Periodic Reporting for period 1 - ANOXIA-MEM (Probing the Memory of Earth Anoxia: New Stable Isotope Constraints on the Rise of Oxygen)
Reporting period: 2016-04-01 to 2018-03-31
Sulfate is an excellent archive of sulfur and oxygen isotope signals in the rock record due to its widespread occurrence and strong preservation and suitable sulfate from around the time of the GOE can be used to test for the presence of the weathering ""memory effect"". Direct evidence for the ""memory effect"" would show up in sulfate records with significant sulfur isotope anomalies that run in parallel to coexisting sulfide records, and sulfate oxygen isotope compositions that indicate the origin of the sulfate from oxidative weathering of older sedimentary sulfides on the continental surface. Such sulfate was recovered in the form of trace barium sulfate (barite) from drill cores from the Turee Creek Group sedimentary sequence from western Australia, circa 2.45 to 2.21 billion years old, in the critical time window of the GOE."
The work performed for the barite measurements included crushing of rock samples into powder, chemical treatment of rock powders to extract barite, purification of the extracted barite, and then subsequent measurement of quadruple sulfur (32S, 33S, 34S, 36S) and triple oxygen (16O, 17O, 18O) isotope compositions of the barite during three separate measurement sessions. The isotope measurements for sulfur and oxygen have different sample preparation and analytical requirements.
In the barite measured for this project, its anomalous sulfur isotope compositions indicate a source of sulfur from when atmospheric oxygen was less than 0.001% but its oxygen isotope compositions reveal that sulfate was being generated by oxidative weathering on the continent in the presence of meteoric waters. Thus, the presence of the ""memory effect"" is revealed.
Due to the Marie Curie project directly, the recipient of funding, Bryan Killingsworth, has already contributed to a Nature Communications submission (presently in review), and is prepping one new first-author manuscript for imminent submission to a top science journal, with another one to follow.
Furthermore, Bryan Killingsworth has shared results of this Marie Curie project at important scientific meetings, including talks at Goldschmidt 2017, AGU 2017, and the Gordon Geobiology Research Seminar 2018, and poster presentations at the Geobiology Meeting in Banff in 2017, Gordon Geobiology Research Conference 2018, the Primitive Earth workshop in St. Etienne 2016."