Article
Geochemistry & Geophysics
Chun Fung Chiu, Tim C. Sweere, Matthew O. Clarkson, Gregory F. de Souza, Rick Hennekam, Derek Vance
Summary: This study investigates the elemental concentrations and isotope compositions of molybdenum (Mo) and uranium (U) in anoxic organic-rich sediments of the Eastern Mediterranean. The high-resolution profiles of Mo and U provide detailed insights into the processes leading to euxinia and the different redox potentials of the sediments. The findings highlight the importance of combining these proxies for reconstructing local redox and hydrographic conditions.
EARTH AND PLANETARY SCIENCE LETTERS
(2022)
Article
Geochemistry & Geophysics
Weiqi Yao, Stefan Markovic, Adina Paytan, Andrea M. Erhardt, Ulrich G. Wortmann
Summary: The study explores the role of biogeochemical sulfur cycling during the Eocene-Oligocene transition, reporting a decline in seawater sulfate isotope values. Quantitative modeling suggests a significant reoxidation of sulfide from shelf sediments, affecting marine pH and alkalinity. The numbers are similar in magnitude to those observed during Pleistocene glaciations.
EARTH AND PLANETARY SCIENCE LETTERS
(2021)
Article
Geochemistry & Geophysics
Richard M. Gaschnig, Christopher T. Reinhard, Noah J. Planavsky, Xiangli Wang, Dan Asael, Matthew G. Jackson
Summary: Molybdenum and uranium isotopes show significant variability in lava samples from Pitcairn, the Samoan Islands, and St. Helena. Most samples have lower δMo-98 values compared to MORB, but similar δU-238 values. Influence of subducted sediments and incorporation of ancient subducted ocean crust may contribute to the observed isotopic compositions.
Article
Geochemistry & Geophysics
Yan Yuan, Tianyu Chen, Feifei Zhang, Yuanyuan Liu, Guolin Xiong, Guang-Yi Wei, Tais W. Dahl, Wen Yan, Hong-Fei Ling, Hai Cheng, Shu-Zhong Shen
Summary: The uranium isotope ratio in marine carbonates is an important tool for reconstructing past oceanic redox conditions. However, diagenetic processes may complicate this proxy by introducing isotopically heavy uranium into the carbonates. This study quantifies the valence states of trace amounts of uranium in geological carbonate samples and finds that modern coral carbonates faithfully record uranium from seawater. Surprisingly, drill core samples from a modern coral carbonate platform show a significant positive correlation between a specific valence state of uranium and the uranium isotope ratio, suggesting the presence of this valence state in marine carbonates and its influence on the uranium isotope ratio. The study suggests that coupled valence and isotope analyses of uranium in marine carbonates could provide critical constraints for reconstructing marine redox evolution.
GEOCHIMICA ET COSMOCHIMICA ACTA
(2023)
Article
Geochemistry & Geophysics
Ashley N. Martin, Monika Markowska, Allan R. Chivas, Stefan Weyer
Summary: Uranium isotopes (238U/235U) are widely used to reconstruct the redox evolution of ancient oceans and the atmosphere. Questions remain about U isotope fractionation during carbonate precipitation and stromatolite formation. This study examines the U isotope composition of modern stromatolites from Shark Bay, Western Australia, and finds that they can be valuable archives of seawater 238U.
GEOCHIMICA ET COSMOCHIMICA ACTA
(2023)
Article
Geosciences, Multidisciplinary
Vittoria Lauretano, Alan T. Kennedy-Asser, Vera A. Korasidis, Malcolm W. Wallace, Paul J. Valdes, Daniel J. Lunt, Richard D. Pancost, B. David A. Naafs
Summary: The study presents a semi-continuous terrestrial temperature record spanning from the middle Eocene to the early Oligocene, using bacterial molecular fossils preserved in lignites from southeast Australia. Results show a gradual decline in mean annual temperatures in southeast Australia, with a step cooling across the Eocene/Oligocene boundary, likely driven by changes in pCO2. Climate model simulations support these findings, indicating the importance of pCO2 decline in influencing temperatures in southeast Australia during this time period.
Article
Geosciences, Multidisciplinary
Saeedeh Senemari, Farah Jalili
Summary: This study investigated the Eocene to Oligocene palaeoenvironmental conditions in the southwest of Izeh, southwestern Iran using data from calcareous nannofossils. The presence of calcareous nannofossils in the upper part of the Pabdeh Formation indicates lithostratigraphic and biostratigraphic changes from the Priabonian to the Chattian. The findings suggest that environmental changes, possibly due to basin shallowing and a bio-event, influenced the marine phytoplankton sensitivity to climate fluctuations during the late Eocene to late Oligocene.
JOURNAL OF PALAEOGEOGRAPHY-ENGLISH
(2021)
Article
Geography, Physical
Marcus V. L. Kochhann, Jairo F. Savian, Flavia Tori, Rita Catanzariti, Rodolfo Coccioni, Fabrizio Frontalini, Luigi Jovane, Fabio Florindo, Simonetta Monechi
Summary: This paper presents a refined calcareous nannofossil biostratigraphy and an orbitally tuned age model for the Monte Cagnero section spanning the middle Eocene to the early Oligocene, revealing the evolution of Earth's climate during this period. The study found that the MECO event coincides with minimum values in the 2.4 Myr and 405 kyr eccentricity cycles, while water cooling occurred after around 36.8 million years ago.
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
(2021)
Article
Geosciences, Multidisciplinary
Matthew O. Clarkson, Tim C. Sweere, Chun Fung Chiu, Rick Hennekam, Fred Bowyer, Rachel A. Wood
Summary: Uranium isotopes (8238U) are used to trace global changes in oceanic anoxia. Poor understanding of the environmental controls on isotope enrichment during reduction leads to large uncertainties in interpretation of seawater records. This study examines the dominant controls on large U isotope enrichments, suggesting limited sedimentary U reduction in weakly euxinic settings or temporally dynamic reducing environments. The findings provide a revised interpretation of the Neoproterozoic seawater record, critical for understanding the relationship of anoxia to the rise of complex life.
EARTH-SCIENCE REVIEWS
(2023)
Article
Environmental Sciences
Anja Reckhardt, Stephan L. Seibert, Tobias Holt, Janis Ahrens, Melanie Beck, Gudrun Massmann, Hans-Jurgen Brumsack
Summary: The study revealed the presence of various redox-sensitive metals in freshwater lenses, where their concentrations are influenced by biogeochemical processes. Additionally, the age and redox characteristics of groundwater are linked to metal concentrations. The sources, removal, and transformation processes of metals differ significantly in different redox environments.
SCIENCE OF THE TOTAL ENVIRONMENT
(2021)
Article
Geochemistry & Geophysics
I. Zivkovic, E. Bura-Nakic, L. Knezevic, G. R. Helz
Summary: This study analyzes the concentrations of Mo, Re, and U in two marine lakes on the Adriatic Coast of Croatia. It provides data on Re for the first time in these lakes. The lakes' characteristics make them useful for testing redox proxies. The study focuses on the Re/Mo ratios as potential redox proxies. The findings show that the ratios in sediments depend on three different supplied components.
GEOCHIMICA ET COSMOCHIMICA ACTA
(2023)
Article
Geosciences, Multidisciplinary
Siavash Omidianfar, Iman Monsef, Mohammad Rahgoshay, Hadi Shafaii Moghadam, Brian Cousens, Ming Chen, Shahrokh Rajabpour, Jianping Zheng
Summary: Eocene-Oligocene magmatic rocks in the region south of Birjand, eastern Iran, provide valuable insights into the magmatic and geodynamic history of the area during the Cenozoic. The rocks are predominantly volcanic and intrusive, with geochemical characteristics indicative of subduction-related magmatism. The ages of these rocks range from approximately 46 Ma to 25 Ma, and their formation is likely linked to the subduction of the Neo-Tethyan oceanic lithosphere and subsequent asthenospheric upwelling. The interaction between the parental magmas and the continental crust during ascent likely played a role in the formation of these magmatic rocks.
GEOLOGICAL MAGAZINE
(2023)
Article
Geochemistry & Geophysics
Annika Vollebregt, Niels A. G. M. van Helmond, Susan Pit, Peter Kraal, Caroline P. Slomp
Summary: Sedimentary trace metals are used to reconstruct past bottom water redox conditions, and the calibration of these metals can be improved as redox proxies for oxygen minimum zones (OMZs). The enrichments of Mo, U, and Re in sediments generally follow ambient redox conditions, supporting their validity as redox proxies. However, Vanadium and Fe do not capture further redox changes in the OMZ, and the absence of a redox trend in sediments' Fe content can be attributed to mildly reducing conditions. Manganese, on the other hand, is depleted in the OMZ sediments and enriched in sediments below the OMZ, indicating loss from OMZ sediments and transfer to deeper sites.
Article
Geography, Physical
Benjamin C. Gill, Tais W. Dahl, Emma U. Hammarlund, Matthew A. LeRoy, Gwyneth W. Gordon, Donald E. Canfield, Ariel D. Anbar, Timothy W. Lyons
Summary: The study revealed widespread oxygen deficiency in the early Paleozoic deep oceans. It also identified significant changes in marine redox conditions in certain regions during the late Cambrian, linked to the SPICE event.
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
(2021)
Article
Geology
Hui-Dong Yu, Hao Zou, Jiang-Han Wu, Leon Bagas, Da-Xing Gong, Hai-Feng Cheng, Chang-Cheng Huang, He Zhu
Summary: The level of the Tethys Sea increased during the deposition of Mesozoic to Cenozoic sediments in the Kuqa Basin, resulting in the formation of evaporite-rich layers potentially containing potash mineralisation. However, the geology of the basin is poorly understood, limiting exploration efforts. This study investigates the geochemistry and fluid inclusions of halite crystals from the Early Eocene in the Kuqa Basin, revealing a high potential for the presence of potash deposits.
ORE GEOLOGY REVIEWS
(2023)
Article
Geochemistry & Geophysics
J. D. Scaife, M. Ruhl, A. J. Dickson, T. A. Mather, H. C. Jenkyns, L. M. E. Percival, S. P. Hesselbo, J. Cartwright, J. S. Eldrett, S. C. Bergman, D. Minisini
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
(2017)
Article
Geosciences, Multidisciplinary
Alexander J. Dickson
Article
Geosciences, Multidisciplinary
Alexander J. Dickson, Benjamin C. Gill, Micha Ruhl, Hugh C. Jenkyns, Donald Porcelli, Erdem Idiz, Timothy W. Lyons, Sander H. J. M. van den Boorn
Article
Multidisciplinary Sciences
Matthew O. Clarkson, Claudine H. Stirling, Hugh C. Jenkyns, Alexander J. Dickson, Don Porcelli, Christopher M. Moy, Philip A. E. Pogge von Strandmann, Ilsa R. Cooke, Timothy M. Lenton
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2018)
Article
Geochemistry & Geophysics
Wanyi Lu, Alexander J. Dickson, Ellen Thomas, Rosalind E. M. Rickaby, Piers Chapman, Zunli Lu
GEOCHIMICA ET COSMOCHIMICA ACTA
(2020)
Article
Geochemistry & Geophysics
Alexander J. Dickson, Erdem Idiz, Donald Porcelli, Sander H. J. M. van den Boorn
GEOCHIMICA ET COSMOCHIMICA ACTA
(2020)
Article
Geochemistry & Geophysics
Wanyi Lu, Rosalind E. M. Rickaby, Babette A. A. Hoogakker, Anthony E. Rathburn, Ashley M. Burkett, Alexander J. Dickson, Gema Martinez-Mendez, Claus-Dieter Hillenbrand, Xiaoli Zhou, Ellen Thomas, Zunli Lu
EARTH AND PLANETARY SCIENCE LETTERS
(2020)
Article
Geochemistry & Geophysics
Alexander J. Dickson, Yu-Te Hsieh, Allison Bryan
GEOCHIMICA ET COSMOCHIMICA ACTA
(2020)
Article
Geochemistry & Geophysics
Tim C. Sweere, Alexander J. Dickson, Hugh C. Jenkyns, Don Porcelli, Micha Ruhl, Melissa J. Murphy, Erdem Idiz, Sander H. J. M. van den Boorn, James S. Eldrett, Gideon M. Henderson
GEOCHIMICA ET COSMOCHIMICA ACTA
(2020)
Article
Geochemistry & Geophysics
John N. Hooker, Micha Ruhl, Alexander J. Dickson, Lars N. Hansen, Erdem Idiz, Stephen P. Hesselbo, Joe Cartwright
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2020)
Article
Geochemistry & Geophysics
Tim C. Sweere, Alexander J. Dickson, Hugh C. Jenkyns, Don Porcelli, Gideon M. Henderson
EARTH AND PLANETARY SCIENCE LETTERS
(2020)
Article
Geochemistry & Geophysics
A. M. Hutchings, A. Basu, A. J. Dickson, A. V. Turchyn
GEOCHIMICA ET COSMOCHIMICA ACTA
(2020)
Article
Geochemistry & Geophysics
Alexander J. Dickson, Hugh C. Jenkyns, Erdem Idiz, Tim C. Sweere, Melissa J. Murphy, Sander H. J. M. van den Boorn, Micha Ruhl, James S. Eldrett, Donald Porcelli
Summary: The study analyzed the molybdenum isotope record in sediments deposited in the southern Cretaceous Western Interior Seaway during OAE 2, finding that there were only minor changes in oceanic deoxygenation during one of the most extreme intervals of global deoxygenation in the Late Phanerozoic.
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
(2021)
Article
Geochemistry & Geophysics
Allison L. Bryan, Alexander J. Dickson, Fern Dowdall, William B. Homoky, Don Porcelli, Gideon M. Henderson
Summary: The study found that cadmium in continental margin sediments exists mainly in organically bound and sulfide forms, with isotopic compositions lighter compared to seawater. These observations indicate a downward diffusive flux of seawater cadmium and redox-driven removal of cadmium during sulfide precipitation.
EARTH AND PLANETARY SCIENCE LETTERS
(2021)
Article
Geochemistry & Geophysics
Lingyu Zhang, Kristoffer Szilas
Summary: This study presents new petrological and geochemical data for the Narssaq Ultramafic Body (NUB) in the Itsaq Gneiss Complex of SW Greenland. The results indicate that the ultramafic rocks of NUB are not mantle residues, but instead represent crustal cumulates derived from high-Mg magmas.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Article
Geochemistry & Geophysics
Rong Xu, Sarah Lambart, Oliver Nebel, Ming Li, Zhongjie Bai, Junbo Zhang, Ganglan Zhang, Jianfeng Gao, Hong Zhong, Yongsheng Liu
Summary: This study investigated the iron isotope compositions of Cenozoic basalts in Southeast China, finding significant variations related to different types of basalts and their respective sources.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Article
Geochemistry & Geophysics
C. J. Ebinger, Miriam C. Reiss, Ian Bastow, Mary M. Karanja
Summary: The East African rift system is formed above mantle upwellings and the formation of rifts is related to lithospheric thinning and magmatic activity. The amount of splitting varies spatially and the fast axes are predominantly parallel to the orientation of the rifts. Thick lithospheric modules have less splitting and different orientations, which may indicate mantle plume flow. Splitting rotates and increases in strength as it enters the rift zones, suggesting that the anisotropy is mainly present at shallow depths.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Correction
Geochemistry & Geophysics
Ekaterina Rojas-Kolomiets, Owen Jensen, Michael Bizimis, Gene Yogodzinski, Lukas Ackerman
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Article
Geochemistry & Geophysics
Robert W. Nicklas, Igor S. Puchtel, Ethan F. Baxter
Summary: Oxygen fugacity is a fundamental parameter for understanding redox processes in igneous systems. This study compares the Fe-XANES oxybarometry method with the V-in-olivine method for evaluating fO(2) in MORB lavas. The results show that the V-in-olivine method is not applicable to samples with low MgO content, and that the majority of Archean komatiite sources have lower fO(2) than modern MORB.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Article
Geochemistry & Geophysics
Chunfei Chen, Stephen F. Foley, Sebastian Tappe, Huange Ren, Lanping Feng, Yongsheng Liu
Summary: The volatile components CO2 and H2O play a major role in mantle melting and heterogeneity. In this study, Ca isotopes were used to trace the lithological heterogeneity in alkaline magmatic rocks. The results revealed the presence of K-richterite and carbonate components as the source of alkaline magmas with low delta 44/40Ca values. These findings highlight the importance of Ca isotopes as a robust tracer of lithological variation caused by volatiles in the Earth's upper mantle.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Article
Geochemistry & Geophysics
Timothee Jautzy, Gilles Rixhon, Regis Braucher, Romain Delunel, Pierre G. Valla, Laurent Schmitt, Aster Team
Summary: Although the current approach to estimate catchment-wide denudation rates using only 10Be concentrations has made significant progress in geomorphology, this study argues for the inclusion of 26Al measurements and testing of steady-state assumptions in slow eroding, formerly glaciated landscapes. The study conducted measurements of both 10Be and 26Al in stream sediments from the Vosges Massif in France and found that elevation, slope, channel steepness, and precipitation were the primary factors controlling denudation rates. The study also revealed a significant relationship between the extent of past glaciation and the cosmogenic (un-)steadiness in the stream sediments.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Article
Geochemistry & Geophysics
Erik van der Wiel, Douwe J. J. van Hinsbergen, Cedric Thieulot, Wim Spakman
Summary: Numerical models of Earth's mantle dynamics can predict the vigour and mixing of mantle flow, and the average slab sinking rates are an unexplored parameter that can provide intrinsic information on these characteristics. Through numerical experiments, it has been found that slab sinking rates are strongly correlated with mantle convection and mixing, and may explain geochemical observations from hotspot volcanoes.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)