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Journal Article•DOI•

Lithium isotope evidence for enhanced weathering during Oceanic Anoxic Event 2

Philip A.E. Pogge von Strandmann1, Hugh C. Jenkyns1, Richard G. Woodfine1•
University of Oxford1
01 Aug 2013-Nature Geoscience (Nature Publishing Group)-Vol. 6, Iss: 8, pp 668-672
TL;DR: The Ocean Anoxic Event 2 (OAE2) about 93.5 million years ago was marked by high atmospheric CO2 concentration, rapid global warming and marine anoxia and euxinia as mentioned in this paper.
Abstract: The Ocean Anoxic Event 2 (OAE2) about 93.5 million years ago was marked by high atmospheric CO2 concentration, rapid global warming and marine anoxia and euxinia. The event lasted for about 440,000 years and led to habitat loss and mass extinction. The marine anoxia is thought to be linked to enhanced biological productivity, but it is unclear what triggered the increased production and what allowed the subsequent rapid climate recovery. Here we use lithium isotope measurements from carbonates spanning the interval including OAE2 to assess the role of silicate weathering. We find the lightest values of the Li isotope ratio (δ7Li) during OAE2, indicating high levels of weathering—and therefore atmospheric CO2 removal—which we attribute to an enhanced hydrological cycle. We use a geochemical model to simulate the evolution of δ7Li and the Ca, Sr and Os isotope tracers. Our simulations suggest a scenario in which the eruption of a large igneous province led to high atmospheric CO2 concentrations and rapid global warming, which initiated OAE2. The simulated warming was accompanied by a roughly 200,000 year pulse of accelerated weathering of mafic silicate rocks, which removed CO2 from the atmosphere. The weathering also delivered nutrients to the oceans that stimulated primary productivity. We suggest that this process, together with the burial of organic carbon, allowed the rapid recovery and stabilization from the greenhouse state.

Summary (1 min read)

Jump to: [Influence of weathering on river and oceanic Li isotope ratios] – [Isotopic constraints on Cretaceous seawater chemistry] and [Implications of enhanced weathering during OAE2]

Influence of weathering on river and oceanic Li isotope ratios

  • Understanding the timing and tempo of continental weathering is critical for testing the OAE model, and for evaluating the role of CO2 drawdown in climatic stabilisation.
  • Hence, if the weathering regime is weathering--limited (thin soils and hence incongruent weathering, with chemical reactions controlled by temperature and runoff) 25 , dissolved δ.
  • All sections also exhibit contemporaneous Li/Ca increases.

Isotopic constraints on Cretaceous seawater chemistry

  • Cation exchange or leaching of clays prior to analysis was monitored by analysing cation/Ca ratios of the calcite samples.
  • Furthermore, C, O and Sr isotopes show similar values in these different profiles and compare well with other sections across the Cenomanian-Turonian boundary 37 .
  • Sr trend to constrain the hydrothermal input, because Sr isotopes are the most sensitive of these systems to this flux, and δ 7 Li to understand the silicate weathering input (see supplemental information for model details).
  • It is possible that these changes caused the observed Li isotope variations.

Implications of enhanced weathering during OAE2

  • Thus the model suggests that explaining the Li isotope data requires the riverine flux to increase ~2-4 times during the OAE in the presence of a lower oceanic Li residence time relative to the present--day.
  • Given the demonstrated response of lighter dissolved δ.
  • Li with increasing modern basaltic weathering rates 14, 24, 42 , the eruption of subaerial basalts just prior to the onset of OAE2 is the most logical choice to explain the isotopic variations.
  • This interval is of similar duration to the ~23kyr proposed between the onset of relatively unradiogenic values of 187 Os/ 188 Os and the OAE itself 9 .
  • This study suggests that in excess of a third of the emitted CO2 was effectively balanced by silicate weathering by the end of the oceanic anoxic event, given that a significant amount of carbon was demonstrably sequestered within OAE black shales.

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Lithium'isotope'evidence'for'enhanced'hydrological'cycling'during'Oceanic'
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Citations
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Journal Article•DOI•
Marine 187Os/188Os isotope stratigraphy reveals the interaction of volcanism and ocean circulation during Oceanic Anoxic Event 2

[...]

Alice D.C. Du Vivier1, David Selby1, Bradley B. Sageman2, Ian Jarvis3, Darren R. Gröcke1, Silke Voigt4 •
Durham University1, Northwestern University2, Kingston University3, Goethe University Frankfurt4
01 Mar 2014-Earth and Planetary Science Letters
TL;DR: In this paper, high-resolution osmium (Os) isotope stratigraphy across the Cenomanian-Turonian Boundary Interval from 6 sections for four transcontinental settings has produced a record of seawater chemistry that demonstrates regional variability as a function of terrestrial and hydrothermal inputs, revealing the impact of palaeoenvironmental processes.

190 citations

Journal Article•DOI•
Riverine Li isotope fractionation in the Amazon River basin controlled by the weathering regimes

[...]

Mathieu Dellinger1, Mathieu Dellinger2, Jérôme Gaillardet2, Jérôme Gaillardet3, Julien Bouchez2, Damien Calmels4, Pascale Louvat2, Anthony Dosseto5, Caroline Gorge2, Lucia Alanoca6, Laurence Maurice6 •
University of Southern California1, Institut de Physique du Globe de Paris2, Institut Universitaire de France3, University of Paris-Sud4, University of Wollongong5, Paul Sabatier University6
01 Sep 2015-Geochimica et Cosmochimica Acta
TL;DR: In this paper, Li isotope composition of river-borne dissolved and solid material in the largest River system on Earth, the Amazon River basin, was analyzed to characterize Li isotopes fractionation at a continental scale.

177 citations

Journal Article•DOI•
Lithium Isotope Geochemistry

[...]

Sarah C. Penniston-Dorland1, Xiao-Ming Liu2, Roberta L. Rudnick3•
University of Maryland, College Park1, University of North Carolina at Chapel Hill2, University of California, Santa Barbara3
01 Jan 2017-Reviews in Mineralogy & Geochemistry
TL;DR: The lithium isotope system is increasingly being applied to a variety of Earth science studies, as the burgeoning literature attests; over 180 papers have been published in the last twelve years that report Li isotope data, including five review papers as discussed by the authors.
Abstract: The lithium isotope system is increasingly being applied to a variety of Earth science studies, as the burgeoning literature attests; over 180 papers have been published in the last twelve years that report lithium isotope data, including five review papers that cover different aspects of lithium isotope applications (Elliott et al. 2004; Tomascak 2004; Tang et al. 2007b; Burton and Vigier 2011; Schmitt et al. 2012), and a book (Tomascak et al. 2016). The upswing in lithium isotope studies over the past decade reflects analytical advances that have made Li measurements readily obtainable. These include the use of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for relatively precise solution measurements (Tomascak et al. 1999a) and secondary ion mass spectrometry (SIMS) for high spatial resolution measurements (Chaussidon and Robert 1998; Kasemann et al. 2005; Bell et al. 2009). In addition, lithium isotope studies are motivated by the large variety of problems for which they may provide insight, including crust–mantle recycling, silicate weathering, fluid–rock interaction, as well as geospeedometry. The great interest in the Li system that spurred the development of these new analytical methods was initiated by the pioneering work of Lui-Heung Chan, who demonstrated not only that Li isotopic fractionation can be very large at or near the Earth’s surface (Chan and Edmond 1988), but also that Li isotopes are strongly fractionated during seawater-basalt interaction (Chan et al. 1992). This discovery naturally led to the search for a recycled slab signature in Li isotopes of arc lavas (some of the earlier studies include Moriguti and Nakamura 1998a; Chan et al. 1999, 2002b; Tomascak et al. 2000, 2002; Leeman et al. 2004; Moriguti et al. 2004), as well as more deeply derived intraplate basalts (e.g., Chan and Frey 2003 …

158 citations

Journal Article•DOI•
Large igneous provinces and organic carbon burial: Controls on global temperature and continental weathering during the Early Cretaceous

[...]

Stéphane Bodin1, P. Meissner1, Nico M.M. Janssen, Thomas Steuber2, Jörg Mutterlose1 •
Ruhr University Bochum1, Petroleum Institute2
01 Oct 2015
TL;DR: In this article, an extended compilation of belemnite-based oxygen, carbon and strontium isotope records covering the Berriasian-middle Albian from the Vocontian Basin (SE France) is presented.
Abstract: There is an abundance of evidence for short intervals of cold climatic conditions during the Early Cretaceous. However, the lack of a high-resolution, long-term Early Cretaceous paleotemperature record hampers a full-scale synthesis of these putative “cold snap” episodes, as well as a more holistic approach to Early Cretaceous climate changes. We present an extended compilation of belemnite-based oxygen, carbon and strontium isotope records covering the Berriasian–middle Albian from the Vocontian Basin (SE France). This dataset clearly demonstrates three intervals of cold climatic conditions during the Early Cretaceous (late Valanginian–earliest Hauterivian, late early Aptian, latest Aptian–earliest Albian). Each of these intervals is associated with rapid and high amplitude sea-level fluctuations, supporting the hypothesis of transient growth of polar ice caps during the Early Cretaceous. As evidenced by positive carbon isotope excursions, each cold episode is associated with enhanced burial of organic matter on a global scale. Moreover, there is a relatively good match between the timing and size of large igneous province eruptions and the amplitude of Early Cretaceous warming episodes. Altogether, these observations confirm the instrumental role of atmospheric CO2 variations in driving Early Cretaceous climate change. From a long-term perspective, the coupling of global paleotemperature and seawater strontium isotopic ratio during the Early Cretaceous is best explained by temperature-controlled changes of continental crust weathering rates.

131 citations

Journal Article•DOI•
Sulfur isotopes track the global extent and dynamics of euxinia during Cretaceous Oceanic Anoxic Event 2

[...]

Jeremy D. Owens1, Benjamin C. Gill2, Hugh C. Jenkyns3, Steven M Bates1, Silke Severmann4, Marcel M. M. Kuypers5, Richard G. Woodfine, Timothy W. Lyons1 •
University of California, Riverside1, Virginia Tech2, University of Oxford3, Rutgers University4, Max Planck Society5
12 Nov 2013-Proceedings of the National Academy of Sciences of the United States of America
TL;DR: Coupled high-resolution carbon- and sulfur-isotope data from four European OAE 2 sections spanning the Cenomanian–Turonian boundary are presented that show roughly parallel positive excursions, challenging previous suggestions that one of the best-documented OAEs was defined by globally pervasive euxinic deep waters.
Abstract: The Mesozoic Era is characterized by numerous oceanic anoxic events (OAEs) that are diagnostically expressed by widespread marine organic-carbon burial and coeval carbon-isotope excursions. Here we present coupled high-resolution carbon- and sulfur-isotope data from four European OAE 2 sections spanning the Cenomanian–Turonian boundary that show roughly parallel positive excursions. Significantly, however, the interval of peak magnitude for carbon isotopes precedes that of sulfur isotopes with an estimated offset of a few hundred thousand years. Based on geochemical box modeling of organic-carbon and pyrite burial, the sulfur-isotope excursion can be generated by transiently increasing the marine burial rate of pyrite precipitated under euxinic (i.e., anoxic and sulfidic) water-column conditions. To replicate the observed isotopic offset, the model requires that enhanced levels of organic-carbon and pyrite burial continued a few hundred thousand years after peak organic-carbon burial, but that their isotope records responded differently due to dramatically different residence times for dissolved inorganic carbon and sulfate in seawater. The significant inference is that euxinia persisted post-OAE, but with its global extent dwindling over this time period. The model further suggests that only ∼5% of the global seafloor area was overlain by euxinic bottom waters during OAE 2. Although this figure is ∼30× greater than the small euxinic fraction present today (∼0.15%), the result challenges previous suggestions that one of the best-documented OAEs was defined by globally pervasive euxinic deep waters. Our results place important controls instead on local conditions and point to the difficulty in sustaining whole-ocean euxinia.

127 citations

References
More filters
Journal Article•DOI•
Geochemistry of oceanic anoxic events

[...]

Hugh C. Jenkyns1•
University of Oxford1
01 Mar 2010-Geochemistry Geophysics Geosystems
TL;DR: In the case of the Cenomanian-Turonian and early Aptian OAEs, a longer-term trend to less radiogenic values was observed as discussed by the authors.
Abstract: [1] Oceanic anoxic events (OAEs) record profound changes in the climatic and paleoceanographic state of the planet and represent major disturbances in the global carbon cycle. OAEs that manifestly caused major chemical change in the Mesozoic Ocean include those of the early Toarcian (Posidonienschiefer event, T-OAE, ∼183 Ma), early Aptian (Selli event, OAE 1a, ∼120 Ma), early Albian (Paquier event, OAE 1b, ∼111 Ma), and Cenomanian–Turonian (Bonarelli event, C/T OAE, OAE 2, ∼93 Ma). Currently available data suggest that the major forcing function behind OAEs was an abrupt rise in temperature, induced by rapid influx of CO2 into the atmosphere from volcanogenic and/or methanogenic sources. Global warming was accompanied by an accelerated hydrological cycle, increased continental weathering, enhanced nutrient discharge to oceans and lakes, intensified upwelling, and an increase in organic productivity. An increase in continental weathering is typically recorded by transient increases in the seawater values of 87Sr/86Sr and 187Os/188Os ratios acting against, in the case of the Cenomanian-Turonian and early Aptian OAEs, a longer-term trend to less radiogenic values. This latter trend indicates that hydrothermally and volcanically sourced nutrients may also have stimulated local increases in organic productivity. Increased flux of organic matter favored intense oxygen demand in the water column, as well as increased rates of marine and lacustrine carbon burial. Particularly in those restricted oceans and seaways where density stratification was favored by paleogeography and significant fluvial input, conditions could readily evolve from poorly oxygenated to anoxic and ultimately euxinic (i.e., sulfidic), this latter state being geochemically the most significant. The progressive evolution in redox conditions through phases of denitrification/anammox, through to sulfate reduction accompanied by water column precipitation of pyrite framboids, resulted in fractionation of many isotope systems (e.g., N, S, Fe, Mo, and U) and mobilization and incorporation of certain trace elements into carbonates (Mn), sulfides, and organic matter. Sequestration of CO2 in organic-rich black shales and by reaction with silicate rocks exposed on continents would ultimately restore climatic equilibrium but at the expense of massive chemical change in the oceans and over time scales of tens to hundreds of thousands of years.

1,144 citations

Journal Article•DOI•
Tectonic and climatic controls on silicate weathering

[...]

A. Joshua West1, Albert Galy1, Mike J. Bickle1•
University of Cambridge1
30 Jun 2005-Earth and Planetary Science Letters
TL;DR: In this article, the authors present a compilation of chemical and physical erosion rates in small catchments and show that silicate weathering rates are not governed by any single parameter but require consideration in multiple dimensions.

817 citations

Journal Article•DOI•
Basalt weathering laws and the impact of basalt weathering on the global carbon cycle

[...]

Céline Dessert1, Bernard Dupré1, Jérôme Gaillardet2, Louis François3, Claude J. Allègre2 •
Centre national de la recherche scientifique1, IPG Photonics2, University of Liège3
30 Dec 2003-Chemical Geology
TL;DR: In this paper, the chemical weathering of basalts and the flux of carbon transferred from the atmosphere to the ocean during this major process at the surface of the Earth were investigated.

762 citations

Journal Article•DOI•
On the ages of flood basalt events

[...]

Vincent Courtillot1, Paul R. Renne2, Paul R. Renne3•
Institut de Physique du Globe de Paris1, Berkeley Geochronology Center2, University of California, Berkeley3
01 Jan 2003-Comptes Rendus Geoscience
TL;DR: This paper reviewed available data constraining the extent, volume, age and duration of all major Phanerozoic continental flood basalts (CFB or traps) and oceanic plateaus (OP), together forming the group of large igneous provinces (LIPs).

761 citations

Journal Article•DOI•
Deep-sea paleotemperature record of extreme warmth during the Cretaceous

[...]

Brian T. Huber1, Richard D Norris2, Kenneth G. MacLeod3•
Smithsonian Institution1, Woods Hole Oceanographic Institution2, University of Missouri3
01 Feb 2002-Geology
TL;DR: Oxygen isotope analyses of well-preserved foraminifera from Blake Nose (30°N paleolatitude, North Atlantic) and globally distributed deep-sea sites provide a long-term paleotemperature record for the late Albian-Maastrichtian interval that is difficult to reconcile with the existence of significant Cretaceous ice sheets as discussed by the authors.
Abstract: Oxygen isotope analyses of well-preserved foraminifera from Blake Nose (30°N paleolatitude, North Atlantic) and globally distributed deep-sea sites provide a long-term paleotemperature record for the late Albian–Maastrichtian interval that is difficult to reconcile with the existence of significant Cretaceous ice sheets. Given reasonable assumptions about the isotopic composition of Cretaceous seawater, our results suggest that middle bathyal water temperatures at Blake Nose increased from ∼12 °C in the late Albian through middle Cenomanian to a maximum of 20 °C during the latest Cenomanian and earliest Turonian. Bottom waters were again ∼12 °C during the middle Campanian and cooled to a minimum of 9 °C during the Maastrichtian. Correlative middle bathyal foraminifera from other ocean basins yield paleotemperature estimates that are very similar to those from Blake Nose. Comparison of global bottom-water temperatures and latitudinal thermal gradients suggests that global climate changed from a warm greenhouse state during the late Albian through late Cenomanian to a hot greenhouse phase during the latest Cenomanian through early Campanian, then to cool greenhouse conditions during the mid-Campanian through Maastrichtian.

672 citations

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Geochemistry of oceanic anoxic events

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Lithium Isotope History of Cenozoic Seawater: Changes in Silicate Weathering and Reverse Weathering

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17 Feb 2012-Science
Sambuddha Misra, Philip N. Froelich
Cretaceous oceanic anoxic event 2 triggered by a massive magmatic episode

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17 Jul 2008-Nature
Steven C. Turgeon, Robert A. Creaser
Carbon-isotope stratigraphy recorded by the Cenomanian–Turonian Oceanic Anoxic Event: correlation and implications based on three key localities

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01 May 2005-Journal of the Geological Society
Harilaos Tsikos, Harilaos Tsikos, Hugh C. Jenkyns, Ben Walsworth-Bell, Maria Rose Petrizzo, Astrid Forster, Sadat Kolonic, Elisabetta Erba, I. Premoli Silva, Marianne Baas, T. Wagner, J. S. Sinninghe Damsté 
Cretaceous oceanic anoxic events: causes and consequences

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01 Oct 2007-Geologie En Mijnbouw
Seymour O. Schlanger, Hugh C. Jenkyns