Minor Sulfur Isotope Constraints on the composition of Earth’s Archean atmosphere

Research output: Contribution to conferenceAbstract


The presence of minor sulfur isotope anomalies in the sedimentary record constrains atmospheric oxygen to trace levels prior to 2.3 billion years ago, and indirectly indicates the presence of a reducing gas (likely H2 or CH4) at this time. The database of mass-independently fractionated sulfur isotopes (MIF-S) has grown substantially in the previous decade and reveals complex time- and facies-dependent changes in MIF-S magnitudes. The complicated structure within the sedimentary MIF-S record suggests that constraints beyond an “on-off” switch for atmospheric O2 are possible is we can better understand the mechanisms that generate and preserve the signal in the rock record.
Recently, I proposed a quantitative framework necessary for accurate predictions of MIF-S generated in the atmosphere (Claire, 2014). One conclusion of this study was that additional constraints on Archean atmospheric chemistry beyond the lack of O2 were not possible without new fundamental laboratory measurements of MIF-S generation mechanisms. Two recent studies have removed some of these roadblocks. Identification of MIF-S arising from the photoexcitation band of SO2 (Whitehill et al. 2013) and new measurements of the SO2 photoabsorbtion cross-section (Endo et al. 2015) provide critical new ground-truth on all 4 isotopes of sulfur, enabling much stronger constraints on the composition of the reducing atmosphere.
This presentation will present 1-D photochemical modeling results using these new fundamental laboratory data in conjunction with sedimentary multiple sulfur isotope data, in order to constrain the steady-state composition of the Archean atmosphere and time-dependent perturbations to it.
Original languageEnglish
Publication statusPublished - 16 Aug 2015


Dive into the research topics of 'Minor Sulfur Isotope Constraints on the composition of Earth’s Archean atmosphere'. Together they form a unique fingerprint.

Cite this