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A new approach is presented in this paper for the dynamic modeling of the chemical and isotopic evolution of C1–3 during the hydrocarbon generation process. Based on systematic data obtained from published papers for the pyrolysis of various hydrocarbon sources (type I kerogen/source rock, type II kerogen/source rock, type III kerogen/source rock, crude oil, and asphalt, etc.), the empirical evolution framework of the chemical and isotopic composition of C1–3 during the hydrocarbon generation process was built. Although the empirical framework was built only by fitting a large amount of pyrolysis data, the chemical and isotopic composition of C1–3 derived from the pyrolysis experiments all follow evolution laws, convincing us that it is applicable to the thermal evolution process of various hydrocarbon sources. Based on the simplified formula of the isotopic composition of mixed natural gas at different maturities (δ13Cmixed), δ13Cmixed = X × n i A × δ 13 C i A + Y × n i B × δ 13 C i B X × n i A + Y × n i B , it can be derived that the cumulative isotopic composition of alkane generated in a certain maturity interval can be expressed by the integral of the product of the instantaneous isotopic composition and instantaneous yield at a certain maturity point, and then divided by the cumulative yield of alkane generated in the corresponding maturity interval. Thus, the cumulative isotopic composition (A(X)), cumulative yield (B(X)), instantaneous isotope (C(X)), and instantaneous yield (D(x)) in the dynamic model, comply with the following formula during the maturity interval of (X0~X). A(X) = ∫ X 0 X C X × D X d x B (X) , where A(X) and B(X) can be obtained by the fitting of pyrolysis data, and D(x) can also be obtained from the derivation of B(X). The dynamic model was applied on the pyrolysis data of Pingliang Shale to illustrate the quantitative evolution of the cumulative yield, instantaneous yield, cumulative isotope, and instantaneous isotope of C1–3 with increasing maturity. The dynamic model can quantify the yield of methane, ethane, and propane, as well as δ13C1, δ13C2, and δ13C3, respectively, during the hydrocarbon generation process. This model is of great significance for evaluating the natural gas resources of hydrocarbon source rock of different maturities and for identifying the origin and evolutionary process of hydrocarbons by chemical and isotopic data. Moreover, this model provides an approach to study the dynamic evolution of the isotope series of C1–3 (including reversed isotopic series), which is promising for revealing the mechanism responsible for isotopic reversal when combined with post-generation studies. [ABSTRACT FROM AUTHOR]

This paper aims to update our understanding of the carbon cycle in the Himalayas, the most intense collisional orogeny globally, by providing new insight into its impact on Cenozoic climate cooling through the use of isotopic variations in both organic and inorganic carbon and an isotopic mass balance model. Our results from 20 selected hot springs show that the relative contributions of dissolved carbon from the mantle, metamorphic decarbonization, aqueous dissolution, and soil organic matter are approximately 2%, 82%, 6%, and 10%, respectively. Approximately 87% ± 5% of CO2 generated in the deep crust precipitates as calcite, while approximately 5.5% ± 1% of this carbon is converted to biomass through microbial chemosynthesis at depths less than 2 km. Our random forests approach yielded a metamorphic carbon flux from the entire Himalayan orogenic belt of approximately 2.7 ∼ 4.5 × 1012 mol/yr. The minor CO2 released into the atmosphere (2.5 ∼ 4.2 × 1011 mol/yr) is comparable to the carbon consumption driven by Himalayan weathering. This paper provides new insights into deep carbon cycling, notably that approximately 93% of deeply sourced carbon is trapped in the shallow crust, rendering orogenic processes carbon neutral and possibly acting as one of the major triggers of long‐term climate cooling in the Cenozoic. Plain Language Summary: Large‐scale deep metamorphic decarbonization and CO2 release into the atmosphere during continental collision orogenesis worldwide have had significant impacts on Cenozoic global climate change. However, the carbon sources and sinks and the mechanisms underlying their impacts on climate change are not fully understood. This paper reports the chemistry of aqueous solutions, carbon isotopic compositions of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC), and helium and carbon isotopic compositions of free gases from hot springs in southern Tibet. The carbon isotope fractionation model between gas and aqueous solutions revealed that the carbon released from depth underwent six different stages. Based on the random forests machine learning algorithm, we estimated the metamorphic carbon flux across the Himalayan orogenic belt. Furthermore, only a small fraction (7%) of deep carbon is eventually released into the atmosphere, and this volume is the same magnitude as the amount of carbon absorbed by silicate weathering on the Tibetan Plateau. This paper emphasizes that the carbon sequestration process in the upper crust may have resulted in nearly carbon‐neutral geological bodies in the Himalayan orogenic belt, thus playing a critical role in Cenozoic climate cooling. Key Points: Approximately 87% of deeply sourced carbon precipitates as calcite, while approximately 5.5% is sequestered as biomass in the shallow crustThe carbon flux across the Himalayan orogenic belt was estimated by the random forests approachCrustal thickening has attenuated long‐term deep carbon emissions from the Himalayas [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency 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.)

Stable carbon isotopes of long-chain n-alkanes in lake sediments have been used for reconstructing past environmental changes. Gas chromatography isotope ratio mass spectrometry coupled to a combustion unit is the commonly applied technique for compound-specific carbon isotope analysis. This paper shows that sulfur in the lacustrine sediment can cause severe interference during the mass spectrometric measurement, leading to significant biases in δ13C of n-alkane. The δ13C deviation could be resulted from additional 12C33S+, 13C32S+ at mass-to-charge ratio (m/z) 45, and 12C34S+, H2C32S+at m/z 46, respectively. Such elemental sulphur interference can be eliminated by the activated copper in the pretreatment procedure. [ABSTRACT FROM AUTHOR]

Waste management is paramount to town planning and ancient civilizations across the world have spent resources and mobilized labor for waste disposal and reuse. The study of waste management practices offers a unique window into the daily lives, social organization, and environmental interactions of ancient societies. In the Indus Valley Civilization, known for its urban planning, understanding waste disposal in rural settlements provides crucial insights into the broader socio-economic landscape. While extensive research has documented sophisticated waste management systems in urban Indus centers, little is known about practices in rural settlements. This gap limits our understanding of regional variations and rural-urban dynamics within the civilization. In this paper, using isotopic and microscopic proxies, we characterize the waste disposed of at the rural Indus settlement of Kotada Bhadli to reconstruct the sources of waste, including heated animal dung, and burned vegetation. We propose that rural agro-pastoral settlements in Gujarat during the Indus Era systematically discarded such waste in specific locations. By characterizing waste produced at Kotada Bhadli, we are also able to reconstruct the natural environment and how the natural and cultural landscape around the settlement was exploited by the residents of the settlement for their domestic and occupational needs. Our identification of the attention paid to waste disposal by the inhabitants of Kotada Bhadli adds significant data to our understanding of waste disposal as an insight into past lives. [ABSTRACT FROM AUTHOR]

The hydrocarbon gases in the L1 gas field of the Lishui-Jiaojiang Sag have been commonly interpreted to be an accumulation of pure sapropelic-type thermogenic gas. In this study, chemical components, stable isotopic compositions, and light hydrocarbons were utilized to shed light on the origins of the hydrocarbon fluids in the L1 gas pool. The hydrocarbon fluids in the L1 gas pool are proposed to be a mixture of three unique components: mid-maturity oil from the middle Paleocene coastal marine Lingfeng source rock, oil-associated (late oil window) gas generated from the lower Paleocene lacustrine Yueguifeng source rock, and primary microbial gas from the paralic deposits of the upper Paleocene Mingyuefeng source rock. Here, for the first time, the hydrocarbon gases in the L1 gas pool are diagnosed as mixed oil-associated sapropelic-type gas and microbial gas via four pieces of principal evidence: (1) The abnormal carbon isotopic distributions of all methane homologues from C1 (CH4 or methane) to C5 (C5H12 or pentane) shown in the Chung plot; (2) the diagnostic 13C-depleted C1 compared with the thermogenic sapropelic-type gas model, while δ13C2 (C2H6 or ethane) and δ13C3 (C3H8 or propane) both fit perfectly; (3) the excellent agreement of the calculated carbon isotopic compositions of the pure thermogenic gas with the results of the thermal simulated gas from the type-II1 kerogen-rich Yueguifeng source rock; and (4) the oil-associated gas inferred from various binary genetic diagrams with an abnormally elevated gas oil ratio. Overall, the natural gases of the L1 gas pool were quantified in this study to comprise approximately 13% microbial gas, nearly 48% oil-associated sapropelic-type gas, and 39% of nonhydrocarbon gas. The microbial gas is interpreted to have been codeposited and entrained in the humic-kerogen-rich Mingyuefeng Formation under favorable low-temperature conditions during the late Paleocene-middle Eocene. The microbial gas subsequently leaked into the structurally and stratigraphically complex L1 trap with oil-associated sapropelic-type gas from the Yueguifeng source rock during the late Eocene—Oligocene uplifting event. A small amount of humic-kerogen-generated oil in the L1 gas pool is most likely to be derived from the underlying Lingfeng source rock. The detailed geological and geochemical considerations of source rocks are discussed to explain the accumulation history of hydrocarbon fluids in the L1 gas pool. This paper, therefore, represents an effort to increase the awareness of the pitfalls of various genetic diagrams, and an integrated geochemical and geological approach is required for hydrocarbon-source correlation. [ABSTRACT FROM AUTHOR]

Copyright of Multipurpose Utilization of Mineral Resources / Kuangchan Zonghe Liyong is the property of Multipurpose Utilization of Mineral Resources Editorial Office 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.)

The paper emphasizes the importance of isotope studies as a unique tool for detecting groundwater contamination with the landfill leachate. The aim of the study was to present an additional and useful method for detecting groundwater contamination, based on stable isotope analysis. The proposed method relies on the interpretation of measured δ13CDIC and δ18O levels (in precipitated carbonates during preparation of a water sample). According to this method, two zones with different isotope composition of groundwater were identified: the first zone with natural groundwater and with low δ13CDIC levels (from -20.6 to -12.4%o) and high δ18O levels (from -13.6 to -8.0%), and the second zone with leachate-contaminated groundwater rich in δ13CDIC (from -10.9 to + 3.6%) and high level of δ18O (from -9.8 to -7.1%). Measuring the isotopic composition of oxygen alone, is insufficient to delimit the contaminated zone due a partial overlap of natural levels with those of the contaminated with groundwater leachates. Determination of δ13CDIC and δ18O in the landfill leachate-contaminated water can provide an effective tool to detect groundwater contamination near municipal landfills, and it can help to minimize the number of samples collected for the analysis of conventional parameters. This proven method may offer an easy-to-use solution for detecting groundwater contamination. [ABSTRACT FROM AUTHOR]

A ground natural gas leaking event at the Fuling shale gas field is reported in this paper. Thirteen leakage spots were discovered in two places near the SW-1 and SW-2 drilling wells. The biggest leak rate was above 1000 m3 per day, and no H2S was identified in any of the 13 leaking spots, according to the field study. The chemical components, carbon isotope properties of the leaking gases, and the geological context of the leaking location were researched in order to determine the reason for the leaking incident. From the geological conditions, the Shimen 1# fault belt cuts the whole strata from bottom to top, according to seismic reverse time migration (RTM), and the fault and leaking spots are located in the range of the surface projection of the horizontal section of the adjacent shale gas well. The fracture development evaluation shows that the Wufeng–Longmaxi Formation, which is also the producing layer of the Fuling shale gas field, has a very high possibility of fracture development. From the geochemical view, the carbon isotope of the leaking gases lies in the range of the Wufeng–Longmaxi Formation, showing that the Wufeng–Longmaxi Formation is the gas source of the leaking gas. [ABSTRACT FROM AUTHOR]

Five core sandstone and carbonate rock samples from the Cretaceous Harshiyat Formation containing oil stains were collected from two wells in the North Hadramaut High area (eastern Yemen) and geochemically analyzed by their sterane and terpane biomarker and stable carbon isotope (δ13C) compositions. This paper studied the geochemical characteristics of the oil stains and their relation to probable potential source rocks. The source rock characteristics include the origin of organic matter input; redox depositional conditions, lithology, and degree of thermal maturity were investigated. The saturated and aromatic hydrocarbon fractions of the analyzed oil stain samples have δ13C values in the range of − 26.5‰ – − 28.6‰ and − 26.3‰ – − 26.7‰, respectively. These δ13C values indicate that the oil stain samples originated from a mixed organic matter input in their source rock. The presence of mixed marine and terrestrial organic matter in the source rock is further concluded from biomarker distributions of n-alkane, isoprenoid, terpane, and sterane. These biomarkers and their ratio parameters suggest that the analyzed oil stain samples were sourced from clay-rich rock deposited in marine-reducing environmental conditions and likely contained mixed planktonic/bacterial organic matter and land plant inputs. Both saturated and aromatic maturity biomarkers suggest that the analyzed oil stains were from a mature source rock, equivalent to a moderate to peak-mature oil window. The environmental biomarker indicators of the studied oil stain samples correlated well with the shales in the Late Cretaceous Harshiyat Formation in the onshore Jiza-Qamar Basin (eastern Yemen), indicating that the analyzed oil stains were generated from a mature Harshiyat source rock in the onshore Jiza-Qamar Basin and subsequently migrated into the Cretaceous Harshiyat sandstone and limestone reservoirs in the North Hadramaut High area (eastern Yemen) through normal faults system. [ABSTRACT FROM AUTHOR]

A new approach is presented in this paper for the dynamic modeling of the chemical and isotopic evolution of C1–3 during the hydrocarbon generation process. Based on systematic data obtained from published papers for the pyrolysis of various hydrocarbon sources (type I kerogen/source rock, type II kerogen/source rock, type III kerogen/source rock, crude oil, and asphalt, etc.), the empirical evolution framework of the chemical and isotopic composition of C1–3 during the hydrocarbon generation process was built. Although the empirical framework was built only by fitting a large amount of pyrolysis data, the chemical and isotopic composition of C1–3 derived from the pyrolysis experiments all follow evolution laws, convincing us that it is applicable to the thermal evolution process of various hydrocarbon sources. Based on the simplified formula of the isotopic composition of mixed natural gas at different maturities (δ13Cmixed), δ13Cmixed = X×niA×δ13CiA+Y×niB×δ13CiBX×niA+Y×niB, it can be derived that the cumulative isotopic composition of alkane generated in a certain maturity interval can be expressed by the integral of the product of the instantaneous isotopic composition and instantaneous yield at a certain maturity point, and then divided by the cumulative yield of alkane generated in the corresponding maturity interval. Thus, the cumulative isotopic composition (A(X)), cumulative yield (B(X)), instantaneous isotope (C(X)), and instantaneous yield (D(x)) in the dynamic model, comply with the following formula during the maturity interval of (X0~X). A(X) = ∫X0XCX×DXdxB(X), where A(X) and B(X) can be obtained by the fitting of pyrolysis data, and D(x) can also be obtained from the derivation of B(X). The dynamic model was applied on the pyrolysis data of Pingliang Shale to illustrate the quantitative evolution of the cumulative yield, instantaneous yield, cumulative isotope, and instantaneous isotope of C1–3 with increasing maturity. The dynamic model can quantify the yield of methane, ethane, and propane, as well as δ13C1, δ13C2, and δ13C3, respectively, during the hydrocarbon generation process. This model is of great significance for evaluating the natural gas resources of hydrocarbon source rock of different maturities and for identifying the origin and evolutionary process of hydrocarbons by chemical and isotopic data. Moreover, this model provides an approach to study the dynamic evolution of the isotope series of C1–3 (including reversed isotopic series), which is promising for revealing the mechanism responsible for isotopic reversal when combined with post-generation studies.

We studied the dynamics of stable carbon (δ13C) and nitrogen (δ15N) isotopes in litter from Norway spruce (NSL) (Picea abies) and Scots pine (SPL) (Pinus silvestris) during in situ decomposition over a period of more than 4 years. Relative to initial values, δ13CNSL showed a weak enrichment (0.33‰), whereas δ13CSPL was depleted (−0.74‰) at the end of decomposition. Both litter types experienced a depletion in δ15N during decomposition; δ15NNSL decreased by −1.74‰ and δ15NSPL decreased by −1.99‰. The effect of the selective preservation of acid-unhydrolyzable residue (AUR) in lowering δ13C of the residual litter was evident only in SPL. In the NSL, only in the initial stage did C/N have a large effect on the δ13C values. In the later stages, there was a non-linear decrease in δ13CNSL with a simultaneous increase in AUR concentrations, but the effect size was large, suggesting the role of lignin in driving δ13C of residues in later stages. Depletion in 15N in the residual litters concomitant with the increase in N concentration suggests bacterial transformation of the litter over fungal components. A consistent decline in δ15N values further implies that bacterial dominance prompted this by immobilizing nitrate depleted in 15N in the residual litter. [ABSTRACT FROM AUTHOR]

Key message: Seven European beech provenances differing largely in growth performance were grown at two common garden sites in Germany and Slovakia. The intra-specific variability of most traits was explained more by phenotypic plasticity than inter-provenance variability, and efficiency-related traits showed a higher phenotypic plasticity than safety-related traits. Context: To maintain climate-resilient future forests, replicated common-garden experiments are suited for developing assisted migration strategies for key tree species. Aims: We analysed the magnitude of inter-provenance variability and phenotypic plasticity for 12 functional traits of European beech (Fagus sylvatica L.) and analysed whether the climate at the place of origin left an imprint. Moreover, we asked whether growth is unrelated to xylem safety and to what extent the foliar, xylem and growth-related traits are coordinated. Methods: Terminal branches were collected from 19-year-old and 22-year-old trees of seven European beech provenances planted at two common garden sites in Germany and Slovakia, respectively. Three hydraulic, three wood anatomical and four foliar traits were measured and related to two growth-related variables. Results: At the two sites, the same pair of provenances showed the highest and lowest growth. Nevertheless, a high degree of phenotypic plasticity was observed, as all traits differed significantly between sites after accounting for provenance effects, with hydraulic safety-related traits showing the lowest and efficiency-related traits the highest plasticity. There was no evidence for inter-provenance variability in xylem embolism resistance (P50) or the foliar carbon isotope signature (δ13C), a proxy for intrinsic water use efficiency (iWUE), and both were unrelated to growth. P50 was positively correlated with the lumen-to-sapwood area ratio and vessel density. Conclusions: Because of the lacking trade-off between embolism resistance and growth, highly productive provenances can be selected without reducing the drought tolerance of the branch xylem. However, as xylem safety is only one element of a trees' drought response, it may be beneficial to select provenances with other more conservative drought adaptations such as smaller vessel lumen areas for increasing xylem safety and small supported total leaf areas for reduction of total transpiration. [ABSTRACT FROM AUTHOR]

In recent years, the typical crude oil from the Cambrian Lower Ordovician source rocks has been found in the Tarim Basin, and it is characterized by 13C enrichment. The stable carbon isotope of the oil is concentrated at approximately −28‰, which is 3‰–6‰ heavier than that of the crude oil from the Middle and Upper Ordovician source rocks. The stable carbon isotope between crude oil and its kerogen is characterized by inversion, with an amplitude of approximately 3‰–4‰. However, the origin of this phenomenon remains controversial, which restricts the next exploration of crude oil in the Cambrian–Lower Ordovician in the Tarim Basin. Samples were collected from seven outcrop profiles in the Kuruketage region. The basic geochemical features of the Cambrian strata, including total organic carbon abundance, δ13Corg, δ13Ccarb, and δ18Ocarb, were studied and compared with those of well TD2. The results show that the lithologies, isotope stratigraphic evolutional curves, and correlations between the organic carbon and inorganic carbon of the profiles from the northern Kuruketage region are successively comparable with those of the profiles from the southern Kuruketage region and the well TD2. In this study, the carbon isotope records are supposed to indicate a vertical gradient Cambrian oceanic mode, including the shallow decoupled isotope zone, middle gradient‐coupled isotope zone, and deep isotope‐decoupled zone. The discovery of this isotope record reflects the formation of stable carbon and oxygen isotope stratified oceans during the Cambrian period. Additionally, it provides important insights into the origin of the 13C enrichment observed in some Lower Cambrian crude oils in the Tarim Basin. [ABSTRACT FROM AUTHOR]

The Devonian–Carboniferous boundary is one of the most important turning points in geological history, marked by the Late Paleozoic Ice Age and Late Devonian extinction. This study investigates the carbon isotope stratigraphy across the Devonian–Carboniferous boundary in Lhasa block, Tibet, China, which was part of the Gondwana continent during that time. The carbon isotope curves show a significant negative excursion trend, consistent with those of the South China block and other regions on the Laurentia continent. This global negative shift may be attributed to the burial of significant amounts of 12C-rich organic matter in strata, a consequence of the Late Devonian extinction event. Based on the carbon isotope curve and stratigraphic data of the Lhasa block, this study determined, for the first time, the specific horizon of the Devonian–Carboniferous boundary in Tibet, which is located between grayish white bioclastic limestone and yellowish-brown sandy limestone in the upper part of the Chaguoluoma Formation (D1C1ĉ). These findings provide a new reference for the international stratigraphic community to reconsider the position of GSSP on the Devonian–Carboniferous boundary, as well as study the Late Devonian mass extinction and Late Paleozoic glaciation. [ABSTRACT FROM AUTHOR]

The Tongde Graphite Deposit in Panzhihua is located in the accretionary zone on the western margin of the Yangtze plate. In this paper, the whole rock geochemical analysis, C isotope determination and Re-Os isotope dating of the ore in Tongde graphite mining area are carried out, the original rock of the ore is restored, and the metallogenic environment is discussed. Research shows that the ore SiO2 is 55.65~61.68%, SiO2/Al2O3 ratio is 4.59~5.42, and Ni/Co ratio is 6.23~12.88. It is rich in Ba, Rb, Sr and other large ion lithophile elements and Nb, Zr, Hf, Th, U and other high field strength elements. Total rare earth elements of ore ΣREE is 149.13×10-6～195.37×10-6, with weak Ce negative anomaly and Eu negative anomaly, representing the anoxic marine sedimentary environment. The Carbon isotope δ13CV-PDB in ore is -25.0‰~-23.5‰, which is within the range of biogenic organic carbon, indicating that the ore-forming carbon mainly comes from organic matter. The Re-Os isotopic age of graphite is 983 ± 72 Ma (MSWD=1.7), belonging to the early Neoproterozoic, earlier than the intrusion age of magmatic rocks around Tongde. The content of re is between 27.66×10-9～79.81×10-9, the contents of ordinary Os and 187Os are 0.52 ×10-9～2.16×10-9, 0.28 × 10-9～0.83×10-9,respectively ,it is significantly enriched relative to the abundance of Re and Os in the crust. The 187re/188os ratio is 122.9~350.5, and the initial Os isotope ratio 187Os/188Os=0.31±0.21. Combined with the field geological survey, the original rock of ore and ore bearing mica quartz schist in Tongde area is restored, and it is concluded that the original rock is sedimentary rock.

The carbon isotope (δ13C) in marine biogenic carbonate is a valuable tool for comprehending the marine carbon cycle. However, the absence of monthly resolved δ13C records before the instrumental era (since 1850) hinders us to fully understand the global carbon cycle. In this study, we present a δ13C record from a modern Tridacna gigas shell (δ13Cshell) collected from the southern South China Sea (SCS) with an average resolution of ∼10 days. The δ13C record illustrates seasonal and interannual cycles which are superimposed by long‐term decreasing trend. We investigate the environmental controls influencing the δ13Cshell on different time scales. We suggest that more positive δ13Cshell values observed during the juvenile stage (first 8–10 years), which correspond to a high growth rate, can be attributed to 13C enrichment of the internal dissolved inorganic carbon pool. This resulted from the exponential increase of symbiotic zooxanthellae, and preferential 12C sequestration by the accelerated buildup of productive tissues. On the interannual time scale, changes in δ13Cshell were likely affected by both internal (vital effect) and external processes (sea water δ13C), as well as being disturbed by the super El Niño‐La Niña event. Seasonal changes of δ13Cshell were mainly dominated by the intensity of photosynthesis and respiration of symbiotic zooxanthellae, which depend on the seasonal solar irradiance variations in association with precipitation and the South Asian summer monsoon. Our study sheds light on the controlling factors of δ13Cshell variations on seasonal timescale and the long‐term trend, providing insight into the carbon cycle over geological history. Plain Language Summary: Tridacna is a marine bivalve that forms symbiotic zooxanthellae in its mantle tissues and has a hard calcium shell. In this study, we analyzed the carbon isotope composition of the Tridacna shell collected from the southern South China Sea and compared it with various climatic and oceanographic records. Our results suggest that the variability of carbon isotope in the Tridacna shell is predominantly controlled by the activity of its symbiotic zooxanthellae in association with solar radiation and growth rate on various time scales. Furthermore, we found that changes in the carbon isotope of Tridacna shell can be influenced by fluctuations in the South Asian summer monsoon and strong El Niño‐La Niña events. Our study sheds light on the factors that control carbon isotope in the Tridacna shell on different time scales, thereby providing valuable insights into the carbon cycle and climate history. Key Points: A high‐resolution δ13C record of Tridacna shell from the southern South China Sea was presentedActivity and density of symbiotic zooxanthellae linked to the solar irradiance dominated the δ13C changes of Tridacna shellsChanges of δ13C of Tridacna shells are also affected by the South Asian summer monsoon and super El Niño‐La Niña event [ABSTRACT FROM AUTHOR]

The Pearl River Mouth Basin (PRMB) is one of the important offshore targets for oil and gas exploration in China and has great potential of oil and gas resources. The Eocene Wenchang Formation is one of the potential source rocks in the PRMB, but its geochemical characteristics are insufficiently studied, particularly for the Wenchang Formation source rocks in deep-water area of the PRMB. Due to the deep burial condition, core samples can rarely be obtained, and most samples are drilling cuttings which are easily to be contaminated by drilling mud, which makes it difficult to directly access the geochemical characteristics of Wenchang Formation source rocks. This paper aims to compare the geochemistry of the Wenchang Formation source rocks in the deep-water and shallow-water areas of the PRMB with an improved catalytic hydropyrolysis method to release the bound hydrocarbons from kerogen macromolecules. Based on the biomarkers and carbon isotopic compositions of individual n-alkanes released, the geochemical characteristics of Wenchang Formation source rocks in deep-water (mainly from Zhu Ⅱ Depression) and shallow water areas (mainly from Zhu Ⅰ Depression) from PRMB are compared. Results indicate that the source rocks of Wenchang Formation in PRMB can be classified into three types including semi-deep to deep lacustrine (WC-Ⅰ), shallow lacustrine (WC-Ⅱ), and semi-deep to deep lacustrine with algal blooming (WC-Ⅲ). The WC-Ⅰ are characterized by low C30 4-methylsteranes (4-Me/C29 < 0.2) and bicadinanes contents, and relatively light carbon isotopic composition of individual n-alkanes (-33‰ to -31‰). The WC-Ⅱ are characterized by low 4-Me/C29 ratios (average=0.06), low to high T/C30H ratios (average=1.04), and relatively heavier carbon isotope composition of individual n-alkanes (-30‰ to -27‰). The WC-Ⅲ are characterized by high content of C30 4-methylsteranes (4-Me/C29=0.66) and heavy carbon isotope compositions of individual n-alkanes (-25‰ to -23‰). The Wenchang Formation source rocks in deep-water and shallow-water areas have semi-deep to deep lacustrine facies (WC-Ⅰ) and shallow lacustrine facies (WC-Ⅱ). In addition, the semi-deep to deep lacustrine source rocks with algal blooming (WC-Ⅲ) also developed in shallow-water areas, but no such type of source rocks were found in deep-water area. This study compared the geochemical characteristics of bound hydrocarbons in source rocks of Wenchang Formation in different regions of PRMB, and found that the semi-deep to deep lacustrine source rocks of Wenchang Formation in shallow-water area can be divided into two types. It provides a scientific basis for a better understanding of the geochemical features of source rocks in different areas of Wenchang Formation in PRMB, and is helpful for oil-source correlations in this area.

Paleosols preserve archives of vegetation history, environmental changes, and sedimentary systems. The changes in vegetation history and environmental conditions in karst areas of the Yunnan–Guizhou plateau of southwestern China since the late Pleistocene were analyzed using δ13C, 14C and the Rb/Sr ratio. Our δ13C results reveal the coexistence of C3 and C4 plants (−10.91 to −30.45‰) in soil organic matter, something that is consistent with the present field vegetation assessment. The large vertical difference in the δ13C value (>4‰) is related to the cultivation of agricultural crops and to changes in environmental conditions. Furthermore, the variation in δ13C values was influenced by the summer monsoon climate of the Indian Ocean and east Asia. We found that total organic carbon (TOC) concentration decreased exponentially with soil depth, indicating high carbon loss. In addition, 14C apparent age of the soil profiles ranged from modern times to 20,605 (±63) years before the present (yrs. BP) and is positively correlated with soil depth. The combined results indicate that, since the late Pleistocene era, environmental conditions in the study area have changed intermittently on a scale of millennia from hot-humid to cold-dry conditions. We speculate that there may have been extreme climate events in the study area 14,750 years BP, which are marked by a drastic change in δ13C and in the Rb/Sr ratio. [ABSTRACT FROM AUTHOR]

Along with tree ring width, carbon isotopes are also good proxies for climate change. Water use efficiency (WUE) can be calculated more quickly and accurately based on carbon isotopes. In this study, according to the principle of dendroclimatology, the sequence of δ13C and WUE of tree rings of Picea meyeri are built. Pearson correlation analysis and multiple regression analysis are used to explore the response of carbon stable isotopes of Picea meyeri to climate change, which revealed the relationship between δ13C of Picea meyeri and climatic factors. Based on δ13C, we calculated the WUE of Picea meyeri and analyzed its response to climate change. The main conclusions are as follows: (1) The δ13C of Picea meyeri decreases year-by-year from 1957 to 2020, in the range from −23.89‰~−21.67‰, and the average value is −22.67‰. The water use efficiency of Picea meyeri increases in the range from 17.26~61.31, with an average of 39.45. (2) The δ13C of Picea meyeri is negatively correlated with temperature, which has the highest correlation with the temperature of the growing season (c5–c9), and its coefficient is higher than that of the mean temperature of each month. (3) There is a significant positive correlation between WUE sequence and temperature. Meanwhile, due to the effect of precipitation and temperature, the Picea meyeri is subject to drought stress to some extent. Above all, temperature is the main climatic factor affecting the δ13C and WUE of Picea meyeri on Luya mountain. [ABSTRACT FROM AUTHOR]

The Kungurian Stage in the early Permian was a transitional glacial age between the late Paleozoic icehouse and the early Mesozoic super-greenhouse period This stage offers an excellent opportunity to study the co-evolution between global carbon cycles and environments. This study presents facies and carbon isotope variations in a new carbonate section in the Lower Yangtze region of South China in order to understand the linkage between carbon cycle fluctuation, sedimentary environment, and climate change. Based on the sedimentary facies analyses of the Chihsia Formation (Kungurian), seven facies types were identified and grouped into lower slope, upper slope, and platform facies associations. The facies analyses show that the Kungurian Stage experiences two transgressive-regressive cycles; paleoclimatic changes controlled the sedimentary records and sea level fluctuations. Early Kungurian carbonate rocks record the presence of the short-lived Kungurian carbon isotopic event (KCIE). The rapid negative carbon isotope of the KCIE was closely related to the huge CO2 emission. A warming climate could have slowed down oceanic ventilation rates and accelerated stratification of seawater. The resulting anoxic environment led to a sharp decline in biological species. In the middle Kungurian, the intensity of volcanic activity gradually weakened and the climate turned cold, which accelerated oceanic ventilation rates and led to increased oxygenation of deep-shelf water masses. The higher Δ13C values supported enhanced primary productivity and photosynthesis, which promote the prosperity of biological species. This study provides a new perspective for better understanding the links between marine carbon cycle fluctuations, climate change, and environments during the icehouse to greenhouse conversion period. [ABSTRACT FROM AUTHOR]

The South Qinling Belt is a key area for understanding the collisional history of the South China and North China blocks during the Lopingian (late Permian) and Triassic. This paper establishes the first integrated timescale based on conodont biostratigraphy and δ13C carb records from a continuous end Permian to the end-Early Triassic succession at Yiwagou, South Qinling Platform (SQP). Ten Early Triassic conodont zones are established. They are, in ascending order, Hindeodus parvus , H. postparvus , Neospathodus dieneri , Eurygnathodus costatus and E. hamadai , Novispathodus waageni - Scythogondolella mosheri , Pachycladina - Parachirognathus assemblage, Triassospathodus hungaricus , Ns. robustispinus and T. clinatus zones. Our record of δ13C carb fluctuations shows close correspondence to known Early Triassic carbon isotope fluctuations and, in combination with the conodont data, helps achieve a high-resolution age model for the region. The use of E. costatus as a good auxiliary marker for the Induan-Olenekian boundary (IOB), within palaeolatitudes of 40°N-40°S, is supported but it can not replace the use of Nv. waageni , because the former is absent in higher-latitude and cooler regions. The conodont faunas from the Palaeo-Tethyan Yiwagou section closely resemble those from the Northern Yangtze Platform (NYP), but they differ somewhat from the contemporaneous Nanpanjiang Basin at species level. Thus, the Qinling Sea was likely well connected with the NYP in the Early Triassic, but was more isolated from the Nanpanjiang Basin. The remarkable reappearance of Hindeodus fauna around the IOB at Yiwagou implies that the shallow-water Qinling Sea was a refuge area for this genus long after its disappearance elsewhere. • Conodont biostratigraphy and δ13C carb records from end Permian to the end-Early Triassic succession at Yiwagou, South Qinling Platform. • Discussion of index conodont for the Induan-Olenekian boundary. • Comparison of the conodont faunas between the eastern Paleo-Tethyan Yiwagou, South China and the western Paleo-Tethyan Europe. • The shallow-water Qinling Sea was a refuge area for Hindeodus fauna after Griesbachian. [ABSTRACT FROM AUTHOR]

Identification and validation of biomarkers and bioindicators to select genotypes with superior tolerance to water deficit (WD) under field conditions are paramount to plant breeding programs. However, the co-occurrence of different abiotic stresses such as WD, heat, and radiation makes it difficult to develop generalized protocols to monitor the physiological health of the plant system. The study assessed the most abundant carbohydrates and sugar alcohols in five faba bean (Vicia faba) genotypes under field conditions and the abundance of naturally occurring carbon isotopes in bulk leaf material to predict water use efficiency (WUE). Plant water status and biomass accumulation were also assessed. Among the accumulated sugars, inter-specific variation in glucose wasmost prevalent and was found at a higher concentration (8.52mg g-1 leaf) in rainfed trial. myo-Inositol concentrations followed that of glucose accumulation in that the rainfed trial had higher amounts compared to the irrigated trial. WUE calculated from carbon isotope abundance was consistently offset with measured WUE from measurements of leaf gas exchange. All genotypes demonstrated significant relationships between predicted and measured WUE (p < 0.05) apart from control variety PBA Warda. Thus, bulk leaf-level carbon isotope abundance can be used to calculate WUE and used as an effective selection criterion for improving WUE in faba bean breeding programs under field conditions. [ABSTRACT FROM AUTHOR]

Water-use efficiency (WUE) is the ratio of biomass produced per unit of water consumed; thus, it can be altered by genetic factors that affect either side of the ratio. In the present study, we exploited natural variation for WUE to discover loci affecting either biomass accumulation or water use as factors affectingWUE. Genome-wide association studies (GWAS) using integrated WUE measured through carbon isotope discrimination (δ13C) of Arabidopsis thaliana accessions identified genomic regions associated with WUE. Reverse genetic analysis of 70 candidate genes selected based on the GWAS results and transcriptome data identified 25 genes affecting WUE as measured by gravimetric and δ13C analyses. Mutants of four genes had higher WUE than wild type, while mutants of the other 21 genes had lower WUE. The differences in WUE were caused by either altered biomass or water consumption (or both). Stomatal density (SD) was not a primary cause of altered WUE in these mutants. Leaf surface temperatures indicated that transpiration differed for mutants of 16 genes, but generally biomass accumulation had a greater effect on WUE. The genes we identified are involved in diverse cellular processes, including hormone and calcium signaling, meristematic activity, photosynthesis, flowering time, leaf/vasculature development, and cell wall composition; however, none of them had been previously linked to WUE. Thus, our study successfully identified effectors of WUE that can be used to understand the genetic basis of WUE and improve crop productivity. [ABSTRACT FROM AUTHOR]

The oil and gas exploration degree of Qinnan sag is low. In this paper, all the 17 crude oil samples from the four reservoirs in the eastern Qinnan sag were taken as the research object. Research methods include GC-MS, stable carbon isotopic of crude oil and group components and other analytical methods. The geochemical characteristics of crude oil were studied by the main parameters, Pr/ph, γ/C31 hopane, Ts/Tm, 4MSI and C29 sterane isomerization. The results show that most of the hydrocarbon generating parent materials of all the 17 crude oils are reductive lacustrine sedimentary organic matter with higher salinity. The crude oil of Es12 is mainly derived from low aquatic algae, and the crude oil of Ed3, Ek and Mz shows the characteristics of a mixed source. The maturation characteristics of crude oils are low mature-mature. The stable carbon isotope of oil and the components is in the range of −30‰ to −26‰, which shows the distribution characteristics of δ13CST

We report carbon isotopic values in total organic carbon (TOC) and pyrogenic carbon (PyC) preserved in two sediment cores from the Ross Sea, Antarctica. The δ13C values of PyC ranged from −10.9‰ to −17.2‰, with distinct differences from the δ13C values of TOC (−24.1‰ to −26.1‰) in the sediments. The radiocarbon ages of PyC were 9,128 and 8,410 years old on average in the two cores but were thousands of years younger than the ages of TOC at the same core depth. These isotopic records provide strong evidence indicating that the PyC was produced from ancient wildfires predominantly in C4 vegetation and transported to Antarctica in the atmosphere. We suggest that ancient wildfires in predominantly C4 grasslands likely frequently occurred on a large scale and at a high intensity in the Southern Hemisphere during the last deglaciation to mid‐Holocene period of 14,800–4,200 years ago. Plain Language Summary: A large fraction of pyrogenic carbon (PyC) is produced from incomplete combustion of biomass fires on Earth and is widely distributed on land and in the oceans. This study presents the first evidence of both radiocarbon and stable carbon isotopes in the PyC preserved in the slope sediments of the Ross Sea in Antarctica. The results revealed that PyC accounted for a significant fraction (10.0%–28.0%) of the sedimentary total organic carbon (TOC) buried in the sediments, and both the Δ14C and δ13C values of PyC showed distinctive differences compared with those of TOC. The well‐defined δ13C (−10.9‰ to −17.2‰) and Δ14C (−415‰ to −843‰) values of PyC in the sediments revealed that in ancient times, PyC was produced from wildfires of C4 vegetation in the Southern Hemisphere and was transported in the atmosphere to Antarctica. The isotopic records of PyC preserved in the Ross Sea sediments provide meaningful evidence for environmental changes. Key Points: Pyrogenic carbon (PyC) constitutes a significant fraction of total organic carbon (TOC) preserved in sediment of the Ross Sea, AntarcticaDistinctive differences in both radiocarbon and stable carbon isotope values exist between PyC and TOC in the Ross Sea sedimentThe isotopic records indicated that the PyC was produced from ancient wildfires in C4 grasslands and transported to Antarctica in atmosphere [ABSTRACT FROM AUTHOR]

Oil group separation, gas chromatography–mass spectrometry analysis of saturated hydrocarbons, carbon isotope analysis of fractions and tests on trace elements were all carried out to determine the origin of shallow Jurassic heavy oils in the northwestern margin of the Junggar Basin, northwestern China. Results showed that all the crude oils had been subjected to different degrees of biodegradation, on an order ranging from PM 6 to 9, which yielded many unresolved complex mixtures (UCM) and formed a huge spike in the mass chromatogram (M/Z = 85). Two heavy oils from the Karamay area underwent slight biodegradation, characterized by the consistent ratios of biomarker parameters. C21/C23 and C23/H of the two samples were 0.81 and 0.85, while G/H, C27/C29 and C28/C29 were 0.38 and 0.40, 0.16 and 0.27, 0.87 and 0.86, respectively. The isomerization parameters of terpane and steranes were 0.50–0.53, and 0.48–0.49, respectively. The above geochemical indices indicated that the crude oils in the study area were in the marginally mature stage. The parent materials were a mixture, consisting of bacteria, algae and some higher plants, formed under reducing depositional conditions, which is in agreement with the source rocks of the Fengcheng Formation in the Mahu depression. The carbon isotopic compositions of saturated hydrocarbon, aromatic hydrocarbon, NSO and asphaltene were –31‰– to –30.3‰, –29.5‰ to –29.03‰, –29.4‰ to –28.78‰ and –28.62‰ to –28.61‰, respectively. These findings are in agreement with the light carbon isotope of kerogen from the lower Permian Fengcheng Formation. Furthermore, V/Ni and Cr/Mo of all the crude oils were 0.01 to 0.032, 0.837 to 10.649, which is in good agreement with the ratios of the corresponding elements of the extracts from the Fengcheng Fm. carbonate source rock. As a result, a two–stage formation model was established: (1) the oil generated from the carbonate source rocks of the Fengcheng Formation migrated to the Carboniferous, Permian and Triassic traps during the Late Triassic, forming the primary oil reservoirs; (2) during the Late Jurassic period, the intense tectonic activity of Yanshan Episode II resulted in the readjustment of early deep primary reservoirs, the escaped oils gradually migrating to the shallow Jurassic reservoir through cross‐cutting faults, unconformities and sand body layers. The oils then finally formed secondary heavy oil reservoirs, due to long–term biodegradation in the later stage. Therefore, joint methods of organic, isotopic and element geochemistry should be extensively applied in order to confirm the source of biodegradation oils. [ABSTRACT FROM AUTHOR]

Diet is a key factor affecting seabird foraging behaviour, ultimately influencing survival, breeding success and long‐term population viability. The density and distribution of prey species in the marine environment are influenced by many factors including climate effects such as El Niño southern oscillation and climate change that alter water temperature.While poor quality diet has been implicated as a contributing factor in the decline of some mainland New Zealand yellow‐eyed penguin (Megadyptes antipodes) populations, little is known about their diet in the subantarctic where the majority of the species breeds.Blood and feather samples (n = 63) were collected for stable isotope analysis of diet from 25 individual birds breeding on subantarctic Enderby Island, Auckland Islands, New Zealand, from 2015 to 2018.Diet data were analysed by factors such as breeding year, sex and foraging behaviour. Stable isotope analysis demonstrated significant changes in diet during each year of the study, which included both El Niño and La Niña conditions.Diet during El Niño conditions comprised lower trophic level prey, which were more benthic, and found closer to shore than diet during La Niña.Coupled with the reported variable breeding success of yellow‐eyed penguins in the subantarctic, variable diet suggests prey availability is likely to be a limiting factor in some years. Prey availability is therefore expected to be a major influence on survival and breeding success of this endangered species in the future, particularly if the effects of climate change become more pronounced.This research highlights an urgent conservation need to identify prey species utilized by the southern population, along with their distribution in time and space, and therefore also the effect of diet on long‐term population stability. [ABSTRACT FROM AUTHOR]

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Copper and associated gold mineralization in the Mundiyawas-Khera area of western India is hosted by the Proterozoic felsic volcanic rocks of rhyo-dacite composition. Signatures of hydrothermal alteration represented by sericite, epidote, scapolite and carbonates are well observed around the ore mineralization zone. The felsic volcanic rocks with gently to flat sloping REE pattern, variable negative Eu anomaly, intermediate abundances of HFSE and moderate to low Zr/Y anomalies are suggested to be FII, FIIIa and FIV type rhyolite. The felsic volcanic host rock for copper mineralization has a depleted and flat HREE pattern and indicates the crustal source, which is garnet free. Negative Eu anomaly in the rock is probably because of the intracrustal partial melting formed in a rift related environment. The high temperature magmatic activities are probably evolved due to the partial melting of crust at shallow to moderate depths, suggesting an evolved continental crust. The δ13C values of the mineralized carbonate veins range between −10.4‰ and −0.9 ‰ (min = −10.6‰, n = 27), whereas the δ18O values show a range of 16.35‰ to 25.23‰ (min = 21.49‰, n = 27), ideally suggesting a mixed source for the ore bearing fluid. Geological, geochemical and stable isotope data of the Mundiyawas-Khera copper deposit suggest it to be a VMS/VHMS setup and these insights will lead to finding new deposits in the nearby areas, having same stratigraphic horizons and similar lithogeochemical assemblages. [ABSTRACT FROM AUTHOR]