A geochemical modelling study of the evolution of the chemical composition of seawater linked to a &amp;quot;snowball&amp;quot; glaciation

Hir, Guillaume Le; Goddéris, Yves; Donnadieu, Yannick; Ramstein, Gilles

doi:10.5194/bg-5-253-2008

Cited by 35 publications

(19 citation statements)

References 59 publications

(80 reference statements)

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“…Elevated oceanic Mg/Ca and/or alkalinity during the Cryogenian may also have been factors that promoted marine dolomite precipitation. These factors have been linked to an increased continental weathering fl ux following the Sturtian glaciation (Le Hir et al, 2008). Dolomite precipitation may also be related to low sulfate levels in Neoproterozoic seas (Baker and Kastner, 1981;see, however, Sánchez-Román et al, 2009), consistent with Cryogenian ocean euxinia.…”

Section: Discussionmentioning

confidence: 88%

Neoproterozoic aragonite-dolomite seas? Widespread marine dolomite precipitation in Cryogenian reef complexes

Hood

Wallace

Drysdale

2011

Geology

106

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The extraordinary abundance of dolomite in the Proterozoic challenges our understanding of Precambrian marine environments. Here we show that synsedimentary marine dolomite precipitation was pervasive within Cryogenian reef complexes from the Adelaide Fold Belt, South Australia. Although these reefs are composed of dolomite, textural evidence indicates an originally aragonitic mineralogy for depositional components, in common with many other Neoproterozoic carbonates. Allochthonous slope debris from the reefs invariably contains both limestone and dolomite clasts, indicating synsedimentary dolomitization in the reefs. We describe several new forms of fi brous marine dolomite cement from the reefs that have a length-slow optical character. These fascicular slow, radial slow, and rhombic dolomite cements have fi nely preserved cathodoluminescent growth zones, and optical characteristics that indicate they originally precipitated as dolomite, rather than replacing calcite or aragonite cements. Abundant early marine dolomite precipitation implies a radically different seawater chemistry for the Cryogenian. Perhaps these aragonite-dolomite seas are associated with extreme Neoproterozoic glacial events and/or ocean anoxia.on June 5, 2015 geology.gsapubs.org Downloaded from

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Section: Discussionmentioning

confidence: 88%

Neoproterozoic aragonite-dolomite seas? Widespread marine dolomite precipitation in Cryogenian reef complexes

Hood

Wallace

Drysdale

2011

Geology

106

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“…This picture is incorrect or at least misleading if the oceans are covered in a crack‐free ice shell over million‐year time scales. Our picture is, however, justified if this ice shell is either fractured or has small areas or oases of open ocean that enable air‐sea gas exchange (Goodman & Strom, ; Higgins & Schrag, ; Le Hir, Goddéris, et al, ; Le Hir, Ramstein, et al, ). Nevertheless, our predicted

normalp {CO}_{2}

minima for the Cryogenian are potentially low.…”

Section: Supercontinental Climate Control In An Evolving Mantle Thermmentioning

confidence: 95%

Ice, Fire, or Fizzle: The Climate Footprint of Earth's Supercontinental Cycles

Jellinek

Lenardic

Pierrehumbert

2020

Geochem Geophys Geosyst

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Supercontinent assembly and breakup can influence the rate and global extent to which insulated and relatively warm subcontinental mantle is mixed globally, potentially introducing lateral oceanic‐continental mantle temperature variations that regulate volcanic and weathering controls on Earth's long‐term carbon cycle for a few hundred million years. We propose that the relatively warm and unchanging climate of the Nuna supercontinental epoch (1.8–1.3 Ga) is characteristic of thorough mantle thermal mixing. By contrast, the extreme cooling‐warming climate variability of the Neoproterozoic Rodinia episode (1–0.63 Ga) and the more modest but similar climate change during the Mesozoic Pangea cycle (0.3–0.05 Ga) are characteristic features of the effects of subcontinental mantle thermal isolation with differing longevity. A tectonically modulated carbon cycle model coupled to a one‐dimensional energy balance climate model predicts the qualitative form of Mesozoic climate evolution expressed in tropical sea‐surface temperature and ice sheet proxy data. Applied to the Neoproterozoic, this supercontinental control can drive Earth into, as well as out of, a continuous or intermittently panglacial climate, consistent with aspects of proxy data for the Cryogenian‐Ediacaran period. The timing and magnitude of this cooling‐warming climate variability depends, however, on the detailed character of mantle thermal mixing, which is incompletely constrained. We show also that the predominant modes of chemical weathering and a tectonically paced abiotic methane production at mid‐ocean ridges can modulate the intensity of this climate change. For the Nuna epoch, the model predicts a relatively warm and ice‐free climate related to mantle dynamics potentially consistent with the intense anorogenic magmatism of this period.

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“…If an equal deposition rate for the cap dolostones and the overlying dolostones, where the MOSD period resides, is assumed, the maximum duration of the MOSD is also estimated to be also ~50 kyr. If we consider Le Hir et al's () ocean chemistry constraint that it would take a minimum of 20 kyr to bring the ocean alkalinity to the level of carbonate precipitation via continental weathering, then the corresponding durations of the cap carbonate deposition and the MOSD event will both be 30 kyr. These estimates are consistent with the previous estimate of a <1 Myr duration for the MOSD event, as inferred independently from two radiometric dates for nearby sections correlated to the Wushanhu section (Killingsworth et al, ), and also from a coupled, four‐box, and quick‐response biosphere‐atmosphere model (Cao & Bao, ).…”

Section: Discussionmentioning

confidence: 99%

Nonmonotonic Postdeglacial Relative Sea Level Changes at the Aftermath of Marinoan (635 Ma) Snowball Earth Meltdown

et al. 2019

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Marinoan snowball Earth offers us a set of sedimentary and geochemical records for exploring glacial isostatic adjustment (GIA) associated with one of the most severe glaciations in Earth history. An accurate prediction of GIA‐based relative sea level (RSL) change associated with a snowball Earth meltdown will help to explore sedimentary records for RSL changes and to place independent constraints on mantle viscosity and on the durations of syndeglaciation (Td) and cap carbonate deposition. Here we mainly examine postdeglacial RSL change characterized by an RSL drop and a resumed transgression inferred from the cap dolostones on the continental shelf in south China. Such a nonmonotonic RSL behavior may be a diagnostic GIA signal for the Marinoan deglaciation resulting from a significantly longer postdeglacial GIA response than that for the last deglaciation. A postdeglacial RSL drop followed by transgression in south China, which is significantly affected by Earth's rotation, is predicted over the continental shelf for models with Td ≤ 20 kyr and a deep mantle viscosity of ~5 × 1022 Pa s regardless of the upper mantle viscosity. The inferred GIA model also explains the postdeglacial RSL changes such as sedimentary‐inferred RSL drops on the continental shelf in northwestern Canada and California at low‐latitude regions insignificantly affected by Earth's rotation. Furthermore, the good match between the predicted and observed RSL changes in south China suggests an approximate duration of ~50 kyr for the Marinoan 17O depletion event, an atmospheric event linked to the post‐Marinoan drawdown of CO2 and the concurrent rise of O2.

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A geochemical modelling study of the evolution of the chemical composition of seawater linked to a "snowball" glaciation

Cited by 35 publications

References 59 publications

Neoproterozoic aragonite-dolomite seas? Widespread marine dolomite precipitation in Cryogenian reef complexes

Neoproterozoic aragonite-dolomite seas? Widespread marine dolomite precipitation in Cryogenian reef complexes

Ice, Fire, or Fizzle: The Climate Footprint of Earth's Supercontinental Cycles

Nonmonotonic Postdeglacial Relative Sea Level Changes at the Aftermath of Marinoan (635 Ma) Snowball Earth Meltdown

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