Organic Geochemistry最新文献

{"title":"Exceptionally high contents of rearranged hopanes in a late Permian section, southern Sydney Basin, Australia","authors":"Inna Kampoli,&nbsp;Simon C. George","doi":"10.1016/j.orggeochem.2025.104986","DOIUrl":"10.1016/j.orggeochem.2025.104986","url":null,"abstract":"<div><div>A suite of 19 late Permian–early Triassic outcrop samples from the southern Sydney Basin were analysed by gas chromatography-mass spectrometry. Three series of rearranged hopanes were identified in the samples: 18α(H)-neohopanes, 17α(H)-diahopanes, and the early-eluting 9,15-dimethyl-25,27-bisnorhopane homologues. There is very large variability in the relative abundance and distribution of rearranged hopanes compared to the 17α(H)-hopanes between samples. There is one group of samples, associated with the “dead zone” after the Permian-Triassic mass extinction event, and deposited above the uppermost coal seam, where rearranged hopanes are not present, while in other samples their abundance is very high, and the C₃₀ diahopane/C₃₀ αβ hopane ratio reaches 93. No dependency on thermal maturity or depositional water salinity were observed, and there is no correlation between the presence and distribution of rearranged hopanes and diasteranes. There is a positive correlation between the presence of monomethylalkanes, interpreted to be associated with cyanobacterial input, and a high relative abundance of rearranged hopanes. The samples with the highest relative abundances of rearranged hopanes and monomethylalkanes are from the Tongarra Coal at Austinmer Beach, where three coal seams are separated by laterally-continuous pale-coloured ash-fall tuffs. The high abundance of terrigenous organic matter, deposited under fresh water sub-oxic conditions, together with extensive volcanic activity, may be the main factors contributed to the formation and enrichment of these exceptional amounts of rearranged hopanes in the Sydney Basin.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104986"},"PeriodicalIF":2.6,"publicationDate":"2025-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143776974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diatom-derived highly branched isoprenoids are diverse and widespread in lakes","authors":"Aaron F. Diefendorf ,&nbsp;Watts L. Dietrich ,&nbsp;Hans Naake ,&nbsp;Megan C. Corcoran ,&nbsp;Andrew J. Kmetz ,&nbsp;Thomas V. Lowell ,&nbsp;Michael D. Schenk ,&nbsp;Gregory C. Wiles ,&nbsp;Mark A. Wilson","doi":"10.1016/j.orggeochem.2025.104993","DOIUrl":"10.1016/j.orggeochem.2025.104993","url":null,"abstract":"<div><div>Diatom-derived highly branched isoprenoid lipids (HBIs) are found extensively in marine sediments, but to date are only reported in a few lacustrine sediments. To expand on prior lake studies, we collected lake surface sediment samples, water samples, and filtered photic zone water from 50 lakes from the Great Plains to the northeastern United States. Samples were collected in May and June and a few sites were revisited in September and October. Studied lakes vary in climate, water chemistry (e.g., pH, salinity, alkalinity), size, and trophic states. They also vary in their diatom species compositions with 344 diatom taxa reported. We characterized HBI assemblages in each lake and found 11 different HBI compounds including one C_20:0 HBI, five C_20:1 HBI isomers, C_21:0 HBI, C_25:2 HBI, two C_25:3 HBIs, and C_25:4 HBI. C_20:0 HBI was present in all but two lakes and was often the most abundant HBI present. HBIs were also detected in nearly all the water filter samples indicating they are produced in the photic zone. C_20:0 HBI was present in all freshwater lakes, but not present or at very low concentration in the highest salinity lakes, which were dominated by C_21:0 HBI and C₂₅ HBIs. Many of the lakes were dominated by diatom genera and species that are not known to be HBI-producing genera, suggesting there are unrecognized HBI-producing diatom taxa. This inventory, illustrating the widespread presence and diversity of HBIs from lakes across large differences in water chemistries and climate, further suggests that HBIs may be useful diatom biomarkers for paleoclimate applications.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"205 ","pages":"Article 104993"},"PeriodicalIF":2.6,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143879109","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":"Identification of novel sulfur-containing petroporphyrins in a natural bitumen: Potential biomarkers for aerobic organisms","authors":"Fang Zheng ,&nbsp;Weisheng Yang ,&nbsp;Yanbin Wang ,&nbsp;Mi An ,&nbsp;Da Huo ,&nbsp;Chunyan Wang ,&nbsp;Qing Cao ,&nbsp;Jing He ,&nbsp;Quan Shi ,&nbsp;Yongge Sun","doi":"10.1016/j.orggeochem.2025.104987","DOIUrl":"10.1016/j.orggeochem.2025.104987","url":null,"abstract":"<div><div>In this study, a serial of novel sulfur-containing petroporphyrins were identified in a natural bitumen by chemical derivatization and solvent extraction. In contrast to previously reported sulfur-containing petroporphyrins, the new petroporphyrins exhibit reduced unsaturation and are characterized by a reduced number of double-bond equivalences (number of rings plus double bonds). Molecular structures of these sulfur-containing petroporphyrins were further elucidated by multiple collision-induced dissociation in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results indicate that sulfur atoms are present as cyclic thioether on the side chain of porphyrin, suggesting that these compounds may have evolved from <em>heme</em> <strong><em>a</em></strong> or <em>heme</em> <strong><em>o</em></strong> in aerobic organisms. We thereby propose a potentially diagenetic pathway of these compounds. Due to the relative stability of cyclic thioethers in the porphyrin structure, potential geochemical information could be carried by these compounds, which warrants further investigation.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104987"},"PeriodicalIF":2.6,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143767652","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":"Nanometer-scale relationships between sedimentary organic matter molecular composition, fluorescence, cathodoluminescence, and reflectance: The importance of oxygen content at low thermal maturities","authors":"Aaron M. Jubb ,&nbsp;Paul C. Hackley ,&nbsp;Ryan J. McAleer ,&nbsp;Jing Qu","doi":"10.1016/j.orggeochem.2025.104990","DOIUrl":"10.1016/j.orggeochem.2025.104990","url":null,"abstract":"<div><div>Molecular characterization of sedimentary organic matter (SOM), termed macerals, is a common goal when seeking to understand petroleum generation as well as other geologic processes in deep time. However, unambiguous measurement of discrete macerals is challenging due to the small size of organic particles in sedimentary rocks, the proximity of different organic matter types to one another, mineral-organic matter interactions, and maceral mixing that occurs during SOM isolation prior to ex situ analysis. The recent advent of infrared spectrometers capable of nanometer-scale resolution and the application of these technologies to geologic samples has enabled advances in rapid, in situ molecular characterization of SOM allowing for insights into paleoenvironmental processes, such as organic matter productivity and preservation, among others. Here we employ one such technology, optical photothermal infrared (OPTIR) spectroscopy, to map SOM functional group distributions at 500-nm resolution in a sample from the Lower Cretaceous Sunniland Limestone of the South Florida Basin. Examined fields of view include occurrences of amorphous organic matter (AOM), inertinite, micrinite, solid bitumen, telalginite, and vitrinite. OPTIR data from these macerals are compared against traditional organic petrographic data from the same organic grains including fluorescence intensity and white light reflectance as well as against cathodoluminescence response, an emerging organic petrographic approach. Maceral oxygen content (using carbonyl functional group abundance as a proxy) is observed to vary widely between maceral types but correlates strongly with fluorescence and cathodoluminescence intensity as well as against reflectance. These findings highlight the important role that oxygen content plays in determining the optical properties of SOM and further demonstrate the ability of OPTIR to discriminate subtle molecular differences between SOM types.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104990"},"PeriodicalIF":2.6,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143767532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"African C3 grass n-alkane distributions & plant chemotaxonomy","authors":"Ruth R. Tweedy ,&nbsp;Caroline A.E. Strömberg ,&nbsp;Tammo Reichgelt ,&nbsp;Rahab N. Kinyanjui ,&nbsp;Mbaluka Kimeu ,&nbsp;Venanzio Munyaka ,&nbsp;Kevin T. Uno","doi":"10.1016/j.orggeochem.2025.104994","DOIUrl":"10.1016/j.orggeochem.2025.104994","url":null,"abstract":"<div><div>Reconstructing past vegetation can elucidate the timing, climate forcings, and biotic mechanisms of ecosystem change. Plant macro- and microfossils are traditionally used to study past vegetation but suffer from production and taphonomic biases, such as underrepresentation of important herbaceous vegetation components. Geochemical proxies can fill this gap, but carbon isotopes (δ¹³C) in isolation are unable to distinguish between structurally different C₃ habitats, such as forests and grasslands. Thus, new geochemical methods to identify grassy C₃ ecosystems are necessary. We present <em>n</em>-alkane chain length distributions of 209 plant specimens from two Kenyan C₃-dominated ecosystems, representing a wide range of plant functional types (PFTs). We find that C₃ PACMAD grasses produce exceptionally high abundances of long chain C₃₃ and C₃₅ <em>n</em>-alkanes (ACL = 32.7, mean C₃₃ + C₃₅ relative abundance = 0.69), unlike other C₃ PFTs which produce low abundances of C₃₃ and C₃₅ (ACL = 28.9–30.3, mean C₃₃ + C₃₅ relative abundance = 0.0–0.21). This finding highlights the importance of measuring and reporting the C₃₅ <em>n</em>-alkane. Our data further demonstrate that <em>n</em>-alkane distributions can serve as a proxy for some African C₃ PACMAD grasses, offering a new paleoecological tool for distinguishing C₃ vegetation types.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"208 ","pages":"Article 104994"},"PeriodicalIF":2.6,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144365586","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":"Analytical inconsistencies in the measurement and reporting of IP25, IPSO25 and related biomarkers for paleo sea ice reconstruction","authors":"Simon T. Belt ,&nbsp;Lukas Smik","doi":"10.1016/j.orggeochem.2025.104989","DOIUrl":"10.1016/j.orggeochem.2025.104989","url":null,"abstract":"<div><div>IP₂₅ and related biomarkers are commonly used for Arctic and Antarctic sea ice reconstruction. With a growing number of laboratories performing their measurement, we reviewed many publications spanning the period 2007–2024 in order to assess analytical rigour. We found a number of common shortfalls in analytical protocols, or at least how they are reported, which may have important implications for future synthesis studies and meta-data analyses. Here, we outline some of these shortcomings and provide suggestions of how to improve both data acquisition and reporting.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104989"},"PeriodicalIF":2.6,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143724185","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry Articles – January 2025","authors":"","doi":"10.1016/j.orggeochem.2025.104984","DOIUrl":"10.1016/j.orggeochem.2025.104984","url":null,"abstract":"","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104984"},"PeriodicalIF":2.6,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143820774","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 – February 2025","authors":"","doi":"10.1016/j.orggeochem.2025.104985","DOIUrl":"10.1016/j.orggeochem.2025.104985","url":null,"abstract":"","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104985"},"PeriodicalIF":2.6,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143820775","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":"Unraveling the origin and charge of Halahatang oils, Tarim Basin","authors":"Peng Sun ,&nbsp;Chunfang Cai ,&nbsp;Daowei Wang ,&nbsp;Yu Qi ,&nbsp;Chenlu Xu ,&nbsp;Paul F. Greenwood","doi":"10.1016/j.orggeochem.2025.104962","DOIUrl":"10.1016/j.orggeochem.2025.104962","url":null,"abstract":"<div><div>Uncertainty about the source of the oils from the Halahatang region of the Tabei Uplift, Tarim Basin (NW China) presents an ongoing challenge to exploration. Previous analyses of several Halahatang oils showed isotopic (δ¹³C &lt; –32 ‰) and aliphatic hydrocarbon distributions (e.g., V-shaped C₂₇-C₂₉ steranes) more typical of regional Ordovician source rocks than the Cambrian rocks that are the predominant source of petroleum of the Tarim Basin, supporting prospects for a second major regional oil source. In pursuit of a more definitive source assignment of Halahatang oils and further insight into their depositional environment and charge history, a detailed molecular appraisal of the aromatic hydrocarbon composition of 27 marine oils and complementary stable sulfur and carbon isotopic analyses were conducted. The oils were from different Halahatang wells resolved into three separate block groups, with variations to the extent molecular and isotopic data was influenced by secondary alteration (i.e., thermal maturity, biodegradation and, possibly, minor thermochemical sulfate reduction) evident among the groups. The major aromatic products of all oils were alkylated naphthalenes, phenanthrenes, dibenzothiophenes and trace levels of thiadiamondoids were detected in a few Group II and III oils. Aryl isoprenoids, typical biomarkers of an euxinic depositional environment, were also conspicuous in lower maturity Group I and II oils (Rc &lt; 0.9 %), but absent in higher maturity oils (Rc up to 1.02 %). Molecular evidence of severe biodegradation (e.g., unresolved complex matter, 25-norterpenoids) was evident in some Group I oils, although some of these also showed coincident non-biodegradation molecular features (e.g., low MW <em>n</em>-alkanes) implying a mixing of biodegraded and non-biodegraded charges. The δ³⁴S values of the bulk oil and their dibenzothiophene and alkyldibenzothiophene products were generally in the range +17 to +23 ‰,although some oils impacted by biodegradation showed slightly heavier δ³⁴S values (&gt;+26 ‰). The Group II oils were not significantly impacted by secondary processes and their aromatic signature (e.g., aryl isoprenoids), δ³⁴S data and whole oil δ¹³C values were closely correlated with regional Lower Cambrian source rocks and are atypical of Upper Ordovician source rocks. These results identify the Halahatang oils as a further representation of Lower Cambrian-derived oils of the Tabei Uplift.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104962"},"PeriodicalIF":2.6,"publicationDate":"2025-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143631874","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":"Clumped 13C–13C isotopes of ethane from laboratory pyrolysis of kerogen: Implications for intramolecular 13C distributions","authors":"Koudai Taguchi ,&nbsp;Yuichiro Ueno ,&nbsp;Alexis Gilbert ,&nbsp;Xiaoqiang Li ,&nbsp;Juske Horita","doi":"10.1016/j.orggeochem.2025.104951","DOIUrl":"10.1016/j.orggeochem.2025.104951","url":null,"abstract":"<div><div>The clumped isotope geochemistry of ¹³C–¹³C bonding offers a valuable tool for distinguishing the formation processes of ethane (C₂H₆) and its thermogenic and abiotic origins. Thermogenic ethane is characterized by isotope distributions that are nearly in thermodynamic equilibrium, whereas abiotic ethane is governed by kinetic isotope effects during C–C bond synthesis. ¹³C–¹³C ordering in thermogenic ethane varies with the source organic material, but limited studies on ethane clumped isotopes from natural gases restrict our understanding of these signatures. To address this, we performed pyrolysis experiments at 310–470 °C on various immature kerogens from the Eocene Green River Formation (Type I), Upper Devonian–Lower Mississippian Woodford Shale (Type II), and Pennsylvanian Springfield Coal Member (Type III). The ethane-clumped isotope compositions aligned with those of natural gas samples and varied based on the starting kerogen’s isotope composition. We propose a thermogenic model that describes isotopic systematics, including ¹³C–¹³C variations in the pyrolysis product ethane, driven by (i) combinatorial isotope effect during C–C bond breaking and (ii) intramolecular isotopic heterogeneity in the starting kerogen. Isotopic and clumped isotope variations suggest a zigzag isotopic pattern in kerogen alkyl chains, similar to that seen in biological fatty acids. We could extend the model to position-specific (PS) isotope signatures in propane, showing that intramolecular isotopic heterogeneity in kerogens also affect PS isotopes, alongside structural heterogeneity, such as isoprenoid versus alkyl. Overall, our findings demonstrate that ¹³C–¹³C clumping is a ubiquitous signature for thermogenic ethane, with variations reflecting isotopic information of the original organic matter.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104951"},"PeriodicalIF":2.6,"publicationDate":"2025-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143631872","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}