WFS News: Did the transition to plate tectonics cause Neoproterozoic Snowball Earth?

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

 Did the transition to plate tectonics cause Neoproterozoic Snowball Earth?

Citation: Stern RJ, Miller NR. Did the transition to plate tectonics cause Neoproterozoic Snowball Earth? Terra Nova2018;30:87–94. https://doi.org/10.1111/ter.12321

When Earth’s tectonic style transitioned from stagnant lid (single plate) to the modern episode of plate tectonics is important but unresolved, and all lines of evidence should be considered, including the climate record. The transition should have disturbed the oceans and atmosphere by redistributing continents, increasing explosive arc volcanism, stimulating mantle plumes and disrupting climate equilibrium established by the previous balance of silicate‐weathering greenhouse gas feedbacks. Formation of subduction zones would redistribute mass sufficiently to cause true polar wander if the subducted slabs were added in the upper mantle at intermediate to high latitudes. The Neoproterozoic Snowball Earth climate crisis may reflect this transition. The transition to plate tectonics is compatible with nearly all proposed geodynamic and oceanographic triggers for Neoproterozoic Snowball Earth events, and could also have contributed to biological triggers. Only extraterrestrial triggers cannot be reconciled with the hypothesis that the Neoproterozoic climate crisis was caused by a prolonged (200–250 m.y.) transition to plate tectonics.

Comparisons of key petrotectonic indicators for plate tectonics and timings of major glacial episodes (vertical blue regions, after Cox et al., 2016) spanning the last 3 byrs. a) Kimberlites provide evidence of mantle ingassing due to subduction (Stern et al., 2016). b) Ophiolites provide evidence of seafloor spreading and horizontal motions consistent with plate tectonics (Stern, Leybourne, & Tsujimori, 2017; modified by Palaeoproterozoic ophiolites from Condie, in press). c) Indicators of subduction zone metamorphism — blueschists, glaucophane‐bearing eclogites, lawsonite‐bearing metamorphic rocks and jadetites — form only in the cool, fluid‐rich environments in and above subduction zones (Stern, Tsujimori, Harlow, & Groat, 2013). d) Ultra‐high pressure metamorphic rocks and the gemstone ruby proxy continental collision and deep subduction of continental crust (Stern et al., 2017). e) Seawater 87Sr/86Sr and δ34S of carbonate rocks, and timing of giant P sedimentary deposits (after Shields, 2007). Note the rapid rise in 87Sr/86Sr during Neoproterozoic time, from ~0.705 to ~0.709, indicating enhanced continental input. f) Seawater δ13C curve. Curve > 900 Ma digitized from Young (2013, Figure 1), the 2600–1600 Ma portion follows Melezhik, Roberts, Fallick, Gorokhov, and Kuznetsov (2005); the 1600–920 Ma portion follows Kah (2004). The 540–920 Ma portion follows Cox et al. (2016), including LIPs; Neoproterozoic C‐isotope excursions B, I, T, Tr and S denote Bitter Springs, Islay, Tayshir, Trezona and Shuram anomalies, respectively. The Phanerozoic portion follows Shields and Mills (2017); note this is a smooth of the composite curve. g) Sedimentary phosphorite abundance as represented by deposits (Planavsky, 2014) [Colour figure can be viewed at wileyonlinelibrary.com]

Comparisons of key petrotectonic indicators for plate tectonics and timings of major glacial episodes (vertical blue regions, after Cox et al., 2016) spanning the last 3 byrs. a) Kimberlites provide evidence of mantle ingassing due to subduction (Stern et al., 2016). b) Ophiolites provide evidence of seafloor spreading and horizontal motions consistent with plate tectonics (Stern, Leybourne, & Tsujimori, 2017; modified by Palaeoproterozoic ophiolites from Condie, in press). c) Indicators of subduction zone metamorphism — blueschists, glaucophane‐bearing eclogites, lawsonite‐bearing metamorphic rocks and jadetites — form only in the cool, fluid‐rich environments in and above subduction zones (Stern, Tsujimori, Harlow, & Groat, 2013). d) Ultra‐high pressure metamorphic rocks and the gemstone ruby proxy continental collision and deep subduction of continental crust (Stern et al., 2017). e) Seawater 87Sr/86Sr and δ34S of carbonate rocks, and timing of giant P sedimentary deposits (after Shields, 2007). Note the rapid rise in 87Sr/86Sr during Neoproterozoic time, from ~0.705 to ~0.709, indicating enhanced continental input. f) Seawater δ13C curve. Curve > 900 Ma digitized from Young (2013, Figure 1), the 2600–1600 Ma portion follows Melezhik, Roberts, Fallick, Gorokhov, and Kuznetsov (2005); the 1600–920 Ma portion follows Kah (2004). The 540–920 Ma portion follows Cox et al. (2016), including LIPs; Neoproterozoic C‐isotope excursions B, I, T, Tr and S denote Bitter Springs, Islay, Tayshir, Trezona and Shuram anomalies, respectively. The Phanerozoic portion follows Shields and Mills (2017); note this is a smooth of the composite curve. g) Sedimentary phosphorite abundance as represented by deposits (Planavsky, 2014) [Colour figure can be viewed at wileyonlinelibrary.com]

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

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