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I‐Type Cosmic Spherules as Proxy for the Δ′ 17 O of the Atmosphere—A Calibration With Quaternary Air
Author(s) -
Fischer Meike B.,
Oeser Martin,
Weyer Stefan,
Folco Luigi,
Peters Stefan T. M.,
Zahnow Fabian,
Pack Andreas
Publication year - 2021
Publication title -
paleoceanography and paleoclimatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.927
H-Index - 127
eISSN - 2572-4525
pISSN - 2572-4517
DOI - 10.1029/2020pa004159
Subject(s) - atmosphere (unit) , cosmic ray , magnetite , cosmic cancer database , geology , wüstite , mineral redox buffer , carbonate , astrobiology , mineralogy , geochemistry , physics , materials science , astrophysics , paleontology , mantle (geology) , metallurgy , thermodynamics
Remnants of shooting stars are preserved in form of cosmic spherules in ice and sediments. The extraterrestrial material is heated and melted upon atmospheric entry and is collected at the Earth's surface as cosmic spherules. A fraction of cosmic spherules (I‐type cosmic spherules) sources from extraterrestrial Fe,Ni metal. These metal particles melt and become oxidized in the atmosphere. The oxygen in the resulting oxides (magnetite, wüstite) sources entirely from the atmosphere. Here, we demonstrate that I‐type cosmic spherules can be used to reconstruct the triple oxygen isotope anomaly of the past atmosphere, which provides information on the gross primary productivity and/or paleo‐CO 2 levels. We present a calibration of the proxy using Antarctic cosmic spherules. We further introduce Δ′ 56 Fe and demonstrate that triple iron isotopes can be used to obtain information about the underlying fractionation mechanism (e.g., kinetic vs. equilibrium fractionation).