Organic Geochemistry最新文献

{"title":"Hydroxylated GDGTs-0 in marine methane seep environments: A putative indicator for archaeal methanogenesis","authors":"Hongxiang Guan ,&nbsp;Lei Liu ,&nbsp;Daniel Birgel ,&nbsp;Jörn Peckmann ,&nbsp;Dong Feng ,&nbsp;Sanzhong Li","doi":"10.1016/j.orggeochem.2024.104862","DOIUrl":"10.1016/j.orggeochem.2024.104862","url":null,"abstract":"<div><div>Marine methane seeps are environments with a high microbial diversity, but are known for one biogeochemical key process, the sulfate-driven anaerobic oxidation of methane (SD-AOM) performed by anaerobic methane-oxidizing archaea (ANME) and sulfate-reducing bacteria (SRB). SD-AOM is also the dominant process at methane seeps in the South China Sea based on the lipid biomarker inventory of authigenic seep carbonates characterized by crocetane, a high <em>sn</em>2-hydroxyarchaeol over archaeol ratio, low contents of glycerol dibiphytanyl glycerol tetraethers (GDGTs), and δ¹³C_{lipid-methane} offsets of −52 ± 4‰. Combined with the dominance of aragonite over other carbonate minerals, such pattern suggests high seepage intensity with a predominance of ANME-2/SRB consortia. Interestingly, the studied seep carbonates also yielded some uncommon biomarkers for these consortia, which may derive from methanogenic archaea. Methylotrophic methanogenesis has been shown to be the dominant mode of methanogenesis in seep environments where non-competitive substrates like methanol or trimethylamine are abundant. The presence of methylotrophic methanogens is possibly indicated by high contents (more than 50% of all GDGTs) of hydroxylated GDGTs-0 (OH-GDGT-0 and 2OH-GDGT-0) with extreme ¹³C-depletion (−128‰ to −116‰); this unique pattern is recognized in only some of the studied seep carbonates, while other carbonates are dominated by typical distributions of ANME-2 lipids, also comprising GDGTs with 0 to 4 rings, but lacking high contents of OH-GDGTs. The overall lack of crenarchaeol, the specific biomarker of planktonic Thaumarchaeota, agrees with the tentative assignment of the highly abundant OH-GDGTs-0 to methanogenic archaea. Such interpretation is necessarily circumstantial considering that the compound and carbon isotope composition of the membranes of ANME and methanogenic archaea is similar. Although production of OH-GDGTs has been previously reported for both planktonic Thaumarchaeota and ANME, OH-GDGT-0 as sole and highly abundant OH-GDGT has only been recognized in one culture of methanogenic archaea. Therefore, the high abundance of ¹³C-depleted hydroxylated GDGTs-0 compared to only minor contents of regular, ANME-derived GDGTs 1–4 with similar ¹³C-depletions can possibly be used as an indicator for methylotrophic methanogenesis in seep environments. Future experimental work is needed and should test if ¹³C-depleted hydroxylated GDGTs-0 are indeed biomarkers of methylotrophic methanogenesis at seeps.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"198 ","pages":"Article 104862"},"PeriodicalIF":2.6,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652443","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 – June 2024","authors":"","doi":"10.1016/j.orggeochem.2024.104849","DOIUrl":"10.1016/j.orggeochem.2024.104849","url":null,"abstract":"","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"196 ","pages":"Article 104849"},"PeriodicalIF":2.6,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142228732","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":"A matter of extraction – Extraction yields and ratios of faecal lipid biomarker from archaeological soils using Soxhlet, microwave-assisted and accelerated-solvent extraction","authors":"Sascha Scherer ,&nbsp;Jago Jonathan Birk ,&nbsp;Stefanie Klassen ,&nbsp;Sabine Fiedler","doi":"10.1016/j.orggeochem.2024.104863","DOIUrl":"10.1016/j.orggeochem.2024.104863","url":null,"abstract":"<div><div>The performance of Soxhlet (SOX), microwave-assisted (MAE) and accelerated-solvent extraction (ASE) in the analysis of faecal lipid biomarkers (FLB, Δ⁵-sterols, stanols, stanones) from archaeological soils was investigated to assess effectiveness and reproducibility of the extraction methods. Results from two Anthrosols that were analysed in six replicates show that SOX achieves significantly higher extraction yields for individual substances and steroid sums than MAE, while ASE produces the lowest lipid yields. Regarding the FLB ratios, which are used for sourcing of faeces, the three extraction methods show comparable values with three out of five ratios differing significantly between different soil samples. The reproducibility of extraction yields decreases with SOX &gt; ASE &gt; MAE, as well as for concentrations &lt;100 <!--> <!-->ng<!--> <!-->g⁻¹ sediment. Analyses of six different soils indicate a weak influence of soil properties (pH, texture, total organic carbon and cation exchange capacity) on the effectiveness of extraction methods. From our study we conclude that the classical SOX is still the preferred extraction approach when reliably higher FLB yields are of foremost interest or low concentrations are expected, as it is most effective and reproducible. However, considering the drawbacks of SOX (high extraction times and high solvent consumption), MAE and ASE appear to be comparably attractive for extracting FLBs in archaeological contexts. In addition to comparable FLB ratios, MAE and ASE are economically more efficient, as they reach a higher sample throughput and waste lower amounts of extractant.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"197 ","pages":"Article 104863"},"PeriodicalIF":2.6,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142417966","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":"Interaction between peptide and solid lignin suggest mechanisms of abiotic covalent bond formation","authors":"João Vitor dos Santos ,&nbsp;Amanda Koenig ,&nbsp;Patrick G. Hatcher","doi":"10.1016/j.orggeochem.2024.104861","DOIUrl":"10.1016/j.orggeochem.2024.104861","url":null,"abstract":"<div><div>The mechanisms behind the formation of soil organic matter (SOM) and associated nitrogen immobilization remain partially elusive, while ongoing research continues to shed light on carbon and nitrogen sequestration in the environment. Studies show that quinone-like structures within alkali-soluble humic extracts of SOM can bond covalently with nitrogen-containing molecules derived from proteinaceous organic matter. However, direct molecular evidence for this chemical bonding with lignin in the solid form and non-solvent-extracted SOM is lacking. Using gel-state ¹H-¹⁵N heteronuclear single quantum coherence (HSQC) high-resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR) spectroscopy, we demonstrate that a ¹⁵N-labeled peptide (glycine-glycine-glycine-arginine, GGGR), can covalently bind to solid, untreated, brown rotted wood as well as 1,2-naphthoquinone, a quinone-model molecule typically found in degraded lignin. The new peaks in both reactions represent a change in the environment surrounding the N-functional groups. Interaction of the ¹⁵N-labeled peptide with the model quinone produced NMR cross peaks that are similar to those of the solid lignin. This suggests that the quinone-like structures are the most likely functional groups to form covalent bonds with peptides in the degraded lignin. Both Michael addition and Schiff base formation is proposed when the peptide GGGR interacts with white oak lignin and 1,2-naphthoquinone. These processes are of considerable importance to N incorporation into SOM and offer insights into how proteinaceous molecules could potentially be preserved and sequestered through covalent bond formation.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"197 ","pages":"Article 104861"},"PeriodicalIF":2.6,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533628","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":"Modified rapid small-scale fractionation method for quantitatively separating pyrrolic nitrogen compounds, phenols-ketones and carboxylic acids fractions from petroleum","authors":"Krzysztof J. Jurek","doi":"10.1016/j.orggeochem.2024.104850","DOIUrl":"10.1016/j.orggeochem.2024.104850","url":null,"abstract":"<div><p>This research outlines a fast and efficient technique for separating the pyrrolic, phenolic-ketonic, and carboxylic acid fractions from oils in a small-scale setting. This approach enables the separation and analysis of neutral nitrogen fractions that contain indoles, carbazoles, and benzocarbazoles, as well as ketonic-phenolic fractions that contain phenols and ketones. The study showcases the potential for accurately measuring petroleum composition. The reliability of the fractions’ concentration results is determined by the mass of the separated fraction, with completely reliable results achievable for masses exceeding 1.4 mg. The fraction’s mass can also be used to evaluate the relative expanded uncertainty of a single separation procedure. As the mass and concentration of the fraction increase, the relative expanded uncertainty of the concentration decreases, and this can be modelled using a power function.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"196 ","pages":"Article 104850"},"PeriodicalIF":2.6,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0146638024001153/pdfft?md5=bb75b2d1640851c10960117df10e01ad&pid=1-s2.0-S0146638024001153-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142040987","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":"From swamp to sea: Quantifying terrestrial dissolved organic carbon in a tropical shelf sea using hydrogen isotope ratios","authors":"A’an Johan Wahyudi ,&nbsp;Nikita Kaushal ,&nbsp;Cristian Gudasz ,&nbsp;Patrick Martin","doi":"10.1016/j.orggeochem.2024.104851","DOIUrl":"10.1016/j.orggeochem.2024.104851","url":null,"abstract":"<div><p>Dissolved organic carbon (DOC) is a key component of coastal biogeochemical cycles, but its composition and reactivity depend on the relative contribution of autochthonous aquatic versus allochthonous terrigenous DOC (tDOC). In complex coastal waters, tDOC is commonly quantified using the bulk DOC stable carbon isotope ratio (<em>δ</em>¹³C_DOC). However, several limitations can hamper the use of <em>δ</em>¹³C_DOC in marine ecosystems, such as (1) the narrow and often overlapping separation of the autochthonous and allochthonous endmembers, and (2) mineralization of tDOC to dissolved inorganic carbon creates a reservoir effect such that autochthonous DOC can acquire a terrigenous-like <em>δ</em>¹³C_DOC. The stable isotope ratio of non-exchangeable hydrogen in the DOC (<em>δ</em>²H_n) has emerged as a new tool that can potentially overcome these limitations: (1) <em>δ</em>²H_n has a large separation between aquatic and terrigenous endmembers (&gt;50‰) and (2) it is not subject to reservoir effects caused by tDOC mineralization. Here, we evaluate the potential of <em>δ</em>²H_n obtained from solid phase-extracted dissolved organic matter (SPE-DOM), by comparing it to <em>δ</em>¹³C_DOC and chromophoric DOM (CDOM) optical properties. We collected samples at a site in Southeast Asia’s Sunda Shelf that experiences substantial seasonal variation in tDOC input, driven primarily by the monsoon-induced physical advection of peatland-derived tDOC. Over a 1-year monthly time series, the terrigenous fraction of DOC (<em>f</em>_terr) determined using <em>δ</em>²H_n of SPE-DOM and <em>δ</em>¹³C_DOC of bulk DOC was well correlated (r² = 0.42), and there was no significant difference in <em>f</em>_terr between the two isotope systems. In fact, <em>δ</em>²H_n displayed slightly stronger correlations with salinity and CDOM optical properties compared to <em>δ</em>¹³C_DOC. Our results indicate that <em>δ</em>²H_n of SPE-DOM is effective for quantifying tDOC across coastal gradients, potentially offering greater sensitivity than <em>δ</em>¹³C_DOC, and is a viable alternative in settings where <em>δ</em>¹³C_DOC is inadequate.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"196 ","pages":"Article 104851"},"PeriodicalIF":2.6,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142040988","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":"Electrospray ionisation suppression in aquatic dissolved organic matter studies – Investigation via liquid chromatography–mass spectrometry","authors":"Jeffrey A. Hawkes","doi":"10.1016/j.orggeochem.2024.104852","DOIUrl":"10.1016/j.orggeochem.2024.104852","url":null,"abstract":"<div><p>Ionisation suppression is a persistent issue in electrospray ionisation mass spectrometry, which decreases the signal of co-eluting analytes. In non-targeted analysis, where analyte and organic matrix identity is unknown, this poses a very challenging analytical problem when it comes to quantitatively assessing differences between samples, including in a compositional sense. In this study, I demonstrate the problems that arise due to ionisation suppression using a very simple sample mixing scheme between a fresh, metabolite rich sample (a leaf leachate) and a forest pond water. Samples were analysed after solid phase extraction on Agilent PPL and using high performance liquid chromatography coupled to electrospray ionisation – Orbitrap mass spectrometry, charged aerosol detector and diode array detector, the latter two allowing quantification of eluting material. I found that more than half of the well-resolved analytes expected to be present (at equal concentration) were completely lost from detection after mixing with pond water DOM. The average recovery of analytical signal (i.e., the signal weighted average), was about 50%, and was highly variable between analytes. Ionisation suppression also affected the signal obtained from the geochemical background DOM, and material recovery decreased slightly when mixing samples and extracting at a higher volume on PPL. Overall, the results showed that ionisation suppression is an extremely important problem for comparison of biogeochemical samples, even when only considering presence and absence of detected features. A multi detector approach and liquid chromatographic separation adds great value in comparison to use of only high resolution mass spectrometry (in direct infusion mode).</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"196 ","pages":"Article 104852"},"PeriodicalIF":2.6,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0146638024001177/pdfft?md5=ea44ab4b9d9bda29a26c158d352410bc&pid=1-s2.0-S0146638024001177-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142083610","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":"Compound-specific radiocarbon analysis of sedimentary fatty acids: Potential as a dating tool for lake sediments of Mt. Fuji volcanic region, Japan","authors":"Shinya Yamamoto ,&nbsp;Yosuke Miyairi ,&nbsp;Yusuke Yokoyama ,&nbsp;Yukihiko Serisawa ,&nbsp;Hisami Suga ,&nbsp;Nanako O. Ogawa ,&nbsp;Naohiko Ohkouchi","doi":"10.1016/j.orggeochem.2024.104860","DOIUrl":"10.1016/j.orggeochem.2024.104860","url":null,"abstract":"<div><p>Compound-specific radiocarbon analysis (CSRA) is a promising tool for dating sediment sequences where traditional dating methods are impractical. However, the applicability of CSRA of short-chain fatty acids as a dating tool remains poorly understood, especially in lacustrine settings. Accordingly, we determined the radiocarbon content (Δ¹⁴C) of individual fatty acids in sediments of Lake Yamanaka (central Japan), as well as their stable carbon and hydrogen isotope ratios, to evaluate the potential of CSRA as a dating tool in volcanic lake environments. We found that the Δ¹⁴C values of plant-derived (C₂₄, C₂₆, and C₂₈) <em>n</em>-fatty acids (–99‰ to –149‰) were considerably lower than the Δ¹⁴C of charred plants (139‰) within the sediments and those of living aquatic plants (–52‰ to –58‰) in Lake Yamanaka, suggesting that contributions from pre-aged terrestrial and aquatic plant materials likely affect these acids. Similarly, the Δ¹⁴C of C₁₆ <em>n</em>-fatty acid (–95‰) in surface sediments was much lower than the Δ¹⁴C of modern aquatic plants (–52‰ to –58‰), as well as the Δ¹⁴C of dissolved organic carbon (DIC) in surface water (–48‰). Together with the stable isotope results, we conclude that in addition to autochthonous aquatic sources, contributions from pre-aged terrestrial carbon sources significantly affect the Δ¹⁴C of C₁₆ <em>n</em>-fatty acids. Comparing fatty acid Δ¹⁴C and concentration data across lakes within the Mt. Fuji region suggests that CSRA of the C₁₆ acid provides valid chronological information only when the C₁₆ originates exclusively from autochthonous aquatic sources, with minor allochthonous terrestrial input.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"196 ","pages":"Article 104860"},"PeriodicalIF":2.6,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141998281","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":"Soil organic matter persistence in hyperhumic colluvial soils caused by palaeofires, root inputs and mineral binding","authors":"Joeri Kaal ,&nbsp;Antonio Martínez Cortizas ,&nbsp;Gerrit Angst ,&nbsp;Cynthia Kallenbach ,&nbsp;Cruz Ferro Vázquez ,&nbsp;Felipe Criado-Boado","doi":"10.1016/j.orggeochem.2024.104848","DOIUrl":"10.1016/j.orggeochem.2024.104848","url":null,"abstract":"<div><p>Understanding the formation of long-term persistent soil organic matter (SOM) is key to optimizing soil management and predicting the response of the terrestrial organic carbon (OC) pool to climate change, yet our knowledge of the soil-type dependent weight of different stabilization pathways (e.g., recalcitrance and mineral binding) is fragmentary. Owing to their stratigraphy, the exceptionally SOM-rich (up to 2 m of mineral soil with &gt;5% OC) colluvial slope deposits of Atlantic Europe (Haplic Umbrisol [colluvic/hyperhumic]) are archives of palaeo-environmental conditions including SOM formation pathways. The objective of this study was to determine how the different drivers of persistent SOM formation influenced the formation of these organic-rich soils. For this purpose, we use Holocene (∼9000 yrs) molecular composition records obtained from pyrolysis-GC–MS (Py-GC–MS) and thermally assisted hydrolysis and methylation (THM-GC–MS). The results emphasize three pathways to stability (i.e., persistence on millennial timescales): 1) palaeofires that generated recalcitrant pyrogenic SOM, 2) release of root-derived aliphatic macromolecules (suberin-like SOM), and 3) formation of microbial necromass. Pathways 1 and 2 are controlled by land use: Pathway 1 was relatively important under intense anthropogenic fire regimes and pyrophytic shrubland expansion; Pathway 2 was stimulated during early forest phases and under pasture conditions, when past societies focused vegetation management on grazing instead of fire; Pathway 3 was controlled by binding with aluminium-dominated mineral phases. However, we found indications that Pathway 2 (suberin input and preservation) relied partially on sorptive preservation as well. Aided by structured equation modeling (SEM), we show that the formation of persistent SOM pools was driven by balanced weights of i) microbial <em>vs.</em> plant-derived SOM and ii) intrinsic chemical properties of SOM (recalcitrance continuum) <em>vs.</em> mineral binding/occlusion, which varied in keeping with interactions between past land use, topography and vegetation. These findings are inconsistent with the prevalent paradigm of persistent SOM formation by sorptive/occlusive preservation of microbial necromass alone.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"195 ","pages":"Article 104848"},"PeriodicalIF":2.6,"publicationDate":"2024-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S014663802400113X/pdfft?md5=38b28a7580aa3f892f9168d1f48580c9&pid=1-s2.0-S014663802400113X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141935210","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":"Five series of benzohopanes in early Cretaceous sediments from the Chaoyang Basin, NE China","authors":"Lian Jiang ,&nbsp;Li Li ,&nbsp;Hans P. Nytoft ,&nbsp;Yunpeng Wang ,&nbsp;Simon C. George","doi":"10.1016/j.orggeochem.2024.104843","DOIUrl":"10.1016/j.orggeochem.2024.104843","url":null,"abstract":"<div><p>Five series of benzohopanes were identified in a set of immature to early-oil-window early Cretaceous sediments from the ZK1006 well, Chaoyang Basin, NE China. Series a (C₃₁-C₃₅), b (C₃₃-C₃₅), and c (C₃₁-C₃₅) benzohopanes form by different pathways, while the newly-found series d (C₃₁-C₃₄, maybe to C₃₅?) and e (C₃₁-C₃₂, maybe to C₃₅?) benzohopanes have similar formation mechanisms. Series a is usually the predominant benzohopane series, but occasionally samples are dominated by series c benzohopanes. Series b benzohopanes may be associated with terrigenous organic matter. Series a and b benzohopanes are possibly influenced by redox properties, while paleosalinity more likely controls the formation and enrichment of series c benzohopanes. Two novel parameters (a benzohopane index, and the C₃₅/C₃₄ benzohopane ratio) are proposed to be useful paleoenvironmental proxies in the study area. A high benzohopane index and C₃₅/C₃₄ benzohopane ratio may indicate an anoxic environment.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"195 ","pages":"Article 104843"},"PeriodicalIF":2.6,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0146638024001086/pdfft?md5=4f48228f7edbb96b94da6c27c1774a94&pid=1-s2.0-S0146638024001086-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883037","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}