Organic Geochemistry最新文献

{"title":"Occurrence and significance of des-A-triterpenoids in the Shahejie formation, Laizhouwan Sag, Bohai Bay Basin: Insights into paleoenvironmental conditions and organic matter origin","authors":"Ning Wang ,&nbsp;Yaohui Xu ,&nbsp;Guo Chen ,&nbsp;Sijun Wang","doi":"10.1016/j.orggeochem.2025.105093","DOIUrl":"10.1016/j.orggeochem.2025.105093","url":null,"abstract":"<div><div>An abundant and diverse suite of <em>des</em>-A-triterpenoids was identified in samples from the Shahejie Formation of the Laizhouwan Sag, Bohai Bay Basin. This suite includes unsaturated <em>des</em>-A-triterpenes, saturated <em>des</em>-A-triterpanes, <em>des</em>-A-nor-series compounds, and mono-, di-, and tri-aromatic <em>des</em>-A-triterpenoids. Compound-specific carbon isotope data of individual hydrocarbons, combined with their co-occurrence and correlation with oleanane, indicate a terrestrial higher plant origin for <em>des</em>-A-oleanane in the studied samples. Significant differences are observed in the geochemical characteristics and the types/abundance of <em>des</em>-A-triterpenoids among the three sections (A, B, and C) of the third member of the Shahejie Formation (E₂s³) from top to bottom. These variations reflect discernible changes in the depositional setting and biological source inputs. Integrating sedimentological evidence with the distribution patterns of <em>des</em>-A-triterpenoids, we propose that the sediments in Section A were deposited in a pro-delta environment. Extensive swamp/marsh environments were likely developed between the lacustrine basin of the Laizhouwan Sag and the adjacent paleo-uplifts (e.g., the Laibei low uplift and the Weibei uplift). High-energy fluvial systems transported substantial amounts of terrigenous higher plant debris from these swamps, providing abundant organic precursors for the formation of <em>des</em>-A-triterpenoids. Furthermore, rapid burial and low thermal maturity (immature stage) are identified as critical factors for the exceptional preservation of these compounds, particularly the less stable <em>des</em>-A-triterpenes, in Section A. In contrast, samples from Sections B and C exhibit a marked decrease in both the diversity and abundance of <em>des</em>-A-triterpenoids. The biomarker composition suggests a reduced contribution from terrestrial higher plants and a corresponding increase in aquatic-derived organic matter. This shift indicates that the fan-delta depositional system prevalent during the deposition of Section A was no longer active. Instead, the environment likely transitioned to a littoral to shallow lacustrine setting during the deposition of these lower sections.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"210 ","pages":"Article 105093"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145620422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Isotopic signatures of organic matter in the Upper Miocene–Pliocene Elbistan coal seam (Turkey): Insights from δ13C and δ15N variability","authors":"Hatice Kara ,&nbsp;Mehmet Ali Ertürk ,&nbsp;Leyla Kalender ,&nbsp;Cihan Yalçın ,&nbsp;Mehmet Deniz Turan ,&nbsp;Emine Cicioğlu Sütçü","doi":"10.1016/j.orggeochem.2025.105086","DOIUrl":"10.1016/j.orggeochem.2025.105086","url":null,"abstract":"<div><div>This study examines the stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope compositions of coal samples from the Upper Miocene–Pliocene (Neogene) Elbistan Basin, Turkey, to constrain the sources of organic matter and the depositional conditions of peat formation. A vertical sequence of samples collected from the Kışlaköy open-pit mine was analysed for total carbon and nitrogen contents, C/N ratios, and δ¹³C–δ¹⁵N values. The δ¹³C values range from −28.09 ‰ to −16.99 ‰, while δ¹⁵N values vary between 1.97 ‰ and 4.99 ‰. The carbon isotope data indicate a predominantly C₃-type plant origin for the organic matter, with minor C₄ contributions inferred from samples exhibiting enriched δ¹³C signatures. Although some δ¹³C enrichment may partly reflect microbial alteration of organic matter, the overall values remain consistent with a dominant C₃ vegetation signal. Elevated δ¹⁵N values suggest fluctuating redox conditions and microbial nitrogen cycling during peat accumulation. In comparison with other Turkish lignite basins and global coal deposits, the Elbistan samples display a broader isotopic range, reflecting a more complex paleoenvironmental evolution. The data suggest that the coal beds formed mainly in freshwater mire settings, where fluctuating water tables, variable redox conditions, and occasional inputs from C₄ plants influenced peat accumulation. These results provide new insights into the paleobotanical and geochemical history of the basin and demonstrate the value of stable isotope analysis for reconstructing depositional environments in coal-bearing successions.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"210 ","pages":"Article 105086"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145413424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Definitive identification of Ordovician-sourced oils in the Tarim Basin: geochemical constraints from biomarkers and sulfur isotopes","authors":"Daowei Wang ,&nbsp;Chunfang Cai ,&nbsp;Haijun Yang ,&nbsp;Zicheng Cao ,&nbsp;Qinghua Wang ,&nbsp;Hao Zhang ,&nbsp;Peng Sun ,&nbsp;Weiquan Zhao ,&nbsp;Wei Wang ,&nbsp;Zhengzhong Liang ,&nbsp;Haoyu Zhang ,&nbsp;Qinghua Zheng","doi":"10.1016/j.orggeochem.2025.105096","DOIUrl":"10.1016/j.orggeochem.2025.105096","url":null,"abstract":"<div><div>The origin of Paleozoic oils in the cratonic Tarim Basin, China, has long been debated, with previous studies attributing most oils to the Cambrian sources. However, the geochemical characteristics and distribution of the Ordovician-sourced oils remain poorly constrained. This study integrates biomarkers, carbon isotopes, and sulfur isotopes to identify the Ordovician-derived oils in the western part of the Shuntuoguole Low Uplift. Two oils (SHB7 and SHB71X) produced from the Ordovician exhibit distinct geochemical signatures, including the absence of aryl isoprenoids, high concentrations of C₃₀ diahopane, elevated Pr/Ph ratios, and low DBT/P ratios, indicative of a clay-rich, suboxic depositional environment. Critically, these oils display significantly lighter bulk δ³⁴S values (4.0‰ and –1.6‰), which closely match those of the Middle-Upper Ordovician kerogen (–6.7‰ to 5.6‰) and are distinctly lower than the Cambrian-sourced oils (15.8‰ to 23.2‰). Individual <em>n</em>-alkanes δ¹³C compositions further support a different genetic origin compared to the typical Cambrian-derived oils. These findings confirm the existence of a previously unrecognized Ordovician-sourced petroleum system in the basin. The distribution of such oils is likely controlled by migration from the Ordovician source kitchens in the Awati Depression or intra-platform depressions. This study underscores the superiority of sulfur isotopes over conventional biomarkers in resolving complex oil-source correlations in multi-source basins like Tarim.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"210 ","pages":"Article 105096"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145620421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transformation of lignin and lipid biomarkers through degradation of plant tissues and soil organic carbon in a salt marsh-mangrove ecotone","authors":"Prakhin Assavapanuvat ,&nbsp;Joshua L. Breithaupt ,&nbsp;Ding He ,&nbsp;Ralph N. Mead ,&nbsp;Thomas S. Bianchi","doi":"10.1016/j.orggeochem.2025.105084","DOIUrl":"10.1016/j.orggeochem.2025.105084","url":null,"abstract":"<div><div>The poleward expansion of mangroves into native salt marshes, because of global warming, has the potential to alter coastal soil organic carbon (SOC) stocks and composition. However, its effects on organic carbon decomposition remain largely unknown. This study compared concentrations and degradation indices of lignin, sterol, triterpenoid, and <em>n</em>-alkane biomarkers between live-and-dead leaf-and-root tissues and SOC down to 45-cm depth across habitats dominated by two mangrove and two salt marsh species in Apalachicola coastal wetlands, Florida, USA. A significant increase in <em>n</em>-alkanes and lignin oxidation products was observed following the senescence of <em>Avicennia germinans</em> mangrove tissues. Dead leaves of all four plant species, especially <em>Spartina alterniflora</em> and <em>Juncus roemerianus</em> salt marshes, became hotspots of fungal colonization as indicated by elevated ergosterol content. Interpretation of biomarker degradation ratios was complicated by their large difference between living root and leaf endmembers. In soil cores from all plant habitats, the predominance of tetracyclic triterpenoid degradation products (tetracylic:pentacylic ratio = 0.6–518) indicated prevalent anaerobic decomposition, agreeing with higher cholestanol/cholesterol and stigmastanol/stigmasterol ratios in SOC (0.53 ± 0.29 and 1.14 ± 0.83), relative to plant tissues (0.16 ± 0.17 and 0.57 ± 0.44, respectively). In contrast, the presence of pentacyclic degradation products in deep mangrove and salt marsh soils suggested localized aerobic degradation, likely due to subsurface oxygen release from plant roots. In conclusion, salt marsh-to-<em>A. germinans</em> mangrove replacement modified degradability of surface litter, yet degradation of deep SOC was more dependent on biogeochemical characteristics of the soils.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"210 ","pages":"Article 105084"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145358841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring clumped isotope fractionation of organic molecules using density functional theory","authors":"Alexis Gilbert ,&nbsp;Jakub Surma ,&nbsp;Naizhong Zhang ,&nbsp;Sebastian Danielache ,&nbsp;Qi Liu","doi":"10.1016/j.orggeochem.2025.105062","DOIUrl":"10.1016/j.orggeochem.2025.105062","url":null,"abstract":"<div><div>The measurement of doubly-substituted (‘clumped’) isotopologues provides important information regarding the source, sink, and potentially the temperature of formation of a given molecule. While currently limited to small molecules such as methane or carbonate, recent technological developments are expected to expand the range of molecules studied, paving the way for clumped isotope measurements in various organic compounds. Theoretical calculations, including those based on density functional theory (DFT), can serve as guidelines for future methodological developments. However, these calculations have so far been reported for a small number of organic molecules and clumping types.</div><div>Here, we report DFT calculations for DD, ¹³CD, ¹³C¹³C, ¹³C¹⁵N, and ¹³C¹⁸O clumping in organic molecules. Using 32 model molecules, we calculate a total of 143 Δ values (Δ representing the deviation from the stochastic distribution due to equilibrium isotope effects) at temperatures ranging from 300 K to 1000 K. The overall trend follows: ΔDD &gt; Δ¹³CD &gt; Δ¹³C¹⁸O &gt; Δ¹³C¹³C ≈ Δ¹³C¹⁵N, with values decreasing as temperature increases. Through multiple correlation analysis, we demonstrate that the reduced mass of the atoms, bond multiplicity, and hybridization collectively explain 80 % of the differences observed between bond types. Given current analytical uncertainties, the potential for a geothermometer is primarily limited to DD and ¹³CD clumping, while ¹³C¹³C, ¹³C¹⁵N, and ¹³C¹⁸O clumping could be applicable at low temperatures (typically 100 K) or with instrumental precision one order of magnitude higher.</div><div>The calculations presented here provide a framework to assess the instrumental precision required for utilizing clumped isotopes in organic molecules as geothermometers. Future improvements in analytical techniques and computational methodologies could further refine these predictions and broaden the applicability of clumped isotope thermometry in organic geochemistry.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"210 ","pages":"Article 105062"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145264125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insights into the complex nature of dissolved organic matter from plant residues using multiple spectroscopic techniques","authors":"Zongtang Yang ,&nbsp;Biswaranjan Mohanty ,&nbsp;Feike A. Dijkstra ,&nbsp;Georg Guggenberger ,&nbsp;Balwant Singh","doi":"10.1016/j.orggeochem.2025.105095","DOIUrl":"10.1016/j.orggeochem.2025.105095","url":null,"abstract":"<div><div>Dissolved organic matter (DOM) is the most active and labile organic fraction in soils, participating in numerous biogeochemical processes. Comprehensive understanding of DOM composition at the molecular level remains a challenge due to limited or contrasting analytical data based on a single technique or limited analysis, which may be addressed using multiple complementary techniques. In this study, we utilized five prevalent and novel spectroscopic and spectrometric techniques, i.e., XPS, FTIR, NEXAFS, NMR, and FT-ICR-MS, coupled with multivariate analysis to decipher the complexity of DOM. We extracted DOM from four decomposed plant residues − pine, eucalyptus, pasture, and wheat. The organic carbon concentration in the DOM samples followed the order: pine &gt; eucalyptus &gt; wheat &gt; pasture. Eucalyptus and pasture DOM exhibited similarities in aromatic compounds but differed in saturation and O-containing groups. Pine DOM was enriched in aromatic and carboxylic compounds, whereas wheat DOM contained more lipid and aliphatic compounds. The differences in the abundance of functional groups and compound families were attributed to the influence of both the original plant residues and microbial degradation. Chemical convergence of the four DOM samples, reflected by their broadly similar spectral composition was possibly due to similar biodegradation processes but in different stages. Multivariate analysis of multiple spectroscopic data comprehensively captured the DOM composition.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"210 ","pages":"Article 105095"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145620424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Compositional convergence of dissolved organic matter from root litter to rhizosphere soil in a semiarid grassland of North China","authors":"Xiaohan Mo ,&nbsp;Zongxiao Zhang ,&nbsp;Mengke Wang ,&nbsp;Qiang Zhang ,&nbsp;Guodong Sun ,&nbsp;Weifeng Hu ,&nbsp;Guoping Chen ,&nbsp;Deliang Kong ,&nbsp;Chengcheng Dong ,&nbsp;Hui Zeng ,&nbsp;Junjian Wang","doi":"10.1016/j.orggeochem.2025.105061","DOIUrl":"10.1016/j.orggeochem.2025.105061","url":null,"abstract":"<div><div>The transformation of litter-derived dissolved organic matter (DOM) in soils is important for carbon cycling in terrestrial ecosystems. However, the linkage between root litter- and rhizosphere soil-derived DOM remains unclear. In this study, using ultrahigh-resolution mass spectrometry and metagenomics, we evaluated the DOM in paired roots and rhizosphere soils for herbaceous plants in a semiarid grassland and their biogeochemical processes. Analyses revealed a decoupling between root- and rhizosphere soil-derived DOM despite being directly attached, with a considerable loss of root-derived aliphatics and proteins, and production of highly unsaturated, aromatic, and carboxyl-rich compounds. From roots to rhizosphere soils, DOM shifted toward a more uniform molecular composition, which was likely the result of a more “specialized” utilization of root-derived DOM and a more “generalized” utilization of rhizosphere soil-derived DOM by the rhizosphere microbial community. Overall, DOM transformation at the root-soil interface occurred along two principal dimensions: 1) the dimension of “root-to-soil variation” with “lability” and “aromaticity” as two end members, and 2) the dimension of “interspecies variation” dominated by bulk and optical DOM components. These findings suggest that root- and rhizosphere soil-derived DOM constitute two distinct carbon sources for rhizosphere microbial communities and provide a framework for future investigations into DOM dynamics and ecosystem functioning at the plant-soil interface.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"210 ","pages":"Article 105061"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145413425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Obituary for Prof. Dr. Dietrich Welte (1935–2025)","authors":"","doi":"10.1016/j.orggeochem.2025.105047","DOIUrl":"10.1016/j.orggeochem.2025.105047","url":null,"abstract":"","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"209 ","pages":"Article 105047"},"PeriodicalIF":2.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145061217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry articles – May 2025","authors":"","doi":"10.1016/j.orggeochem.2025.105043","DOIUrl":"10.1016/j.orggeochem.2025.105043","url":null,"abstract":"","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"209 ","pages":"Article 105043"},"PeriodicalIF":2.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145060898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deamination of alicyclic and aromatic amines under geologically relevant hydrothermal conditions","authors":"Yiju Liao ,&nbsp;Alexandria Aspin ,&nbsp;Xuan Fu ,&nbsp;Kirtland Robinson ,&nbsp;Ziming Yang","doi":"10.1016/j.orggeochem.2025.105060","DOIUrl":"10.1016/j.orggeochem.2025.105060","url":null,"abstract":"<div><div>Amines are a particular group of organic compounds of interest to deep-sea biology, organic geochemistry, and astrobiology research, in large part due to their involvement in biological metabolism, such as in the form of amino acids and proteins, participation in the subsurface carbon (C) and nitrogen (N) cycles, as well as their relevance to biomolecular precursors on early Earth and potential biosignatures beyond Earth. Although there have been many studies on the deamination of amines under hydrothermal conditions, few have determined the relative deamination rates and degradation mechanisms among different amine structures. In this study, we investigate the reaction kinetics and pathways of a group of aromatic and alicyclic amines, including aniline, benzylamine, cyclohexylamine, and cyclohexylmethylamine, under geologically relevant temperatures (200–275 °C) and pH ranges (5–9) for up to 120 h. Among the studied amines, the amine reactivity generally follows a trend of aniline &lt; cyclohexylamine &lt; cyclohexylmethylamine &lt; benzylamine. Alcohols and secondary amines/imines are observed as the major products of amines, whose formation could follow a nucleophilic substitution (S_N1 or S_N2) mechanism. Hydrothermal experiments at different pH also show that deamination occurs more readily under acidic than alkaline hydrothermal conditions, indicating that the aminium form (R-NH₃⁺) accelerates deamination. These results suggest that the kinetics and pathways of hydrothermal amine transformations are controlled by both the amine structure and solution pH, which have implications for predicting the deamination processes of organic N, release of inorganic N (e.g., ammonia), and N cycling in geologically relevant hydrothermal systems.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"209 ","pages":"Article 105060"},"PeriodicalIF":2.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144997622","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}