Academic literature on the topic 'Trace element palaeoredox proxies'
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Journal articles on the topic "Trace element palaeoredox proxies"
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Mänd, Kaarel, Stefan V. Lalonde, Kärt Paiste, Marie Thoby, Kaarel Lumiste, Leslie J. Robbins, Timmu Kreitsmann, et al. "Iron Isotopes Reveal a Benthic Iron Shuttle in the Palaeoproterozoic Zaonega Formation: Basinal Restriction, Euxinia, and the Effect on Global Palaeoredox Proxies." Minerals 11, no. 4 (March 31, 2021): 368. http://dx.doi.org/10.3390/min11040368.
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The Zaonega Formation in northwest Russia (~2.0 billion years old) is amongst the most complete successions that record the middle of the Palaeoproterozoic era. As such, geochemical data from the formation have played a central role in framing the debate over redox dynamics in the aftermath of the Great Oxidation Event (GOE). However, uncertainty over local redox conditions and the degree of hydrographic restriction in the formation has led to contradictory interpretations regarding global oxygen (O2) fugacity. Here, we provide new iron (Fe) isotope data together with major and trace element concentrations to constrain the local physiochemical conditions. The Zaonega Formation sediments show authigenic Fe accumulation (Fe/Al ≫ 1 wt.%/wt.%) and δ56Fe ranging from −0.58‰ to +0.60‰. Many of the data fall on a negative Fe/Al versus δ56Fe trend, diagnostic of a benthic Fe shuttle, which implies that Zaonega Formation rocks formed in a redox-stratified and semi-restricted basin. However, basin restriction did not coincide with diminished trace metal enrichment, likely due to episodes of deep-water exchange with metal-rich oxygenated seawater, as evidenced by simultaneous authigenic Fe(III) precipitation. If so, the Onega Basin maintained a connection that allowed its sediments to record signals of global ocean chemistry despite significant basinal effects.
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Li, Jun, Herong Gui, Luwang Chen, Pei Fang, Xiaoping Li, Jie Zhang, and Yingxin Wang. "Geochemistry of upper Palaeozoic ‘thin-layer’ limestones in the southern North China Craton: implications for closure of the northeastern Palaeotethys Ocean." Geological Magazine 159, no. 4 (November 8, 2021): 494–510. http://dx.doi.org/10.1017/s0016756821001126.
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AbstractDuring the late Palaeozoic Era, a series of related marine strata dominated by multi-layer limestones were deposited in the southern North China Craton. In order to gain new insights into the systematic geochemistry of the carbonate succession of the representative formation (Taiyuan Formation), we examined 59 limestone samples collected from the Huaibei Coal Basin (HCB), with a view towards quantitatively determining the major and trace elements and stable isotope compositions. The data obtained can provide essential evidence for reconstruction of the depositional palaeo-environment and tectonic setting of the Taiyuan Formation. Both X-ray diffraction analyses and palaeoredox proxies (e.g. V/Cr, V/(V + Ni) and authigenic U) indicated that the limestone layers were deposited in an oxic–dysoxic zone, with calcite as the main component. Moreover, palaeomagnetic evidence provided support for the conclusion that these limestones were laid down within an epicontinental sea depositional environment under a warm or hot palaeoclimate during the transition between late Carboniferous and early Permian time. Additionally, evidence obtained from our analyses of trace and rare earth elements revealed that the tectonic setting of the Taiyuan Formation (L1–L5) in the HCB transited from an open ocean to a passive continental margin, thereby indicating that this transformation stemmed from the subduction closure of the northeastern Palaeotethys Ocean. The findings of this study would be of interest to those working on the upper Palaeozoic marine strata in the southern North China Craton.
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Sondi, Ivan, Nevenka Mikac, Neda Vdović, Maja Ivanić, Martina Furdek, and Srečo D. Škapin. "Geochemistry of recent aragonite-rich sediments in Mediterranean karstic marine lakes: Trace elements as pollution and palaeoredox proxies and indicators of authigenic mineral formation." Chemosphere 168 (February 2017): 786–97. http://dx.doi.org/10.1016/j.chemosphere.2016.10.134.
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Pérez-Huerta, Alberto, Anthony E. Aldridge, Kazuyoshi Endo, and Teresa E. Jeffries. "Brachiopod shell spiral deviations (SSD): Implications for trace element proxies." Chemical Geology 374-375 (May 2014): 13–24. http://dx.doi.org/10.1016/j.chemgeo.2014.03.002.
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Xu, Guangping, Judith L. Hannah, Bernard Bingen, Svetoslav Georgiev, and Holly J. Stein. "Digestion methods for trace element measurements in shales: Paleoredox proxies examined." Chemical Geology 324-325 (September 2012): 132–47. http://dx.doi.org/10.1016/j.chemgeo.2012.01.029.
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Markulin, Krešimir, Melita Peharda, Regina Mertz-Kraus, Bernd R. Schöne, Hana Uvanović, Žarko Kovač, and Ivica Janeković. "Trace and minor element records in aragonitic bivalve shells as environmental proxies." Chemical Geology 507 (March 2019): 120–33. http://dx.doi.org/10.1016/j.chemgeo.2019.01.008.
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Oonk, Paul B. H., Harilaos Tsikos, Paul R. D. Mason, Susann Henkel, Michael Staubwasser, Lindi Fryer, Simon W. Poulton, and Helen M. Williams. "Fraction-specific controls on the trace element distribution in iron formations: Implications for trace metal stable isotope proxies." Chemical Geology 474 (December 2017): 17–32. http://dx.doi.org/10.1016/j.chemgeo.2017.10.018.
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Reuer, Matthew K., Edward A. Boyle, and Julia E. Cole. "A mid-twentieth century reduction in tropical upwelling inferred from coralline trace element proxies." Earth and Planetary Science Letters 210, no. 3-4 (May 2003): 437–52. http://dx.doi.org/10.1016/s0012-821x(03)00162-6.
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Johnson, K. R., C. Hu, and G. M. Henderson. "Testing seasonal resolution trace element and stable isotope proxies of East Asian monsoon rainfall." Geochimica et Cosmochimica Acta 70, no. 18 (August 2006): A296. http://dx.doi.org/10.1016/j.gca.2006.06.600.
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Zinke, Jens, Juan P. D'Olivo, Christoph J. Gey, Malcolm T. McCulloch, J. Henrich Bruggemann, Janice M. Lough, and Mireille M. M. Guillaume. "Multi-trace-element sea surface temperature coral reconstruction for the southern Mozambique Channel reveals teleconnections with the tropical Atlantic." Biogeosciences 16, no. 3 (February 4, 2019): 695–712. http://dx.doi.org/10.5194/bg-16-695-2019.
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Abstract. Here we report seasonally resolved sea surface temperatures for the southern Mozambique Channel in the SW Indian Ocean based on multi-trace-element temperature proxy records preserved in two Porites sp. coral cores. Particularly, we assess the suitability of both separate and combined Sr∕Ca and Li∕Mg proxies for improved multielement SST reconstructions. Overall, geochemical records from Europa Island Porites sp. highlight the potential of Sr∕Ca and Li∕Mg ratios as high-resolution climate proxies but also show significant differences in their response at this Indian Ocean subtropical reef site. Our reconstruction from 1970 to 2013 using the Sr∕Ca SST proxy reveals a warming trend of 0.58±0.1 ∘C in close agreement with instrumental data (0.47±0.07 ∘C) over the last 42 years (1970–2013). In contrast, the Li∕Mg showed unrealistically large warming trends, most probably caused by uncertainties around different uptake mechanisms of the trace elements Li and Mg and uncertainties in their temperature calibration. In our study, Sr∕Ca is superior to Li∕Mg to quantify absolute SST and relative changes in SST. However, spatial correlations between the combined detrended Sr∕Ca and Li∕Mg proxies compared to instrumental SST at Europa revealed robust correlations with local climate variability in the Mozambique Channel and teleconnections to regions in the Indian Ocean and southeastern Pacific where surface wind variability appeared to dominate the underlying pattern of SST variability. The strongest correlation was found between our Europa SST reconstruction and instrumental SST records from the northern tropical Atlantic. Only a weak correlation was found with ENSO, with recent warm anomalies in the geochemical proxies coinciding with strong El Niño or La Niña. We identified the Pacific–North American (PNA) atmospheric pattern, which develops in the Pacific in response to ENSO, and the tropical North Atlantic SST as the most likely causes of the observed teleconnections with the Mozambique Channel SST at Europa.
Dissertations / Theses on the topic "Trace element palaeoredox proxies"
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Bryan, Sean Patrick. "Calibration of trace element paleoceanographic proxies in benthic foraminifera." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1446083.
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Lear, Caroline Helen. "Evolution of Cenozoic ocean composition and temperature from foraminiferal trace element proxies." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392755.
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Jamieson, Robert Andrew. "Trace element geochemistry of Belizean and Bermudan stalagmites : new tools, proxies and applications." Thesis, Durham University, 2017. http://etheses.dur.ac.uk/12055/.
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Speleothem trace elements are an important and effective tool for palaeoenvironmental reconstruction. They can be used to reconstruct a plethora of climate variables, and are a vital tool for improving our understanding of the climate system. This is particularly important given the on-going challenges of comprehending and tackling anthropogenic climate change. Only by thoroughly understanding controls on climate variability can we attempt to predict future change. This thesis presents a broad study of current speleothem trace element proxies. In addition to reviewing the current state of knowledge, this thesis presents several additions and developments to the speleothem trace element toolkit. The 22 year ATM-7 trace element record from Belize has a greater than seasonal resolution, and a highly precise chronology. As a result of this exceptional chronology, combined with extremely high resolution LA-ICP-MS analysis, it is possible to detect the geochemical indicators of volcanic ash deposition. Principal Component Analysis identifies a clear signal of a multi-elemental input of trace elements at the beginning of the wet season following volcanic eruptions with ash reaching the cave site. U/Ca variability in aragonitic speleothems is strongly influenced by the occurrence of Prior Aragonite Precipitation. The U/Ca record in Belizean stalagmite YOK-G strongly suggests that modern drying has occurred in Belize, primarily caused by a reduction in wet season rainfall. This is consistent with published stable isotope data from YOK-G, previously interpreted as the result of southward ITCZ displacement. These results strongly suggest that U/Ca values in aragonitic speleothems are excellent proxies for rainfall variability. This new tool, combined with the exceptional chronological control characteristic of aragonitic stalagmites and the high spatial resolution afforded by modern microanalytical techniques, should facilitate the construction of new exquisitely resolved rainfall records, providing rare insights into seasonality changes as well as long-term changes in local recharge conditions. In the Bermudan stalagmite BER-SWI-13, magnesium concentrations record, via varying prior calcite precipitation, changes in local rainfall which appear to correspond to variation in the North Atlantic Oscillation (NAO). Through a different mechanism, phosphorous also correlates with changes in the NAO. We infer that local effective rainfall changes, influenced by NAO state, influence bioproductivity above the cave and thus the amount of phosphorous in dripwaters. Surprisingly, for a location such as Bermuda, we see no evidence of clear direct anthropogenic influence on speleothem chemistry. These results V suggest that Bermudan speleothems are well situated to record basin scale climate changes in the North Atlantic. Together, these three separate studies demonstrate the strength and versatility of high- resolution trace element analysis of speleothems. They establish new techniques of data analysis, new proxies, and the applications of existing proxies in new contexts to reconstruct palaeoenvironmental variables. Looking forward, these discoveries demonstrate that speleothem trace elements continue to have a great deal to offer to the field of palaeoclimate reconstruction, and that there are still new techniques and applications to be developed.
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Ni, Yunyan. "Evaluation of boron isotopes and trace element abundances in planktonic foraminifers as palaeo-oceanographic proxies." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431620.
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Evans, Guy Nathaniel. "Trace element proxies and mineral indicators of hydrothermal fluid composition and seafloor massive sulfide deposit formation processes." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111731.
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Thesis: Ph. D. in Marine Geology, Joint Program in Marine Geology and Geophysics (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017.Cataloged from PDF version of thesis.
Includes bibliographical references.
This thesis analyzes compositions of seafloor massive sulfide (SMS) deposits and related hydrothermal vent fluids to identify proxies of reaction zone conditions (host-rock lithology, hydrothermal fluid temperature and chemistry). Chapter 2 investigates the morphology, mineralogy, and geochemistry of SMS deposits from six vent fields along the Eastern Lau Spreading Center (ELSC), demonstrating that ELSC SMS deposits record differences in hydrothermal fluid temperature, pH, sulfur fugacity and host-rock lithology related to proximity to the nearby Tonga Subduction Zone. Chapters 3 and 4 focus on partitioning of Co, Ni, Ga, Ag, and In between hydrothermal vent fluids and chalcopyrite lining fluid conduits in black smoker chimneys. Chapter 3 develops secondary ion mass spectrometry (SIMS) as a technique to measure Co, Ni, Ga, Ag, and In in chalcopyrite and identifies a correlation between Ga and In in chalcopyrite and hydrothermal fluid pH. Chapter 4 presents new data on these elements in ELSC hydrothermal fluids that, combined with SIMS analyses of chalcopyrite chimney linings and previously published data on vent fluids from the Manus Basin, provide evidence that supports partitioning of Ag a lattice substitution for Cu. Together, concentrations of Ga, In, and Ag in chalcopyrite provide proxies of hydrothermal fluid pH and metal (i.e., Ag and Cu) contents.
by Guy Nathaniel Evans.
Ph. D. in Marine Geology
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Gilbert, Ashley Nicole. "LATEST QUATERNARY PALEOCLIMATE RECONSTRUCTION UTILIZING STABLE ISOTOPIC AND TRACE ELEMENT PROXIES IN A STALAGMITE FROM CULVERSON CREEK CAVE, WEST VIRGINIA." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/21.
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A reconstruction of regional climate variability in southern West Virginia that spans the last glacial/interglacial transition is presented. Paleoclimate interpretations obtained from the 50-cm long stalagmite provide key insights regarding the timing, magnitude, and forcing mechanisms responsible for past climate variability. Stable isotopic (δ18O and δ13C) and trace element (Ba, Sr, Mg) signatures from samples contiguously milled along the growth-axis of a 230Th-dated stalagmite which grew between approximately 20 and 5 thousand years before present (kyr BP) provide critical constraints for above-cave mean annual temperature, seasonality of moisture mean annual precipitation, and potential vegetation shifts. Specifically, the stalagmite record reveals subcentennial-scale variations in the proxy records, and strong multimillennial-scale features that correlate to well-known patterns of sea-surface variability in the North Atlantic Ocean (i.e., Bond cycles). The large-scale glacial/interglacial transition is sufficiently resolved to show that regional climate changes largely paralleled climatic transitions preserved in low-latitude (Chinese monsoon records; Cariaco Basin) and high-latitude (Greenland Ice Sheet) paleo-archives. However, the Younger Dryas interval in the south-central Appalachian Mountains is not as prominent a feature as in other records.
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Taylor, Sarah Louise. "Trace element distributions in ridge flank sediments from the east Pacific Rise, and their use as proxies of past ocean conditions." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/65673/.
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The eastern equatorial and tropical Pacific regions are areas of significant carbon fluxes from the atmosphere to the ocean interior. Changes in the function of marine biogeochemical cycles in this region potentially exert an important control on global climate. Understanding controls on and changes to ocean chemistry and circulation in this region is therefore of great importance. Redox sensitive metal distributions in hydrothermal sediments have yet to be exploited effectively as proxies of past ocean conditions. This work presents a 740 ka sediment record from an archived core collected at 14o47’S overlying 1.1 Ma crust on the western flank of the EPR. The metalliferous sedimentation is overprinted by diagenetic mobilisation arising from variations in the sediment redox status of the sediments. Amorphous ferrihydrite phases delivered to the sediment have undergone significant alteration to more stable crystalline forms. Under glacial conditions, the transformation of ferrihydrite appears to be impeded, which is inferred to be a function of a distinct change in the redox status of the sediments under glacial conditions. Oxyanions coprecipitated with Fe and Mn (hydr)oxides from the hydrothermal plume (P, V, U) are partitioned during Fe-oxide alteration. V is preferentially incorporated into goethite and residual phases, locking the plume derived V within the sediment. Sediment P/Fe ratios are lower than overlying plume values, and vary systematically with variations in ferrihydrite transformation to goethite on glacial-interglacial timescales. This transformation is inferred to lead to P loss from the particulate/sediment phase. Uranium is highly enriched in sulphide rich EPR plume particles and the sediments at 14oS. U/Fe ratios indicate there has been enhanced release of U under interglacial conditions, and preservation of plume U/Fe ratios under glacial conditions. Mo/Mn ratios are used to confirm the changes in redox status on glacial-interglacial timescales at this site. There is a general trend over Marine Isotope Stages 1-14 of a deepening of the sediment redox front through interglacial stages with a shallowing at the onset of glaciation. Enhanced sub-oxic conditions associated with glacial conditions (in particular MIS 12) are attributed to enhanced productivity (and carbon export to the seafloor) and decreased bottom water O2 (and therefore reduced ventilation of the deep water). This is consistent with paleoproductivity data from other parts of the Eastern Pacific and adds new information of past conditions in a region which has not been studied.
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Hall, Philip Anthony. "Elemental, isotopic and molecular signatures of Early Cambrian marine sediments and a phantom petroleum system in South Australia." Thesis, 2012. http://hdl.handle.net/2440/81757.
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The aim of the research study is to apply mass spectrometric geochemical techniques to the investigation of palaeoenvironmental, chemostratigraphic and provenance questions from several South Australian Phanerozoic basins. Results of a multi-pronged palaeoenvironmental investigation of Early Cambrian marine sediments, employing trace and REE abundances, TOC and stable isotopes (C, S) are reported from three formations in the Stansbury Basins; Heatherdale Shale, Emu Bay Shale and Talisker Formation. The multiproxy approach in conjunction with sedimentological information provides a powerful tool for interpreting palaeoenvironmental conditions. Prevalent palaeoredox conditions of the Heatherdale Shale and Talisker Formation were dysoxic, evolving progressively more reducing natures up section. The Emu Bay Shale conversely demonstrates consistently aerobic interpretations for the redox proxies. Comparison of trace element and REE distributions to similar sequences of the Yangtze platform, South China shows striking similarities, Analogous basinal environments and common provenance may have lead to the seawater trace element chemistry of the Palaeo Pacific & Asian oceans exhibiting a homogenous nature. The Emu Bay Shale biota is the richest Burgess Shale-type (BST) fauna in the southern hemisphere. The implied oxic water column during accumulation appears difficult to reconcile with the exceptional preservation exhibited. Micro-scale sealed vessel (MSSV) pyrolysis of isolated kerogen and δ¹³Corg values provided confirmation of its redox status and implicate cyanobacteria in the preservation mechanism. Molecular signatures diagnostic of Gloeocapsomorpha prisca were identified, the first indication that microbial mats were involved in the taphonomy of a BST deposit. The biostratigraphic definition of GSSP horizons though the use of cosmopolitan taxa biohorizons is problematical for sections such as lower Cambrian deposits where few candidate fossils exist. Instead, an integrated approach comprising chemostratigraphy and/or sequence stratigraphy with the known biostratigraphy greatly increases our ability to make high-resolution correlations., δ¹³Ccarb profiles from three South Australian basins; the Stansbury, the Arrowie and the Officer are correlated regionally with the existing data from the Flinders Ranges. Globally identified excursions such as the negative ROECE and AECE event and the positive CARE and MICE events, are recognised in the profiles. This chemostratigraphic interpretation appears to support the biostratigraphic assignment of the sections. Asphaltic bitumens are long known to strand along coastlines of southern Australia and as far afield as New Zealand and Macquarie Island. Widely regarded as artefacts of an unidentified submarine oil seepages, a common source is interpreted from remarkably uniform compositions. An important consideration when attempting to locate their point of origin is the degree of weathering exhibited, which will reflect the residence time in the marine environment and proximity of the seep to the stranding site. Biomarker signatures and n-alkane C-isotopic profiles from interior and weathered exterior sub-samples of asphaltum from four localities in South Australia and New Zealand were compared. No distinction could be made between strandings despite their widely separated localities. The degree of degradation and isotopic variance suggest an origin from low intensity seeps in the western Otway Basin as strandings on the Limestone Coast and Kangaroo Island appear less weathered than those from Eyre Peninsula and New Zealand.Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2012
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Haynes, Laura. "The Influence of Paleo-Seawater Chemistry on Foraminifera Trace Element Proxies and their Application to Deep-Time Paleo-Reconstructions." Thesis, 2019. https://doi.org/10.7916/d8-x2x2-da06.
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The fossilized remains of the calcite shells of foraminifera comprise one of the most continuous and reliable records of the geologic evolution of climate and ocean chemistry. The trace elemental composition of foraminiferal shells has been shown to systematically respond to seawater properties, providing a way to reconstruct oceanic conditions throughout the last 170 million years. In particular, the boron/calcium ratio of foraminiferal calcite (B/Ca) is an emerging proxy for the seawater carbonate system, which plays a major role in regulating atmospheric CO2 and thus Earth’s climate. In planktic foraminifera, previous culture studies have shown that shell B/Ca increases with seawater pH, which is hypothesized to result from increased incorporation of borate ion (B(OH)4 -) at high pH; increasing pH increases the [B(OH)4 -] of seawater. However, further experiments showed that B/Ca responds to both pH and seawater dissolved inorganic carbon concentration (DIC), leading to the hypothesis that B/Ca is driven by the [B(OH)4 -/DIC] ratio of seawater. Because pH (and thus B(OH)4 -) can be determined via the δ11B composition of foraminiferal calcite, B/Ca therefore may provide an opportunity to determine seawater DIC in the geologic past.
The magnesium/calcium ratio (Mg/Ca) of foraminifer shells is a well-established proxy for seawater temperatures, where foraminiferal Mg/Ca increases at greater temperatures. However, foraminifera shell chemistry such as B/Ca and Mg/Ca ratios also depend on the major ion chemistry of seawater. For example, the seawater Mg/Ca ratio (Mg/Casw), which has increased significantly over the last 60 million years, is known to affect the sensitivity of the Mg/Ca proxy to temperature. In addition, the seawater boron concentration ([B]sw) has also increased across the Cenozoic. The dependence of B/Ca proxy relationships on Mg/Casw and [B]sw composition remains unknown.
During the Paleogene era (65-34 Ma), Earth’s climate was characterized by a number of rapid warming events termed ”hyperthermals”. Evidence from the sedimentary record suggests that hyperthermals were catalyzed by rapid carbon release and caused widespread ocean acidification and deep-sea deoxygenation. These hyperthermal events present the best geologic analog conditions to anthropogenic climate change, and their study can therefore help to illuminate how the Earth system responds to rapid carbon release and warming. Planktic foraminiferal B/Ca records from the largest hyperthermal event, the Paleocene-Eocene Thermal Maximum (PETM), show a large decrease, which agrees with the theory that ocean acidification should cause B/Ca to decline. However, the decrease is larger than can be reconciled from existing proxy calibrations conducted in modern seawater, begging the question of whether the low Mg/Casw of the Paleogene Ocean affected the sensitivity of B/Ca to the seawater carbonate system. Because there are also a number of outstanding uncertainties regarding the controls on B/Ca- including seawater [Ca] and shell growth rate, light intensity, and phosphate concentration- it is also possible that these factors contributed to the PETM B/Ca excursion. The influence of these additional parameters on B/Ca, as well as the influence of Mg/Casw, needs to be tested in controlled culture experiments.
To address these outstanding questions in proxy development, I conducted a series of culture experiments in three living planktic foraminifer species- Orbulina universa, Trilobatus sacculifer, and Globigerinoides ruber (pink). In order to refine our understanding of proxy controls on foraminiferal B/Ca, I investigated how foraminiferal B/Ca is affected by variable light intensity, growth rate (indirectly via seawater [Ca] manipulation), and seawater [B]. Subsequently I tested the influence of low seawater Mg/Ca, analogous to that of the Paleocene ocean, on B/Ca-carbonate chemistry relationships. In Chapters 2 and 3, I detail how my results support the notion that planktic foraminiferal B/Ca in these three symbiont-bearing species is driven by the B(OH)4 -/DIC ratio of seawater and is not compromised by growth rate effects. Furthermore, the sensitivity of B/Ca to B(OH)4 -/DIC is increased under low Mg/Casw in both O. universa and T. sacculifer. In Chapters 2 and 3, I hypothesize that this increased sensitivity is due to decreased cellular pH regulation under low Mg/Casw, leading to a greater sensitivity of the foraminiferal microenvironment’s carbon system to external forcing. I define new culture calibrations that can be applied to records from Paleocene seawater in Chapter 3, and use these calibrations to reconstruct surface ocean DIC and the overall size of the carbon system perturbation across the PETM in Chapter 4. Finally, in Chapter 5, I show how foraminiferal Mg/Ca responds to seawater Mg/Ca and the carbon system from these same experiments, with implications for accounting for carbon system influences on Mg/Ca from early Cenozoic proxy records.
Book chapters on the topic "Trace element palaeoredox proxies"
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Hillenbrand, Ian, Michael L. Williams, Michael J. Jercinovic, Matthew T. Heizler, and Daniel J. Tjapkes. "Petrochronologic constraints on Paleozoic tectonics in southern New England." In Laurentia: Turning Points in the Evolution of a Continent. Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.1220(25).
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ABSTRACT The Appalachian Mountains were formed through multiple phases of Paleozoic orogenesis associated with terrane accretion. The timing, tempo, and significance of each event in New England are obscured by overprinting, the limits of geochronologic tools, and differences between lithotectonic domains. We present new monazite and xenotime geochronology, 40Ar/39Ar thermochronology, and major- and trace-element thermobarometry from major tectonic domains in southern New England and across multiple structural levels. These data show contrasting pressure-temperature-time (P-T-t) paths across tectonic domains and highlight eastward metamorphic overprinting associated with younger tectonic events. Our data and geochemical proxies suggest two major periods of crustal thickening, ca. 455–440 Ma and 400–380 Ma, and a heterogeneous record of thinning/exhumation. Ordovician (Taconic) crustal thickening postdates the interpreted accretion of the Moretown terrane by ~20 m.y. and may have been related to shallow subduction after subduction polarity reversal. Subsequent cooling and exhumation (440–430 Ma) may have been related to the end of the Taconic orogeny and opening of the Connecticut Valley basin. (Neo)Acadian tectonometamorphism is recognized in accreted terranes of New England and is absent in the Taconic block. Amphibolite- to (high-pressure) granulite-facies metamorphism, slow cooling, and protracted anatexis ca. 400–340 Ma support the existence of a long-lived orogenic plateau in southern New England. Exhumation, which began at 340–330 Ma, may have involved ductile (channel) flow. The boundary between continental Laurentia and accreted terranes has been reactivated at multiple times and is presently manifested as a 12–15 km Moho step. At the latitude of our samples, Alleghanian-age tectonism (ca. 310–285 Ma) was limited to retrograde metamorphism, and relatively minor loading and exhumation in the vicinity of the Pelham dome. Our results highlight the sensitivity of the integrative petrochronologic approach and the transition of the eastern margin of Laurentia from terrane accretion to the formation of a high-elevation plateau.
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Cao, Kang, Zhi-Ming Yang, Zeng-qian Hou, Noel C. White, and Chao Yu. "Contrasting Porphyry Cu Fertilities in the Yidun Arc, Eastern Tibet: Insights from Zircon and Apatite Compositions and Implications for Exploration." In Tectonomagmatic Influences on Metallogeny and Hydrothermal Ore Deposits: A Tribute to Jeremy P. Richards (Volume II), 231–55. Society of Economic Geologists, 2021. http://dx.doi.org/10.5382/sp.24.13.
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Abstract The Yidun arc, part of the Sanjiang Paleo-Tethyan orogenic belt in eastern Tibet, hosts several porphyry Cu deposits in its southern section, whereas abundant contemporaneous but barren granitoid intrusions occur in the northern section. Here we present an integrated, temporally constrained dataset of zircon and apatite compositions together with whole-rock geochemical results for both the fertile and barren suites in the Yidun arc. We investigate the probable factors leading to such contrasting porphyry Cu fertilities and also assess the application of geochemical and mineral proxies for porphyry Cu exploration. Both the fertile and barren suites in the Yidun arc share similar petrographic and geochemical characteristics typical of arc magmas. However, the two suites have distinct differences in certain trace elements and element ratios (e.g., Sr, Y, Sr/Y, V/Sc, Eu anomaly). The fertile suites have adakite-like character, with high Sr/Y, La/Yb, and V/Sc ratios, and show no or minimal negative Eu anomalies, indicating early dominant amphibole with limited plagioclase fractionation. By contrast, the barren suites have low Sr/Y, La/Yb, and V/Sc ratios, and display minimal to significant negative Eu anomalies. These barren suites probably formed by crystal fractionation dominated by plagioclase, with limited amphibole crystallizing from the same parental magma. Zircon geochemical data for both suites combined with Rayleigh fractionation modeling show that zircon compositions (e.g., Hf, Ti, [Yb/Dy]N, Eu/Eu*, Ce/Nd) are affected by the compositions, water content, and redox state of the parental magma, as well as by prior or concurrent crystallization of minerals (e.g., plagioclase, amphibole, apatite, titanite). For the fertile suites, the high zircon Eu/Eu* (0.43–0.91), ΔFMQ (0.8–2.4; where ΔFMQ is the log fO2 difference between the sample value and the fayalite-magnetite-quartz mineral buffer), the presence of the assemblage amphibole + titanite + quartz + magnetite, and high whole-rock Fe2O3/FeO, Sr/Y and V/Sc ratios, collectively indicate that associated magmas were hydrous and oxidized. For the barren suites, the common presence of the assemblage amphibole + ilmenite, low zircon Eu/Eu* (0.01–0.34) and ΔFMQ (–3.3 to +0.5), and low whole-rock Fe2O3/FeO, Sr/Y, and V/Sc ratios, together indicate that the related magmas were hydrous but reduced. Magmatic apatites in the fertile suites have higher SO3 contents (0.07–0.79 wt %) than those in the barren suites (<0.04 wt % SO3). The estimated magmatic sulfur contents for the fertile suites are 35 to 160 ppm, whereas for the barren suites, their related magmas were sulfate poor. Compared to the hydrous, oxidized, and S-rich fertile suites in the southern Yidun arc, the reduced and sulfate-poor characteristics of the barren suites hinder the transport of adequate S and metals to form porphyry Cu deposits, even though they are hydrous; thus there is little potential for porphyry Cu deposits in the northern Yidun arc. Whole-rock Sr/Y (>20), V/Sc (>32.5–0.385 × wt % SiO2), Eu/Eu* (~1) and 10,000*(Eu/Eu*)/Y (>400) ratios, zircon Eu/Eu* (>0.4) and ΔFMQ (>1), and apatite SO3 contents (>0.1 wt %) can help to discriminate porphyry Cu intrusions from barren granitoids in the Yidun arc, indicating their usefulness as porphyry Cu fertility indicators. The zircon Ce anomaly (Ce4+/Ce3+, Ce/Ce*, Ce/Nd), however, overlaps between the oxidized fertile and reduced barren suites, hampering its use to estimate relative magmatic redox state and as a robust porphyry Cu fertility indicator. The combination of whole-rock analyses and zircon and apatite compositions helps focus porphyry Cu exploration on prospective areas, coupled with investigations of structural geology, geophysical surveys, and mapping of hydrothermal alteration.
Conference papers on the topic "Trace element palaeoredox proxies"
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Ruga, Mikaela R., John Warren Huntley, and Michael Glascock. "TRACE ELEMENT ANALYSIS OF TWO HOLOCENE BIVALVE TAXA, CYRENODONAX FORMOSANA AND POTAMOCORBULA AMURENSIS, AS PROXIES FOR TEMPERATURE AND PRODUCTIVITY IN THE PEARL RIVER DELTA, CHINA." In 52nd Annual North-Central GSA Section Meeting - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018nc-312272.
Full textReports on the topic "Trace element palaeoredox proxies"
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Gadd, M. G., J. M. Peter, T A Fraser, and D. Layton-Matthews. Paleoredox and lithogeochemical indicators of the environment of formation and genesis of the Monster River hyper-enriched black shale showing, Yukon. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/328004.
Full textAbstract:
Northern Yukon hosts occurrences of Middle Devonian hyper-enriched black shale (HEBS) Ni-Mo-Zn-platinum-group element-Au-Re mineralization, including the Monster River showing in the Ogilvie Mountains. This mineralization has been documented predominantly in the Paleozoic Richardson trough; however, the Monster River showing is atypical, occurring within the Blackstone trough, more than 200 km to the west on the southern margin of the Yukon block. The ambient paleoredox conditions of the marine water column and sediments may be primary controlling factors in HEBS formation. We use major and trace element lithogeochemistry to better understand ambient paleoenvironmental redox conditions through the application of robust redox proxies to HEBS mineralization and host rocks. Uniformly negative Ce anomalies (0.6-0.9) indicate that the water column was predominantly suboxic throughout the deposition interval, even during HEBS mineralization. Although there is a strong terrigenous influence on the rare earth element-yttrium (REE-Y) abundances of the sedimentary rocks, superchondritic Y/Ho ratios (&gt;27) indicate that seawater contributed REE-Y to the host rocks and HEBS. High (&gt;10) authigenic Mo/U ratios indicate that a Fe-Mn particulate shuttle operated in the water column; this is corroborated by negative Ce anomalies and high Y/Ho ratios. The data indicate that metalliferous sedimentary rocks formed by hydrogenous metal enrichment (e.g. Ni, Mo, Pt) caused by ferromanganese oxyhydroxide particulate shuttling as chemical sediments; moreover, the REE- and Mo-based paleoenvironmental indicators suggest a complexly redox-stratified depositional environment with an abundant supply of metals, metalloids, and sulfur.