar Ranges (IMR), which constitute the southeastern extension of the Indus‐Yarlung‐Tsangpo Suture. Petrographic and geochemical studies were taken up to determine their origin and paleo‐oceanic depositional environments. Cryptocrystalline quartz is intimately mixed with iron oxides and clay minerals containing poorly preserved radiolarians. Geochemical signatures indicate a predominantly biogenic origin for the NHO cherts, which were derived from radiolarians and other siliceous microfossils. Rare earth elements and trace element abundances indicate predominant contribution by scavenging from seawater with the minor influence of low‐temperature hydrothermal activity. Most of the NHO cherts were deposited in an open ocean basin where oxic conditions prevailed. Geochemical signatures endorsed by field relations of chert, pillow basalts, and limestone within the oceanic plate indicate that chert formation continued in the vicinity of oceanic islands. Organic matter played a pivotal role in regulating oxic‐anoxic conditions during deposition, as evidenced by redox‐sensitive trace elements. These cherts, envisaged to have been originally part of the Tethys, were tectonically emplaced during the Middle Eocene. They now constitute part of the NHO along the IMR. [ABSTRACT FROM AUTHOR]

Excavations at Saruq al-Hadid, Dubai, UAE, discovered a stone tool technology with backed microliths dating to the Wadi Suq period and Late Bronze Age (ca. 1750–1300 BCE). The stone technology is a contemporary with metal production in the region, and the assemblage was recovered from a thick bone midden deposit at this multi-period site on the edge of the Rub' al-Khali Desert. Small cobbles of chert were imported to the site and were reduced into flakes by hard-hammer percussion. Cores were frequently rotated during knapping and the reduction strategy was ad hoc, lacking hierarchical reduction stages. Flake tools were used as-is or modified by retouching. Some flakes were selected for backing into geometric microliths, and backing techniques often reflected high levels of stoneworking skill to produce stylised scalene shapes. A review of contemporary archaeological evidence, and the context of the Saruq al-Hadid assemblage, suggest that microliths may have been made as stone armatures for arrows despite the contemporary use of copper-based arrowheads. [ABSTRACT FROM AUTHOR]

Copyright of Intersecciones en Antropología is the property of Universidad Nacional del Centro de la Provincia de Buenos Aires, Facultad de Ciencias Sociales and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)