A CO2 greenhouse efficiently warmed the early Earth and decreased seawater 18O/16O before the onset of plate tectonics

The low 18O/16O stable isotope ratios (δ18O) of ancient chemical sediments imply ∼70 °C Archean oceans if the oxygen isotopic composition of seawater (sw) was similar to modern values. Models suggesting lower δ18Osw of Archean seawater due to intense continental weathering and/or low degrees of hydrothermal alteration are inconsistent with the triple oxygen isotope composition (Δ’17O) of Precambrian cherts. We show that high CO2 sequestration fluxes into the oceanic crust, associated with extensive silicification, lowered the δ18Osw of seawater on the early Earth without affecting the Δ’17O. Hence, the controversial long-term trend of increasing δ18O in chemical sediments over Earth’s history partly reflects increasing δ18Osw due to decreasing atmospheric pCO2. We suggest that δ18Osw increased from about −5‰ at 3.2 Ga to a new steady-state value close to −2‰ at 2.6 Ga, coinciding with a profound drop in pCO2 that has been suggested for this time interval. Using the moderately low δ18Osw values, a warm but not hot climate can be inferred from the δ18O of the most pristine chemical sediments. Our results are most consistent with a model in which the “faint young Sun” was efficiently counterbalanced by a high-pCO2 greenhouse atmosphere before 3 Ga.

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Glendonite-Like Carbonate Aggregates from the Lower Ordovician Koporye Formation (Russian Part of the Baltic Klint): Detailed Mineralogical and Geochemical Data and Paleogeographic Implications

Minerals ◽

10.3390/min9090524 ◽

2019 ◽

Vol 9 (9) ◽

pp. 524

Author(s):

Mikhailova ◽

Vasileva ◽

Fedorov ◽

Ershova ◽

Vereshchagin ◽

...

Keyword(s):

Oxygen Isotopic Composition ◽

Geochemical Data ◽

Time Interval ◽

Oxygen And Carbon Isotope ◽

Russian Part ◽

Carbon Isotopic ◽

Lower Ordovician ◽

Bituminous Shale ◽

Oxygen Isotopic ◽

The Baltic

Stellate and plate-like carbonate bodies, traditionally called anthraconites, are found throughout the Baltic-Ladoga Klint in bituminous shale of the Koporye Formation (Tremadocian, Lower Ordovician). Although this time interval is usually considered as a greenhouse, there is some evidence for the existence of at least temporary cold conditions during the Cambrian–Ordovician. However, the origin of anthraconites is still strongly debated. We studied the mineralogical, petrographic, cathodoluminescence, geochemical, and isotopic characteristics of anthraconites from five sections of the Russian part of the Baltic paleobasin. A close similarity between the morphological, petrographic, cathodoluminescence, and isotopic characteristics of the studied anthraconites with those of glendonites allow us to suggest that these bodies formed in a similar paleo-environment and should be considered as pseudomorphs of the mineral ikaite. The oxygen and carbon isotope ratios reveal that ikaite precipitation occurred in low-temperature conditions on the seafloor. The carbon isotopic values reveal influence of inorganic seawater carbon along with organic matter decomposition and/or methane oxidation during ikaite-glendonite transformations. The oxygen isotopic composition significantly changed after deposition due to meteoric diagenesis. We propose that the studied Tremadocian anthraconites formed under a region of upwelling, where cold phosphate-rich deep waters rose to the relatively shallow part of the Baltic paleobasin, providing favorable conditions for ikaite precipitation. Based on our cathodoluminescence study, we suggest that ikaite was transformed to calcite over several stages during diagenesis. Mineralogical studies also reveal that primary calcite was transformed to sulfate (gypsum) or dolomite during late superimposed processes.

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Venus’ light slab hinders its development of planetary-scale subduction and habitability

10.21203/rs.3.rs-1104964/v1 ◽

2022 ◽

Author(s):

Junxing Chen ◽

Hehe Jiang ◽

Ming Tang ◽

Jihua Hao ◽

Meng Tian ◽

...

Keyword(s):

Plate Tectonics ◽

Carbon Sink ◽

Global Scale ◽

Climate Feedback ◽

Early Earth ◽

Crustal Rocks ◽

Planetary Scale ◽

Habitable Planet ◽

Missing Carbon Sink

Abstract Terrestrial planets Venus and Earth have similar sizes, masses, and bulk compositions, but only Earth developed planetary-scale plate tectonics. Plate tectonics generates weatherable fresh rocks and transfers surface carbon back to Earth’s interior, which provides a long-term climate feedback, serving as a thermostat to keep Earth a habitable planet. Yet Venus shares a few common features with early Earth, such as stagnant-lid tectonics and the possible early development of a liquid ocean. Given all these similarities with early Earth, why would Venus fail to develop global-scale plate tectonics? In this study, we explore solutions to this problem by examining Venus’ slab densities under hypothesized subduction-zone conditions. Our petrologic simulations show that eclogite facies may be reached at greater depths on Venus than on Earth, and Venus’ slab densities are consistently lower than Earth’s. We suggest that the lack of sufficient density contrast between the high-pressure metamorphosed slab and mantle rocks may have impeded self-sustaining subduction. Although plume-induced crustal downwelling exists on Venus, the dipping of Venus’ crustal rocks to mantle depth fails to transition into subduction tectonics. As a consequence, the supply of fresh silicate rocks to the surface has been limited. This missing carbon sink eventually diverged the evolution of Venus’ surface environment from that of Earth.

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The long-term climate evolution and planetary habitability – Onset timing of the plate tectonics in early Earth

10.5194/egusphere-egu2020-9209 ◽

2020 ◽

Author(s):

Takashi Nakagawa

Keyword(s):

Plate Tectonics ◽

Planetary System ◽

Early Earth ◽

Volcanic Degassing ◽

Deep Mantle ◽

Onset Timing ◽

Climate Evolution ◽

Plate Subduction ◽

Volatile Cycling

The plate tectonics is an essential geophysical/geological process on the deep mantle water and carbon cycling, which may also control the long-term climate evolution because the volcanic degassing induced by the plate subduction seems to change the atmospheric condition. However, as suggested by the geological evidence on the onset timing of the plate tectonics in early Earth, which is modeled by the transition from the stagnant lid tectonics to the plate subduction, this timing may have great uncertainty. Here, two questions are addressed: 1. How can the deep mantle volatile cycling would be affected by the onset timing of the plate tectonics in the planetary system evolution?; 2. As a result of the successful scenario of the deep mantle volatile cycling explained for the observational constraints of the subduction flux of the water and carbon, how can the climate evolution be responded as a function of the history of the deep mantle volatile cycling such as the subduction flux? To address these questions, a simplified model of whole planetary system evolution based on the thermal history computation of the silicate mantle coupled with the energy balance climate evolution and deep mantle volatile is used with controlling both heat transfer and volatile cycling associated with the transition between stagnant lid and plate tectonics.&#160;The main result indicates that plate tectonics may be essential for the mild and stable climate that allows having liquid water over billions of years of the time scale. This is because a sufficient amount of volcanic degassing can be found for the vigorous plate tectonics rather than the stagnant lid state to get the long-term mild climate. For the stagnant lid state, the snowball limit cycle can be found. Thus, the vigorous plate motion may contribute to stabilizing the warm climate.&#160;To find out the constraint on the present-day surface environment, the transition timing from the stagnant lid to the vigorous plate subduction for explaining the present-day amount of volatiles and their subduction flux would range from 1 to 3 Ga. And, around 5 to 10 ocean masses of the water in the total planetary system is required so that the deep mantle melting should be continuously found to supply the volatile component to the atmosphere associated with the plate subduction, which is worked for the reducing the melting temperature of the silicate mantle. However, the subduction flux for finding the mild climate is one to two orders of magnitude larger than the expected from the geological constraint &#8211; 1012 to 1013 kg/yr as well as some difficulty for explaining the global sea-level change. In the presentation, some improvements on including the big storage capacity of the volatiles in the mantle transition zone will be provided for giving a better understanding of both the deep mantle volatile cycle and climate evolution in the plate-mantle evolution system.

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Revealing the climate of snowball Earth from Δ17O systematics of hydrothermal rocks

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1422887112 ◽

2015 ◽

Vol 112 (17) ◽

pp. 5337-5341 ◽

Cited By ~ 34

Author(s):

Daniel Herwartz ◽

Andreas Pack ◽

Dmitri Krylov ◽

Yilin Xiao ◽

Karlis Muehlenbachs ◽

...

Keyword(s):

Isotopic Composition ◽

Oxygen Isotope ◽

Water Samples ◽

Isotope Composition ◽

Oxygen Isotopic Composition ◽

Snowball Earth ◽

Climate Conditions ◽

Oxygen Isotopic ◽

Mass Dependent ◽

Insight Into

The oxygen isotopic composition of hydrothermally altered rocks partly originates from the interacting fluid. We use the triple oxygen isotope composition (17O/16O, 18O/16O) of Proterozoic rocks to reconstruct the 18O/16O ratio of ancient meteoric waters. Some of these waters have originated from snowball Earth glaciers and thus give insight into the climate and hydrology of these critical intervals in Earth history. For a Paleoproterozoic [∼2.3–2.4 gigayears ago (Ga)] snowball Earth, δ18O = −43 ± 3‰ is estimated for pristine meteoric waters that precipitated at low paleo-latitudes (≤35°N). Today, such low 18O/16O values are only observed in central Antarctica, where long distillation trajectories in combination with low condensation temperatures promote extreme 18O depletion. For a Neoproterozoic (∼0.6–0.7 Ga) snowball Earth, higher meltwater δ18O estimates of −21 ± 3‰ imply less extreme climate conditions at similar paleo-latitudes (≤35°N). Both estimates are single snapshots of ancient water samples and may not represent peak snowball Earth conditions. We demonstrate how 17O/16O measurements provide information beyond traditional 18O/16O measurements, even though all fractionation processes are purely mass dependent.

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Stable oxygen and carbon isotopes from brachiopods of southern England and northwestern Germany: estimation of Upper Turonian palaeotemperatures

Geological Magazine ◽

10.1017/s0016756800004696 ◽

2000 ◽

Vol 137 (6) ◽

pp. 687-703 ◽

Cited By ~ 21

Author(s):

SILKE VOIGT

Keyword(s):

Carbon Isotopes ◽

Isotope Composition ◽

Oxygen Isotopic Composition ◽

Oxygen And Carbon Isotopes ◽

Lower Saxony ◽

Southern England ◽

The North ◽

The North Sea ◽

Oxygen Isotopic ◽

Climate Cooling

More than 190 articulate brachiopods from Turonian sections in northwestern Germany and southern England were studied for their stable carbon and oxygen isotopic composition, and some of them for their elemental composition. Most of the brachiopod shells are well preserved, and oxygen isotope composition reflects the temperate conditions of the European epicontinental sea. Upper Turonian mean δ18O values from Lower Saxony and southern England show bottom-water temperatures in the range of 14.2 to 18.2 °C (δ18Ow = −1.5‰ SMOW for an ice-free world). The relative trend of mean brachiopod oxygen and carbon isotopes shows a short-term (200 k.y.) increase in the mid-Upper Turonian horizons that confirms the climate cooling (∼ 2 °C) observed in bulk-rock samples at different sites in Europe. Interbasinal comparisons between England and Germany show similar δ13C values in both basins, whereas oxygen isotopes are heavier in northwestern Germany than in England, suggesting a cool-water influence from the North Sea basin and temperate conditions in the Anglo-Paris basin.

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C and O isotope composition of secondary carbonates in the volcanites of the pre-Jurassic complex of the Western-Siberian Plate

Moscow University Bulletin. Series 4. Geology ◽

10.33623/0579-9406-2019-5-38-43 ◽

2019 ◽

pp. 38-43

Author(s):

A. V. Krasnova ◽

Yu. V. Rostovtseva ◽

A. E. Gavrilov

Keyword(s):

Isotopic Composition ◽

Western Siberia ◽

Isotope Composition ◽

Oxygen Isotopic Composition ◽

Hydrothermal Solutions ◽

Tomsk Region ◽

Oxygen Isotopic ◽

O Isotope

The carbon and oxygen isotopic composition of secondary carbonates from acidic effusives fro investigated. Ϭ13С (VPDB) and Ϭ18О (VSMOW) values of siderite vary from –6,6 to –2,4‰ m the top of the Western Siberia pre-Jurassic complex (Tomsk Region) was and from 7,8 to 12,3‰, while Ϭ13С and Ϭ18О values of calcite vary from –8,9 to –8,4‰ and from 2,5 to 3,7‰ respectively. Light oxygen isotopic composition indicates formation of studied carbonates from heated hydrothermal solutions.

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Nutrient distribution and nitrogen and oxygen isotopic composition of nitrate in water masses of the subtropical South Indian Ocean

10.5194/bg-2018-511 ◽

2019 ◽

Author(s):

Natalie C. Harms ◽

Niko Lahajnar ◽

Birgit Gaye ◽

Tim Rixen ◽

Kirstin Dähnke ◽

...

Keyword(s):

Indian Ocean ◽

Isotope Composition ◽

Oxygen Isotopic Composition ◽

Subtropical Gyre ◽

Nutrient Concentrations ◽

Stable Isotope Composition ◽

Nutrient Distribution ◽

South Indian ◽

Oxygen Isotopic ◽

Transformation Processes

Abstract. Vast subtropical gyres are important areas for the exchange of carbon between atmosphere and ocean in spite of low nutrient concentrations, and supposedly for the influx of reactive nitrogen to the ocean by dinitrogen fixation. To identify sources and transformation processes in the nitrogen cycle of the southern Indian Ocean subtropical gyre, we investigated concentrations of water column nutrients and stable isotope composition of nitrate of samples from two expeditions in 2016 (MSM 59) and 2017 (SO 259) in the subtropical gyre between ~ 30 °S and the equator. Low nitrate and phosphate concentrations mark the thick mixed layer of the oligotrophic gyre with values of

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Hydrogeological responses in tropical mountainous springs

Memorias del I Congreso Internacional de Ciencias Exactas y Naturales ◽

10.15359/cicen.1.37 ◽

2019 ◽

Author(s):

Ricardo Sánchez-Murillo

Keyword(s):

Costa Rica ◽

Isotope Composition ◽

Central Valley ◽

Distribution Functions ◽

Geochemical Composition ◽

Transit Times ◽

Management Plans ◽

Best Fit ◽

Term Data

This study presents a hydrogeochemical analysis of spring responses (2013-2017) in the tropical mountainous region of the Central Valley of Costa Rica. The isotopic distribution of δ18O and δ2H in rainfall resulted in a highly significant meteoric water line: δ2H = 7.93×δ18O + 10.37 (r2=0.97). Rainfall isotope composition exhibited a strong dependent seasonality. The isotopic variation (δ18O) of two springs within the Barva aquifer was simulated using the FlowPC program to determine mean transit times (MTTs). Exponential-piston and dispersion distribution functions provided the best-fit to the observed isotopic composition at Flores and Sacramento springs, respectively. MTTs corresponded to 1.23±0.03 (Sacramento) and 1.42±0.04 (Flores) years. The greater MTT was represented by a homogeneous geochemical composition at Flores, whereas the smaller MTT at Sacramento is reflected in a more variable geochemical response. The results may be used to enhance modelling efforts in central Costa Rica, whereby scarcity of long-term data limits water resources management plans.

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Changes of Ionic and Oxygen Isotopic Composition of the Snowpack at the Glacier Austre Okstindbreen, Norway, 1995

Hydrology Research ◽

10.2166/nh.1998.0001 ◽

1998 ◽

Vol 29 (1) ◽

pp. 1-20 ◽

Cited By ~ 20

Author(s):

Peter Raben ◽

Wilfred H. Theakstone

Keyword(s):

Isotopic Composition ◽

Sea Level ◽

Oxygen Isotopes ◽

Oxygen Isotopic Composition ◽

Isotopic Ratios ◽

Vertical Variations ◽

Oxygen Isotopic ◽

The Difference ◽

Liquid Precipitation ◽

Different Altitudes

Marked vertical variations of ions and oxygen isotopes were present in the snowpack at the glacier Austre Okstindbreen during the pre-melting phase in 1995 at sites between 825 m and 1,470 m above sea level. As the first meltwater percolated from the top of the pack, ions were moved to a greater depth, but the isotopic composition remained relatively unchanged. Ions continued to move downwards through the pack during the melting phase, even when there was little surface melting and no addition of liquid precipitation. The at-a-depth correlation between ionic concentrations and isotopic ratios, strong in the pre-melting phase, weakened during melting. In August, concentrations of Na+ and Mg2+ ions in the residual pack were low and vertical variations were slight; 18O enrichment had occurred. The difference of the time at which melting of the snowpack starts at different altitudes influences the input of ions and isotopes to the underlying glacier.

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Chilling Out

10.1093/oso/9780198717867.003.0010 ◽

2018 ◽

Author(s):

Roy Livermore

Keyword(s):

Plate Tectonics ◽

Volcanic Eruptions ◽

Atmospheric Temperature ◽

Ocean Currents ◽

Mountain Ranges ◽

Continental Rifts ◽

Earth’S Climate ◽

The One ◽

Tectonic Forces

The Earth’s climate changes naturally on all timescales. At the short end of the spectrum—hours or days—it is affected by sudden events such as volcanic eruptions, which raise the atmospheric temperature directly, and also indirectly, by the addition of greenhouse gases such as water vapour and carbon dioxide. Over years, centuries, and millennia, climate is influenced by changes in ocean currents that, ultimately, are controlled by the geography of ocean basins. On scales of thousands to hundreds of thousands of years, the Earth’s orbit around the Sun is the crucial influence, producing glaciations and interglacials, such as the one in which we live. Longer still, tectonic forces operate over millions of years to produce mountain ranges like the Himalayas and continental rifts such as that in East Africa, which profoundly affect atmospheric circulation, creating deserts and monsoons. Over tens to hundreds of millions of years, plate movements gradually rearrange the continents, creating new oceans and destroying old ones, making and breaking land and sea connections, assembling and disassembling supercontinents, resulting in fundamental changes in heat transport by ocean currents. Finally, over the very long term—billions of years—climate reflects slow changes in solar luminosity as the planet heads towards a fiery Armageddon. All but two of these controls are direct or indirect consequences of plate tectonics.

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