Geochemistry Geophysics Geosystems最新文献

{"title":"How Did Westward Volcaniclastic Deposits Accumulate in the Deep Sea Following the January 2022 Eruption of Hunga Volcano?","authors":"Marcus Chaknova,&nbsp;Thomas Giachetti,&nbsp;Joali Paredes-Mariño,&nbsp;Adam Soule,&nbsp;Alexa R. Van Eaton,&nbsp;Roxanne Beinart,&nbsp;Martin Crundwell,&nbsp;Shane J. Cronin,&nbsp;Martin Jutzeler,&nbsp;Kristen E. Fauria,&nbsp;Michael A. Clare,&nbsp;Isobel A. Yeo,&nbsp;Shawn Arellano,&nbsp;Liam Kelly,&nbsp;Sally Watson,&nbsp;Rebecca Carey,&nbsp;Taaniela Kula,&nbsp;Craig M. Young","doi":"10.1029/2024GC011629","DOIUrl":"https://doi.org/10.1029/2024GC011629","url":null,"abstract":"<p>Most volcanic eruptions on Earth take place below the ocean surface and remain largely unobserved. Reconstruction of past submerged eruptions has thus primarily been based on the study of seafloor deposits. Rarely before the 15 January 2022 eruption of Hunga volcano (Kingdom of Tonga) have we been able to categorically link deep-sea deposits to a specific volcanic source. This eruption was the largest in the modern satellite era, producing a 58-km-tall plume, a 20-m high tsunami, and a pressure wave that propagated around the world. The eruption induced the fastest submarine density currents ever measured, which destroyed submarine telecommunication cables and traveled at least 85 km to the west to the neighboring Lau Basin. Here we report findings from a series of remotely operated vehicle dives conducted 4 months after the eruption along the Eastern Lau Spreading Center-Valu Fa Ridge. Hunga-sourced volcaniclastic deposits 7–150 cm in thickness were found at nine sites, and collected. Study of the internal structure, grain size, componentry, glass chemistry, and microfossil assemblages of the cores show that these deposits are the distal portions of at least two ∼100-km-runout submarine density currents. We identify distinct physical characteristics of entrained microfossils that demonstrate the dynamics and pathways of the density currents. Microfossil evidence suggests that even the distal parts of the currents were erosive, remobilizing microfossil-concentrated sediments across the Lau Basin. Remobilization by volcaniclastic submarine density currents may thus play a greater role in carbon transport into deep sea basins than previously thought.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011629","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Analysis of Paleointensity Results Under Different Interpretation Approaches: A Case Study on the Korkhi Volcanic Sequence (Lesser Caucasus, Georgia)","authors":"Elisa M. Sánchez-Moreno,&nbsp;Manuel Calvo-Rathert,&nbsp;Avto Goguitchaichvili,&nbsp;George T. Vashakidze,&nbsp;Lisa Tauxe,&nbsp;Pierre Camps,&nbsp;Juan Morales-Contreras,&nbsp;Vladimir A. Lebedev,&nbsp;Néstor Vegas,&nbsp;Nayeli Pérez-Rodriguez,&nbsp;Ketino Gabarashvili","doi":"10.1029/2023GC011382","DOIUrl":"https://doi.org/10.1029/2023GC011382","url":null,"abstract":"<p>In this study we focus on the investigation of the absolute intensity records of two volcanic subsequences, aiming to enrich the global paleointensity database for the last 5 Ma, which currently shows important dispersion. We present new absolute paleointensities obtained from the Plio-Pleistocene volcanic sequence of Korkhi (Djavakheti Highland, Georgia) (41°27′31″N, 43°27′55″E). Korkhi is divided into two lava flow subsequences dated at 3.11 ± 0.20 Ma and 1.85 ± 0.08 Ma. Paleomagnetic directions previously published (Sánchez-Moreno et al., 2018, https://doi.org/10.1029/2017GC007358) show a normal polarity in the lower Korkhi subsequence and a reverse-to-intermediate polarity in the upper Korkhi subsequence. The new paleointensity determinations are obtained through two different Thellier-type protocols (Thellier-Thellier and IZZI) and the corrected multispecimen method. We utilize different selection criteria and interpretation approaches (TTB, CCRIT, BiCEP and multimethod), and we make a critical evaluation on their application on complex magnetic behaviors, such as often found in volcanic rocks. Finally, we obtained a paleointensity of 70 μT in upper Korkhi and 14 paleointensities in lower Korkhi that vary between 5.2 and 37.2 μT. These results agree with a recently proposed non-Geocentric Axial Dipole (GAD) hypothesis for the last ∼1.5 Ma (Cych et al., 2023, https://doi.org/10.1029/2023JB026492), and with low field strength for the 3–4 Ma.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GC011382","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143786975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Linking Cenozoic Magmatism in the North-Central Tibetan Plateau With Plateau Growth","authors":"Peng Guo,&nbsp;Ting Yang,&nbsp;Wei-Qiang Ji","doi":"10.1029/2024GC011898","DOIUrl":"https://doi.org/10.1029/2024GC011898","url":null,"abstract":"<p>Accurate reconstruction of paleo-crustal and lithospheric thicknesses is crucial for understanding the deep geodynamic processes driving the uplift and growth of the Tibetan Plateau (TP) and their association with Cenozoic magmatism. We reconstruct the Cenozoic crustal thickness evolution of the north-central TP using a machine learning model for intermediate to felsic rocks, and estimate the lithospheric thickness based on geobarometers for mafic magmas. We find that the northern Qiangtang terrane (QT) underwent crustal thickening during the late Cretaceous-early Eocene, with the crust thickening to 60.2 ± 4.8 km by 45 Ma, while the lithospheric thickness was only 60.9 ± 4.5 km. This suggests wholesale delamination of the lithospheric mantle shortly before ∼45 Ma, explaining the formation of high MgO adakitic rocks and the uplift of the Tanggula Mountain to ≥5 km. To the south, the southern QT crust thickened by ∼16 km during the late Eocene-early Oligocene, contributing to ≥2 km uplift of the valley south of the Tanggula Mountain. To the north the Songpan-Ganzi terrane (SGT) had a crustal thickness of 60.6 ± 3.6 km at ∼18 Ma and underwent ∼25 km of lithospheric thinning during ∼16–13 Ma. This process contributed to the formation of Miocene shoshonitic mafic rocks and adakitic rocks in the SGT, and the uplift of the Hoh-Xil Basin to its present elevation. The recovered crustal and lithospheric thickness evolution demonstrates that progressive removal of the lower lithosphere following crustal shortening is the main driver for the uplift and magmatism of different regions in the TP.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011898","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143793722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Construction of Ultraslow-Spreading Oceanic Crust: New Insights on Volcanic Processes and Deposits From High-Resolution Mapping at the Mohns Ridge","authors":"Håvard Hallås Stubseid,&nbsp;Anders Bjerga,&nbsp;Ryan Portner,&nbsp;Haflidi Haflidason,&nbsp;Rolf Birger Pedersen","doi":"10.1029/2024GC012141","DOIUrl":"https://doi.org/10.1029/2024GC012141","url":null,"abstract":"<p>The volcanic activity at ultraslow-spreading ridges is less understood compared with that at faster-spreading ridges. Studies of year-to-year changes along the faster-spreading ridges have provided important information regarding the size and frequency of eruptions. However, ultraslow-spreading ridges produce less frequent eruptions, limiting the possibility to study short-term changes in the seafloor morphology to understand longer-term volcanic processes. Therefore, a different approach is needed to estimate the size and frequency of volcanic eruptions at the slowest spreading ridges. Here, we use meter-scale bathymetric maps and backscatter data together with visual observations and geochronology of both basalts and sediments to study the construction of three axial volcanic ridges (AVRs) along the northern half of the ultraslow-spreading Mohns Ridge. Our study finds that most eruptions produce low-effusion rate pillow lavas (82% of the volcanic terrain). We define “lava flow units” as mappable building-blocks of the ARVs, each with a coherent morphology, which may be emplaced during multiple eruptions, but we envision over a relatively short time span (years to decades). These units vary in size from individual hummocks to larger edifices (0.42 × 10⁶ to 38 × 10⁶ m³). Moreover, we estimate the eruptive frequencies per AVR to be on a hundred-year scale. These spatial-temporal constraints in AVR volcanism offer insight into long-term magma flux and spatial focusing along magma-starved ultraslow spreading ridge systems.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012141","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143786848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Tracing the Contribution of Abiotic Methane in Deep Natural Gases From the Songliao Basin, China Using Bulk Isotopes and Methane Clumped Isotopologue 12CH2D2","authors":"Jiacheng Li,&nbsp;Qingmei Liu,&nbsp;Wenmin Jiang,&nbsp;Yun Li,&nbsp;Yanhua Shuai,&nbsp;Yongqiang Xiong","doi":"10.1029/2024GC011705","DOIUrl":"https://doi.org/10.1029/2024GC011705","url":null,"abstract":"<p>The identification and evaluation of abiotic methane remain an active research area due to uncertainties in traditional indicators that may lead to “false-positive” detections. As an emerging isotopic tool, methane clumped isotope can provide novel information about the generation and post-generation processes of methane gases. Using six deep natural gas samples from the Songliao Basin, we explored the potential of clumped isotopes in identifying abiotic methane. The results indicate that the Δ¹³CH₃D values of all samples are consistent with the thermodynamic equilibrium values at the inferred formation temperatures, whereas the Δ¹²CH₂D₂ values show small but detectable deficits (1∼6‰) relative to equilibrium. This particular non-equilibrium clumped isotopic signature of natural gas from the Songliao Basin is similar to the clumped isotopic signature of abiotic methane predicted by an isotopologue-specific kinetic model, suggesting a possible contribution of abiotic methane in the studied natural gases. However, we found that the mixing of abiotic and thermogenic gases could not fully explain the isotope data of all the samples. The proportion of abiotic gas calculated based on clumped isotopes would be underestimated because methane isotopic bond re-ordering at the late burial temperatures partially erases the disequilibrium signatures inherited from the original mixtures. The carbon isotopic reversals in C₁–C₃ of the samples provide additional constraint for evaluating the contribution of abiotic gas. Therefore, the coupling of intra-molecular clumped isotope and inter–molecular carbon isotope signatures may be a more robust approach for identifying abiotic methane, which can help us to quantitatively evaluate abiotic methane in petroleum systems.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011705","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143778426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Effect of Cleaning Procedures on the Mg/Ca Ratio of Single-Specimen Planktic Foraminifera","authors":"P.-T. Lee,&nbsp;S. L. Ho,&nbsp;J. Groeneveld,&nbsp;M. Mohtadi,&nbsp;C.-C. Shen,&nbsp;C.-C. Su","doi":"10.1029/2024GC011975","DOIUrl":"https://doi.org/10.1029/2024GC011975","url":null,"abstract":"<p>Single-specimen analysis of planktic foraminiferal geochemistry has gained increasing popularity for its potential in reconstructing climate variability. However, the comparability between single-specimen and conventional multi-specimen Mg/Ca data remains unclear, which has raised questions concerning the suitability of multi-specimen Mg/Ca-temperature calibrations for single-specimen data. This study developed and evaluated the effects of four single-specimen cleaning procedures on the Mg/Ca ratio of <i>Trilobatus sacculifer</i>. These procedures varied in their inclusion or exclusion of the reductive step and heating for chemical reactions. The most effective single-specimen cleaning procedure (procedure D_single) incorporated the oxidative step while excluding the reductive step and heating. This procedure was subsequently applied to five additional planktic foraminifera species. With procedure D_single, we obtained statistically indistinguishable mean Mg/Ca values for single-specimen and multi-specimen samples of <i>T. sacculifer, Orbulina universa</i>, and <i>Pulleniatina obliquiloculata</i>, regardless of the intensity of the multi-specimen cleaning procedures. For single-specimen samples of <i>Globigerinoides ruber</i> and <i>Neogloboquadrina dutertrei</i>, the mean Mg/Ca values only matched those of the multi-specimen samples when procedures excluded the reductive step and heating. In contrast, single-specimen mean Mg/Ca values of <i>Globorotalia menardii</i> were consistently higher than those obtained through multi-specimen cleaning. The mean Mg/Ca differences between single-specimen and multi-specimen cleaning procedures across species are likely attributable to differences in the microstructure of the calcite tests. In summary, when cleaning procedures involving identical steps and heating conditions were utilized, both single-specimen and multi-specimen analyses yielded comparable mean Mg/Ca values, suggesting that the multi-specimen Mg/Ca calibrations are applicable to single-specimen data.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011975","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143778427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Processes and Products of Turbidity Currents and Submarine Landslides in a Glacierized Fjord (Southwind Fjord, Baffin Island)","authors":"Alexandre Normandeau,&nbsp;Kevin MacKillop,&nbsp;Clark Richards,&nbsp;Genevieve Philibert,&nbsp;Jean-Carlos Montero-Serrano,&nbsp;Meaghan Macquarrie,&nbsp;Robbie Bennett","doi":"10.1029/2024GC011710","DOIUrl":"https://doi.org/10.1029/2024GC011710","url":null,"abstract":"<p>Sediment transported to fjords is redistributed by turbidity currents and sometimes fails on steep sidewall slopes, forming marine geohazards that are known to impact infrastructure. Since marine geohazards are poorly understood in Arctic Fjords due to lack of data and monitoring, a comprehensive study of Southwind Fjord, Baffin Island, was undertaken to assess the modern processes leading to marine geohazards and their products on the seabed. Repeat measurements of bathymetric changes and flow measurements from moorings revealed that turbidity currents with measured speeds up to 1.75 ms⁻¹ lead to the migration of cyclic steps in the submarine channel of the prodelta. Fast and dense heads of turbidity currents transport sand kilometers away from the channel-mouth during larger events and remain confined in the prodelta channel and on the fjord basin floor. Clayey silts are deposited on the sidewalls of the fjord as a result of both overflowing turbidity currents and settling of meltwater plumes. Since sand is confined to the fjord bottom, there is no regional weak layer on the sidewall that is responsible for the large number of submarine landslides observed on the slopes. Low factor of safety of sidewall sediment (1.7 at 2.5 m depth) indicates that limited environmental loading of the sediment can trigger shallow (≤3 m) failures. This is confirmed by repeat bathymetric and core data showing asynchronous failures caused by icebergs and subaerial debris flows. This study provides a comprehensive overview of modern seabed processes and provides new perspectives on the wide variability of causes of marine geohazards in glacierized fjords that will be useful to interpret other similar environments with limited seafloor data.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011710","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143770275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Investigating the Lid Effect on the Generation of Ocean Island Basalts: 2. Geodynamical Simulations","authors":"Shihao Jiang,&nbsp;Thomas Duvernay,&nbsp;Mark J. Hoggard,&nbsp;Rhys Hawkins,&nbsp;Ian H. Campbell,&nbsp;D. Rhodri Davies","doi":"10.1029/2024GC012123","DOIUrl":"https://doi.org/10.1029/2024GC012123","url":null,"abstract":"<p>The concept that oceanic lithosphere mechanically limits upwelling and decompression melting of mantle plumes is known as the <i>lid effect</i> and is backed up by observations of ocean island basalt (OIB) geochemistry. Nevertheless, in a recent companion study on OIB geochemistry, several additional factors were identified that further influence OIB compositions including a <i>melt-flux filter</i>, whereby plumes with small melt fluxes progressively fail to be sampled in regions of thicker lithosphere. Here, we use 3-D coupled geochemical-geodynamical simulations of decompression melting in a single-lithology mantle plume to predict basalt trace element concentrations for comparison with observations. In addition to supporting the role of the <i>lid effect</i> and <i>melt-flux filter</i>, our models demonstrate that, if it is possible to extract local melts from across the melting domain without complete homogenization, much of the spread in OIB geochemistry observed at individual ocean islands can be reproduced using a single source lithology. Nevertheless, we also find that an OIB source composed solely of primitive mantle contains insufficient rare earth element enrichment, necessitating a recycled crustal component.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012123","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143770276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Comment on “Unveiling the Transition From Paleolake Lisan to Dead Sea Through the Analysis of Lake Paleoshorelines and Radiometric Dating of Fossil Stromatolites” by Jara-Muñoz et el.","authors":"A. Torfstein,&nbsp;S. L. Goldstein,&nbsp;Y. Bartov,&nbsp;M. Stein,&nbsp;Y. Enzel","doi":"10.1029/2024GC011972","DOIUrl":"https://doi.org/10.1029/2024GC011972","url":null,"abstract":"<p>Jara-Muñoz et al. report a new set of U-Th and ¹⁴C dates obtained from stromatolites scattered along the western slopes of the Dead Sea escarpment and use them to establish a new lake-level curve for part of the last glacial cycle. This curve is fundamentally different from previous reconstructions (Bartov et al., 2002, 2003; Hazan et al., 2005; Lisker et al., 2009; Machlus et al., 2000; Torfstein, Goldstein, Stein, &amp; Enzel, 2013) and is characterized by very significant vertical uncertainties, which in practice, ignore the millennial-timescale resolution of Lake Lisan dynamics that has been widely discussed before (Bartov et al., 2003; Haase-Schramm et al., 2004; Torfstein, Goldstein, Stein, &amp; Enzel, 2013), with important implications for understanding regional hydroclimate regimes and linkage to global climate engines. The differences between the new and previous lake-level reconstructions warrant a critical evaluation of the new findings. We argue that rather than strengthening and refining the existing body of observations, the new data have been used separately, resulting in a misleading record.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011972","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143741563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Seismic Stratigraphy of Valdivia Bank, South Atlantic and Implications for Oceanic Plateau Evolution, Sedimentation, and Thermal Rejuvenation","authors":"E. Contreras,&nbsp;W. Sager,&nbsp;V. Spiess,&nbsp;N. Fekete,&nbsp;B. Wu,&nbsp;H. Zhou","doi":"10.1029/2024GC011833","DOIUrl":"https://doi.org/10.1029/2024GC011833","url":null,"abstract":"<p>Valdivia Bank (VB) is an oceanic plateau in the South Atlantic that formed from hotspot-ridge volcanism during the Late Cretaceous at the Mid-Atlantic Ridge (MAR). It is part of Walvis Ridge (WR), a quasi-linear seamount chain extending from offshore Namibia to Tristan da Cunha and Gough Islands. To understand Valdivia Bank evolution, we interpret the seismic stratigraphy from multichannel seismic data paired with coring results from International Ocean Discovery Program (IODP) Expedition 391, which recovered mostly pelagic nannofossil ooze and chalks. The seismic section can be divided into three seismic units (SU), a lower transparent interval which is faulted and conforms to basement, a middle, moderate to high amplitude interval which is thick in local depocenters such as rifts, and an upper, subparallel transparent interval. Notable features include regional unconformities, dipping clinoforms, mass transport and contourite deposits, and volcanic structures. Additionally, three infilled rifts are observed across the plateau. Our analysis implies that following a period of sedimentation in the Campanian, the edifice was faulted through the Paleocene, coinciding with a South Atlantic tectonic reorganization. Local depocenters formed as a result of rifting. Subsequently, the plateau experienced thermal rejuvenation and regional uplift during the Eocene. Volcanic mounds were emplaced atop Cretaceous sediments and intrusives were emplaced within the sediments. During the Cenozoic, sedimentation was punctuated, likely in response to changes in the carbonate compensation depth and bottom current intensification. VB sedimentation was complex and largely influenced by the paleoceanographic context of the plateau, as well as thermal rejuvenation and tectonism.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011833","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143741564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}