Blar i forfatter "Kirsimae, Kalle"

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    • Identifying global vs. basinal controls on Paleoproterozoic organic carbon and sulfur isotope records 

      Paiste, Kärt; Lepland, Aivo; Zerkle, Aubrey L.; Kirsimae, Kalle; Kreitsmann, Timmu; Mänd, Kaarel; Romashkin, Alexander E.; Rychanchik, Dimitry V.; Prave, Anthony R (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-03)
      Paleoproterozoic sedimentary successions are important archives of the redox evolution of Earth’s atmosphere and oceans. Efforts to unravel the dynamics of our planet’s early oxygenation from this archive rely on various geochemical proxies, including stable carbon and sulfur isotopes. However, ancient metasedimentary rocks often experienced early- and late-stage (bio)geochemical processes making ...

    • Putative fossils of chemotrophic microbes preserved in seep carbonates from Vestnesa Ridge, off northwest Svalbard, Norway 

      Himmler, Tobias; Cremiere, Antoine; Birgel, Daniel; Wirth, Richard; Orphan, Victoria J.; Kirsimae, Kalle; Knies, Jochen; Peckmann, Jörn; Lepland, Aivo (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-20)
      The microbial key players at methane seeps are methanotrophic archaea and sulfate-reducing bacteria. They form spherical aggregates and jointly mediate the sulfate-dependent anaerobic oxidation of methane (SD–AOM: CH4 + SO42– → HCO3– + HS– + H2O), thereby inducing the precipitation of authigenic seep carbonates. While seep carbonates constitute valuable archives for molecular fossils of SD–AOM-mediating ...

    • Small calcium isotope fractionation at slow precipitation rates in methane seep authigenic carbonates 

      Blättler, Clara L.; Hong, Wei-Li; Kirsimae, Kalle; Higgins, John A.; Lepland, Aivo (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-01)
      Natural calcium carbonate minerals express a range of calcium isotope fractionations, with the precipitated mineral typically enriched in the lighter isotopes of calcium relative to source fluids. Experimental and theoretical evidence shows a strong dependence on precipitation rate, although this relationship has not been well quantified over the range of precipitation rates observed in natural ...