Archean beaches in Berlin: a report from the ICDP BASE sampling party
What did the surface of Earth look like more than three billion years ago? What kinds of microbes lived there and when did they start producing oxygen? And what was the temperature and composition of the ancient oceans and atmosphere? Big questions like these is what drew a group of 41 scientists to sunny Berlin last week, including our Associate professor Desiree Roerdink.
Studying the Archean Earth (4.0 to 2.5 billion years ago) comes with its particular challenges. There are not many places on Earth where rocks that old have been preserved, as plate tectonics has erased much of the rock record from this time. But even where they are found, such as in the Barberton Greenstone Belt of South Africa, weathering by rainwater, microbes and oxygen in the atmosphere has often reset chemical signatures in the rocks that we want to use for stuyding the early surface environments. As a result, we need to drill deep into the subsurface to obtain fresh rocks that have escaped weathering.
An international team of scientists therefore set out to South Africa with the International Continental Scientific Drilling Program (ICDP) to obtain 8 drill cores from some of the oldest known sedimentary succesions on Earth. The BASE project (Barberton Archean Surface Environments) specifically targeted the rocks of the 3.2 billion year old Moodies Group. Here we find sandstones and conglomerates that were deposited in ancient rivers, beaches, tidal zones and shallow marine basins, and several horizons contain extensive microbial mats. This coastal environment of the Moodies Group provides scientists with a fantastic opportunity to study life and geological processes in the transition from sea to land, more than three billion years ago.
But how do you divide nearly 3000 meters of drill core over the group of eager early Earth enthusiasts in the BASE Science team? This was the purpose of the sampling party that was organized from 10-14 September at the BGR Core Repository in the Berlin suburb of Spandau, where all the BASE drill cores are stored. With the weather on our side, we were able to lay out all the 503 core boxes in the parking lots and pick out the samples that we wanted in bright sunshine. An impressive number of about 1000 pieces of core were cut, bagged up and labelled in only three days time, ready to be analyzed by 24 different research teams. In the coming two years, my team will use the samples that we collected to study the sulfur cycle in these early coastal settings using stable isotope analyses.
More information: ICDP BASE is led by the Science Management Team under coordination of Prof. Christoph Heubeck (Jena University, Germany) and Prof. Nic Beukes (now deceased). Further details and photos from the drilling project can be found at the ICDP website.