17/10/2017

Drilling into the deep past


Between 5th-10th October, it took place a workshop intended to the localization of drilling points in the Barberton Greenstone Belt, South Africa, one of the only two places in the world, together with the Pilbara region, in which there are continental sedimentary deposits from the early Archean period. It was organized by the International Continental Scientific Drilling Programme (ICDP), and David Fernández Remolar, member of the Atmospheric Science Group, took part in the campaign.

The Moodies Group

The Barberton Greenstone Belt, included in the Kaapvaal craton, harbours the Moodies Group, a stratigraphic unit of sedimentary rocks 3.22 billion years old showing one of the oldest well-preserved records of strata formed within shallow continental waters during the Archean eon (4,000 to 2,500 million years ago).

Sample of rock with gypsum concretions.
Credit: David Fernández Remolar

However, the outcrops in the zone have been submitted to weathering and modified by biological activity over time, so it would be convenient to localize points from which extracting fresh samples in order to go into depth in the better characterization of the Archean atmosphere, oceans, and surface, as well as the interaction processes between them. On the other hand, a thorough and well-aimed sampling would be crucial for the understanding of the distribution and nature of early surface life.
The workshop’s main outcome, therefore, will be the proposal for initiating a proper drilling campaign in the points of the formation in which such information can be obtained by collecting better preserved samples.
David Fernández Remolar took advantage of the workshop to gather samples from fossilized microbial mats formed within the oldest continental deposits, and also from rocks with gypsum concretions in which it is very likely that bacterial fossils preserved by pseudomorphosis are entrapped. Part of this samples were collected in the first Archean delta identified so far, from rocks formed under evaporitic conditions in supratidal areas. The further analysis of the samples will provide, hopefully, remarkable insights into the ecology of the Archean but, moreover, and with regards to Mars exploration, they will contribute knowledge about the progress of evaporites and the preservation of biosignatures in them, providing clues for the understanding of the processes which took place in those found on the planet.