Organic Geochemistry最新文献

{"title":"Dual-pressure pyrolysis apparatus unravelling how fluid and lithostatic pressure matter in hydrocarbon expulsion","authors":"Weijiao Ma,&nbsp;Yunpeng Wang,&nbsp;Jinzhong Liu,&nbsp;Jinbu Li","doi":"10.1016/j.orggeochem.2025.104932","DOIUrl":"10.1016/j.orggeochem.2025.104932","url":null,"abstract":"<div><div>Improvement in thermal simulation technology will increases the accuracy of predictive geochemistry. A dual-pressure pyrolysis apparatus was developed, to precisely control the fluid pressure and lithostatic pressure during simulated source rock maturation. Two series of pyrolysis experiments were carried out, simulating the same generation process but different expulsion fluid pressure condition. Episodic hydrocarbon expulsion from source rocks under controlled lithostatic pressure and fluid pressure was for the first time observed through thermal simulation experiments. The results were applied to (1) hydrocarbon expulsion efficiency (HEE) analysis, and (2) compositional analysis of oil and gas expelled under different pressures. Results show that HEE is strongly influenced by both fluid and lithostatic pressures. If the oil discharged during depressurization and normal pressure is taken into account, the calculated HEE was 2–31 times the HEE that only considers the high fluid pressure expelled oil. Compared with previous experimental results, HEE under controlled dual pressure is also lower. Therefore, before applying the results of thermal simulation experiments to unconventional and deep oil/gas evaluation, sufficient attention should be paid to the pressure conditions of the experiments. Within the oil window, when the temperature and hydrostatic pressure of source rocks are dropped due to tectonic events such as uplift, they can discharge more oil and gas than before uplift, as a consequence of adjustment of over-pressured fluid to re-equilibrate to the adjacent hydrostatic conditions. In addition, during pressure and temperature reduction, the expelled fluids have a higher gas to oil ratio. This helps to indicate that sedimentary basins that experienced tectonic events still have great exploration potential. The temperature program, pressure setup, expulsion conditions in the two-series experiments is a tentative work tested on a representative source rock from the Triassic Yanchang Formation (Ordos Basin), indicating that control of fluid and lithostatic pressure are essential for improving the accuracy of thermal simulation predictions. The dual-pressure pyrolysis apparatus has high exploration relevance, particularly when quantitative results are integrated with the depositional, tectonic and thermal histories of specific source rocks.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"203 ","pages":"Article 104932"},"PeriodicalIF":2.6,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464517","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":"Molecular and isotope characterization of hydrocarbon products from organic-sulfur-rich mudstones during closed hydrous-pyrolysis","authors":"Jaime Cesar ,&nbsp;Julito Reyes ,&nbsp;Omid H. Ardakani ,&nbsp;Levi J. Knapp","doi":"10.1016/j.orggeochem.2025.104963","DOIUrl":"10.1016/j.orggeochem.2025.104963","url":null,"abstract":"<div><div>A series of mudstones with varying organic sulfur content were subjected to hydrous pyrolysis and the produced oil and gas were analyzed. The samples come from the late Devonian Duvernay Formation (Canada), the late Miocene Onnagawa Formation (Japan), and the early Jurassic Gordondale Member of the Fernie Formation (Canada), in order of increasing organic sulfur content. Comparison of molecular parameters in the produced oils and residual extracts showed that these have almost identical values, with linear correlation near 1:1, except for polycyclic aromatics such as alkylphenanthrenes and alkyldibenzothiophenes. The excellent correlation suggests that in an ideal scenario, in the absence of long-distance migration, hydrocarbon mixing, and secondary alteration, produced oils and residual bitumen would have very similar molecular properties. In addition, for the same %VR_eqv, samples with higher sulfur content exhibit an apparent higher thermal maturity according to molecular ratios such as Pr/<em>n</em>C₁₈ and C₃₀Hopane/C₃₀Moretane. Generated gases showed source effects on their molecular and carbon isotope composition for the maturity interval analyzed herein (0.57 to 1.42 % VR_eqv). H₂S gas was generated only from the Gordondale samples and the isotope values are presented in this study.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"202 ","pages":"Article 104963"},"PeriodicalIF":2.6,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143438187","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":"Aromatic carotenoids and their aryl isoprenoid derivatives in the early Paleozoic rocks and crude oils of the Tarim Basin, China","authors":"Huiyuan Yang ,&nbsp;Jiaquan Zhou ,&nbsp;Jian Ma ,&nbsp;Xingqian Cui","doi":"10.1016/j.orggeochem.2025.104950","DOIUrl":"10.1016/j.orggeochem.2025.104950","url":null,"abstract":"<div><div>Emerging viewpoints suggest dynamic oceanic redox states and notable biotic turnovers in the early Paleozoic, but these aspects remain controversial and require further investigation. The Tarim Basin, which harbors significant marine hydrocarbon source rocks, records a typical phase of marine deposition of the early Paleozoic. In this study, we investigated biomarker compositions and patterns of selected rocks and crude oils of Early Cambrian to Late Ordovician ages from the Tarim Basin, China. Of particular importance are fossilized C₄₀ aromatic carotenoids and their biogenic aryl isoprenoid derivatives, which originate specifically from phototrophic sulfur bacteria inhabiting the euxinic photic zone and are indicative of redox conditions of ancient oceans. The prevalence of 2,3,6-aryl isoprenoids and isorenieratane indicates a biological origin of green sulfur bacteria, implying that the Tarim Basin witnessed euxinia in the subsurface photic zone during a certain period of the early Paleozoic. Along with other biomarker-based proxies, especially steroids and hopanoids, our results from the Tarim Basin suggest the dominance of reducing oceanic water column in the early Cambrian and the late evolution of partially oxygenated water column.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"202 ","pages":"Article 104950"},"PeriodicalIF":2.6,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422292","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":"Geochemical constraints on the hydrocarbon generation and expulsion in source rocks with different primary organic matter compositions: A case study on the Lucaogou Formation in the Jimusaer Sag, Junggar Basin, Northwest China","authors":"Shiju Liu ,&nbsp;Gang Gao ,&nbsp;Xiangyun Shi ,&nbsp;Wenzhe Gang ,&nbsp;Baoli Xiang ,&nbsp;Ming Wang ,&nbsp;Wenzhi Zhao","doi":"10.1016/j.orggeochem.2025.104952","DOIUrl":"10.1016/j.orggeochem.2025.104952","url":null,"abstract":"<div><div>This study investigates the effects of different types of primary organic matters on hydrocarbon generation and expulsion of source rocks. Samples representing three typical source rocks from the Lucaogou Formation in the Jimusaer Sag were collected and analyzed by hydrous pyrolysis, total organic carbon, Rock-Eval, gas chromatography-mass spectrometry, organic petrology, and scanning electron microscopy. Distinct differences in crude oil biomarkers were observed between telalginite- and lamalginite-rich source rocks. Telalginite-rich source rocks exhibit higher abundances of pristane, phytane, <em>β</em>-carotane, gammacerane, and C₂₉ regular steranes, while lamalginite-rich source rocks are characterized by enrichments of C₂₄ tetracyclic terpane, C₂₉ hopane, and C₂₈ regular steranes. These biomarkers provide insights into the primary types of organic matter and their depositional environments with high water salinity of telalginite and low salinity of lamalginite. Hydrous pyrolysis results reveal that telalginite-rich source rocks demonstrate early hydrocarbon generation and a wider oil window than lamalginite-rich source rocks. Compared to lamalginite-rich source rocks, telalginite-rich source rocks produced better quality of crude oil, exhibit a smaller specific surface area of organic matter, and greater development of organic-inorganic pores, which contribute to their higher oil expulsion. These findings are helpful to the understanding of the constraints imposed by different primary organic matters on hydrocarbon generation and expulsion of the source rocks, and the insights have significant implications for exploration and development of the shale oil resources.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"202 ","pages":"Article 104952"},"PeriodicalIF":2.6,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422291","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":"Optimized method for sequential extraction and analysis of polycyclic aromatic hydrocarbons, anhydrosugars and lipid biomarkers in speleothem carbonate and drip waters","authors":"Zhao Wang ,&nbsp;Jonathan D. Smolen ,&nbsp;Michael T. Hren ,&nbsp;Yuval Burstyn ,&nbsp;Isabel P. Montañez ,&nbsp;Jessica L. Oster ,&nbsp;Aida Zyba ,&nbsp;Erica A. Scarpitti","doi":"10.1016/j.orggeochem.2025.104961","DOIUrl":"10.1016/j.orggeochem.2025.104961","url":null,"abstract":"<div><div>Organic molecules such as <em>n</em>-alkyl lipids, terpenoids, anhydrosugars (AHs), and polycyclic aromatic hydrocarbons (PAHs) are found in karst systems, including cave deposits and drip waters, and provide a potential record of surface climate, ecosystem, and fire. However, it is analytically challenging to separate and measure multiple classes of organic compounds in these low-abundance matrices. Here, we present a simple, solid-phase sequential extraction method for the separation and purification of organic matter in carbonates (∼0.5 g, powder) and drip waters (300 mL, freeze-dried). This method offers efficient extraction and separation of hydrocarbons (<em>F_H</em>) (saturated and PAHs) (hexane/dichloromethane; 70/30; v/v) and polar lipid compounds (<em>F_P</em>) (e.g., AHs, sterols, and diterpenoids) (acetone) with a high recovery of standards in <em>F_H</em> (78 ± 7 %, on average) and <em>F_P</em> (90 ± 6 %, on average) across multiple matrices (i.e., speleothems and waters). Acid digestion was applied to the post-initial sequential extraction speleothem samples to fully liberate any remaining molecules trapped in the calcite crystals. We found that ∼10% of <em>n</em>-alkanes (C₂₀-C₃₂) and the smallest PAHs (naphthalene, methylated naphthalene, and fluorene) of total extractable hydrocarbons were left in the acid digestion, indicating that modification of the sequential extraction could be applied based on the target of interests. In total, this sequential solid-phase extraction method provides reliable separation of geochemically significant compound classes across different matrices within karst systems.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"203 ","pages":"Article 104961"},"PeriodicalIF":2.6,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143520529","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":"Study on the main controlling factors on the differential accumulation of natural gas in multiple (ultra-)deeply-buried marine strata","authors":"Zezhang Song ,&nbsp;Ziyu Zhang ,&nbsp;Bing Luo ,&nbsp;Wenjin Zhang ,&nbsp;Changqi Liu ,&nbsp;Xingwang Tian ,&nbsp;Dailin Yang ,&nbsp;Luya Wu ,&nbsp;Bingfei Ge ,&nbsp;Shigui Jin ,&nbsp;Jiutao Yuan","doi":"10.1016/j.orggeochem.2024.104918","DOIUrl":"10.1016/j.orggeochem.2024.104918","url":null,"abstract":"<div><div>Ultra-deep natural gas is characterized by significant burial depth, high maturity, limited biomarkers, and complicated gas-source relationships. Ultra-deep gas accumulations generally underwent complex modifications during their long evolution, making it challenging to clarify the controlling factors of gas accumulation. This study focuses on gas accumulations in multiple (ultra-)deep marine carbonate strata, ranging from the Sinian Dengying (Z₂dn) to the Permian Maokou (P₂m) formations, in the Penglai gas area of the central Sichuan Basin. Using unsupervised machine learning algorithms, we conducted clustering analysis on natural gas composition and isotopes (δ¹³C and δ²H). Furthermore, we combined reservoir microscopic analysis, isotope data (δ¹³C of kerogen and solid bitumen; and δ¹⁸O, δ¹³C, and ⁸⁷Sr/⁸⁶Sr of dolomite), and fluid inclusion analysis to determine the main controlling factors that differentiate gas accumulation in multiple marine carbonate strata. The results indicate that: (1) Natural gases from Z₂dn-P₂m strata in the Penglai gas area are mainly dry gas (dryness &gt; 0.996). Specifically, Z₂dn natural gas exhibits high non-hydrocarbon content, low C₂H₆, δ¹³C_C₂H₆, and δ²H_CH₄. Conversely, the Cambrian (Є) natural gas demonstrates the opposite characteristics. The natural gas in P₂m has relatively high C₂H₆, greater δ¹³C_C₂H₆ and δ²H_CH₄ values. (2) The natural gas from Z₂dn-P₂m in the Penglai gas area is oil-cracking gas and mainly sourced from Є₁q. Due to maturity, hydrocarbon gases are dominated by CH₄. He and N₂ are from inorganic, deep Earth sources and show differential enrichment. Influenced by hydrothermal alteration and TSR, H₂S and CO₂ are enriched in Z₂dn. The δ¹³C_C₂_H₆ in natural gas follows the order: Z₂dn &gt; P₂m &gt; Cambrian. The δ¹³C_CH₄ in natural gas follows the order: Z₂dn ≥ P₂m &gt; Cambrian. (3) Overall, the Z₂dn-P₂m differential accumulation in the Penglai gas area is primarily influenced by various factors, including multiple source rocks, deep hydrothermal transformation, and strike-slip faults.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"201 ","pages":"Article 104918"},"PeriodicalIF":2.6,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378489","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":"Study on hydrocarbon retention and expulsion of kerogen based on centrifugal swelling method","authors":"Tian Liang ,&nbsp;Feng Zhu ,&nbsp;Zhao-Wen Zhan ,&nbsp;Xiao-Hui Lin ,&nbsp;Yan-Rong Zou ,&nbsp;Ping’an Peng","doi":"10.1016/j.orggeochem.2024.104921","DOIUrl":"10.1016/j.orggeochem.2024.104921","url":null,"abstract":"<div><div>Centrifugal swelling experiments using <em>n</em>-hexadecane and 1-methylnaphthalene were carried out to explore the connection between hydrocarbon retention and expulsion in type Ⅰ kerogen. A driving force-hydrocarbon expulsion model was innovatively established through the results of differential centrifugation experiments and low field nuclear magnetic resonance. Additionally, the hydrocarbon expulsion process of kerogen was categorized into three distinct stages based on the driving force, including free, intergranular state and immovable state (adsorption and swelling) hydrocarbon expulsion. A linear correlation also was established between the T₁/T₂ signal and the liquid hydrocarbon content during the swelling process, revealing that low-field NMR technology could effectively detect the retention of alkane compounds in kerogen. The study revealed that when the driving force is greater than 647.4 g N, most of the shale oil retained in the kerogen is in an immobile state, which cannot be exploited. Additionally, the hydrocarbon expulsion model based on the centrifugal experiment presents several advantages, including low equipment requirements, straightforward operation, and a broad range of applications. This model can effectively support various types of laboratories conducting shale oil retention assessment work, especially those in oilfields with relatively simple experimental setups.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"201 ","pages":"Article 104921"},"PeriodicalIF":2.6,"publicationDate":"2025-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143373026","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":"Biomarker signatures in host rocks and their co-occurring fossil plants from northern Scotland","authors":"Olumuyiwa T. Akinsanpe ,&nbsp;Adebola O. Akinsanpe ,&nbsp;Solomon A. Adekola ,&nbsp;Oluwaseye P. Oyetade ,&nbsp;Waheed G. Akande ,&nbsp;Musa B. Usman ,&nbsp;Abdulwahab M. Bello ,&nbsp;Uzochukwu K. Benjamin ,&nbsp;Adeniyi O. Olusanya ,&nbsp;Chikezie Emele","doi":"10.1016/j.orggeochem.2025.104948","DOIUrl":"10.1016/j.orggeochem.2025.104948","url":null,"abstract":"<div><div>The Devonian Period paleogeographic setting fostered the growth of diverse terrestrial and marine organisms, enhancing organic matter production and preserving terrestrial organic matter (TOM). Northern Scotland shows rock sequences with well-preserved TOM, including distinctive fossil plant fragments. The biomarker record of host rock-fossil plant system is notably fragmented. Nonetheless, the exposed outcrops of Old Red Sandstone in northern Scotland allow detailed sampling and biomarker analysis of the Devonian rocks and their co-existing fossil plants. The biomarker record of the host rocks and the co-occurring plant fossils show that the organic matter of the Rhynie Chert, Newton of Kinkell and Kerrera siltstones were derived from vascular plants. The plant biomarkers detected in the Rhynie Chert includes tetracyclic diterpenoids (kaurane and beyerane), cadalene and methylnaphthalene. These biomarkers except cadalene were also present in Den of Morphie samples, Achanarras Quarry, Kerrera plant and Newton of Kinkell siltstone-plant samples. The similarity in biomarker signatures between fossil plants and host rocks in Achanarras suggested a shared origin of organic matter. Also, the sulfur-rich euxinic conditions in the studied areas, the hydrothermal permineralization and presence of pyrite framboids in the Rhynie Chert preserved the organic matter. This was indicated by low Pr/Ph ratios and high sulfur content, enhancing preservation and reducing organic matter degradation. The study concluded that the biomarker record of the host rock-plant fossil system in northern Scotland aids the understanding of terrestrialization process and higher plant evolution in the Devonian.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"201 ","pages":"Article 104948"},"PeriodicalIF":2.6,"publicationDate":"2025-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143373025","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":"Protocols to assist deconvolution of co-eluting 5β– and 5α–steranes by gas chromatography–mass spectrometry","authors":"Luke M. Brosnan,&nbsp;Paul F. Greenwood,&nbsp;Peter Hopper,&nbsp;Kliti Grice","doi":"10.1016/j.orggeochem.2024.104916","DOIUrl":"10.1016/j.orggeochem.2024.104916","url":null,"abstract":"<div><div>Molecular parameters based on the relative abundance of various sterane isomers contribute valuable information about sources and thermal history of organic-matter-rich sediments. However, this application is limited for 5β– and 5α–steranes due to their co-elution on common gas chromatography (GC) columns: e.g., relative retention index of 5β20<em>R</em> and 5α20<em>S</em> cholestanes on Agilent DB1 columns = 28.081 and 28.065, respectively. Selected ion monitoring (SIM) and tandem (MS/MS) mass spectral protocols were developed to improve the analytical resolution of these compounds, exploiting slight differences in mass fragmentation patterns. Protocols were optimised on a 1:1 mixture of authentic 5α20<em>R</em> and 5β20<em>R</em> cholestane standards (5α20<em>R</em> in place of 5α20<em>S</em>). Parameters offering 5α:5β selectivity (e.g., SIM: 149/151 Da; MRM: [149 → 79]/[151 → 79]) were tested on a suite of 5α20<em>R</em>:5β20<em>R</em> standards and show an excellent correlation (<em>R</em>² &gt; 0.99) with substrate composition. The capacity to quantify the relative contribution of co-eluting 5α20<em>S</em> and 5β20<em>R</em> in more complex samples was tested by analyses of a crude oil (Blina-4, Canning Basin, Western Australia) known to have high abundances of C_27-29 5α20<em>S</em> steranes (20<em>S</em>/[20<em>S</em> + 20<em>R</em>] ≈ 0.5) and spiked with 5β20<em>R</em> cholestane. The relative proportions of 5α20<em>S</em> and 5β20<em>R</em> were determined using 5α20<em>R</em>:5β20<em>R</em> calibration curves with good consistency and accuracy. Values deviated from the target when either analyte was particularly dominant (≥80 %), probably due to differences in ion density compared to the resolved standards. This issue may be improved with further method refinement and the true sterane deconvolution value offered by this approach will become apparent with further application to a diverse range of samples.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"201 ","pages":"Article 104916"},"PeriodicalIF":2.6,"publicationDate":"2025-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143373039","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":"Assessing tetraether lipids as a paleotemperature proxy on western edge of the Chinese Loess Plateau: A cautionary tale","authors":"Jingjing Guo ,&nbsp;Louise Fuchs ,&nbsp;Martin Ziegler ,&nbsp;Youbin Sun ,&nbsp;Francien Peterse","doi":"10.1016/j.orggeochem.2025.104947","DOIUrl":"10.1016/j.orggeochem.2025.104947","url":null,"abstract":"<div><div>The 130,000-year long, high-resolution paleotemperature record obtained from branched glycerol dialkyl glycerol tetraethers (brGDGTs) stored in a loess-paleosol sequence from Yuanbao on the western Chinese Loess Plateau (CLP) does not follow global temperature variations, whereas these are recorded by traditional loess proxy records from the same section. Specifically, reconstructed temperatures are lowest during Marine Isotope Stage 5 (MIS5), even indicating colder interstadials than stadials, which contradict brGDGT-based records from other sections on the CLP. The overall low temperatures during wet periods may be explained by an increase in soil moisture availability, which dampens land surface temperatures by increasing the soil heat capacity. However, comparison of brGDGT distributions at Yuanbao with those in modern surface soils from the CLP and the global soil calibration dataset reveals a lack of modern analogues during the interval from ∼73 to 63 ka. Notably, the Isomer Ratio (IR) rapidly increases from 0.2 to 0.6 (corresponding to a pH shift of ∼2 units) during this period, indicating a drastic shift in the composition of the bacterial community that in turn may have influenced the MBT′_5Me-temperature relationship. This community shift occurs after Chinese Stadial-20 around 73 ka, a weak monsoon event tentatively linked to oceanic reorganizations after the Toba eruption, suggesting that this drastic change in (hydro)climate might have impacted brGDGT producers. We thus recommend thoroughly assessing brGDGT distributions and understanding the environmental background prior to interpretating brGDGT-based temperatures in a paleoclimatic context.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"201 ","pages":"Article 104947"},"PeriodicalIF":2.6,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145071","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}