The products of these reactions carry distinct isotopic compositions which allow them to be recognized in the rock record and, consequently, for reducing surficial conditions to be identified in geological time. Because of this, a large amount of data has been gathered from Archean sulfur minerals. However, the vast majority of studies have targeted sulfide minerals hosted by marine sedimentary rocks, creating a significant bias in the current data record. In particular, the amount of data collected from terrestrial sedimentary rocks is extremely limited, which has left the isotopic composition of terrestrial sulfur reservoirs poorly defined and our understanding of the Archean sulfur cycle incomplete. Four sulfur isotope data have been collected from sulfide minerals hosted by a variety of terrestrial sedimentary rocks occurring on the South African Kaapvaal Craton. Here, that data will be presented and used to constrain the isotopic composition of terrestrial sulfur reservoirs. It will be shown that these reservoirs preserved a mixture of a specific species of atmospheric sulfur and non-atmospheric sulfur likely sourced from igneous rocks. This data will then be compared and contrasted within new data collected from marine sedimentary rocks from the same stratigraphic sequences and literature data to show that terrestrial and marine sedimentary sulfur reservoirs preferentially preserved different atmospheric sulfur species. Possible reasons for this will be discussed, including differences in the solubility of different atmospheric sulfur species and differences in the mechanisms by how different sulfur species are preserved within the rock record.
Followed by drinks and nibbles
Dinner RSVP on the seminar room noticeboard