American Journal of Science最新文献

{"title":"Resetting of Shallow-Water Carbonate Boron Isotope Values During Marine Burial Diagenesis","authors":"Mingyu Zhao, B. Beaty, L. Tarhan, Noah Planavsky","doi":"10.2475/001c.91398","DOIUrl":"https://doi.org/10.2475/001c.91398","url":null,"abstract":"The boron isotopic composition (δ11B) of bulk carbonates may provide an archive to reconstruct changes in ocean pH. Reconstructions from ancient carbonates typically assume that no significant resetting of δ11B occurred during marine burial diagenesis. However, our understanding of B isotopic behavior associated with this process remains limited. Here we provide measurements of B/Ca and B isotopic composition (δ11B) from a modern peri-platform carbonate sequence near the Great Bahama Bank that has undergone marine burial diagenesis. Our results reveal significant decreases in both δ11B (~13 ‰) and B/Ca (~80 %) of bulk carbonates with depth. We attribute this pattern to the release of isotopically light B (δ11B ~20 ‰) to porewater during aragonite dissolution, with uptake of substantially isotopically lighter borate ions (δ11B ~-1 ‰) from porewater by newly forming low-Mg calcite. A quantitative model adds further support for this interpretation and provides an estimate of average neomorphism rate ( k0) in the range of 1×10-6 to 5×10-6 yr-1, which is comparable to previous rate estimates for neomorphism and/or recrystallization during meteoric diagenesis. Our results demonstrate the strong potential for resetting δ11B signatures in bulk carbonates during recrystallization, which must be considered in future attempts to reconstruct pH and pCO2 from these records and may require reinterpretation of existing records. Our results also suggest the potential of B isotopes as a proxy for carbonate recrystallization/neomorphism and original carbonate mineralogy.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"103 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139444745","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":"Eating behaviour, body image, and mental health: updated estimates of adolescent health, well-being, and positive functioning in Aotearoa New Zealand.","authors":"Katie M Babbott, Nathan S Consedine, Marion Roberts","doi":"10.1071/HC23048","DOIUrl":"10.1071/HC23048","url":null,"abstract":"<p><p>Introduction Body image dissatisfaction and its associated challenges have been related to poorer health outcomes among adolescents worldwide, including disordered eating behaviour, depression, and anxiety. However, current prevalence estimates of these issues in Aotearoa New Zealand or, relatedly, the estimates of positive attitudes and behaviours, such as intuitive eating and body appreciation are dated. Aim The primary aim of this paper was to provide updated estimates for a variety of constructs related to eating behaviours and body image, sourced from a diverse range of early adolescent participants. Methods For this report, a brief online survey was advertised to adolescents throughout Aotearoa New Zealand (n  = 893) via school and community noticeboards. Results Approximately one-in-three male participants and one-in-two female participants reported body image dissatisfaction. One in four participants reported clinically significant symptoms of depression and anxiety. Discussion Given such issues, there is clearly still much progress to be made in advancing positive health among early adolescents. Identifying potentially protective constructs such as intuitive eating and body appreciation may offer guidance into the best targets for prevention and early intervention.</p>","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"11 1","pages":"297-307"},"PeriodicalIF":1.2,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90903529","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 Cenozoic Record of Deep Oceanic Zn Isotopic Composition in Ferromanganese Crusts","authors":"Mingyu Zhao, Noah Planavsky, Xiangli Wang, Yiyue Zhang, J. Hein","doi":"10.2475/001c.89628","DOIUrl":"https://doi.org/10.2475/001c.89628","url":null,"abstract":"The zinc (Zn) isotopic composition (δ66Zn) of the deep ocean (>1000 m) can provide insights into the carbon cycle, the biological pump, and hydrothermal activity. However, we have an incomplete view of the temporal and spatial evolution of deep-ocean Zn isotopes. Here, we present new δ66Zn values of Fe-Mn crusts from the Pacific Ocean, which we used to reconstruct the evolution of deep-ocean δ66Zn for the Cenozoic. Our results suggest that the δ66Zn values remain stable in the deep Pacific Ocean at around ~ 0.5‰ through the Cenozoic. Our results limit the extent of change in organic zinc burial through the Cenozoic. However, given uncertainties in the global mass balance and analytical error, variations of roughly 20% in organic zinc burial are still possible.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"26 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139269385","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insights Into the Terminal Ediacaran Marine Carbonate Record From Shale-Hosted Carbonate Carbon Isotopes","authors":"Fred Bowyer, Mariana Yilales, Rachel Wood, Simon W. Poulton","doi":"10.2475/001c.88082","DOIUrl":"https://doi.org/10.2475/001c.88082","url":null,"abstract":"The marine carbon isotope record (δ 13 C) used for chemostratigraphy and reconstruction of carbon cycle dynamics is commonly assembled using carbonate rocks. There is, however, evidence that carbonate cements hosted within fine-grained clastics (shales and mudstones) in some settings may also express δ 13 C trends that covary with the record from carbonates. We present new carbon and oxygen isotopic data from shale-hosted carbonate cements (herein termed δ 13 C carb-sh and δ 18 O carb-sh, n = 107, <16 wt% CaCO 3 ) of the terminal Ediacaran Nama Group, Namibia (≥550.5 to <539.6 Million years ago; Ma). These data are compared with the published carbon and oxygen isotopic record from coeval carbonates (δ 13 C carb and δ 18 O carb , n = 1611) and total organic carbon (TOC) concentrations. We show that, in the Nama Group, δ 13 C carb-sh compositions in samples of intermediate to high CaCO 3 /TOC (>0.4) can approximate contemporaneous δ 13 C carb in open marine mixed carbonate-clastic settings. By contrast, δ 13 C carb-sh values in samples with low CaCO 3 /TOC (<0.4) that were deposited in clastic settings distant from the locus of carbonate deposition are more negative than contemporaneous δ 13 C carb . These data suggest that δ 13 C carb-sh may approach seawater composition in samples with low TOC when deposited in settings characterized by high CO 3 2- concentration, where carbonate can rapidly precipitate from seawater during early diagenesis. However, the use of δ 13 C carb-sh to infill gaps in the existing δ 13 C carb record remains uncertain, even when these criteria are fulfilled. Intervals of δ 13 C-δ 18 O co-variability in the Nama Group succession appear to correlate with units where seawater mixing with meteoric fluids was more likely during early diagenesis, such as clastic-dominated settings, which also show significant decreasing δ 18 O through time with gradual sub-basin infill. We further consider uncertainties in lithostratigraphic correlation of the upper Urusis Formation of the Nama Group that enable three new possible correlations to be proposed for δ 13 C carb-sh data within the terminal Ediacaran to lower Cambrian (<542.65 Ma to >532 Ma) regional and global δ 13 C carb records.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":" 36","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135341432","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":"Oxygen Isotopes of Iron Oxides as a Diagnostic Tool for Iron Formation-Hosted High-Grade Magnetite-Hematite Deposits","authors":"Flávia Cristina Silveira Braga, Carlos Alberto Rosière, Andreas Pack, Steffen G. Hagemann, João Orestes Schneider Santos","doi":"10.2475/001c.88909","DOIUrl":"https://doi.org/10.2475/001c.88909","url":null,"abstract":"Coarse-grained granoblastic magnetite-hematite and sheared platy hematite iron orebodies comprise several small deposits (5 to 30 Mt each) on the eastern margin of the São Francisco Craton, bordering the Ediacaran–Cambrian Brasiliano Orogenic belt. Three main mineralization stages are associated with the Brasiliano Orogeny: (1) syn- to the late-collisional stage ( ca . 580–560 Ma) with development of lens-shaped schistose orebodies along thrust planes. (2) late- to the post-collisional stage ( ca . 560–530 Ma) with the formation of massive magnetite bodies by contact metamorphic-metasomatism with pegmatite. (3) Post-tectonic stage with crystallization of granular hematite associated with late pegmatite ( ca . 530–490 Ma). In order to better evaluate the fluid oxygen signature of each mineralization stage, new oxygen isotopes measurements were performed on ore bodies associated with the three stages. These stages are followed by changes in the oxygen isotope signature, with a progressive decrease of the δ18O from the iron formation (1.7 to 8.1‰) to high-grade ore (-1.6 to 2.6‰) that appears to be a common aspect of the mineralization of iron formations. In the present cases, magmatic fluids (δ 18 O from 4.6 to 13.1‰) have imprinted a relatively “heavier” signature than the most hypogene iron formation high-grade ores worldwide that was progressively modified by meteoric water percolated along extensional fractures. The iron oxides from the contact zones of pegmatitic yielded intermediate δ 18 O values (1.8 to 5.0‰), indicating a higher magmatic fluid/rock ratio.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134908788","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":"Chemical Alteration of Riverine Particles in Seawater and Marine Sediments: Effects on Seawater Composition and Atmospheric CO₂","authors":"Klaus Wallmann, Sonja Geilert, Florian Scholz","doi":"10.2475/001c.87455","DOIUrl":"https://doi.org/10.2475/001c.87455","url":null,"abstract":"Numerous studies have shown that riverine particles react with seawater. Reactions include dissolution of reactive silicate minerals (e.g., feldspars) and formation of authigenic clays and carbonates. Previous studies have either focused on mineral dissolution (marine silicate weathering) or authigenic phase formation (reverse weathering). A comprehensive study that assesses all processes affecting the marine alteration of riverine particle has -to our knowledge- not yet been conducted. Our contribution aims to fill this gap. We first quantify cation exchange between seawater and riverine particles that occurs when particles enter the marine realm and show that significant global cation fluxes are induced by this process (-1.3 Tmol Na yr -1 , -0.2 Tmol K yr -1 , -0.4 Tmol Mg yr -1 , +1.2 Tmol Ca yr -1 ) where the positive sign indicates cation release into seawater while the negative sign denotes uptake on particles. We then use thermodynamic and kinetic modeling to investigate how much of the suspended particle load dissolves in contact with seawater and estimate corresponding global release rates for dissolved cations and silica assuming congruent dissolution (+0.06 Tmol Na yr -1 , +0.15 Tmol Ca yr -1 , +2.8 Tmol Si yr -1 ). Subsequently, we investigate rates of mineral dissolution and authigenic clay and carbonate formation in marine sediments applying reactive transport modeling, porewater data and mass balance calculations. Our best estimates for net fluxes across the sediment/water interface (dissolution–mineral formation) result as +1.5 Tmol Na yr -1 , -2.5 Tmol K yr -1 , -2.0 Tmol Mg yr -1 , +2.5 Tmol Ca yr -1 , and +1.9 Tmol Si yr -1 where most of the Na and Ca release is induced by plagioclase dissolution, K is taken up in authigenic clays and Mg is removed from solution by authigenic clay and carbonate formation. We conclude that the alkalinity of seawater is not significantly affected by marine silicate alteration since cation release fluxes (Na, Ca) are as high as cation uptake fluxes (K, Mg) on equivalent basis. Moreover, marine silicate weathering and reverse weathering are closely coupled since Al required for clay formation is mostly provided by feldspar dissolution while Al removal in authigenic clay promotes and maintains feldspar dissolution in marine sediments. Authigenic carbonate formation in anoxic subsurface sediments sequesters significant amounts of carbon (2.5 Tmol C yr -1 ) according to our estimates where most of the Ca and alkalinity required for carbonate formation are provided by the dissolution of Ca-bearing silicate minerals. This hidden sedimentary cycle provides a sink for dissolved inorganic carbon that may drive a slow draw-down of atmospheric CO 2 on geological timescales. Marine silicate alteration has an even stronger effect on the geochemical evolution of seawater by generating large fluxes of dissolved K, Mg, Ca and Si.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135060618","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":"The Influence of Warming on Phosphorus Burial in Continental Margin Sediments","authors":"Mingyu Zhao, L. Tarhan, N. Planavsky, T. Isson","doi":"10.2475/001c.85110","DOIUrl":"https://doi.org/10.2475/001c.85110","url":null,"abstract":"The marine phosphorus cycle plays a critical role in regulating rates of primary productivity and thus the size of the marine biosphere. Yet, the cumulative effects of temperature change—and warming, in particular—on marine phosphorus burial remain poorly understood. Here, we explore a benthic biogeochemical model that accounts for the compounded effect of temperature on the kinetics of key diagenetic reaction pathways, diffusion coefficients, seawater pH, dissolved O2 concentration and bioturbation, in order to provide a new predictive framework for understanding the temperature response associated with P burial in continental margin settings. We find that temperature has a direct and positive impact on marine phosphorus burial, as it directly increases the formation rate of key mineral P-removal pathways—foremost carbonate fluorapatite (CFA). The increase in authigenic P burial during climate warming is likely to partially counter the effects of increased water-column P regeneration rate during climate warming events, and thus influence the extent of oceanic anoxia and organic matter burial, a factor that should be considered when assessing the response of the P cycle in the face of warming.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"1 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2023-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43236384","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":"Isotope Ratio – Discharge Relationships of Solutes Derived From Weathering Reactions","authors":"J. Druhan, P. Benettin","doi":"10.2475/001c.84469","DOIUrl":"https://doi.org/10.2475/001c.84469","url":null,"abstract":"To date, the vast majority of studies seeking to link discharge to solute concentrations have been based on representations of fluid age distributions in watersheds that are time-invariant. As increasingly detailed spatial and temporal datasets become available for weathering-derived riverine solute concentrations, the capacity to link this mass flux to transient routing of reactive fluids through Critical Zone environments is vital to quantitative interpretation. Relationships between fluid age distributions and the stable isotope ratios of these geogenic solutes are even less developed, yet these signatures are vital to parsing the suite of water-rock-life interactions that create concentration-discharge relationships. Here we offer the first merging of a hydrological model featuring time-variant fluid age distributions with a geochemical model for isotopically fractionating weathering reactions. Using SiO2(aq) and the corresponding silicon isotope ratio δ30Si as an example, we show that the stable isotope signatures of riverine solutes produced by weathering reactions reflect a component of the fluid age distribution that is unique to the corresponding solute concentrations. This distinct sensitivity is the result of a stronger link between isotope ratios and the age distribution parameters describing a given watershed. This novel modeling framework is used to provide a quantitative basis for the interpretation of SiO2(aq) and δ30Si in six low-order streams spread across a diversity of climates, geologies, and ecosystems. To our knowledge, this is the first forward and process-based model to describe the isotopic signatures of solutes derived from weathering reactions in watersheds subject to time-varying discharge.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2023-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46281840","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":"[Prognostic value of periprocedural dynamics of left ventricular ejection fraction and subclinical pulmonary congestion in patients with myocardial infarction].","authors":"T M Timofeeva, Z D Kobalava, A F Safarova, F Cabello Montoya","doi":"10.26442/00403660.2023.04.202159","DOIUrl":"10.26442/00403660.2023.04.202159","url":null,"abstract":"<p><strong>Aim: </strong>To assess the joint prognostic value of periprocedural dynamics of the left ventricular ejection fraction (PPD of LVEF) and subclinical pulmonary congestion during lung stress ultrasound in patients with first acute myocardial infarction (AMI) and percutaneous coronary intervention (PCI) in relation to the development of heart failure (HF) in the postinfarction period.</p><p><strong>Materials and methods: </strong>Our prospective, single-centre, observational study included 105 patients with a first MI with no HF in the anamnesis and successful PCI. All patients underwent standard clinical and laboratory tests, NT-proBNP level assessment, echocardiography, lung stress ultrasound with a 6-minute walk test. All patients had no clinical signs of heart failure at admission and at discharge. Criteria for PPD of LV EF: improvement in LV EF≥50%; ∆LV EF more than 5%, but LV EF<50%. According to the results of lung stress ultrasound, pulmonary congestion was diagnosed: mild (2-4 B-lines), moderate (5-9 B-lines) and severe (≥10 B-lines). The end point was hospitalization for HF for 2.5 years.</p><p><strong>Results: </strong>Upon admission, LV EF of 50% or more was registered in 45 patients (42.9%). Positive PPD was registered in 31 (29.5%) patients. After stress ultrasound of the lungs, 20 (19%) patients had mild subclinical pulmonary congestion, 38 (36%) moderate and 47 (45%) severe according to the criteria presented. During the observation period, patients with no PPD of LVEF were significantly more likely to be hospitalized for the development of HF (in 44.4% of cases) compared with patients with positive PPD (in 15.2% of cases) and with initial LV EF≥50% (in 13.4% of cases; <i>p</i>=0.005). When performing logistic regression analysis, the best predictive ability was found in the combination of the absence of PPD of LV EF and the sum of B-lines ≥10 on exercise (relative risk 7.45; 95% confidence interval 2.55-21.79; <i>p</i><0.000).</p><p><strong>Conclusion: </strong>Evaluation of the combination of PPD of LV EF and the results of stress lung ultrasound at discharge in patients with first AMI and successful PCI with no HF in anamnesis allows us to identify a high-risk group for the development of HF in the postinfarction period.</p>","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"27 1","pages":"296-301"},"PeriodicalIF":0.3,"publicationDate":"2023-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90921804","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":"INTEGRATED LITHO-, CHEMO- AND SEQUENCE-STRATIGRAPHY OF THE EDIACARAN GAMETRAIL FORMATION ACROSS A SHELF-SLOPE TRANSECT IN THE WERNECKE MOUNTAINS, YUKON, CANADA","authors":"J. Busch, Thomas H. Boag, E. Sperling, J. Higgins, J. Strauss","doi":"10.1130/abs/2020am-356393","DOIUrl":"https://doi.org/10.1130/abs/2020am-356393","url":null,"abstract":"The Ediacaran Gametrail Formation of northwestern Canada chronicles the evolution of a complex carbonate ramp system in response to fluctuations in relative sea level and regional tectonic subsidence alongside exceptional global change associated with the Shuram carbon isotope excursion (CIE). Here, we use extensive outcrop exposures of the Gametrail Formation in the Wernecke Mountains of Yukon, Canada, to construct a shelf-slope transect across the Shuram CIE. Twelve stratigraphic sections of the Gametrail Formation are combined with geological mapping and a suite of geochemical analyses to develop an integrated litho-, chemo-, and sequence stratigraphic model for these strata. In the more proximal Corn/Goz Creek region, the Gametrail Formation represents a storm-dominated inner to outer ramp depositional setting, while slope depositional environments in the Nadaleen River region are dominated by hemipelagic sedimentation, turbidites, and debris flows. The magnitude of the Shuram CIE is largest in slope limestones which underwent sediment-buffered diagenesis, while the CIE is notably smaller in the inner-outer ramp dolostones which experienced fluid-buffered diagenesis. Our regional mapping identified a distinct structural panel within the shelf-slope transect that was transported ~30 km via strike-slip motion during the Mesozoic–Cenozoic Cordilleran orogeny. One location in this transported structural block contains a stromatolite reef complex with extremely negative carbon isotope values down to ~ -30‰, while the other location contains an overthickened ooid shoal complex that does not preserve the characteristic negative CIE associated with the Shuram event. These deviations from the usual expression of the Shuram CIE along the shelf-slope transect in the Wernecke Mountains, and elsewhere globally, provide useful examples for how local tectonic, stratigraphic, and/or geochemical complexities can result in unusually large or completely absent expressions of a globally recognized CIE.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2023-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44227452","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}