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

Abstract

No consensus has yet been reached on which slope of the reference line should be chosen. We choose a reference line with a slope of 0.528 in order to have a consistent terminology across disciplines (see discussion, e.g., in Miller & Pack, 2021, Pack & Herwartz, 2014, or Sharp & Wostbrock, 2021). However, any of the definitions of Δ' 17 O used in the literature, does not change the interpretation of triple oxygen isotope data. Modern tropospheric O 2 has a composition of δ 18 O = 24‰ (i.e., the 18 O/ 16 O ratio is 2.4% higher than in ocean water) and Δ′ 17 O = −0.432 ± 0.010‰ (

Oxygen Ablation during Atmospheric Entry: Its Influence on the Isotopic Composition of Micrometeorites

“…We have compiled oxygen isotope data (423) from the literature for (404) MMs that were analyzed using multiple techniques including Isotope Ratio Mass Spectrometry (IRMS) and in situ ion microprobe analyses (Clayton et al 1986;Engrand et al 1999Engrand et al , 2005Taylor et al 2005;Yada et al 2005;Matrajt et al 2006;Suavet et al 2010;Cordier et al 2011Cordier et al , 2012; (Clayton et al 1986;Engrand et al 1999Engrand et al , 2005Taylor et al 2005;Suavet et al 2010;Cordier et al 2011;Rudraswami et al 2015Rudraswami et al , 2020Van Ginnekan et al 2017;Suttle et al 2020;Goderis et al 2020;Fischer et al 2021). The TFL and CCAM lines are shown for reference.…”

“…The data on the oxygen isotope composition can be obtained from the references in the Appendix. Rudraswami et al 2015Rudraswami et al , 2020Van Ginneken et al 2017;Goderis et al 2020;Fischer et al 2021) to identify the effects of atmospheric entry and relate this to CABMOD data (Figure 1, references to the compiled oxygen isotope data are provided in supplementary material). The scoriaceous oxygen isotope composition has a relatively narrow spread in δ 18 O among the cosmic spherules, along with relict-bearing particles.…”

“…Previous studies on MMs have assumed that their precursors are essentially either CI or CM chondrites, though other chondrites need to be treated for completion (e.g., Brownlee et al 1997;Taylor et al 2000;Prasad et al 2013Prasad et al , 2015Rudraswami et al 2019). (Clayton et al 1986;Engrand et al 1999Engrand et al , 2005Taylor et al 2005;Suavet et al 2010;Cordier et al 2011;Rudraswami et al 2015Rudraswami et al , 2020Van Ginnekan et al 2017;Suttle et al 2020;Goderis et al 2020;Fischer et al 2021). The peak temperatures given in the table are approximate values that are taken from various references (rounded to the nearest hundred).…”

“…Even the unmelted particles have undergone some alteration or diffusion between the phases, but oxygen isotope data from these particles can be interpreted as preserved. Unmelted particles retain the isotopic composition of their precursors, in contrast to I-type cosmic spherules, which derive oxygen solely during their atmospheric entry (Tomkins et al 2016;Pack et al 2017;Fischer et al 2021).…”

“…Figure 1. Compiled oxygen three-isotope plot for different types of MMs obtained from the literature(Clayton et al 1986;Engrand et al 1999Engrand et al , 2005Taylor et al 2005;Suavet et al 2010;Cordier et al 2011;Rudraswami et al 2015Rudraswami et al , 2020 Van Ginnekan et al 2017;Suttle et al 2020;Goderis et al 2020;Fischer et al 2021). The TFL and CCAM lines are shown for reference.…”