CIMERA-Agouron GOE and Biomarker Drilling Project, Transvaal Supergroup, South Arica.
Background
The Agouron Institute in Pasadena, California has funded drilling of four diamond drill cores during 2016 from selected stratigraphic units of the Neoarchean-Early Paleoproterozoic Transvaal Supergroup in South Africa (Sumner and Bowring, 1996; Sumner and Beukes, 2006). Their purpose is to access fresh material for study by earth scientists interested in improved understanding of the timing and geobiological consequences of the GOE. The drill holes were located such that core samples can be analyzed to address to two main questions, namely:
- The exact timing, nature and geochemical characteristics of the so-called Great Oxidation Event (GOE) as currently essentially defined by the disappearance of sulfur mass-independent fractionation (S-MIF) signatures from the sedimentary record.
- Whether lipid biomarkers indicative of the presence of eukaryotes, would also be absent in ultraclean collected drill core samples of the Neoarchean Campbellrand carbonate platform succession on the Kaapvaal Craton compared to broadly correlative strata of the Jeerinah Formation and Carawine Dolomite of the Pilbara Craton where the conclusion reached by the 2012 – 2015 Australian Agouron Biomarker Project (French et al., 2013) was that such biomarkers detected in core samples during earlier studies (Brocks et al., 2003; Waldbauer et al., 2009), represented modern contaminants.
Selection of the locations for the new cores was partly based on the paper of Luo et al. (2016) which identified a probable GOE section in the Upper Rooihoogte Fm in three closely spaced cores from near to Carltonville, South Africa (Fig. 1). That paper suggested possible correlative sections in the Duitschland succession. Thus, Beukes et al proposed that new drill cores be obtained from Duitschland, Gopane and Ngodwana (Fig. 2) to intersect the GOE. In addition a core was obtained that intersected the Gamohaan Formation and upper part of the Lime Acres Member of the Late Neoarchean Campbellrand carbonate platform succession near Kuruman (Fig. 2) for biomarker studies.
Research Team
The Lead Scientists of the project are Nic Beukes (University of Johannesburg), Woody Fischer (Caltech), Dawn Sumner (UC-Davis) and Christian Hallmann ( University of Bremen, Germany).
Current team members of the research project are Roger Summons (MIT) working with post-doc fellow Gareth Izon on sulfur, nitrogen and organic carbon isotopes, Ronny Schoenberg (Tuebingen University, Germany) working on Mo and Se isotopic compositions plus supporting major and trace element analyses, Stefan Schroeder (Manchester University) looking at the detailed sedimentology integrated with petrographic and chemical analyses of the carbonates intersected in the GOE cores, Woody Fischer is looking at carbonate-bounded sulfur isotope compositions, Nic Beukes at detrital zircon populations, and Stefan Lalonde (European Institute for Marine Sciences, Plouzane, France) did detailed continuous XRF line scans of the cores. Biomarker studies of the Campbellrand core are undertaken by Christian Hallmann, Roger Summons and Jochen Brocks.
The drilling contractor was Geoserve Exploration Drilling (Pty) Ltd and the Geological Drilling Manager was Aleck Birch.
Figure.1. Delta33S data and a sulfur isotope cross plot obtained from samples from the Carltonville cores EBA-2, EBA-4 and KEA-4 as published by Luo et al., 2016.
Curation Localities of Cores and Contact Details for Research Proposals
The cores were split with one half stored in the Department of Geology at the University of Johannesburg. The other half was send to France where Stefan Lalonde performed detailed continuous XRF core scans. From there the cores are to be shipped to the US where they would be stored at the American Museum of Natural History in New York.
The cores are open for study by anyone that may be interested barring approval of a scientific proposal by the four lead scientists mentioned above that constitute a management group to avoid duplication of studies.
The best is to contact Nic Beukes (nbeukes@uj.ac.za) for more information and enquiries about submission of proposals and sampling of the cores both in South Africa and at the American Museum of Natural History. He shall then liaise with the other lead scientists.
Figure 2. Localities of the Agouron Cores. The GOE cores are those at Ngodwana, Duitschland and Gopane in the Transvaal outcrop area of the Transvaal Supergroup. The Biomarker core is that at Hartland near Kuruman in the Griqualand West outcrop area.
Stratigraphy Intersected in Cores
The cores at Ngodwana (ANW-1) and Gopane (AGP-1) intersected the lowermost Timeball Hill Formation and entire Rooihoogte Formation (considered correlative to the Duitschland Formation) of the Pretoria Group of the Transvaal Supergroup. A second core drilled at Gopane (AGP-2), due to unexpected deep weathering in the area, intersected fresh pyritic shale of the lowermost Timeball Hill Formation and the entire upper Rooihoogte Formation.
The core on Duitschland was planned such that it intersected the argillaceous unit in the Duitschland Formation that does not outcrop because of deep weathering, but that is the interval in which the GOE should be located based on the Delta33S data presented by Guo et al. (2009) (Fig. 3).
The Biomarker core at Hartland intersected the entire Gamohaan succession, below the Kuruman Iron Formation, down into limestone of the Lime Acres Member of the Campbellrand Subgroup (Fig. 4).
Figure 3. Stratigraphic interval intersected in core ADL-1 on Duitschland indicated here as the “Unknown” or GOE interval in the type profile of the Duitschland Formation
Figure 4. Stratigraphic interval intersected in the Biomarker core (AHL-4) on Hartland near Kuruman
Simplified Logs of Cores
Simplified logs of cores ADL-1 and AGP-1 and 2 as prepared by Stefan Schroeder are presented below.
More detailed logs are available on the website via secure pin numbers supplied to active scientific collaborators as approved by the lead scientific committee.
Core ADL-1 Duitschland
Core AGP-1 Gopane
Core AGP-2
References
French, K.L., Hallmann, C., Hope, J.M., Buick, R., Brocks, J.J. and Summons, R.E., 2013, August. Archean hydrocarbon biomarkers: Archean or not. In Proceedings of Goldschmidt Conference, Florence, Italy(pp. 25-30).
Guo, Q.J., Strauss, H., Kaufman, A.J., Schroder, S., Gutzmer, J., Wing, B., Baker, M.A., Bekker, A., Jin, Q.S., Kim, S.T., Farquhar, J., 2009. Reconstructing earth’s surface oxidation across the Archean-Proterozoic transition. Geology 37, 399-402.
Hallmann, C. 2012. Agouron Pilbara Drilling, June-July 2012: Sampling protocol. Unpublished report, Agouron Institute, 6 pp.
Luo G., Ono S., Beukes N.J, Wang D.T., Xie S. and Summons R.E., 2016. Rapid oxidation of Earth’s atmosphere 2.33 billion years ago. Science Advances 2: e1600134.
Sumner, D.Y., and Bowring, S.A., 1996. U-Pb geochronologic constraints on deposition of the Campbellrand Subgroup, Transvaal Supergroup, South Africa. Precambrian Research, 78, 25-35.
Sumner, D.Y., Beukes, N.J., 2006. Sequence Stratigraphic Development of the Neoarchean Transvaal carbonate platform, Kaapvaal Craton, South Africa. South African Journal of Geology 109, 11-22.
Waldbauer, J.R., Sherman, L.S., Sumner, D.Y., Summons, R.E. 2009. Late Archean molecular fossils from the Transvaal Supergroup record the antiquity of microbial diversity and aerobiosis. Precambrian Res., 169, 28-47.
