Organic Geochemistry最新文献

{"title":"Environmental indications and controls of bacterial membrane lipids in a tropical peatland from Panama","authors":"V. Schneider ,&nbsp;J.M.W. Antoszkiewicz ,&nbsp;M. Vreeken ,&nbsp;S.M.K. Cheung ,&nbsp;Z. Zeng ,&nbsp;D.Agudo Atencio ,&nbsp;A.V. Gallego-Sala ,&nbsp;J. Blewett ,&nbsp;R.D. Pancost ,&nbsp;B.D.A. Naafs","doi":"10.1016/j.orggeochem.2025.105094","DOIUrl":"10.1016/j.orggeochem.2025.105094","url":null,"abstract":"<div><div>Lipid biomarkers are widely used to trace microbial activity and environmental changes, yet gaps remain in our understanding of their environmental occurrence, including in tropical peatlands. We analyzed the bacterial lipid abundance in a series of 2 m long peat cores from the Republic of Panama, focusing on the diether glycerol with C_15:0 <em>n</em>-alkyl chains (C_15:0 DEG), 13,16-dimethyl octacosanedioic acid (<em>iso</em>-diabolic acid: <em>iso</em>-DA), and branched Glycerol Dialkyl Glycerol Tetraethers (brGDGTs) and combined these with novel genomic data from the same cores. In addition to understanding these compounds’ environmental occurrence, we present the first environmental insights into the co-occurrence of brGDGT-Ia with its potential precursors C_15:0 DEGs and <em>iso</em>-DA. Our results show that <em>iso</em>-DA is found only in the occasionally dry top peat layer and is absent in water-saturated peat horizons. We suggest that the production of <em>iso</em>-DA in this peatland dependents on oxygen availability, likely due to the metabolism of the source organisms and consistent with limited available culture data of acidobacteria. In contrast, C_15:0 DEGs and brGDGTs (mainly in the form of brGDGT-Ia) persist across all depths with increasing concentrations at greater depths. Although these contrasting trends in abundance could reflect the greater persistence of ether lipids relative to acyl/acid lipids due to differences in preservation rates, they could also suggest that <em>iso</em>-DA is not a major precursor in the biosynthetic pathway of brGDGTs in these settings. When combined with novel genomic data, we show that acidobacteria, one of the few known <em>iso</em>-DA and brGDGT producers, were detected at all sites and depths, forming a stable proportion of the prokaryotic community. Their consistent presence aligns more with the brGDGT and C_15:0 DEG distribution than <em>iso</em>-DA. Combining the results from our study with experimental evidence, it appears that multiple pathways for brGDGT biosynthesis exist in tropical peats, with the phylogenetic and environmental control on their expression yet to be elucidated.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"210 ","pages":"Article 105094"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145620423","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":"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":"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":"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":"Paleoenvironmental and diagenetic effects on porphyrin distributions in the End-Devonian Exshaw Formation, Western Canada","authors":"Sanjukta Dhar,&nbsp;James M. Fulton","doi":"10.1016/j.orggeochem.2025.105090","DOIUrl":"10.1016/j.orggeochem.2025.105090","url":null,"abstract":"<div><div>Porphyrin distributions were studied across 20 locations in the Western Canada Sedimentary Basin, particularly focusing on sediments deposited at the base of the Exshaw Shale, spanning the Devonian-Carboniferous boundary and contemporaneous with the Hangenberg mass extinction. Locations along a north–south transect represent thermally immature kerogen, while locations from east to west show a gradient of increasing thermal maturity. The study aimed to identify regional variability in <em>syn</em>-depositional environmental conditions and post-burial diagenesis influencing porphyrin preservation along the two transects. The relative abundance of three major categories of vanadyl porphyrins – cycloalkanoporphyrins, bicycloalkanoporphyrins, and etioporphyrins from the different sites exhibit notable spatial diversity, with the primary factor affecting their distribution being thermal maturity. Effects of paleoredox conditions and degree of organic matter decomposition were evaluated using trace element enrichments, thermal Rock Eval data, sterane and homohopane maturity indices.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"210 ","pages":"Article 105090"},"PeriodicalIF":2.5,"publicationDate":"2025-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145575910","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":"Plant-wax n-alkanes from the central Congo Basin as palaeo-environmental and -climatic proxies","authors":"Mélanie Guardiola ,&nbsp;Gaël U.D. Bouka ,&nbsp;Carolia Abaye ,&nbsp;Johanna Menges ,&nbsp;Frauke Rostek ,&nbsp;Guillaume Leduc ,&nbsp;Edouard Bard ,&nbsp;Enno Schefuß ,&nbsp;Yannick Garcin","doi":"10.1016/j.orggeochem.2025.105092","DOIUrl":"10.1016/j.orggeochem.2025.105092","url":null,"abstract":"<div><div>The central Congo Basin is home to the world’s largest tropical peatland complex and is covered with swamp forest. In the face of climate change and future human activities in the region, it is important to understand the factors that determine the nature and dynamics of the peatland vegetation cover. One way to gain insight into these factors is to reconstruct the history of the central Congo Basin peatlands. Analysing lipid biomarkers extracted from peat cores such as plant wax <em>n-</em>alkanes enables past environmental and climatic conditions to be reconstructed. However, there is currently no information on how the production of plant waxes by different plant species influences the abundance and isotopic composition of <em>n-</em>alkanes in peat and other archives in the Congo Basin. In this study we analysed plant wax <em>n-</em>alkane abundances, δ¹³C and δD values according to photosynthetic pathways (C₃ vs. C₄), angiosperm subclasses (dicotyledons vs. monocotyledons), and source water δD values in the dominant plant types (trees, shrubs, and herbs) in the peatland area of the Cuvette Department in the Republic of the Congo. Our dataset enables the definition of a new <em>n</em>-alkane distribution index, named GRIND, that distinguishes between C₃ (mostly dicotyledons) and C₄ (monocotyledons) plants as follows: (<em>n-</em>C₂₇ + <em>n-</em>C₃₃ + <em>n-</em>C₃₅)/(<em>n-</em>C₂₅ + <em>n-</em>C₂₇ + <em>n-</em>C₂₉ + <em>n-</em>C₃₁ + <em>n-</em>C₃₃ + <em>n-</em>C₃₅). This index may therefore be used to analyse Central African peat deposits and derive the relative abundance of C₃ and C₄ plant waxes in the past, independently of δ¹³C measurements. Furthermore, δ¹³C values from the central Congo Basin and other African sites suggest that environments with high relative humidity (&gt; 80%) are characterised by very negative δ¹³C values (i.e., &lt; –37‰) of <em>n-</em>C₂₉ and <em>n-</em>C₃₁ alkanes. This observation highlights the potential of <em>n-</em>alkane δ¹³C in deriving climatic information under high relative humidity conditions in Central African lowlands, and contribute to palaeo-climatic reconstructions. Finally, the δD values of <em>n</em>-C₂₉ and <em>n</em>-C₃₁ alkanes demonstrate that, despite contrasting apparent fractionation values associated with photosynthetic pathways and plant functional types — which can be accounted for using δ¹³C and pollen data in sedimentary deposits — they reliably reflect the δD of environmental water. This confirms that plant wax <em>n</em>-alkane δD values are effective tools for reconstructing palaeo-climatic changes in equatorial regions.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"212 ","pages":"Article 105092"},"PeriodicalIF":2.5,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145659138","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":"Isolation of 2,3,6- & 2,3,4-trimethyl aryl isoprenoids using argentation silica gel column chromatography for compound-specific isotopic analysis","authors":"Tian Ao ,&nbsp;Xianxin Meng ,&nbsp;Hong Lu ,&nbsp;Youping Zhou ,&nbsp;Ping’an Peng","doi":"10.1016/j.orggeochem.2025.105089","DOIUrl":"10.1016/j.orggeochem.2025.105089","url":null,"abstract":"<div><div>Trimethyl aryl isoprenoids (TMAIPs) provide significant insights into the biological and geochemical processes in modern and ancient aquatic environments. Obtaining carbon isotope (δ¹³C) data for these carotenoid-derived biomarkers can greatly enhance their interpretative value, as non-sulfur bacterial sources can be distinguished by their carbon isotope compositions from sulfur bacterial sources. However, δ¹³C measurement for individual TMAIPs is particularly challenging due to their low relative abundance in complex hydrocarbon mixtures. We present an argentated (with silver nitrate) silica gel column chromatography (Ag-CC)-based method for isolation of TMAIPs in the aromatic hydrocarbon fraction of crude oils. The effectiveness of the method was demonstrated by the successful isolation of the co-occurring 2,3,6- &amp; 2,3,4- TMAIPs in two crude oil samples sourced from the hypersaline lacustrine environment of the Jianghan Basin in China, enabling reliable δ¹³C and δ²H analysis for the TMAIPs and other target biomarkers such as <em>n</em>-alkyl benzenes. The δ¹³C values of the 2,3,6-TMAIPs (−19.4‰ to −17.2‰) were found to be significantly higher than those of the 2,3,4-TMAIPs (−25.9‰ to −20.8‰), but the δ²H values of the 2,3,6-TMAIPs (−187.4‰ to −171.7‰) were significantly lower than those of the 2,3,4-TMAIPs (−140.3‰ to −106.7‰). Future work should be focused on the elucidation of the controlling factors of the TMAIPs isotopic compositions (promised by the new technique) and their broader geological implications.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"210 ","pages":"Article 105089"},"PeriodicalIF":2.5,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145575909","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":"Composition and distributional patterns of C3- and C4-alkylbenzenes in oils and source rocks from Meso–Neoproterozoic to Cenozoic","authors":"N.V. Oblasov ,&nbsp;I.V. Eftor ,&nbsp;I.V. Goncharov ,&nbsp;S.V. Fadeeva","doi":"10.1016/j.orggeochem.2025.105091","DOIUrl":"10.1016/j.orggeochem.2025.105091","url":null,"abstract":"<div><div>This study presents the results of an investigation into the distribution patterns of C₃- and C₄-alkylbenzenes in oils derived from hydrocarbon source rocks of varying geological age and origin. The study utilized analytical results from 515 oil samples collected from wells at 199 fields across various petroleum basins of Eurasia, most of which are located in Russia (including the West Siberian Basin, Siberian Platform (or Eastern Siberia), Northwestern Greater Caucasus, Middle Caspian, Sakhalin, Volga-Ural Basin, Timan-Pechora Basin, and the Baltic Basin (Kaliningrad), Belarus (Pripyat Trough), and Africa (Eastern Algeria). These samples cover a wide range of oil ages and genetic diversity. The obtained results significantly advance our understanding of the relationships between C₃- and C₄-alkylbenzene compositions in oils and the following factors: redox conditions during deposition of the source organic matter, photic zone anoxia in the depositional basin, type of primary producers, age of source rocks, and catagenesis. Linear discriminant analysis (LDA) was applied to characterize C₃- and C₄-alkylbenzene distributions in two variants based on: 1) genetic grouping of oils and 2) grouping by Pr/Ph values and <em>tert</em>-butylbenzene content. To enable global application of LDA models, we publish key foundational data − including analytical workflow, minimum/maximum relative concentration ranges, and discriminant function coefficients − enabling researchers to apply this framework to any petroleum basin worldwide. C₄-alkylbenzenes are benzene derivatives of terpenoids and may have direct biological origins or originate from higher molecular weight components (e.g., aryl carotenoids). Consequently, they exhibit superior discriminative power for classifying oils into genetic groups compared to C₃-alkylbenzenes. Oils with the most distinctive C₄-alkylbenzene composition originate from (1) the Bazhenov Formation (West Siberia), (2) Domanik deposits of the Volga-Ural and Timan-Pechora basins, (3) non-marine Jurassic sequences in Western Siberia and the Greater Caucasus northwest, and (4) reservoirs of the Nepa-Botuoba Anteclise (Siberian Platform). The study revealed significant concentrations of <em>tert</em>-butylbenzene, which were detected in oils from: the Baikit Anteclise (Riphean age), Baltic Syneclise (Cambrian–Ordovician–Silurian), selected Algerian fields (Silurian–Devonian) and in isolated Palaeozoic-sourced oils of Western Siberia. Components that have a decisive influence on the position of the oils in the discriminant function coordinates were identified; these components can characterize source organic matter, its age, and redox conditions.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"210 ","pages":"Article 105091"},"PeriodicalIF":2.5,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145575911","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":"Hopanoid breakdown products (HBPs) and their influence on tetracyclic and tricyclic terpane (cheilanthane) oil-source rock parameters","authors":"Tharika Liyanage ,&nbsp;Lennart M. van Maldegem ,&nbsp;Janet Hope ,&nbsp;Philippe Schaeffer ,&nbsp;Pierre Adam ,&nbsp;Hans Peter Nytoft ,&nbsp;Dianne Edwards ,&nbsp;Jochen Brocks","doi":"10.1016/j.orggeochem.2025.105085","DOIUrl":"10.1016/j.orggeochem.2025.105085","url":null,"abstract":"<div><div>Tricyclic and tetracyclic terpane ratios are used as biomarker proxies for depositional environments and to classify crude oils and source rocks. However, the biological precursors and diagenetic drivers of these proxies are not well understood. This study reports on the discovery of tricyclic and tetracyclic breakdown products of pentacyclic hopanoids that co-elute with 14α-C₁₉ and βα-C₂₀–C₂₂ cheilanthanes and C₂₄ tetracyclic terpane in gas chromatograms. This includes hopanoid breakdown products (HBPs) that are identical to 14α-C₁₉ cheilanthane and C₂₄ tetracyclic terpane, biomarkers that are commonly used as indicators of terrigenous organic matter in source rocks and their derived hydrocarbon products. These HBPs were generated by pyrolysis of C₃₀ diplopterol, a common compound found in the cell membranes of almost all hopanoid-producing bacteria, some lichens and higher plants. HBPs are common in rock-extracted bitumens and crude oils from the Neoproterozoic to the Cenozoic and across a wide range of thermal maturities. Comparison of the relative abundance of HBPs and cheilanthanes against commonly used tricyclic and tetracyclic terpane parameters shows that HBPs can drive or strongly influence terpane-based paleoenvironmental proxies. This study begins to rationalise why some of these parameters indicate specific depositional environments and proposes new ratios that quantify the impact of HBPs on biomarker proxies.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"210 ","pages":"Article 105085"},"PeriodicalIF":2.5,"publicationDate":"2025-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474236","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 – August 2025","authors":"","doi":"10.1016/j.orggeochem.2025.105079","DOIUrl":"10.1016/j.orggeochem.2025.105079","url":null,"abstract":"","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"211 ","pages":"Article 105079"},"PeriodicalIF":2.5,"publicationDate":"2025-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733062","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}