Barberton Field Workshop 2016: Young SPP-Scientists study Archean rocks
During August 18-27, 19 Junior Scientists and 9 Senior researchers of the SPP 1833 visited the Archean rocks of the Barberton Supergroup. These rocks provide a unique record of the surface conditions of primordial Earth.
The Barberton granitoid-greenstone terrane is a key area for studying early Earth’s geodynamic processes and surface environments. It consists of the 3.55 to 3.22 Ga Barberton Greenstone Belt and surrounding granitoid domes and intrusive sheets. It represents a type locality of Palaeoarchaean sequences and consists of a NE-SW striking succession of supracrustal rocks.
The stratigraphy, processes of metamorphism and competing tectonic models have been discussed intensively in the field with internationally highly visible scientists (e.g. Gary Byerly, Carl Anhaeusser, Martin van Kranendonk, Alex Kisters, Alfred Kröner, Axel Hofmann, Christoph Heubeck).
Three main study areas were visited. The first base of the Field Workshop was the “Cradle of Life” venue in Badplaas. Starting here, key localities of the Onverwacht-group have been inspected and the controversial theories about evolution of the folded strata have been discussed in the field and during lectures at the conference venue.
Around Barberton, our group followed followed Christoph Heubeck across the Barberton-Makhonjwa Geotrail (www.geotrail.co.za). As a conclusion of the Barberton-part of the workshop, a “braai” (South African term for barbecue) at the Barberton Golfclub was organized by the local tourism office. This event was also attended by the local media (see article).
In the White Mfolozi River Valley, the Archaean Pongola Supergroup was studied. It comprises a volcano-sedimentary succession that was deposited ca. 3.0-2.9 Ga ago on continental crust of the south-eastern part of the Kaapvaal Craton. The range of textures and flow forms and primary volcanic structures gives insight into the processes of eruption, effusion rates and depositional environment at that time. Most basalts in here were formed as submarine deposits and exhibit a range of textural types which include massive (sheet), pillowed and brecciated flow units. Furthermore, the shale/BIF succession of the Vlakhoek Member (see photo), which has been the focus of several studies, was inspected. It is represented by a 12 m thick succession of dark grey shale, BIF and dark to light green ferruginous shale.
All participants took samples in the field, but additionally had the opportunity to sample drill cores of the “ICDP Barberton Drilling Project”, carried out in 2011/12. Five drill cores between 420 and 900 m length are stored in the University of Johannesburg. Sampling them for their individual studies was a unique chance for the SPP 1833-researchers.
A further benefit of the field workshop was that links were forged within the SPP 1833 community which will further enhance the cooperation and interdisciplinarity of the project.
Photos: D. Hülle
