Geological Time Research Articles

Tectonic Evolution and Structural Control of Dike-Hosted Orogenic Gold Deposits in the Yana–Kolyma Collision Orogen (Eastern Siberia): Insights from the Eastern Margin of the Siberian Craton

The Yana–Kolyma collision orogen, Eastern Siberia, is one of world-class gold economic belts, where large gold deposits are localized, mainly in the Upper Paleozoic and Lower Mesozoic clastic rocks. Dike-hosted orogenic gold deposits are found and to a lesser extent studied, but they are important for understanding the structural control of mineralization within the framework of the orogen. Orogenic gold deposits of the Vyun ore field are hosted in Kimmeridgian–Titonian mafic, intermediate and felsic dikes, but they have no genetic connection with dikes. The late formation of deposits led to the fact that previously reactivated polydeformed structures were subsequently mineralized. The study of the structural control of mineralization is also complicated by superimposed late tectonic events. Based on the analysis of collected field materials, this paper presents the results of the study of deformation structures of the Vyun ore field within the framework of the Mesozoic evolution history throughout the geological time of the eastern convergent margin of the Siberian Craton. Four stages of deformations are identified. The pre-mineralization deformations and metamorphic and magmatic events share a common NE-SW shortening (D1 phase), which is related to the subduction of the Oymyakon oceanic slab and collision of the Kolyma–Omolon superterrane from the eastern margin of the Siberian Craton. This first stage is characterized by the superposition of several tectonic events under conditions of compression and progressive deformations (D1/1 and D1/2). Ore mineralization was formed at the end of compression in the same stress field (D1/2). Its structural control is determined by reactivation of older dikes and faults. Dikes are areas of heterogeneous stress and heterogeneous strain, being favorable for the concentration of ore fluids. The metallogenic time of formation of the gold mineralization is synchronous with the tectonic event, which likely reflects the final stages of the Kolyma–Omolon microcontinent–Siberian Craton collision of the Valanginian during crustal thickening. The main impulse of the Au mineralization D1/2 phase coincided with a slowdown in convergence. The post-mineralization tectonic regime was related to the Aptian–Late Cretaceous tectonic transition from compression to transpression. Transpressional tectonics were determined accordingly by W-E (D2 phase) and N-S (D3 phase) stress fields caused by several accretion events in the Cretaceous on the northern and eastern margins of Siberia. D4 phase extensional structures were caused by the opening of the Eurasian Oceanic basin in the Arctic in the Paleocene. The obtained results have a first-order impact on the understanding of the structural control of orogenic gold deposits and their relationship to the evolution of the host orogen. The new findings improve the tectonic knowledge of an area of interest for ore deposit exploration targeting orogenic gold deposits in Phanerozoic terranes of craton margins.

Alkaline rocks and their economic and geodynamic significance through geological time

Alkaline igneous rocks have a relative excess of alkalis over silica. Most are silica undersaturated and contain normative nepheline and real feldspathoids (nepheline, leucite). Although alkaline rocks make up only about 1% of total igneous rocks by volume, their diverse mineralogy accounts for 90% of all igneous rock names proposed by the IUGS. They occur in all tectonic settings; in the ocean basins and on the continents, along mid-ocean ridges (rare), on oceanic islands, in subduction zones in the oceans and along continental margins, as well as along rift zones. Alkaline rocks commonly include alkali basalts and foidites, tephrites, phonolites, trachytes and their intrusive equivalents, including lamprophyres and carbonatites. In the literature, a plethora of local names for alkaline rocks from different localities have been created and many geoscientists still consider them as petrological curiosities. However, their study can significantly aid the interpretation of mantle evolution, ancient terranes and their geodynamic settings. Additionally, alkaline rocks may host world-class precious- and rare-metal mineralization. During recent years, the exploration interest in critical and rare metal deposits (Nb, rare earth elements (REEs) and Th) has increased dramatically as they represent vital resources for the so-called ‘green energy transition’. This Special Publication presents new comprehensive data, results and findings on alkaline rocks from different terranes worldwide and uses their mineralogy and geochemical fingerprints in order to elucidate their petrogenesis, tectonic settings and mineralization potential. This volume is not only of interest for igneous petrologists, but also for exploration geologists prospecting for precious- and rare-metal mineralization worldwide.

Forward Modeling Complex Diffusive Gradients and Matching Measured Bimodal Diffusive and Quasi-Equilibrium Fluid Distributions in Connected Reservoirs

Summary Given enough time after the onset of hydrocarbon charge, well-connected oil columns might be expected to exhibit equilibrated fluid gradients. However, a well-connected tilted sheet reservoir, deepwater Gulf of Mexico/America exhibits a bimodal compositional distribution where asphaltenes, solution gas-oil ratio (GOR), and methane carbon isotopes at the base of the column all exhibit a quasi-equilibrium gradient, whereas the GOR and methane carbon isotopes at the top of the column exhibit a diffusional gradient. In addition, the solution gas methane shows a large diffusive gradient of biogenic methane at the top of the oil column, whereas the base of the oil column shows solution gas methane that is 50% biogenic and 50% thermogenic. A proposed origin of this enigmatic oil column was recently proposed. Here, we explore this proposed origin with a compositional simulator. We simulated the history of reservoir charge over geologic time, investigated the origin of complex fluid compositional variations, and forward-modeled diffusive gradients at the top of the column and well-mixed fluids in the bottom half of the column, explaining present-day fluid realizations. With this capability, the model has predictive capabilities to examine fluid distributions in undeveloped sections of the reservoir. Oil samples were geochemically evaluated showing increasing biogenic gas toward the top of the oil column, while the lower half of the column remained largely invariant. Extreme variation of GOR was measured in the upper half of the oil column. Simulations were performed to evaluate the origin of complex fluid distributions. We modeled diffusional fluxes to evaluate the upper half of the column, implemented the cubic equation of state (EoS) to model the GOR gradient in the lower half, and fit asphaltene gradients with the Flory-Huggins-Zuo equation of state (FHZ EoS). Gas charged into the base of the oil column and the induced convection accounted for the well-mixed biogenic and thermogenic methane in the solution gas in the lower half of the oil column. Various diffusion models were tested to determine a reliable model for long geologic times. Modeling approaches were compared, including black-oil vs. compositional simulators, and we investigated parameters controlling diffusion timelines, such as dip angle and subsidence time. Simulations of gas charge at a point source into an undersaturated oil reservoir showed rapid gas dissolution into oil and excellent convective mixing. With excess gas charge, saturation pressure was attained and subsequent gas charge remained as a separate gas phase and migrated to the top, forming a gas cap. After the gas charge was completed, subsidence increased saturation pressure, thereby enabling gas diffusion into the oil column. Diffusion modeling with a compositional simulator allows gas components from the gas cap to diffuse down as well as light components in the oil to diffuse up. This has resulted in the elimination of the phase boundary (no meniscus), which depends on the initial volumetrics of the charge fluids, among other factors. In the present day, the upper half of the oil column (thus the whole oil column) is far from equilibrium; the dynamics of diffusion dominate. We found that compositional simulators are more accurate than black-oil simulators for our objective as they account for the diffusion of both gas components into the oil column and light-end oil components up into the gas cap.

Harnessing Microbes to Weather Native Silicates in Agricultural Soils for Scalable Carbon Dioxide Removal

ABSTRACTAnthropogenic carbon emissions contribute significantly to the greenhouse effect, resulting in global warming and climate change. Thus, addressing this critical issue requires innovative and comprehensive solutions. Silicate weathering moderates atmospheric CO2 levels over geological time, but it occurs too slowly to counteract anthropogenic emissions effectively. Here, we show that the microorganism Bacillus subtilis strain MP1 promotes silicate weathering across different experimental setups with various levels of complexity. First, we found that MP1 was able to form a robust biofilm in the presence of feldspar and significantly increased (p < 0.05) silicate dissolution rates, pH, and calcium carbonate formation in culture experiments. Second, in mesocosm experiments, we found that MP1 enhanced the silicate weathering rate in soil by more than six times compared to the untreated control. In addition, soil inorganic carbon increased by 20%, and the concentrations of ions, including calcium, magnesium, and iron, were also elevated under the MP1 treatment. More importantly, when applied as a seed treatment on eight soybean fields, we found that MP1 significantly (p < 0.05) boosted soil inorganic carbon, leading to a gross accrual of 2.02 tonnes of inorganic carbon per hectare annually. Our findings highlight the potential of enhancing native silicate weathering with microorganisms in agricultural fields to increase soil inorganic carbon, contributing to climate change mitigation.

PrePatom trough oil and gas potential and fluid dynamic system

The purpose of the conducted research was to assess the oil and gas potential of the PrePatom trough and the leading role of geofluid dynamic processes in the formation of hydrocarbon generation centers. The study used the data of drilling and geophysical works, as well as research materials published in the open press. Many researches recognise the Riphean pericratonic troughs of the Siberian Platform as the main oil and gas generating structures within which the process of hydrocarbon generation had taken place, and probably is still going on with subsequent migration of hydrocarbons into favorable tectonic structures of the platform. The dynamic system generating and concentrating hydrocarbons is a function of geological space and time. The Riphean sediment strata characterized by great thickness, wide distribution over the platform area and diversity of lithological composition are the most ancient oil and gas generating sediments on the planet. The giant Kuyumba-Yurubchen-Tokhom oil and gas accumulation area is confined to the Riphean sediments. It is a unique object not only for the Siberian platform but also for the entire planet. The fluid dynamic system of the Riphean-Vendian-Lower Cambrian strata of the PrePatom trough ensures the formation of hydrocarbon generation centers and formation mechanism of hydrocarbon deposits, which is controlled by a combination of factors of geological development of the trough, its tectonic structure features, lithological composition, as well as large thicknesses of sedimentary cover deposits.

Urban Sprawls and Land Use Change analysis of Karnal City: Using Remote Sensing and GIS Techniques

Urban sprawls are transition zones with indefinite borders between rural and urban areas. Many factors cause urban sprawl such as population increase, socio-economic factors, technological development and development policies. This surface has been recording changes throughout geological times but with recent rapid urban expansion this change has been occurring at a much faster rate. This change needs to be detected, mapped and measured at frequent intervals so that we can have real time information on it. The study area Karnal is an agricultural-industrial district in the north-central part of Haryana. It has become synonymous with the National Highway 44 (NH-44), which is popularly known as GT Karnal Road (Grand Trunk Karnal Road). Present paper has tried to find out the changes which have taken place in landscape of Karnal City in Haryana from 2000-2021. Study has used open-source satellite images of Landsat data downloaded from www.glovis.usgs.gov/. Besides satellite images Toposheet No 53 C/14 (Survey of India) and guide map of Karnal city has been used for ancillary information. The objective of study has been to find out the pattern of sprawl of Karnal city and changes in land use from 1990-2020. Supervised classification using ISODATA algorithm has been carried out for land use classification. Further the change in these categories from 2000-2021 has been measured and mapped Software’s like ERDAS IMAGINE 9.0, ARC GIS 10.1 and MS OFFICE 2007 have been used. Sprawl of the city has taken place in two main areas. One is area between Delhi-Ambala main railway track and National Highway No.44. Secondly it has spread along National Highway No.44 in the eastern part of the city. The study has found that major change in land use has taken place in urban built and crop/vegetation land.

Hydrogen isotopic evidence for a core component in Baffin Island lavas.

The nature of chemical exchange between Earth's core and mantle is fundamental to understanding their evolution. Tungsten-182 and helium-3 anomalies in volcanic rocks from deeply sourced mantle plumes have been attributed to core-mantle exchange. Hydrogen (H) is potentially abundant in the core. Therefore, H may also be a sensitive tracer of core-mantle exchange. We measured 2H/1H ratios (reported as δD) in olivine-hosted basaltic melt inclusions from a Baffin Island lava to test whether mantle plumes contain H from the core. The average δD value (-144±24 per mil) is lower than some estimates for the average depleted upper mantle (δD≈-60±20 per mil). The low δD composition likely derives from isotopic diffusion or H leakage from the core, not isotopic fractionation during magmatism or crustal contamination. Over geologic time, core-mantle exchange of H may have overprinted the isotopic composition of mantle plume source regions and much of the upper mantle.

Darwinian soil evolution: A review

Soils diversified through geological time with the evolution life on land, from microbes in Archean soils, to fungi and amoebozoa in early Proterozoic soils, and lichens in late Proterozoic soils. Ordovician non-vascular land plants lived in Entisols and Aridisols, but trees created clayey subsurface horizons of Alfisols and Ultisols, and ferruginous horizons of Spodosols. Finally, sod grasslands creating distinctive surface horizons of Mollisols. Organisms can be adapted to particular environments, but also adapted by natural selection to other organisms in coevolutionary pairs, such as grasses and grazers, or trees and termites. Coevolution is notable for creating communities that can change the environment, such as ice ages brought on by evolution of forests and of grasslands. If life can be defined as a system capable of Darwinian evolution by natural selection, the same can also be said of soils. Even before the evolution of life, clay formation in soils that were like carbonaceous chondrite meteorites would have maintained a place in the sun and rain for the formation of more clay. Soils at matric potential for water were like multicellular creatures with tiny reactive centers within menisci of water between grains. They would have been a starter system for entirely organic-based life capable of natural selection with the same aim: hold the ground against erosion.

Persistent Habitat Instability and Patchiness, Sexual Attraction, Founder Events, Drift and Selection: A Recipe for Rapid Diversification of Orchids.

Orchidaceae is one of the most species-rich families of flowering plants, with most current diversity having evolved within the last 5 My. Patterns associated with species richness and rapid diversification have been identified but have not often been associated with evolutionary processes. We review the most frequently identified correlates of diversity and suggest that the processes and rate by which they occur vary geographically and are largely dependent on persistent pulses of habitat instabilities, especially for epiphytes. Aggressive orogenesis creates fragmented habitats while global climatic cycles exacerbate the ecological instabilities. The need for repeated cycles of dispersal results in frequent founder events, which sets the stage for allopatric diversification via bouts of genetic drift and natural selection. The allopatry requirement can be bypassed by pollination systems involving flowers attracting pollinators through the production of sex signaling semiochemicals. The drift-selection model of diversification, coupled with persistent habitat instability throughout ecological and geological time scales, and sex signaling are the likely components of a multifactorial process leading to the rapid, recent diversification in this family.

Temperatures of albitization of plagioclase in sandstones from the Norwegian continental shelf

Albitization is a widely recognized aspect of sandstone burial diagenesis, but its temperature of occurrence has been only partly constrained by previous studies. Temperatures of albitization of plagioclase in sandstone samples of Devonian to Miocene age from the Norwegian continental shelf were therefore studied by combining thin-section petrography with temperature measurements from wells. The investigated samples cover burial depths of 504 - 5120 m and a temperature range of 23 - 183°C. Albite grains with a morphology indicative of a diagenetic origin are present at temperatures of 88°C and higher, whereas calcic plagioclase was found solely at temperatures below 88°C. Oil inclusions in albitized plagioclase are with one exception present only at temperatures above 87°C. Moreover, albitized grains with a characteristic brown cathodoluminescence (CL) color that differentiates them from detrital albite with red and yellow CL colors are in all but one of the wells examined with CL confined to sample s where temperatures exceed 88°C. The non-albitized grains of calcic plagioclase show a variety of CL colors; pink, pale green, yellow to orange and pale brown, and these CL colors are seen only at temperatures less than 88°C. The data therefore suggest that albitization has in practically all cases taken place around 88°C, and that the reaction is rapid on a geological time scale. These results have several useful applications. Fixing the temperature of albitization constrains sandstone provenance and magnitude of uplift because albitization in a sandstone located at the surface or at shallow depth indicates uplift from depths where temperature was at least 88°C, and in situ albitized plagioclase suggests that the sandstone is not sourced solely from older sandstones once buried to temperatures in excess of 88°C as such a sand source would not provide reactive plagioclase. Many of the examined reservoirs are presently filled with oil or wet gas, and most of these hydrocarbon-filled reservoirs contain oil inclusions within albitized plagioclase, indicating oil emplacement at temperatures less than 88°C

Reconstructing the phylogeny and evolutionary history of freshwater fishes (Nemacheilidae) across Eurasia since early Eocene

Eurasia has undergone substantial tectonic, geological, and climatic changes throughout the Cenozoic, primarily associated with tectonic plate collisions and a global cooling trend. The evolution of present-day biodiversity unfolded in this dynamic environment, characterised by intricate interactions of abiotic factors. However, comprehensive, large-scale reconstructions illustrating the extent of these influences are lacking. We reconstructed the evolutionary history of the freshwater fish family Nemacheilidae across Eurasia and spanning most of the Cenozoic on the base of 471 specimens representing 279 species and 37 genera plus outgroup samples. Molecular phylogeny using six genes uncovered six major clades within the family, along with numerous unresolved taxonomic issues. Dating of cladogenetic events and ancestral range estimation traced the origin of Nemacheilidae to Indochina around 48 mya. Subsequently, one branch of Nemacheilidae colonised eastern, central, and northern Asia, as well as Europe, while another branch expanded into the Burmese region, the Indian subcontinent, the Near East, and northeast Africa. These expansions were facilitated by tectonic connections, favourable climatic conditions, and orogenic processes. Conversely, aridification emerged as the primary cause of extinction events. Our study marks the first comprehensive reconstruction of the evolution of Eurasian freshwater biodiversity on a continental scale and across deep geological time.

Reconstructing the phylogeny and evolutionary history of freshwater fishes (Nemacheilidae) across Eurasia since early Eocene.

Eurasia has undergone substantial tectonic, geological, and climatic changes throughout the Cenozoic, primarily associated with tectonic plate collisions and a global cooling trend. The evolution of present-day biodiversity unfolded in this dynamic environment, characterised by intricate interactions of abiotic factors. However, comprehensive, large-scale reconstructions illustrating the extent of these influences are lacking. We reconstructed the evolutionary history of the freshwater fish family Nemacheilidae across Eurasia and spanning most of the Cenozoic on the base of 471 specimens representing 279 species and 37 genera plus outgroup samples. Molecular phylogeny using six genes uncovered six major clades within the family, along with numerous unresolved taxonomic issues. Dating of cladogenetic events and ancestral range estimation traced the origin of Nemacheilidae to Indochina around 48 mya. Subsequently, one branch of Nemacheilidae colonised eastern, central, and northern Asia, as well as Europe, while another branch expanded into the Burmese region, the Indian subcontinent, the Near East, and northeast Africa. These expansions were facilitated by tectonic connections, favourable climatic conditions, and orogenic processes. Conversely, aridification emerged as the primary cause of extinction events. Our study marks the first comprehensive reconstruction of the evolution of Eurasian freshwater biodiversity on a continental scale and across deep geological time.

Controls on CaCO3 Polymorphism: From Laboratory Precipitation to Biomineralization across Geological Time

Calcium carbonate (CaCO3) forms various mineral polymorphs, including calcite, aragonite, and vaterite, each with distinct physicochemical properties. To benefit from these properties, marine organisms have evolved (some) control on the polymorphs from which their biomineral structures are built. This is achieved by modulating the conditions at their calcification sites and the nature of functional organic macromolecules that can serve as templates for carbonate crystallization. Environmental factors, such as seawater chemistry and ocean acidification, also affect polymorph selection, impacting organisms’ calcification pathways. Across geologic time, mass extinction events have influenced evolutionary-scale skeletal mineralogy trends. The organismal controls on CaCO3 polymorphism have significant implications for ecological and industrial applications, offering insights into the development of environmentally friendly materials with tailored properties.

The Viability of Glycine Fermentation in Titan’s Subsurface Ocean

Abstract Energy and nutrient sources for life could be delivered to Titan’s subsurface water ocean from both its surface above and its core below. Organic matter forming de novo in Titan’s atmosphere and depositing on the surface may hydrolyze upon descent into the ocean with impact-generated melt pools sinking through the ice, adding to a primordial inventory released by the core during differentiation and/or across geologic time. This raises the possibility that abiotic organic carbon could fuel heterotrophic carbon assimilation into biomass in Titan’s ocean if it is inhabited. Glycine fermentation is one possible metabolism of interest, because mechanisms exist to transport glycine to Titan’s ocean and anaerobic fermentations do not rely on additional strong oxidants which may not be present on Titan. Using bioenergetic modeling, we show that while conditions favorable to glycine fermentation may exist, they are highly dependent on temperature. Additionally, the ability of that metabolism to fuel a global biosphere is limited by the slow delivery of glycine by impact melt pools (<10 nmolal yr−1 optimistically, with a >1 mmolal primordial component). A total population of 1014–1017 cells (a few kilograms of carbon) can be sustained, amounting to less than 1 cell kg–1 water when diluted through the entire ocean. Constraining notionally detectable biospheres on Titan will therefore require (i) considering localized environments that may concentrate cells, (ii) better characterizing other candidate metabolisms (e.g., degradation of acetylene or polyaromatic hydrocarbons) for quantitative bioenergetic modeling, and (iii) resolving new mechanisms to deliver organics and oxidants for life.

Oxygen and Carbon Isotopes in Marine Carbonates: A Biogenic Climate Archive Built Upon Disequilibria

The stable isotopic composition of marine biogenic carbonates is one of the main archives for paleoclimate reconstructions. Reading these archives accurately requires understanding of how different organisms make carbonate minerals, and how various biomineralization processes influence stable isotope fractionation. New developments in stable isotope measurements, laboratory experiments, and biomineralization modeling have progressively enabled us to disentangle the environmental and biological controls on the stable isotope proxies, and offer promise for a deeper understanding of how calcifying organisms record and respond to changes in Earth’s climate and carbon cycle through geologic time.

Is the Geodynamo Characterized by a Distinct Geomagnetic Secular Variation Regime During the Cretaceous Normal Superchron?

AbstractThe Earth's magnetic field stochastically reversed its polarity over geological time, yet enigmatically interrupted this process during the Cretaceous Normal Superchron (CNS; 84–121 Ma). Two scenarios have been proposed in terms of either gradual or abrupt changes to describe the transition of the geodynamo from the CNS to a period with frequent polarity reversals. To discriminate between these two scenarios, we sampled 136 volcanic flows emplaced 66–73 Ma in the eastern part of the Okhotsk‐Chukotka Volcanic Belt (NE Eurasia). The 1,700 collected paleomagnetic samples provide, after correction for serial correlation, a robust data set of 112 independent paleodirections characterizing the behavior of the geomagnetic field at a paleolatitude of N shortly after the end of the CNS. Compared to paleomagnetic data from Chukotka and Northern Canada emplaced at similarly high paleolatitude, the dispersion of the virtual geomagnetic poles, used as a proxy for paleosecular variation (PSV), is 19% (resp. 55%) higher at 66–73 Ma than at the end of CNS when transitional directions are discarded (resp. retained). In contrast, our value at 66–73 Ma is, whatever the filtering strategy, statistically indistinguishable from the value at 0–10 Ma derived from the Antarctica and Spitsbergen volcanics. From the viewpoint of PSV observed at high paleolatitude (70–80), our new results are consistent with an abrupt change between two geodynamo regimes. Nevertheless, once the geodynamo starts reversing its polarity, the vigor of PSV does not seem to correlate with the reversal rate.

Spatio-temporal distribution of global stromatolites through geological time identified by a large language model approach

IntroductionA substantial amount of data embedded within diverse literature makes it time-consuming to manually extract and compile extensive datasets. The use of large language models has become essential for the efficient extraction and analysis of big data. This study utilizes ChatGPT-4 to reconstruct a global database of stromatolites, spanning from the Precambrian to the present, to enhance our understanding of their spatial and temporal dynamics throughout geological time.MethodsThe data extraction process involved several steps: First, PDF documents containing stromatolite literature were gathered and converted into text format. Second, ChatGPT-4 was employed to extract data on stromatolite occurrences, including locations, ages, strata, and facies types from each sentence in the documents. Third, duplicates were removed, and the data were organized into three categories: 3,248 unique location-age pairs, 2,723 strata-age pairs, and 1,723 strata-age-facies type combinations. Additionally, 2,565 paleogeographical locations of stromatolite-bearing rocks were reconstructed using modern latitude and longitude coordinates and corresponding Phanerozoic ages.ResultsThe newly obtained dataset reveals that stromatolite occurrences peaked during the Proterozoic, declined during the Early Phanerozoic, and exhibited fluctuations throughout the Phanerozoic. Seven global stromatolite hotspots were identified: the United States, Australia, India, Canada, China, England, and Russia. From the Cambrian to the Jurassic, stromatolites were predominantly distributed in low and middle latitudes, shifting to higher latitudes from the Cretaceous to the Quaternary. The proportion of inland aquatic stromatolites relative to marine stromatolites varied, ranging from 10% to 30% from the Mesoarchean to the Middle Mesoproterozoic, decreasing to less than 10% from the Late Mesoproterozoic to the Early Paleozoic, increasing to 10%–30% from the Devonian to the Jurassic, and remaining high (39%–53%) from the Cretaceous to the Quaternary.DiscussionThe findings highlight the temporal and spatial variability of stromatolite occurrences, shedding light on the evolution of these microbial structures over geological time. The distribution patterns suggest significant shifts in environmental conditions and provide valuable insights into paleogeographical and ecological dynamics. The use of ChatGPT-4 to extract and organize data from a large body of literature demonstrates the potential of large language models for advancing research in paleobiology and geology.

The modern and ancient Central-Mediterranean gateways

Gateways, seaways and straits are physical elements of sedimentary basins that are hierarchically distinguished based on their dimensions and temporal persistence. The term ‘gateway’ applies to any oceanographic or marine connection, regardless of its size (width and length), duration and depth (shallow v. deep water). Seaways are broad marine passages, spanning from hundreds to thousands of kilometres in width, and active in the range from hundreds of years to tens of kiloyears in geological time. Straits are narrower passageways, connecting sub-basins within larger marine areas, persisting for no longer than 10 kyr and producing distinct sedimentary records as individual depositional systems. In this paper, we focus on the Modern Central-Mediterranean Gateway, now represented by the coalescent Strait of Sicily, the Egadi Islands and the Messina Strait. These connections, linking the western with the eastern Mediterranean sub-basins, drive continuous tidally modulated water exchange and sediment transport, representing an example of a modern gateway. We then provide field-based examples of the sedimentary record of the former gateway, referred to as the Ancient Central-Mediterranean Gateway, here represented by four major straits that developed during the Pliocene epoch and Quaternary period along localized graben dissecting the southernmost edge of the Italian peninsula. We discuss the geological features of each of these straits, along with their depositional architectures and facies. These elements record the initiation of specific depositional processes, possibly enhanced by a stronger penetration of the Atlantic water inflow from the Gibraltar Strait, reinforced by the onset of the Northern Hemisphere glaciation.

EPR Dating of Clay Minerals Formation Through Geological Times: Benchmarking From the Quaternary to the Neoproterozoic Era

Revealing the environment and timing of clay formation in the geosphere is of major importance to understand and model the evolution of geological systems at the surface or near-surface of the continents, such as weathering covers, sedimentary basins or hydrothermal systems. Dating clay minerals by electron paramagnetic resonance spectroscopy (EPR) is a promising method that relies on the measurement of stable radiation-induced defects (RIDs) accumulating in their structure over time due to natural radioactivity. This approach has not yet been challenged by the inter-comparison with other geochronological methods, mostly because clay minerals accurately dated with methods independent from the EPR approach and also suitable for the EPR dating remain scarce in the geological record. Herein, an up-to-date protocol for the EPR dating and benchmarking are provided and developed by analyzing selected clay samples. The series includes a Mesoproterozoic illite (Thelon Basin, Canada), two paleosol kaolinites (Ukraine, Estonia) from at least late Ediacaran period, an Ypresian sedimentary kaolinite from the Aquitan Basin (France) and two Miocene and Pliocene kaolinites from lateritic duricrusts (Amazonia, Brazil). Despite some discussed uncertainties mainly related to the Th distribution in the samples, the time variation of dose rate and the thermal history of some clay samples, the EPR ages show a trend close to the 1/1 line with ages determined by other dating methods. These results bring promising support to the EPR dating methodology of clay minerals and extend its potential application field over a time-range spanning from Quaternary to Proterozoic.

Reading the carnivoran skeletal story: An acetabular viewpoint, with suggested implications across geological time

AbstractWe compared acetabular traits among canid and non‐canid museum specimens, using the same pre‐established protocols. We hypothesized conserved, intersecting development‐growth and insult‐response biology, reflecting morphologically and being highly similar across carnivoran taxa. We evaluated acetabular traits from dry bone museum specimens of Vulpes lagopus, Vulpes vulpes, Nyctereutes procyonoides, Urocyon cinereoargenteus, Canis lupus familiaris and Canis latrans. The same was done from Procyon lotor (Procyonidae), Taxidea taxus (Mustelidae) and Lynx rufus (Felidae). We assessed intra‐articular structures as: (a) acetabular fossa; (b) medial articular margin; (c) lateral articular margin; and (d) articular surface. Each scoring category included multiple subcategories. The primary observed traits across taxa included variably shaped mineralized foci, bony rimming of articular margins and rough‐surfaced or worn articular bone. These traits occurred in a very similar fashion across taxa. We then evaluated only the most frequently occurring 80% of the data within the scoring category, observing only minor differences among taxa. The consistency of trait expression supports broad conservation and intersection of development and response capacities. The exact phylogenetic nature of the trait relationships requires further evaluation across development and growth; usually undetected early life damage; degrees of parallel responses across multiple diarthrodial joints within taxon; and the extent of morphological similarity across other carnivorans and non‐carnivorans.