Carbon Isotope Analysis Research Articles

Hydrocarbon generation, expulsion, and retention characteristics of the Permian Fengcheng shale and Lucaogou shale in the Junggar Basin: implications for the exploration of lacustrine shale oil

Hydrocarbon generation patterns are crucial for defining favorable exploration maturity intervals and targets for shale oil. The Permian Fengcheng shale and Lucaogou shale in the Junggar Basin, as significant targets for shale oil exploration, study on their hydrocarbon generation, expulsion, and retention characteristics are insufficient. This study establishes hydrocarbon generation patterns for the Fengcheng shale and Lucaogou shale using a semi-open thermal simulation system, combined with rock pyrolysis, vitrinite reflectance (Ro), total organic carbon (TOC) analysis, carbon isotope analysis, gas chromatography-mass spectrometry (GC-MS), mercury porosimetry, and nitrogen adsorption. Additionally, a multivariate regression model was employed to systematically evaluate the primary controlling factors of hydrocarbon expulsion ratio. Based on these results, favorable exploration maturity intervals and targets for the Fengcheng shale and Lucaogou shale were identified. The results indicate that the hydrocarbon generation potential of Fengcheng shale was superior to that of Lucaogou shale, whether considering gas yield or oil yield. However, Lucaogou shale began the thermal degradation earlier than Fengcheng shale and has a broader degradation window. The corresponding (TR) is slightly higher for Fengcheng shale. The Lucaogou shale exhibited significantly higher hydrocarbon expulsion ratios compared to Fengcheng shale, with a maximum hydrocarbon expulsion ratio 2.1 times that of Fengcheng shale. Mesopore volume and its connectivity were critical factors affecting the hydrocarbon expulsion ratio, whereas oil mobility and macropore volume have relatively limited effects. The optimal maturity interval for shale oil exploration as Ro = 1.0%–1.1% for the Fengcheng shale and Ro = 0.9%–1.1% for the Lucaogou shale. Exploration of the Fengcheng shale should focus on lithofacies assemblages, the dolomitic mixed rock-shale assemblages in the shore-shallow lake facies represent the primary exploration target. Exploration of the Lucaogou shale should focus on source-reservoir assemblages, with a higher reservoir-to-shale thickness ratio being the primary exploration target. These findings provide support for the exploration and development decisions of shale oil in the Junggar Basin.

Deepwater Sharks at Their Northern Limits—Distribution, Diet and Trophic Relations

ABSTRACTDeepwater areas and continental slope regions south and west off Iceland are characterized by a relatively high species diversity and abundance of sharks that likely play a critical ecological role within this ecosystem. The study investigates trophic ecology of the sharks employing stomach content analysis and stable isotope analysis of nitrogen and carbon. In a standardized groundfish survey in Icelandic waters spanning 28 years, sharks were exclusively caught south of the Greenland–Iceland ridge and west of the Iceland–Faroe ridge, likely due to significantly lower seawater temperatures prevailing north of the ridges. The sharks exhibited a diverse diet primarily comprising secondary, and tertiary consumers, placing them within the lower spectrum of the fourth trophic level with estimated trophic levels ranging from 4.1 to 4.5 depending on the species or method employed. Three distinct feeding categories emerged: the first characterized by a main predation on various fish species, the second involving a specialized predation on mesopelagic fish and the third strategy encompassing a significant feeding on crustaceans. Resource portioning was evident through low to medium diet overlap indices among some of the shark species. Ontogenetic changes were observed in two of the most abundant and data‐rich species, namely the black dogfish (Centroscyllium fabricii) and great lanternshark (Etmopterus princeps). As these sharks increased in size, there was a dietary shift from crustaceans to fish, reflected in higher trophic levels based on δ15N values. Given the scarcity of sharks in stomachs of demersal fish within the study area, coupled with low fishing pressure on sharks off Iceland, it is plausible that their abundance is currently regulated primarily by bottom‐up processes or environmental factors.

Comfort in stratification and trophic flexibility: argentine anchovy, Engraulis anchoita, larvae life traits in relation to their food sources

Fish larvae feeding success is crucial for adult recruitment, which affects both fisheries and ecosystem regulation processes. Engraulis anchoita is a species of great ecological and fishing relevance in the South-West Atlantic Ocean, with a wide latitudinal distribution and active spawning throughout the year and strongly associated with frontal areas. E. anchoita larvae have been described as exclusively feeding on small copepods and their early developmental stages. In this study, the diet, nutritional condition, and daily growth of E. anchoita larvae were estimated in different environmental scenarios in the South-West Atlantic Ocean. Carbon and Nitrogen stable isotopes analysis, otolith microstructure analysis, and RNA/DNA index determination were performed. The larval diet, which was evaluated based on the availability of potential prey, varied with respect to the water column stability. It was observed that the larvae tend to feed on microphytoplankton in stratified waters and on calanoid copepods in waters with a homogeneous vertical structure. The growth and nutritional condition indexes responded to ontogeny, presenting higher values at larger larval sizes. Growth indexes also responded positively to the stratified water column structure in comparison to the homogeneous one. The nutritional condition index was only explained by the size of the individuals. This study found that E. anchoita larvae had greater trophic flexibility than previously suspected, as they included microphytoplankton as the main food item under certain oceanographic conditions without negative impacts on their growth or nutritional condition.

In-situ carbon isotope analysis of diamond using LA-MC-ICP-MS inspired from the distributions of ions and isotope ratios in the ICP

Carbon stable isotopes of diamonds provide clues regarding their growth processes. Thus, an accurate, efficient, and affordable method to determine the carbon isotope ratio is extremely urgent. Accurate and precise...

Light Oil Reservoir Source and Filling Stage in the Chepaizi Uplift, Junggar Basin Evidence from Fluid Inclusions and Organic Geochemistry

The light oil wells within the Neogene Shawan Formation have been extensively drilled in the Chepaizi Uplift, reflecting an increase that provides new targets for unconventional resources in the Junggar Basin of northwestern China. However, the original sources of light oil remain controversial, as several source rocks could potentially generate the oil. For this study, we collected light oils and sandstone cores for biomarker detection using gas chromatography–mass spectrometry (GC-MS). Additionally, fluid inclusions were observed and described, and the homogenization temperatures of saltwater inclusions were measured to confirm the oil charging history in conjunction with well burial and thermal history analysis. Based on these geochemical characteristics and carbon isotopic analysis, the results indicate that light oil in the Chepaizi Uplift zone primarily originates from Jurassic hydrocarbon source rocks in the Sikeshu depression, with some contribution from Cretaceous hydrocarbon source rocks. Jurassic hydrocarbon source rocks reached a peak of hydrocarbon generation in the middle to late Neogene. The resulting crude oil predominantly migrated along unconformities or faults to accumulate at the bottom of the Cretaceous or Tertiary Shawan Formation, forming anticlinal or lithologic oil reservoirs. Some oil reservoirs contain mixtures of Cretaceous immature crude oil. During the Neogene light oil accumulation process, the burial rate of reservoirs was high, and the efficiency of charging and hydrocarbon supply was relatively high as well. Minimal loss occurred during the migration of light oil, which significantly contributed to its rapid accumulation.

Beyond the herd: investigating livestock feeding strategies in the Iron Age Iberian Peninsula (3rd c. BC) through a multi-isotope analysis

During the Iron Age, north-eastern Iberian communities relied on crop cultivation and animal husbandry for their subsistence. The latter was mainly focused on caprine, with sheep being prominent due to their suitability to the Mediterranean climate, orography, and environment. Despite the pivotal role of sheep in livestock husbandry, information on Iberian communities’ feeding strategies for this species is limited. To address this lacuna, this study investigates the livestock feeding habits at four Catalan sites dating back to the 3rd century BC: Mas Castellar de Pontós, Tossal de Baltarga, Sant Esteve d’Olius, and Turó de la Rovira. Bulk carbon and nitrogen isotope analyses (δ13C and δ15N) of bone collagen and sequential carbon and oxygen analyses (δ13C and δ18O) of dental enamel were performed on 74 remains (43 bones, 31 teeth) from 51 sheep. Additionally, 153 bone remains from other domestic and wild species from the four sites were analysed. Our results revealed the complex and adaptive livestock feeding strategies of Iron Age Iberian populations. Sheep exhibited minimal diet variations, mainly consuming C3 plants across the four sites. Nevertheless, their feeding habits changed seasonally depending on pasture availability and settlement requirements. The other main domestic species were subject to individualised and variable feeding strategies within the same settlement. This diversified feeding management unveiled the complex and adaptive nature of the husbandry practices employed by Iron Age Iberian communities. Finally, the extensive number of remains analysed provides the first data on livestock feeding strategies for the Middle/Late Iron Age in the north-eastern Iberian Peninsula.

Spatial palaeoecology of large-herbivore hominin prey-species at Salzgitter-Lebenstedt, Lower Saxony, Germany: multi-isotope analysis of sequentially-sampled tooth enamel from Rangifer tarandus and Equus sp.

The application of high-resolution methods to reconstruct the ecology and behavior of large-herbivores within Late Pleistocene contexts in Europe has revealed increasing evidence for variability in diet, habitat preference, ranges and mobility patterns through time and space. This data has major implications for interpretations of hominin subsistence strategies in terms of prey-species selection, which rest to a large extent, on the spatial ecology of these animals and their resulting availability in the environment. To this end, multi-isotope analysis of faunal remains from archaeological sites has been shown to provide direct information in herbivore movements and ranges that move beyond assumptions of consistency in animal behavior through time. The Middle Paleolithic site of Salzgitter-Lebenstedt, Northern Germany, has been put forward as a prime example of specialized hunting of a single taxon – reindeer – by Neanderthals. However, questions remain around the number and season of hunting events. Here we employ strontium (87Sr/86Sr) isotope analysis in combination with stable oxygen (δ18O) and carbon (δ13C) isotope analysis of sequentially-sampled tooth enamel from reindeer (Rangifer tarandus) and horse (Equus sp.) to reconstruct the sub-annual dietary and ranging behaviors of these prey-species at Salzgitter. We find that reindeer exhibit parallel seasonal shifts in diet and likely experienced similar environmental conditions. While the majority of the reindeer display the potential for long-distance climate-induced migrations, mobility patterns and seasonal ranges appear to have differed between individuals. This may be indicative of behavioral flexibility, particularly in migratory behavior of reindeer, during this period in Northern Germany. Horses analyzed here likely consumed a graze-based diet year-round, while potentially undertaking more residential movements on a seasonal basis. We briefly discuss potential implications of these findings on Neanderthal hunting strategies at the site. Finally, we discuss the challenges to the application of 87Sr/86Sr as a provenancing tool in Central Europe, and the importance of multi-isotope approaches and development of additional spatial proxies.

High-resolution isotopic data link settlement complexification to infant diets within the Roman Empire.

Our study explores the potential relationship between infant feeding practices and settlement complexity in the Roman Empire through high-resolution Bayesian-modeled stable isotope measurements from incremental dentine. We compiled isotopic data from permanent first molars of individuals from various Roman sites: five from Bainesse (UK), 30 from Thessaloniki (Greece), along with new carbon and nitrogen isotope analyses from four individuals from Pompeii and six from Ostia Via del Mare (AVM). Our results reveal significant inter-site variability in breastfeeding durations, ranging from 1.5 years to approximately 5 years. Notably, individuals from the highly complex urban centers of Pompeii and Thessaloniki ceased breastfeeding around or below the 2-year weaning threshold recommended by Roman physicians. In contrast, individuals from the rural site of Ostia AVM and the site of Bainesse, near the northern frontier of the Roman Empire, generally ceased breastfeeding after 2 years of age. The link between settlement complexity and duration of breastfeeding observed in our study may have resulted from adherence to medical guidelines, support infrastructures, and/or strategies to mitigate financial constraints within households.

New isotopic evidence for micro and mesothermal valleys camelids from Northwest Argentina

IntroductionDomestic and wild camelids were the most significant meat resource for pre-Hispanic agropastoral societies in the Argentine Northwest's micro valleys (between 2,500 and 3,400 masl) and mesothermal valleys (2,500 and 1,500 masl), with varying relative importance in comparison to cultivated and collected plants. Examining pastoral movement techniques, as well as the areas available for wild resource gathering, allows us to acquire a better understanding of the nature and scale of social structure among these human communities. Stable isotope analyses of carbon (13C/12C; δ13C) and nitrogen (15N/14N; δ15N) provide efficient tools for understanding these features.MethodsThe article shows the bone collagen measurements of a sample of camelid bones from archaeofaunas recovered from Soria 2 sites (n = 7) and structure 93 of Loma l'Ántigo (n = 5), all in Catamarca province. The first is a residential unit in the Yocavil valley (2,400 masl), and its chronology corresponds to the beginning of the region's Formative Period. The second is in the Cajón Valley (2,700 masl) and dates to the Regional Developments Period. Bone specimens were previously categorized to genus or species rank employing morphological and osteometric criteria.ResultsOur results suggest that C4 plants have been important in animal diets since the Formative period. At the same time, access to pastures or wildlife at high altitudinal levels persisted during the Regional Developments, with the possibility of a fodder intensification strategy also based on C3 plants.DiscussionSuch kind of data allows us to assess whether a livestock intensification plan based on corn provision coincided with social, political, and economic changes in the early second millennium AD.

Top predators, shared prey: isotopic niche dynamics and trophic interactions among dusky, tiger and white sharks

Assessing the trophic relationships among sympatric marine predators is crucial for ecosystem and fisheries management. This study used carbon and nitrogen stable isotope analysis to elucidate resource use and sharing of dusky Carcharhinus obscurus, tiger Galeocerdo cuvier and white Carcharodon carcharias sharks in eastern Australia. The individuals included in the dataset had similar size ranges (148-400 cm total length [TL]) and migratory movements, meaning they could be used to compare patterns in resource use. Using a Bayesian inference framework, we quantify the isotopic niche of each species and estimate niche overlap to compare their roles in this ecosystem. Tiger sharks had the largest isotopic niche (1.1 ‰2), followed by dusky sharks (0.9 ‰2). The isotopic niche of white sharks is substantially smaller (0.5 ‰2), suggesting these sharks are less of a generalist predator than dusky and tiger sharks. Most white shark niches overlapped with dusky and tiger sharks (84 and 72%, respectively), indicating white sharks use resources with similar isotopic values. Sex did not influence isotopic values, and weak significant relationships existed between TL and δ15N values in tiger sharks. Given the smaller isotopic niche and associated specialised role of white sharks <400 cm TL, this species may be more vulnerable to food web perturbations than generalist tiger and dusky sharks. This study gives new insight into the trophic interactions of these co-occurring shark species in eastern Australia and is crucial for understanding the ecological role of these predators required for sound ecosystem management.

Life and death in Trypillia times: Interdisciplinary analyses of the unique human remains from the settlement of Kosenivka, Ukraine (3700-3600 BCE).

We present an interdisciplinary analysis of finds from the Trypillia settlement of Kosenivka, Ukraine (ca. 3700-3600 BCE, Trypillia C1-2), that links information on human, faunal, and botanical remains with archaeological data to provide exceptionally detailed insights into life and death at a giant Trypillia settlement. We obtained osteological, palaeopathological, morphological and histotaphonomic data from human bone fragments; performed carbon and nitrogen stable isotopic analysis of human and animal bone to calculate food webs; modelled newly generated radiocarbon dates to refine the site's chronology; and contextualised the finds within the phenomenon of a general lack of human remains in Early and Middle Trypillia times through a literature review. Regarding the sphere of life, the biological profile of seven identified individuals reconstructed from the highly fragmented and partially burnt bones represents a demographic cross-section of the population. We documented disease symptoms common in the Chalcolithic and two cases of perimortem cranial trauma. Furthermore, food web calculations demonstrate the large contribution of cereals to the protein component of the human diet, which is supported by dental observations. We suggest that livestock were a major manure producer for crop cultivation, while meat contributed less than 10% to the human diet. Regarding the sphere of death, multidisciplinary data suggest a deadly fire event as one probable scenario for the formation of the Kosenivka find assemblage. This could be a rare example that sheds light on household size in prehistoric times. Furthermore, it adds to the extremely small number of human bone finds in Early and Middle Trypillia sites (A-C1), preceding the shift to extramural burials in its late phase (C2) in some regions. Altogether, our results indicate the huge explanatory potential that has yet to be unlocked in the rare and often poorly preserved bioarchaeological archives of the Cucuteni-Trypillia phenomenon.

Dietary reconstruction of domestic mammals in the Keriya Valley (Xinjiang, China) during the Bronze and Iron Ages using stable isotope analysis of animal hair

Textiles can provide a wealth of information about the practices of ancient cultures. Here we present the carbon and nitrogen stable isotope analyses of a large corpus of well-preserved animal fibres from two Bronze and Iron Age sites in the Keriya Valley (Xinjiang, NW China), an area which lies at the crossroads of exchange and circulation of goods, practices and culture in Eurasia. Our aim is to reconstruct the diets of domesticated herbivores (goat, sheep, cattle, camel) found at these sites in order to shed light on pastoral practices. Caprines and cattle relied heavily on C3 plants with a δ13C mean ratio of −19.8 ± 1.5 ‰ and −20.3 ± 1.8 ‰ respectively, in accordance with other studies in Xinjiang. Occasional consumption of C4 plants is also observed in caprines. These variations may be due to herd mobility and/or seasonal availability of local vegetation or textile trade. Two Iron Age individuals (a camel and a bovid) show a high C4 plants intake. This diet is highly unusual in this context and specific herding practices with millet feeding could be considered.

Parasitism in coral reefs: Trophic ecology of crustacean ascothoracidan parasites and their coral hosts from Malaysia

Coral reefs house a great variety of symbiotic associations, including parasitism. One of the crucial issues in the host-symbiont interactions is the parasites’ feeding mode. Does the parasite/symbiont use the host’s tissues for nutrition, steal food from the host’s digestive system, or take food directly from the environment? However, most of the parasitism in corals is endosymbiotic (endoparasitic). Their trophic interactions are difficult to identify since they only occur in intact associations. This work uses stable isotope analysis (SIA) of carbon and nitrogen and morphological analysis to study the trophic relationship between the crustacean endoparasites, the Ascothoracida (genera Baccalaureus, Sessilogoga, and Zibrowia) and their various coral hosts ranging from Zoantharia (Palythoa) to Antipatharia (Antipathes), and Scleractinia (Dendrophyllia). The hosts belong to different coral taxa and obtain food from different sources, reflected in their stable isotope values. The SIA, supported by the morphological analysis, suggests that the Zibrowia parasite feeds directly on its Dendrophyllia host. Sessilogoga retains vagility within and around the black coral colony. It has typical generalized piercing mouth parts with numerous teeth and denticles. Sessilogoga may use antipatharian tissues for food directly as well as sucks food fluids from the host’s gastrovascular system. There is no clear trophic shift trend between Palythoa and its parasite Baccalaureus. Such differences exclude the possibility of the parasite feeding predominantly on its host’s tissues and suggest a broad spectrum of food sources. Thus, SIA reveals that endosymbiotic ascothoracidans may not always be true parasitic but also opportunistic feeders, which steal food directly from the host gastric cavity.

The dynamics of Bovini exploitation strategies on the Central Plains of China from the Middle Neolithic to the Bronze Age

Bos and Bubalus are important Bovini resources worldwide and were widely exploited on the Central Plains of China during the Neolithic and Bronze Ages. However, distinguishing between Bos and Bubalus remains were challenging due to their similar morphological traits, which leaves the interaction between them poorly understood. This study is the first to combine Zooarchaeology by Mass Spectrometry (ZooMS) with zooarchaeological methods to identify Bos and Bubalus in China at the Tuchengwang (5600–4300 cal. BP), and Pingliangtai (4200–3900 cal. BP) sites. This was accompanied by carbon and nitrogen isotope analyses of bone collagen to discuss their diets on the Central Plains. Our findings indicate that these exploitation strategies are dynamic. Aurochs (Bos primigenius) and water buffaloes (Bubalus mepistopheles) were exploited before the introduction of cattle (Bos taurus), and this exploitation continued into the Bronze Age. The exploitation of local wild Bovini resources may have influenced the adoption of cattle during the End Neolithic. By this time, cattle predominated in Bovini remains at most sites, but the adoption of cattle was not a phenomenon of unison, and their exploitation strategies became more diverse, especially in ritual practices. Wild water buffaloes had evolved into privilege goods by the Bronze Age, especially during the late Shang. This study contributes to a deeper understanding of human-animal-environment relationships between Bovini and ancient people.

Diverse dolomitization models in the Aptian Dariyan (Shu'aiba) Formation in the Persian Gulf, Iran: Evidence from petrography, geochemistry and impact on reservoir quality

This study investigates dolomitization as one of the key diagenetic processes influencing the reservoir quality of the Dariyan Formation (Aptian) in three oil/gas fields in the Persian Gulf. To achieve this goal, petrographic studies of core samples and thin-sections are integrated with cathodoluminescence microscopy, carbon and oxygen isotopic analyses, and fluid inclusion studies. The formation exhibits two main dolomitization models, including hydrothermal-related saddle dolomites and stylolite-associated dolomites, as well as two minor models including bacterial activity-related dolomites and mixed meteoric and marine waters. Hydrothermal dolomitization, associated with deep burial diagenesis, results in saddle dolomites filling fractures and voids, characterized by high-temperature and salinity formation conditions. Stylolite-related dolomitization occurs in mud-dominated facies, as fine to medium crystals with a cloudy center and a clear rim, concentrated along the solution seams and stylolites. Bacterial activity-related dolomitization is distinguished in Lithocodium–algal facies, highlighting the role of microbial mediation in dolomite formation at low temperatures. Mixed-water dolomitization is observed in grain-dominated shoal and lagoonal facies, where the interaction of meteoric and marine waters leads dolomite cementation. Geochemical (δ13C and δ18O) and cathodoluminescence data support the diagenetic model, indicating varying stages and conditions of dolomite formation. Fluid inclusion analyses of saddle and stylolite-related dolomites reveal salinity (9.5 wt% NaCl equiv.) and temperature (105 °C) conditions consistent with burial diagenesis. The paragenetic sequence shows a diagenetic history encompassing marine, meteoric, and burial environments. Marine diagenesis includes early (microbial and mixing type) dolomitization, bioturbation, micritization and isopachous cementation, while meteoric diagenesis comprises dissolution, cementation and recrystallization during prolonged (>1 Myr) exposure at the end of Aptian. Burial diagenesis involves compaction, hydrothermal and stylolite-related dolomitization, cementation, and recrystallization, critically controlling reservoir quality. This study demonstrates that dolomitization significantly enhances permeability, with the highest reservoir quality found in dolomitized facies of the lower carbonate unit of the Dariyan Formation. This study highlights the complexity of diagenetic processes in the Dariyan Formation, providing valuable insights into the factors controlling its reservoir quality. The findings emphasize the importance of integrated geological and geochemical approaches for accurate reservoir evaluation and prediction in dolomitized carbonate formations.

Large-Volume Injection and Assessment of Reference Standards for n-Alkane δD and δ13C Analysis via Gas Chromatography Isotope Ratio Mass Spectrometry.

Compound-specific stable isotope analysis of hydrogen (δD) and carbon (δ13C) in organic compounds is a valuable tool in biogeochemical research. A key limitation of this method is the relatively large amount of sample required to achieve desirable precision. We developed a large-volume (20 μL) injection method that allows for high throughput analysis of less concentrated samples and tested it for δ13C and δD measurements of n-alkanes. We also conducted a comparison of reference standards and assessed several methods to normalize and correct n-alkane δD and δ13C measurements. The mean precision of the δD method based on 233 environmental n-alkane samples (two to three replications per sample) is 4.0‰ (1σ, estimated from the weighted mean of the pooled unbiased standard deviations) and 0.46‰ (1σ) for δ13C from 37 environmental samples (two to three replications per sample). The evaluation of reference standards shows that the use of n-alkane standards with large offsets in δD values in adjacent n-alkane chains can lead to biases in measurement correction. The large-volume injection method shows good reproducibility of δ13C and δD measurements of n-alkanes and reduces the required sample concentration by about 80%. We propose that for δD measurements, a reference standard set should be used in which each reference standard has a limited range of δD values and no adjacent n-alkane chains, to minimize memory effects.

Attributes of karst lakes in sustaining net autotrophy and carbon sink effects

Natural lakes are significant global sources of CO2 emissions; however, data from lakes in karst regions, which cover 15.2 % of the Earth’s surface, remain insufficiently categorized. This study seeks to elucidate the carbon budget processes and drivers in karst lakes by selecting representative karst and non-karst lakes within the same region. Utilizing high-resolution monitoring, carbon isotope analysis, and mathematical modeling, we investigated the carbon source-sink functions and their controlling factors across different lithologies. Our findings reveal that metabolic processes, quantified using a bookkeeping model, are crucial for driving the diurnal coupling of hydrochemistry and carbon cycling, with karst lakes displaying a pronounced net autotrophic state. Carbon sink fluxes, determined via the boundary layer method, were estimated to be 38 t C km−2 yr−1 for the karst lake, and 11 t C km−2 yr−1 for the non-karst lake. This indicates that despite high dissolved inorganic carbon (DIC) concentrations, the metabolic processes in karst waters, facilitated by their high pH and efficient DIC fertilization, lead to a lower CO2 emission. Furthermore, the low Revelle factor (3.8–4.8) highlights the strong carbonate buffering capacity of karst lakes against CO2. These findings emphasize the capacity of karst lakes to maintain net autotrophy and function as carbon sinks, together with the need to consider lithological differences in future assessments of regional or global lake carbon budgets.

Shining a new light on the classical concepts of carbon-isotope dendrochronology.

Retrospective information about plant ecophysiology and the climate system are key inputs in Earth system and vegetation models. Dendrochronology provides such information with large spatiotemporal coverage, and carbon-isotope analysis across tree-ring series is among the most advanced dendrochronological tools. For the past 70 years, this analysis was performed on whole molecules and, to this day, 13C discrimination during carbon assimilation is invoked to explain isotope variation and associated climate signals. However, recently it was reported that tree-ring glucose exhibits multiple isotope signals at the intramolecular level (see Wieloch etal., 2024). Here, I estimated the signals' contribution to whole-molecule isotope variation and found that downstream processes in leaf and stem metabolism each introduce more variation than carbon assimilation. Moreover, downstream processes introduce most of the climate information. These findings areinconsistent with the classical concepts/practices of carbon-isotope dendrochronology. More importantly, intramolecular tree-ring isotope analysis promises novel insights into forest metabolism and the climate of the past.

Tracking Depositional Architecture and Diagenetic Evolution in the Jurassic Carbonates, Trans Indus Ranges, NW Himalayas

The evolution of Jurassic carbonates is globally significant for understanding the depositional framework, diagenetic phases and sedimentary characteristics of shallow marine shelf deposits. For this purpose, two outcrop sections of the Jurassic carbonates with a road distance of 121 km in the Trans Indus Ranges, NW Himalayas, were included in this study. Geological fieldwork was conducted for sedimentological data, and representative samples were collected for microfacies analysis and diagenetic evolution complemented by carbon and oxygen isotope analysis. Results show that eight microfacies were identified in both sections where mudstone microfacies was only present in the Chichali section, whereas wackestone and packstone facies widely existed in both sections. The diagenetic evolution interpreted that dolomitization and stylolization were pronounced in the Paniala section, while micritization and calcite cementation were prevalent in the Chichali section. The interpreted depositional setting implies the wide range from supratidal to outer ramp shallow marine for the Chichali section, suggesting a wide range and relatively deeper environment, alongside merely intertidal to middle ramp settings for Paniala section. Diagenetic evolution suggests marine to meteoric influence in the Chichali section, while burial and uplift phases were dominant in the Paniala section. The diagenetic events were also validated by the isotopic analysis, where most of the samples with values up to −4‰ VPDB δ18O, corresponding to a carbon isotope range of up to +4‰, were interpreted as the burial phase of diagenesis; meanwhile, a few samples with −2 δ13C and −7‰ VPDB δ18O isotope signatures were marked as meteoric influx in the Paniala section. This study indicates the diversity of the depositional environment and diagenetic heterogeneity by integration of thin sections using isotope data, which are quite applicable to shallow marine carbonates.

Morphology, epidermal features and δ13C signature of Lopingian (late Permian) conifers

Conifers, the most successful group of Permian gymnosperms, dominate the famous Bletterbach (Dolomites, NE-Italy) plant fossil assemblage, a highly diverse and well-documented late Permian (Lopingian) flora. An integrated analysis of morphology, cuticles and isotope geochemistry was carried out on approximately 50 conifer shoots across five genera (Ortiseia, Majonica, Dolomitia, Pseudovoltzia and Quadrocladus) and eight species, including three (Pseudovoltzia sjerpii, Quadrocladus solmsii, Quadrocladus cf. orobiformis) described for the first time from Bletterbach. Taxon-specific carbon isotope analyses reveal intra-specific and/or intra-generic variability, identifying a unique geochemical composition for Majonica alpina, which may reflect a possible species-specific geochemical signature or adaptation to particular environmental conditions. The isotopic differences observed between leaves and axes indicate the preservation of distinct isotopic ratios in photosynthetic versus heterotrophic tissues, underscoring the importance of sampling multiple plant parts to accurately capture individual and taxonomic isotopic variability. The study of stable isotopes of organic carbon on well-preserved plant remains is enhanced the paleoenvironmental reconstruction of the Bletterbach flora.