Rare Earth Elements in early-diagenetic foraminifer ‘coatings’: Pore-water controls and potential palaeoceanographic applications

Skinner, Luke C; Sadekov, Aleksey; Brandon, Margaux; Greaves, Mervyn; Plancherel, Yves; Fuente, Maria de la; Gottschalk, Julia; Souanef-Ureta, S.; Sevilgen, Duygu S.; Scrivner, A. E.

doi:10.1016/j.gca.2018.10.027

Cited by 43 publications

(41 citation statements)

References 44 publications

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“…Trace element profiles, including selected light REEs plus yttrium (hereafter REY), were measured using an Analyte G2 excimer laser (Teledyne Photon Machines Inc, Omaha, NE, USA) coupled with Thermo i‐CapQ ICP‐MS at the University of Cambridge, following the methods later outlined in Gabitov et al () and Skinner et al (). Only selected REYs were measured because of counting statistics at the time of analysis.…”

Section: Methodsmentioning

confidence: 99%

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Chemical Composition of Carbonate Hardground Cements as Reconstructive Tools for Phanerozoic Pore Fluids

Erhardt

Turchyn

Dickson

et al. 2020

Geochem Geophys Geosyst

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In this study, we report the chemical composition of early carbonate cement precipitates in carbonate hardgrounds to understand the geochemical signature of near‐surface carbonate mineral precipitation. As carbonate hardgrounds lithify at or near the sediment‐water interface, they acquire cements that may be minimally evolved from paleoseawater. Using a suite of chemical measurements, we explore the potential of carbonate hardground cements as paleoenvironmental proxies. Trace metal and isotopic ratios, including some rare earth elements, Mg/Ca, manganese, and strontium concentrations, δ18O, δ13C, and 87Sr/86Sr, were analyzed in the carbonate cements from 17 Phanerozoic carbonate hardgrounds. The sensitivity of the geochemical signal to alteration depends on the geochemical analysis in question and the environmental water‐rock ratio. Of these samples, only our modern sample has measurements consistent with primary precipitation from seawater; all other samples precipitated from chemically evolved seawater or were influenced by meteoric water, even if only minimally changed. The more recent samples from the Cenozoic had seawater 87Sr/86Sr. The Mesozoic samples, in contrast, did not preserve seawater 87Sr/86Sr, even though the Mg/Ca, δ18O, and δ13C values were consistent with precipitation from seawater. Finally, the Paleozoic samples preserved expected seawater 87Sr/86Sr, though rare earth element and δ18O suggest primary precipitation was from evolved seawater. Additionally, we place our results in the context of open versus closed system precipitation using transects of the Mg/Ca ratios across individual cements. Overall, we stress that one geochemical measurement provides only a partial record of fluid composition, but multiple measurements allow a potential understanding of the seawater geochemical signal.

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Section: Methodsmentioning

confidence: 99%

“…The differences between these are likely due to inhomogeneity of the carbonate material. Further information on long‐term internal and external precision are outlined in Skinner et al (). Our results are normalized to post Archean Australian Shale (Pourmand et al, ) to allow for comparison with average crustal values.…”

Section: Methodsmentioning

confidence: 99%

Chemical Composition of Carbonate Hardground Cements as Reconstructive Tools for Phanerozoic Pore Fluids

Erhardt

Turchyn

Dickson

et al. 2020

Geochem Geophys Geosyst

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“…In the modern ocean, a tight relationship is observed between apparent oxygen utilization and the δ 13 C signature of dissolved inorganic carbon (Eide et al 2017), providing the basis of the use of the benthic δ 13 C as an indirect "paleoventilation" proxy (Duplessy et al 1988). More recently, it has also been suggested that the REE composition of early diagenetic surface enrichments of planktonic foraminifera can be used to inform on past changes in the oxygen supply to sediments from seawater (Boiteau et al 2012;Skinner et al 2019). In oxic seawater, Ce will be present in the less soluble IV oxidation state, unlike its neighboring trivalent REE, La and Nd, resulting in the loss of Ce from the water column and a characteristic Ce depletion (or "Ce anomaly").…”

Section: Consistent Evidence For a Marked Ventilation Change During Tmentioning

confidence: 99%

“…In oxic seawater, Ce will be present in the less soluble IV oxidation state, unlike its neighboring trivalent REE, La and Nd, resulting in the loss of Ce from the water column and a characteristic Ce depletion (or "Ce anomaly"). Despite early hopes that the special behavior of Ce might lend itself to the use of Ce-anomalies in marine sediments as a proxy for past water oxygenation (Liu et al 1988;German and Elderfield 1990), it appears that REE signatures preserved in marine sediments, for example in early diagenetic surface enrichments on foraminifera, record a significant pore-water influence (German and Elderfield 1990;Skinner et al 2019). While this would preclude their use as direct indicators of seawater composition, it has been argued that oxygen supply to sediments from seawater could nonetheless still influence the progressive "erosion" of Ce-anomalies recorded in foraminifer surface enrichments (Skinner et al 2019), producing a Ce-enrichment (relative to an expected seawater depletion), analogous to authigenic Uranium enrichment under low oxygen conditions (Klinkhammer and Palmer 1991;Boiteau et al 2012).…”

Section: Consistent Evidence For a Marked Ventilation Change During Tmentioning

confidence: 99%

Radiocarbon Dating of Small-sized Foraminifer Samples: Insights into Marine sediment Mixing

et al. 2020

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Radiocarbon ( 14 C) can be used to build absolute chronologies and reconstruct ocean ventilation over the last 40 ka. Sample size requirements have restricted 14 C measurements in marine cores with low foraminifer content, impeding 14 C-based studies focused on abrupt climate events. Recent developments have demonstrated that small-sized foraminifer samples can now be dated using a gas introduction system at the cost of a small decrease in precision. We explore the potential of gas measurements on benthic and planktonic foraminifers from core SU90-08 (43°03 0 1 00 N, 30°02 0 5 00 W, 3080 m). Gas measurements are accurate, reproducible within 2σ uncertainty and comparable to graphite measurements. Both techniques yield negative 14 C benthic-planktonic (B-P) age-offsets after Heinrich event 1. We argue that negative B-P ages result from bioturbation and changes in foraminifer abundances, with the chance of negative B-P especially increased when the 14 C age gradient between the deep and surface waters is decreased. Small-sized 14 C measurements seem to capture the variance of the foraminifera age distribution, revealing the active mixing in those archives. Sediment deposition and mixing effects possibly pose a greater obstacle for past 14 C-based dating and ocean ventilation reconstructions than the measurement precision itself, particularly in relatively low sedimentation rate settings.

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“…A particulate phase acting as a sink when in contact with seawater will provide the best record of changes in ocean conditions through time. However, a phase that continues to act as a sink during burial will have any original seawater signature diagenetically overprinted as has already been proposed for biogenic phosphates and foraminifera (Palmer and Elderfield, 1985;Toyoda and Tokonami, 1990;Takahashi et al, 2015;Trotter et al, 2016;Zhang et al, 2016;Skinner et al, 2019).…”

Section: Introductionmentioning

confidence: 96%

Are Clay Minerals the Primary Control on the Oceanic Rare Earth Element Budget?

2019

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The rare earth elements (REEs) are an important tool for understanding biogeochemical cycling and sedimentary processes in the global ocean. However, ambiguities in the marine REE budgets, including questions around the dominant source of REEs to the ocean, hinder the application of this tool. A bottom-up model for REE release into the ocean has recently been proposed, driven by early diagenetic processes such as sediment dissolution, with potentially significant implications for the interpretation of marine REE and Nd isotope paleo-records. Here, our goal is to identify the phase or phases that interact with the pore waters to drive such a benthic flux. We use new pore water REE, microbeam imaging and mineralogical data in combination with published pore water REE data to evaluate potential sedimentary REE host phases. Mineralogical and direct imaging observations suggest that authigenic Fe or Mn oxyhydroxides, which are widely considered a dominant REE host phase, are not sufficiently abundant sediment components to account for the high Nd concentrations recovered in reductive leaches, and are unlikely to be the primary source of pore water REEs. Pore water REE signatures similar to river sourced clays indicate a detrital clay dissolution source, while the spread in heavy to light REE enrichment in pore waters and bottom waters relative to this clay source is best explained by fractionation during authigenic clay uptake of REEs. We therefore conclude that clay mineral dissolution and authigenesis are likely the primary influences on the REE cycling near the seafloor. We propose that the balance between dissolution and authigenesis controls the concentration, ratio of heavy and light REE abundances, and the isotopic composition of the pore waters. We discuss the implications of this hypothesis on an oceanic REE budget controlled by a benthic flux from a sedimentary REE source, and the use of authigenic neodymium isotopes as a paleoproxy for shifts in ocean circulation.

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Rare Earth Elements in early-diagenetic foraminifer ‘coatings’: Pore-water controls and potential palaeoceanographic applications

Cited by 43 publications

References 44 publications

Chemical Composition of Carbonate Hardground Cements as Reconstructive Tools for Phanerozoic Pore Fluids

Chemical Composition of Carbonate Hardground Cements as Reconstructive Tools for Phanerozoic Pore Fluids

Radiocarbon Dating of Small-sized Foraminifer Samples: Insights into Marine sediment Mixing

Are Clay Minerals the Primary Control on the Oceanic Rare Earth Element Budget?

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