Widespread lithogenic control of marine authigenic neodymium isotope records? Implications for paleoceanographic reconstructions

Abbott, April N.; Löhr, Stefan; Payne, Antony J.; Kumar, H.; Du, Jianghui

doi:10.1016/j.gca.2021.11.021

Cited by 29 publications

(25 citation statements)

References 82 publications

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“…However, Fanton et al (2002) also found that conodont apatite records the same ɛNd(t) as the acid-soluble phase of the carbonate host rock, and interpret that the mobile Nd reservoir in the insoluble phase has ɛNd(t) identical to that of the acidsoluble phase. This contrasts with a compilation of ɛNd(t) measurements of primarily pelagic sediments that demonstrates covariance between detrital and authigenic phases, suggesting a primary detrital influence on ɛNd(t) of both authigenic Fe-Mn phases and bioapatite deposited in detrital-rich sediments (Abbott et al, 2021). We note that the carbonate content of these pelagic deposits (generally <30 wt% carbonate) is less than is typical for Ordovician carbonates (generally >70-80 wt% carbonate; Fanton et al, 2002), therefore we would expect less of an influence from leaching of detrital sediments in our samples than has been demonstrated in pelagic sediments.…”

Section: Fidelity and Timing Of Isotopic Signals 87 Sr/ 86 Sr Signalcontrasting

confidence: 97%

“…Comparison of acid leaching methods for digestion of carbonate sediments for ɛNd(t) analysis demonstrates that overly strong leaching methods can liberate Nd from detrital phases with implications for the ɛNd(t) composition of the acid-soluble phase (Abbott et al, 2016(Abbott et al, , 2021. This has also been demonstrated in Ordovician carbonates, where Fanton et al (2002) found a positive correlation between wt% insoluble residue (generally <20-30%) and Nd concentration using our same leaching method (6 M HCl).…”

Section: Fidelity and Timing Of Isotopic Signals 87 Sr/ 86 Sr Signalsupporting

confidence: 63%

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Supplemental Material: Nd isotopic evidence for enhanced mafic weathering leading to Ordovician cooling

Conwell¹,

al.²

2022

Preprint

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Section: Fidelity and Timing Of Isotopic Signals 87 Sr/ 86 Sr Signalcontrasting

confidence: 97%

Section: Fidelity and Timing Of Isotopic Signals 87 Sr/ 86 Sr Signalsupporting

confidence: 63%

Supplemental Material: Nd isotopic evidence for enhanced mafic weathering leading to Ordovician cooling

Conwell¹,

al.²

2022

Preprint

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“…In contrast, the studies of Abbott et al. (2022) and Blaser et al. (2019) are from high‐latitude North Atlantic cores that were influenced by either significant inputs of reactive volcanics from Iceland (with highly radiogenic Nd isotope signatures, which are not seen in core MD77‐191), or by temporally varying inputs of glacial flour or detrital carbonates in Heinrich layers.…”

Section: Resultsmentioning

confidence: 97%

“…While dissolved-particulate exchange processes and porewater imprints can impact the authigenic ɛ Nd signature extracted from marine sediments at continental margins (Abbott et al, 2022;Blaser et al, 2019;Wilson et al, 2012), these effects are likely to scale with sediment reactivity and detrital sedimentation rates (Abbott et al, 2022;Blaser et al, 2019), which are expected to have remained near-constant over the last 17 kyr in this setting (Figure S1 in Supporting Information S1). In contrast, the studies of Abbott et al (2022) and Blaser et al (2019) are from high-latitude North Atlantic cores that were influenced by either significant inputs of reactive volcanics from Iceland (with highly (Yu et al, 2018). Deep water Nd isotope records are from ODP 758 (Burton & Vance, 2000), SK157-20 (Naik et al, 2019), and SK129-CR2 .…”

Section: Millennial Variability Of Seawater Nd Isotopes In the Northe...mentioning

confidence: 99%

Millennial Variability in Intermediate Ocean Circulation and Indian Monsoonal Weathering Inputs During the Last Deglaciation and Holocene

Colin

Wilson

et al. 2022

Geophysical Research Letters

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The relationship between ocean circulation and monsoon systems over orbital to sub‐millennial timescales is a crucial but poorly constrained component of the climate system. Here, using foraminiferal and detrital neodymium (Nd) isotope records from the intermediate‐depth northern Indian Ocean, we provide new evidence revealing that both monsoon‐driven weathering inputs and water mass advection from the Southern Ocean influenced past seawater Nd isotope changes in this region. Our results suggest that Indian Summer Monsoon weakening coincided with enhanced northward Antarctic Intermediate Water (AAIW) advection during the last deglaciation, reflecting a strong interhemispheric coupling. In contrast, the Early Holocene was characterized by enhanced monsoon strength but persistently strong AAIW inflow, indicating a relationship in the opposite sense. These differing interhemispheric relationships indicate asynchronous changes in the global atmosphere—ocean—climate system, and may represent a previously unrecognized component of the ocean‐atmosphere reorganization during the deglacial to Holocene transition.

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“…Combining these records allows for detailed paleoenvironmental reconstruction via a range of biological, sedimentological, mineralogical and geochemical proxies (Chamley, 1989;Bristow et al, 2009;Flügel and Munnecke, 2010). However, post-depositional processes, which include burial or meteoric diagenesis, hydrothermal activity and varying grades of metamorphism may alter the sediment and the proxy records it contains (Day-Stirrat et al, 2010;Arvidson and Morse, 2014;Rafiei and Kennedy, 2019;Skinner et al, 2019;Frank et al, 2020;Abbott et al, 2022). Once re-exposed at the Earth surface, these partially overprinted sedimentary rocks are subjected to erosion and alteration, starting a new round of weathering and rock recycling.…”

Section: Introductionmentioning

confidence: 99%

Earth system science applications of next-generation SEM-EDS automated mineral mapping

et al. 2022

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Sedimentary rocks contain a unique record of the evolution of the Earth system. Deciphering this record requires a robust understanding of the identity, origin, composition, and post-depositional history of individual constituents. Petrographic analysis informed by Scanning Electron Microscope - Energy Dispersive Spectroscopy (SEM-EDS) mineral mapping can reveal the mineral identity, morphology and petrological context of each imaged grain, making it a valuable tool in the Earth Scientist’s analytical arsenal. Recent technological developments, including quantitative deconvolution of mixed-phase spectra (producing “mixels”), now allow rapid quantitative SEM-EDS-based analysis of a broad range of sedimentary rocks, including the previously troublesome fine-grained lithologies that comprise most of the sedimentary record. Here, we test the reliability and preferred mineral mapping work flow of a modern Field-Emission scanning electron microscope equipped with the Thermofisher Scientific Maps Mineralogy mineral mapping system, focusing on mud/siltstones and calcareous shales. We demonstrate that SEM-EDS mineral mapping that implements 1) a strict error minimization spectral matching approach and 2) spectral deconvolution to produce ‘mixels’ for mixed-phase X-ray volumes can robustly identify individual grains and produce quantitative mineralogical data sets comparable to conventional X-ray diffraction (XRD) analysis (R2 > 0.95). The correlation between SEM-EDS and XRD-derived mineralogy is influenced by mineral abundance, processing modes and mapped area characteristics. Minerals with higher abundance (>10 wt%) show better correlation, likely the result of increased uncertainty for XRD quantification of low-abundance phases. Automated spectral deconvolution to produce ‘mixels’ greatly reduces the proportion of unclassified pixels, especially in the fine-grained fraction, ultimately improving mineral identification and quantification. Mapping of larger areas benefits bulk mineralogy analysis, while customized area size and shape allows high-resolution in situ mineralogical analysis. Finally, we review SEM-EDS-based mineral mapping applications in the Earth Sciences, via case studies illustrating 1) approaches for the quantitative differentiation of various mineral components including detrital (allogenic), syndepositional (authigenic) and burial diagenetic phases, 2) the origin and significance of lamination, 3) the effectiveness and appropriateness of sequential leaching in geochemical studies, and 4) the utility of mineral maps to identify target grains within specific petrological contexts for in situ geochemical or geochronological analysis.

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Widespread lithogenic control of marine authigenic neodymium isotope records? Implications for paleoceanographic reconstructions

Cited by 29 publications

References 82 publications

Supplemental Material: Nd isotopic evidence for enhanced mafic weathering leading to Ordovician cooling

Supplemental Material: Nd isotopic evidence for enhanced mafic weathering leading to Ordovician cooling

Millennial Variability in Intermediate Ocean Circulation and Indian Monsoonal Weathering Inputs During the Last Deglaciation and Holocene

Earth system science applications of next-generation SEM-EDS automated mineral mapping

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