Pub Date : 2026-01-21DOI: 10.1016/j.orggeochem.2026.105136
Xueyou Tan , Sijia Nie , Xijun Wang , Wei Peng , Xu Wang , Suyang Cai , Jingwen Zheng , Xiaoyong Wang , Zhushi Ge , Liangliang Ren , Jiang Wei
The dibenzothiophene (DBT or SF), dibenzofuran (DBF or OF) and fluorene (F) series compounds are characterized by high structural stability and are widely used in sedimentary environment discrimination and maturity assessment. However, their diagnostic parameters can be overprinted by thermal effects at high maturity. To investigate this, we conducted closed-system pyrolysis experiments (275–450℃) on a saline lacustrine source rock from the Paleogene Shahejie Formation and analyzed the products using gas chromatography-mass spectrometry (GC–MS). Specific results show that: (1) The DBT series dominated throughout, with reaction pathways shifting from methylation below 325℃ to demethylation above this threshold. (2) The DBF series exhibited lower thermal stability with a “decrease–increase–decrease” pattern, whereas the F series was more stable at medium to high temperatures. (3) Traditional proxies like the DBT/P–Pr/Ph cross-plot showed an environment trend from marine to coal-derived with increasing temperature, which misrepresents the constant high-salinity, reducing conditions of the source rock, highlighting a significant maturity overprint. In contrast, a new discrimination diagram based on parameters derived from the combined DBT, DBF, and F series effectively minimized thermal interference, consistently and correctly indicating the original depositional environment. This demonstrates the greater robustness of the ‘3Fs’ series over individual compounds for paleoenvironment reconstruction, especially in high-maturity samples.
{"title":"Thermal evolution characteristics of dibenzothiophene, dibenzofuran and fluorene and their homologues and their geochemical implications","authors":"Xueyou Tan , Sijia Nie , Xijun Wang , Wei Peng , Xu Wang , Suyang Cai , Jingwen Zheng , Xiaoyong Wang , Zhushi Ge , Liangliang Ren , Jiang Wei","doi":"10.1016/j.orggeochem.2026.105136","DOIUrl":"10.1016/j.orggeochem.2026.105136","url":null,"abstract":"<div><div>The dibenzothiophene (DBT or SF), dibenzofuran (DBF or OF) and fluorene (F) series compounds are characterized by high structural stability and are widely used in sedimentary environment discrimination and maturity assessment. However, their diagnostic parameters can be overprinted by thermal effects at high maturity. To investigate this, we conducted closed-system pyrolysis experiments (275–450℃) on a saline lacustrine source rock from the Paleogene Shahejie Formation and analyzed the products using gas chromatography-mass spectrometry (GC–MS). Specific results show that: (1) The DBT series dominated throughout, with reaction pathways shifting from methylation below 325℃ to demethylation above this threshold. (2) The DBF series exhibited lower thermal stability with a “decrease–increase–decrease” pattern, whereas the F series was more stable at medium to high temperatures. (3) Traditional proxies like the DBT/P–Pr/Ph cross-plot showed an environment trend from marine to coal-derived with increasing temperature, which misrepresents the constant high-salinity, reducing conditions of the source rock, highlighting a significant maturity overprint. In contrast, a new discrimination diagram based on parameters derived from the combined DBT, DBF, and F series effectively minimized thermal interference, consistently and correctly indicating the original depositional environment. This demonstrates the greater robustness of the ‘3Fs’ series over individual compounds for paleoenvironment reconstruction, especially in high-maturity samples.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"213 ","pages":"Article 105136"},"PeriodicalIF":2.5,"publicationDate":"2026-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035817","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}
Pub Date : 2026-01-17DOI: 10.1016/j.orggeochem.2026.105128
Shun-Feng Yan , Xiao-Min Zheng , Lin Li , Hai-Yan Zheng , Mao-Wen Yuan , M. Santosh , Sheng-Rong Li
This study investigates the role of bitumen in the metallogenesis of the Erdaokan Ag-Pb-Zn deposit. Using in situ high-pressure diamond anvil cell (DAC) experiments, natural metal-rich bitumen from the deposit was reacted with water up to 623 K. Optical microscopy revealed that bitumen transitions into a mobile, partially dissolved phase at high temperature. Upon subsequent cooling to ∼473 K, new spherical particles precipitated from the fluid. Raman spectroscopy identified these new precipitates as metal halides. This finding is geochemically consistent with the Pb-rich nature of the source bitumen and the Ag-Pb-Zn signature of the deposit. Significantly, the experimental precipitation temperature (∼473 K) aligns closely with the upper temperature boundary of the natural mineralization stage derived from fluid inclusion studies (∼464 K). These results provide direct experimental evidence that bitumen can function as an active ore fluid, capable of transporting metals at high temperatures and precipitating them as intermediate metal halides during cooling. This mechanism is interpreted as a key process in the enrichment and formation of the Erdaokan deposit.
{"title":"Experimental evidence on the bitumen role of the metal enrichment in the Erdaokan Ag-Pb-Zn deposit","authors":"Shun-Feng Yan , Xiao-Min Zheng , Lin Li , Hai-Yan Zheng , Mao-Wen Yuan , M. Santosh , Sheng-Rong Li","doi":"10.1016/j.orggeochem.2026.105128","DOIUrl":"10.1016/j.orggeochem.2026.105128","url":null,"abstract":"<div><div>This study investigates the role of bitumen in the metallogenesis of the Erdaokan Ag-Pb-Zn deposit. Using in situ high-pressure diamond anvil cell (DAC) experiments, natural metal-rich bitumen from the deposit was reacted with water up to 623 K. Optical microscopy revealed that bitumen transitions into a mobile, partially dissolved phase at high temperature. Upon subsequent cooling to ∼473 K, new spherical particles precipitated from the fluid. Raman spectroscopy identified these new precipitates as metal halides. This finding is geochemically consistent with the Pb-rich nature of the source bitumen and the Ag-Pb-Zn signature of the deposit. Significantly, the experimental precipitation temperature (∼473 K) aligns closely with the upper temperature boundary of the natural mineralization stage derived from fluid inclusion studies (∼464 K). These results provide direct experimental evidence that bitumen can function as an active ore fluid, capable of transporting metals at high temperatures and precipitating them as intermediate metal halides during cooling. This mechanism is interpreted as a key process in the enrichment and formation of the Erdaokan deposit.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"213 ","pages":"Article 105128"},"PeriodicalIF":2.5,"publicationDate":"2026-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035818","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}
Pub Date : 2026-01-16DOI: 10.1016/j.orggeochem.2026.105129
Volker Thiel, Manuel Reinhardt, Maria Thirase, Alina Klick, Volker Karius
Seagrass meadows are regarded to play an important role in mitigating climate change by acting as a sink of organic carbon (C) in their underlying sediments. This study investigates the C sequestration potential of seagrass in coarse-grained nearshore deposits near Poel Island in the southwestern Baltic Sea. Four ∼60 cm long sediment cores from Zostera marina meadows were analyzed for the nature and quantity of particulate organic C. Emphasis was placed on the questions (i) whether seagrass coverage would lead to an enhanced C storage in this high-energy proximal setting, and (ii) whether the stored C has a seagrass origin or derives from other, marine or terrestrial sources. We observed that total organic C (TOC) contents in the rhizosphere of seagrass vegetated areas are currently very low (0.05–0.22%) and similar to unvegetated areas. However, a several-cm-thick, dark brown layer, residing at a depth of 40–60 cm, was strongly enriched in TOC (up to 17%) and contained most of the organic matter stored in the sediment profiles studied. A combination of lipid biomarkers, scanning electron microscopy, 14C age dating, and 13C measurements in TOC and individual lipids revealed that the organic matter in this layer originated from seagrass. This material was abruptly buried ∼2000 years ago, possibly because of a storm event. Our findings highlight that event-driven burial of seagrass biomass can provide a critical pathway for Blue Carbon storage over relevant (102–103 yrs) timespans in coarse-grained proximal sediments.
{"title":"Organic signatures from modern and ancient seagrass in coarse-grained sediments near Poel Island, Baltic Sea","authors":"Volker Thiel, Manuel Reinhardt, Maria Thirase, Alina Klick, Volker Karius","doi":"10.1016/j.orggeochem.2026.105129","DOIUrl":"10.1016/j.orggeochem.2026.105129","url":null,"abstract":"<div><div>Seagrass meadows are regarded to play an important role in mitigating climate change by acting as a sink of organic carbon (C) in their underlying sediments. This study investigates the C sequestration potential of seagrass in coarse-grained nearshore deposits near Poel Island in the southwestern Baltic Sea. Four ∼60 cm long sediment cores from <em>Zostera marina</em> meadows were analyzed for the nature and quantity of particulate organic C. Emphasis was placed on the questions (i) whether seagrass coverage would lead to an enhanced C storage in this high-energy proximal setting, and (ii) whether the stored C has a seagrass origin or derives from other, marine or terrestrial sources. We observed that total organic C (TOC) contents in the rhizosphere of seagrass vegetated areas are currently very low (0.05–0.22%) and similar to unvegetated areas. However, a several-cm-thick, dark brown layer, residing at a depth of 40–60 cm, was strongly enriched in TOC (up to 17%) and contained most of the organic matter stored in the sediment profiles studied. A combination of lipid biomarkers, scanning electron microscopy, <sup>14</sup>C age dating, and <sup>13</sup>C measurements in TOC and individual lipids revealed that the organic matter in this layer originated from seagrass. This material was abruptly buried ∼2000 years ago, possibly because of a storm event. Our findings highlight that event-driven burial of seagrass biomass can provide a critical pathway for Blue Carbon storage over relevant (10<sup>2</sup>–10<sup>3</sup> yrs) timespans in coarse-grained proximal sediments.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"214 ","pages":"Article 105129"},"PeriodicalIF":2.5,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146070972","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}
Pub Date : 2026-01-14DOI: 10.1016/j.orggeochem.2025.105125
Ibrahim Atwah , Maram Alsaif
Lower and higher diamondoids persist from early oil generation into high-maturity condensates and can fingerprint fluids when classical biomarkers are depleted. However, routine measurement of higher diamonoids has been limited by their trace abundances and poor fragmentation. A method based on pseudo-Multiple Reaction Monitoring (pMRM) on gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-MS/MS) was developed to detect and quantify diamondoids using nine diverse petroleum and rock-extract samples. In pMRM, the molecular ion was monitored in the first and third quadrupoles while a modest collision energy was applied in the collision cell to suppress interferences. Relative to selected ion monitoring, signal-to-noise for higher diamondoids increased markedly, enabling confident peak detection in the late-elution window. Optimal collision energies followed cage size, approximately 20 electron-volts for triamantane, 40 for tetramantanes, and 50 for pentamantanes and cyclohexamantane. The limit of detection (LOD) and limit of quantitation (LOQ) of the method were assessed to be 0.01 and 0.05 ng ml−1, respectively. Utilizing pMRM, many crude oils were suitable for direct injection (“dilute and shoot”), whereas rock extracts, heavy and biodegraded crudes, and some condensates benefited from a silica-gel preparation step. In those cases, approximately 60 mg of sample was sufficient to prepare a saturated, n-alkane free fraction suitable for detecting higher diamondoids using pMRM. The pMRM method demonstrated high analytical reproducibility across chemically diverse matrices including rock extracts, crude oils, and condensates, with relative standard deviations for normalized higher diamondoids typically below 10% over a three month monitoring period, confirming the stability and robustness of Quantitative Extended Diamondoid Analysis (QEDA) measurements using the pMRM approach. These results indicate that pseudo multiple reaction monitoring enables routine, high sensitivity measurement of higher diamondoids and provides molecular fingerprints that support oil-oil, oil-condensate, and condensate-source rock correlations, which were previously difficult to achieve due to the inherent compositional variability among these sample types.
从早期生油到高成熟的凝析油，低和高的金刚石持续存在，当经典生物标志物耗尽时，它们可以作为流体的指纹。然而，由于其痕量丰度和破碎性差，对高级类金刚石的常规测量受到限制。建立了一种基于气相色谱-三重四极杆串联质谱（GC-MS/MS）的伪多重反应监测（pMRM）方法，对9种不同的石油和岩石提取物样品进行了diamondoids的检测和定量。在pMRM中，分子离子在第一和第三四极进行监测，同时在碰撞单元中施加适度的碰撞能量以抑制干扰。相对于选定的离子监测，高diamondids的信噪比显著增加，从而在洗脱后期窗口中实现可靠的峰检测。最佳碰撞能量遵循笼形尺寸，三烷约为20电子伏，四烷约为40电子伏，五烷和环己烷约为50电子伏。方法的检出限和定量限分别为0.01和0.05 ng ml−1。利用pMRM，许多原油适合直接注入（“稀释后注入”），而岩石提取物、重质原油和生物降解原油以及一些凝析油则受益于硅胶制备步骤。在这些情况下，大约60毫克的样品足以制备饱和的、无正构烷烃的馏分，适用于使用pMRM检测较高的金刚石。pMRM方法在包括岩石提取物、原油和凝析油在内的多种化学基质中具有很高的分析重现性，在三个月的监测期内，标准化高diamondids的相对标准偏差通常低于10%，证实了使用pMRM方法进行定量扩展diamondids分析（QEDA）测量的稳定性和鲁棒性。这些结果表明，伪多重反应监测能够实现常规的、高灵敏度的高diamondoids测量，并提供支持油-油、油-凝析油和凝析油-烃源岩相关性的分子指纹图谱，而这在以前由于这些样品类型之间固有的成分变异性而难以实现。
{"title":"Novel diamondoid detection technique using pMRM (GC-MS/MS): Enabling source rock-oil-condensate correlations","authors":"Ibrahim Atwah , Maram Alsaif","doi":"10.1016/j.orggeochem.2025.105125","DOIUrl":"10.1016/j.orggeochem.2025.105125","url":null,"abstract":"<div><div>Lower and higher diamondoids persist from early oil generation into high-maturity condensates and can fingerprint fluids when classical biomarkers are depleted. However, routine measurement of higher diamonoids has been limited by their trace abundances and poor fragmentation. A method based on pseudo-Multiple Reaction Monitoring (pMRM) on gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-MS/MS) was developed to detect and quantify diamondoids using nine diverse petroleum and rock-extract samples. In pMRM, the molecular ion was monitored in the first and third quadrupoles while a modest collision energy was applied in the collision cell to suppress interferences. Relative to selected ion monitoring, signal-to-noise for higher diamondoids increased markedly, enabling confident peak detection in the late-elution window. Optimal collision energies followed cage size, approximately 20 electron-volts for triamantane, 40 for tetramantanes, and 50 for pentamantanes and cyclohexamantane. The limit of detection (LOD) and limit of quantitation (LOQ) of the method were assessed to be 0.01 and 0.05 ng ml<sup>−1</sup>, respectively. Utilizing pMRM, many crude oils were suitable for direct injection (“dilute and shoot”), whereas rock extracts, heavy and biodegraded crudes, and some condensates benefited from a silica-gel preparation step. In those cases, approximately 60 mg of sample was sufficient to prepare a saturated, n-alkane free fraction suitable for detecting higher diamondoids using pMRM. The pMRM method demonstrated high analytical reproducibility across chemically diverse matrices including rock extracts, crude oils, and condensates, with relative standard deviations for normalized higher diamondoids typically below 10% over a three month monitoring period, confirming the stability and robustness of Quantitative Extended Diamondoid Analysis (QEDA) measurements using the pMRM approach. These results indicate that pseudo multiple reaction monitoring enables routine, high sensitivity measurement of higher diamondoids and provides molecular fingerprints that support oil-oil, oil-condensate, and condensate-source rock correlations, which were previously difficult to achieve due to the inherent compositional variability among these sample types.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"213 ","pages":"Article 105125"},"PeriodicalIF":2.5,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975562","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}
Pub Date : 2026-01-11DOI: 10.1016/j.orggeochem.2026.105126
Yongbin Quan , Yiming Hu , Jinhai Yang , Xi’nong Xie , Lei Tuo , Fang Hao , Heqing Feng
The Qiongdongnan Basin exhibits substantial heterogeneity in hydrocarbon composition and origin. Accurately characterizing this variation is critical for refining hydrocarbon generation models in marginal basins. The depositional facies of source rocks fundamentally control the composition and genetic types of hydrocarbons, yet this critical constraint remains poorly understood. To address this gap, biomarker profiling via GC–MS, and δ13C analysis of individual n-alkanes, benzenes, and toluene via GC-IRMS were conducted on three major thermogenic accumulations. Results identify three distinct genetic gas types tied to depositional environments: (1) Y13 is coal-type gas derived from paralic facies source rocks with dominate higher plant input, deposited under oxygenated, non-stratified conditions; (2) L17 also exhibit coal-type gas, but was derived from terrigenous-marine facies source rocks deposited in a suboxic environment with reduced higher plant input; and (3) B21 represents oil-type gas derived from shallow marine facies source rocks deposited in suboxic-dysoxic setting with further reduce terrigenous input. All hydrocarbons originate from the Oligocene Yacheng Formation, with heterogeneity arising from spatially varying depositional facies within the basin, ranging from paralic in the west to shallow marine in the east, correlating with the earlier regional subsidence and marine transgression in the east. This facies-controlled mechanism differs from traditional models that attribute gas variations to maturity, source rock intervals, or post-generation modification. This study provides a template for interpreting hydrocarbon compositions and genetic types, offering a refined framework for source rock evaluation and resource assessment in analogous marginal basins worldwide.
{"title":"Three genetic types of natural gas derived from the Oligocene Yacheng Formation deposited in various environments within the Qiongdongnan Basin, South China Sea","authors":"Yongbin Quan , Yiming Hu , Jinhai Yang , Xi’nong Xie , Lei Tuo , Fang Hao , Heqing Feng","doi":"10.1016/j.orggeochem.2026.105126","DOIUrl":"10.1016/j.orggeochem.2026.105126","url":null,"abstract":"<div><div>The Qiongdongnan Basin exhibits substantial heterogeneity in hydrocarbon composition and origin. Accurately characterizing this variation is critical for refining hydrocarbon generation models in marginal basins. The depositional facies of source rocks fundamentally control the composition and genetic types of hydrocarbons, yet this critical constraint remains poorly understood. To address this gap, biomarker profiling via GC–MS, and δ<sup>13</sup>C analysis of individual <em>n</em>-alkanes, benzenes, and toluene via GC-IRMS were conducted on three major thermogenic accumulations. Results identify three distinct genetic gas types tied to depositional environments: (1) Y13 is coal-type gas derived from paralic facies source rocks with dominate higher plant input, deposited under oxygenated, non-stratified conditions; (2) L17 also exhibit coal-type gas, but was derived from terrigenous-marine facies source rocks deposited in a suboxic environment with reduced higher plant input; and (3) B21 represents oil-type gas derived from shallow marine facies source rocks deposited in suboxic-dysoxic setting with further reduce terrigenous input. All hydrocarbons originate from the Oligocene Yacheng Formation, with heterogeneity arising from spatially varying depositional facies within the basin, ranging from paralic in the west to shallow marine in the east, correlating with the earlier regional subsidence and marine transgression in the east. This facies-controlled mechanism differs from traditional models that attribute gas variations to maturity, source rock intervals, or post-generation modification. This study provides a template for interpreting hydrocarbon compositions and genetic types, offering a refined framework for source rock evaluation and resource assessment in analogous marginal basins worldwide.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"212 ","pages":"Article 105126"},"PeriodicalIF":2.5,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145972763","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}
Pub Date : 2026-01-08DOI: 10.1016/j.orggeochem.2026.105127
Alice Fradet , Philippe Schaeffer , Leo-Paul Magnin , Lauriane Lenen , Jan Pańczak , Bernard Gomez , Vincent Grossi , Pierre Adam
Although the presence of sulfur in amber has been previously reported, its origins and nature are not precisely known. The recent identification by NMR of sulfides related to tricyclic resin acids in a Cretaceous amber sample unambiguously showed that sulfur occurs in amber as organic sulfur compounds (OSC), at least to some extent. Molecular investigation of a large set of ambers from various botanical/geological origins and ages using GC–MS revealed that OSC are relatively widespread in ambers which was previously unknown. Their proportions relative to non-sulfurized terpenoids are variable among amber samples, and some samples proved to be devoid of OSC. In addition, it has been shown that OSC in ambers present a wide structural diversity, and comprise compounds related to tricyclic resin acids and labdanoids. Several structures could be proposed notably based on comparison with sulfurized labdanoids previously identified in sulfur-rich sediments. Laboratory sulfurization experiments involving functionalized diterpenoids from the resins of Cedrus atlantica and Araucaria columnaris and polysulfides successfully resulted in the formation of OSC identical or analogous to the natural compounds occurring in amber. This validates the predominant proposed pathways for the formation of OSC from amber. The early diagenetic sulfurization of diterpenoids in resin thus appears to be a key geochemical process influencing amber composition and contributing to the molecular diversity observed in fossil resins. The diverse OSC occurring in several amber types could potentially be used as geochemical markers of specific palaeoenvironments where sulfates are available and where the conditions of sedimentation promote, at least locally or in microenvironments, the establishment of anaerobic conditions favourable for the development of sulfate-reducing microorganisms.
{"title":"The widespread occurrence and wide structural diversity of sulfurized diterpenoids in ambers","authors":"Alice Fradet , Philippe Schaeffer , Leo-Paul Magnin , Lauriane Lenen , Jan Pańczak , Bernard Gomez , Vincent Grossi , Pierre Adam","doi":"10.1016/j.orggeochem.2026.105127","DOIUrl":"10.1016/j.orggeochem.2026.105127","url":null,"abstract":"<div><div>Although the presence of sulfur in amber has been previously reported, its origins and nature are not precisely known. The recent identification by NMR of sulfides related to tricyclic resin acids in a Cretaceous amber sample unambiguously showed that sulfur occurs in amber as organic sulfur compounds (OSC), at least to some extent. Molecular investigation of a large set of ambers from various botanical/geological origins and ages using GC–MS revealed that OSC are relatively widespread in ambers which was previously unknown. Their proportions relative to non-sulfurized terpenoids are variable among amber samples, and some samples proved to be devoid of OSC. In addition, it has been shown that OSC in ambers present a wide structural diversity, and comprise compounds related to tricyclic resin acids and labdanoids. Several structures could be proposed notably based on comparison with sulfurized labdanoids previously identified in sulfur-rich sediments. Laboratory sulfurization experiments involving functionalized diterpenoids from the resins of <em>Cedrus atlantica</em> and <em>Araucaria columnaris</em> and polysulfides successfully resulted in the formation of OSC identical or analogous to the natural compounds occurring in amber. This validates the predominant proposed pathways for the formation of OSC from amber. The early diagenetic sulfurization of diterpenoids in resin thus appears to be a key geochemical process influencing amber composition and contributing to the molecular diversity observed in fossil resins. The diverse OSC occurring in several amber types could potentially be used as geochemical markers of specific palaeoenvironments where sulfates are available and where the conditions of sedimentation promote, at least locally or in microenvironments, the establishment of anaerobic conditions favourable for the development of sulfate-reducing microorganisms.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"213 ","pages":"Article 105127"},"PeriodicalIF":2.5,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035819","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}
Pub Date : 2025-12-24DOI: 10.1016/j.orggeochem.2025.105120
Tim Marten , Lorenz Schwark
Hopanoids are among the most abundant natural products on Earth. Despite their widespread occurrence in soils, coals, sediments, sedimentary rocks and crude oils, their diagenetic pathways have not been fully resolved. Here, we present a diverse suite of aliphatic and aromatic hopanoids from a single sample of a thermally immature Lower Jurassic black shale. All extended saturated and Δ17,21-unsaturated hopanoid species occur as 2α-methyl analogues, which exhibit a carbon number distribution matching that of the desmethyl hopanes. This suggests similar precursor organisms for 2-methyl and desmethyl hopanoids favouring the genesis of C30+ hopanoids. Potential precursor organisms are assumed to include marine diazotrophic cyanobacteria or α-proteobacteria both affiliated with the nitrogen-cycle. Polyaromatic hopanoids occur in high concentrations, especially the C24 tetraaromatic hopane, and deviate from the extended hopanoid species in terms of carbon number distribution and A-ring methylation, indicating different origins for these hopanoids. The high aromaticity of these hopanoids suggests an origin from soil bacteria, which is consistent with an accelerated hydrological cycle and evidence for enhanced soil erosion during the early Toarcian. The co-occurrence of a multitude of hopanoid species within one sample exemplifies the complexity of hopanoid transformation products during stages of very early diagenesis. Preservation of this hopanoid complexity during diagenesis in the geosphere over a period of 183 Ma is exceptional because labile hopanoids commonly are destroyed by thermal maturation. It must be assumed that other sediments contained comparably complex hopanoid distributions, which upon later diagenesis suffered reduced variability seen in most sedimentary rocks and oils.
{"title":"A plethora of hopanoid transformation products co-exist in a thermally immature Jurassic black shale I: hopanoid hydrocarbons","authors":"Tim Marten , Lorenz Schwark","doi":"10.1016/j.orggeochem.2025.105120","DOIUrl":"10.1016/j.orggeochem.2025.105120","url":null,"abstract":"<div><div>Hopanoids are among the most abundant natural products on Earth. Despite their widespread occurrence in soils, coals, sediments, sedimentary rocks and crude oils, their diagenetic pathways have not been fully resolved. Here, we present a diverse suite of aliphatic and aromatic hopanoids from a single sample of a thermally immature Lower Jurassic black shale. All extended saturated and Δ<sup>17,21</sup>-unsaturated hopanoid species occur as 2α-methyl analogues, which exhibit a carbon number distribution matching that of the desmethyl hopanes. This suggests similar precursor organisms for 2-methyl and desmethyl hopanoids favouring the genesis of C<sub>30+</sub> hopanoids. Potential precursor organisms are assumed to include marine diazotrophic cyanobacteria or α-proteobacteria both affiliated with the nitrogen-cycle. Polyaromatic hopanoids occur in high concentrations, especially the C<sub>24</sub> tetraaromatic hopane, and deviate from the extended hopanoid species in terms of carbon number distribution and A-ring methylation, indicating different origins for these hopanoids. The high aromaticity of these hopanoids suggests an origin from soil bacteria, which is consistent with an accelerated hydrological cycle and evidence for enhanced soil erosion during the early Toarcian. The co-occurrence of a multitude of hopanoid species within one sample exemplifies the complexity of hopanoid transformation products during stages of very early diagenesis. Preservation of this hopanoid complexity during diagenesis in the geosphere over a period of 183 Ma is exceptional because labile hopanoids commonly are destroyed by thermal maturation. It must be assumed that other sediments contained comparably complex hopanoid distributions, which upon later diagenesis suffered reduced variability seen in most sedimentary rocks and oils.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"212 ","pages":"Article 105120"},"PeriodicalIF":2.5,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837441","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}
Pub Date : 2025-12-24DOI: 10.1016/j.orggeochem.2025.105121
Tim Marten , Lorenz Schwark
Hopanoids are ubiquitous in sediments and sedimentary rocks and are commonly applied tools for paleoenvironment reconstruction. Biohopanoids during diagenesis transform to geohopanoids when they successively lose their structural diversity. Prior to elevated thermal maturity, where only hopanes and benzohopanes persist, a large variety of intermediate hopanoid transformation products can be intermittently abundant in immature sediments. We presented in a companion paper the highly diverse hopanoid hydrocarbon inventory in one immature black shale sample from the Toarcian Posidonia Shale at Hondelage, NW-Germany that was deposited under euxinic conditions. Here, the focus is on the plethora of oxo- and thiohopanoids co-existing in the same sample. The formation of hopanoic acids requires oxic conditions whereas thiohopanoid require sulfidic conditions. These contrasting requirements suggest spatial and temporal separation of hopanoic acid versus thiohopanoid formation prior to or after incorporation into the sediment. Hopanoic acids presumably form in the oxic upper water column with potential minor contributions from oxic microniches and/or seasonally induced brief suboxic events at the sediment/water interface. In contrast, thiohopanoids presumably originate within the sulfidic water column and/or the sediment. Persistent euxinic conditions during deposition of the Posidonia Shale at Hondelage favoured formation of a variety of thiohopanoids in a shallow marine setting below a salinity-stratified water column. Thiohopanoids include previously unidentified hop-17(21)-ene thiolanes and hopane thiophenes extending to C38. Since hopanoids extending past C35 are absent for other hopanoid species, extended hopane thiophenes likely result from microbially mediated early diagenetic alkylation at the C35 position. Hopanoic acids as well as thiohopanoids occur as 2-methyl analogues and exhibit elevated abundances of C33 homologues, which dominate in desmethyl hopanoids. Precursor organisms for 2-methyl hopanoids are most likely nitrogen cycle-affiliated α-proteobacteria and/or diazotrophic cyanobacteria.
{"title":"A plethora of hopanoid transformation products co-exist in a thermally immature Jurassic black shale II: Oxo- and thiohopanoids","authors":"Tim Marten , Lorenz Schwark","doi":"10.1016/j.orggeochem.2025.105121","DOIUrl":"10.1016/j.orggeochem.2025.105121","url":null,"abstract":"<div><div>Hopanoids are ubiquitous in sediments and sedimentary rocks and are commonly applied tools for paleoenvironment reconstruction. Biohopanoids during diagenesis transform to geohopanoids when they successively lose their structural diversity. Prior to elevated thermal maturity, where only hopanes and benzohopanes persist, a large variety of intermediate hopanoid transformation products can be intermittently abundant in immature sediments. We presented in a companion paper the highly diverse hopanoid hydrocarbon inventory in one immature black shale sample from the Toarcian Posidonia Shale at Hondelage, NW-Germany that was deposited under euxinic conditions. Here, the focus is on the plethora of oxo- and thiohopanoids co-existing in the same sample. The formation of hopanoic acids requires oxic conditions whereas thiohopanoid require sulfidic conditions. These contrasting requirements suggest spatial and temporal separation of hopanoic acid versus thiohopanoid formation prior to or after incorporation into the sediment. Hopanoic acids presumably form in the oxic upper water column with potential minor contributions from oxic microniches and/or seasonally induced brief suboxic events at the sediment/water interface. In contrast, thiohopanoids presumably originate within the sulfidic water column and/or the sediment. Persistent euxinic conditions during deposition of the Posidonia Shale at Hondelage favoured formation of a variety of thiohopanoids in a shallow marine setting below a salinity-stratified water column. Thiohopanoids include previously unidentified hop-17(21)-ene thiolanes and hopane thiophenes extending to C<sub>38</sub>. Since hopanoids extending past C<sub>35</sub> are absent for other hopanoid species, extended hopane thiophenes likely result from microbially mediated early diagenetic alkylation at the C35 position. Hopanoic acids as well as thiohopanoids occur as 2-methyl analogues and exhibit elevated abundances of C<sub>33</sub> homologues, which dominate in desmethyl hopanoids. Precursor organisms for 2-methyl hopanoids are most likely nitrogen cycle-affiliated α-proteobacteria and/or diazotrophic cyanobacteria.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"212 ","pages":"Article 105121"},"PeriodicalIF":2.5,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837382","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}
Pub Date : 2025-12-24DOI: 10.1016/j.orggeochem.2025.105124
Gemma Baker , James Bendle , Lydia K. Greene , Kweku Afrifa Yamoah , Matthew Allison , Sarah E. Greene
The diet of an animal reflects its species’ ecology and local food availability and is often a key metric for monitoring the health and welfare of endangered species. However, determining diets across individuals and through space and time, is an inherent challenge within ecology, being expensive and time-intensive to accomplish with observations. Faeces offer the opportunity for non-invasive sample collection and can provide a snapshot of the ingested diet of the producer. In modern ecology, faecal samples have been a prime target for genetic analyses of diet and the gut microbiome. Here, however, we explore whether high molecular weight (HMW) n-alkane biomarkers extracted from faeces can provide useful information about diet. HMW n-alkanes are commonly employed in palaeoecological reconstructions. Combining faecal HMW n-alkane analyses with gut microbiome composition and detailed foraging data applied to two species of lemur in captivity with access to naturalized forest enclosures, we show that recovered HMW n-alkanes are completely dietary in origin and not correlated to the gut microbiome. Signatures are significantly different between our two focal lemur species and seasons, reflecting differences in ingested diet. It is possible to infer changes in the relative contributions of major plant parts, particularly leaves and fruits, based on the faecal HMW n-alkane concentrations. Whereas n-alkane signatures alone are perhaps ill-suited to pinpoint plant species in animals with complex herbivorous diets, when integrated with other complementary methodologies can provide a more comprehensive dietary reconstruction. HMW n-alkanes are simple to identify and measure; only requiring commonly available and relatively affordable analytical chemistry instruments (e.g. GC-FID). Beyond discussing downstream uses of our methodology to captive and wild lemurs, other primates and herbivorous and omnivorous animals globally, our pilot study hints at the promise of the organic geochemist’s toolkit applied to dietary ecology.
{"title":"Faecal n-alkanes differ significantly between two lemur species reflecting differences in consumed diet","authors":"Gemma Baker , James Bendle , Lydia K. Greene , Kweku Afrifa Yamoah , Matthew Allison , Sarah E. Greene","doi":"10.1016/j.orggeochem.2025.105124","DOIUrl":"10.1016/j.orggeochem.2025.105124","url":null,"abstract":"<div><div>The diet of an animal reflects its species’ ecology and local food availability and is often a key metric for monitoring the health and welfare of endangered species. However, determining diets across individuals and through space and time, is an inherent challenge within ecology, being expensive and time-intensive to accomplish with observations. Faeces offer the opportunity for non-invasive sample collection and can provide a snapshot of the ingested diet of the producer. In modern ecology, faecal samples have been a prime target for genetic analyses of diet and the gut microbiome. Here, however, we explore whether high molecular weight (HMW) <em>n</em>-alkane biomarkers extracted from faeces can provide useful information about diet. HMW <em>n-</em>alkanes are commonly employed in palaeoecological reconstructions. Combining faecal HMW <em>n</em>-alkane analyses with gut microbiome composition and detailed foraging data applied to two species of lemur in captivity with access to naturalized forest enclosures, we show that recovered HMW <em>n</em>-alkanes are completely dietary in origin and not correlated to the gut microbiome. Signatures are significantly different between our two focal lemur species and seasons, reflecting differences in ingested diet. It is possible to infer changes in the relative contributions of major plant parts, particularly leaves and fruits, based on the faecal HMW <em>n</em>-alkane concentrations. Whereas <em>n</em>-alkane signatures alone are perhaps ill-suited to pinpoint plant species in animals with complex herbivorous diets, when integrated with other complementary methodologies can provide a more comprehensive dietary reconstruction. HMW <em>n</em>-alkanes are simple to identify and measure; only requiring commonly available and relatively affordable analytical chemistry instruments (e.g. GC-FID). Beyond discussing downstream uses of our methodology to captive and wild lemurs, other primates and herbivorous and omnivorous animals globally, our pilot study hints at the promise of the organic geochemist’s toolkit applied to dietary ecology.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"213 ","pages":"Article 105124"},"PeriodicalIF":2.5,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145947984","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}
Pub Date : 2025-12-17DOI: 10.1016/j.orggeochem.2025.105098
Ahmed Khairy , Clement N. Uguna , Waleed Sh. El Diasty , Kenneth E. Peters , Christopher H. Vane , Colin E. Snape , Sherif Farouk , Will Meredith
Biomarkers are powerful tools to assess thermal maturity of oil and rock extracts and for oil-source rock correlation. While temperature effects on biomarker evolution have been widely studied, the impact of pressure remains largely underexplored. This study examines the effect of high water pressure (up to 900 bar) on biomarker maturation in expelled oil and extracted bitumen from pyrolysis experiments on a rock sample from the Campanian–Maastrichtian Duwi Formation, Red Sea Basin, Egypt. Extracted bitumens exhibited higher maturity under anhydrous conditions compared to low-pressure hydrous samples, and this was more pronounced at 350°C. The extracted bitumen displayed higher biomarker maturity ratios than the corresponding expelled oil at 350°C, likely due to prolonged interactions of the bitumen with the rock mineral matrix. In contrast, δ13C values were similar for extracted bitumen and the corresponding expelled oil. At 320°C, high pressure reduced values of biomarker maturity ratios, particularly C31–C35 homohopane isomerisation, Ts/Tm, Ts/H30, and C29Ts/H29 ratios, whereas sterane ratios remained unaffected. At 350°C, pressure effects were less significant, with some anomalous variations, suggesting a non-systematic influence on biomarker maturation at higher temperatures. These findings demonstrate the complex role of pressure in biomarker evolution, emphasising the need to consider pressure in biomarker-based maturity assessment, particularly in overpressured basins and deep petroleum systems, where high pressure may be a dominant factor. Based on 12 source-related biomarker and isotopic ratios, chemometric analysis reveals that artificially generated oils and South Malak-1 oils from southwestern onshore Gulf of Suez are quite different, and both groups differ significantly from other natural oils from the central and northern parts of the basin. This may be due to facies variations and the effects of mixing from multiple source horizons under natural subsurface conditions.
{"title":"Effect of water pressure on bitumen and expelled oil biomarker evolution: Insights from laboratory simulation experiments","authors":"Ahmed Khairy , Clement N. Uguna , Waleed Sh. El Diasty , Kenneth E. Peters , Christopher H. Vane , Colin E. Snape , Sherif Farouk , Will Meredith","doi":"10.1016/j.orggeochem.2025.105098","DOIUrl":"10.1016/j.orggeochem.2025.105098","url":null,"abstract":"<div><div>Biomarkers are powerful tools to assess thermal maturity of oil and rock extracts and for oil-source rock correlation. While temperature effects on biomarker evolution have been widely studied, the impact of pressure remains largely underexplored. This study examines the effect of high water pressure (up to 900 bar) on biomarker maturation in expelled oil and extracted bitumen from pyrolysis experiments on a rock sample from the Campanian–Maastrichtian Duwi Formation, Red Sea Basin, Egypt. Extracted bitumens exhibited higher maturity under anhydrous conditions compared to low-pressure hydrous samples, and this was more pronounced at 350°C. The extracted bitumen displayed higher biomarker maturity ratios than the corresponding expelled oil at 350°C, likely due to prolonged interactions of the bitumen with the rock mineral matrix. In contrast, δ<sup>13</sup>C values were similar for extracted bitumen and the corresponding expelled oil. At 320°C, high pressure reduced values of biomarker maturity ratios, particularly C<sub>31</sub>–C<sub>35</sub> homohopane isomerisation, Ts/Tm, Ts/H<sub>30</sub>, and C<sub>29</sub>Ts/H<sub>29</sub> ratios, whereas sterane ratios remained unaffected. At 350°C, pressure effects were less significant, with some anomalous variations, suggesting a non-systematic influence on biomarker maturation at higher temperatures. These findings demonstrate the complex role of pressure in biomarker evolution, emphasising the need to consider pressure in biomarker-based maturity assessment, particularly in overpressured basins and deep petroleum systems, where high pressure may be a dominant factor. Based on 12 source-related biomarker and isotopic ratios, chemometric analysis reveals that artificially generated oils and South Malak-1 oils from southwestern onshore Gulf of Suez are quite different, and both groups differ significantly from other natural oils from the central and northern parts of the basin. This may be due to facies variations and the effects of mixing from multiple source horizons under natural subsurface conditions.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"212 ","pages":"Article 105098"},"PeriodicalIF":2.5,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787554","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}
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