I‐Type Cosmic Spherules as Proxy for the Δ′ ¹⁷ O of the Atmosphere—A Calibration With Quaternary Air

Remnants of shooting stars are preserved in form cosmic spherules ice and sediments. The extraterrestrial material is heated melted upon atmospheric entry collected at the Earth's surface as spherules. A fraction (I-type spherules) sources from Fe,Ni metal. These metal particles melt become oxidized atmosphere. oxygen resulting oxides (magnetite, wüstite) entirely Here, we demonstrate that I-type can be used to reconstruct triple isotope anomaly past atmosphere, which provides information on gross primary productivity and/or paleo-CO2 levels. We present a calibration proxy using Antarctic further introduce Δ′56Fe iron isotopes obtain about underlying fractionation mechanism (e.g., kinetic vs. equilibrium fractionation).