Flash Floods In The Mid-Archean

Photographs of slabs from the regionally correlative layers of accretionary lapilli and ash (numbered 1–9) near the top of H5c, which immediately underlie H6 around the Onverwacht Anticline. Each individual fall-deposited bed <2 cm thick occurs across this entire distance except where H5c is covered by younger strata or faulted out (Fig. 2). Their continuity provides substantial evidence that this contact is not an erosional unconformity. The dark gray “layers” and irregular areas within the volcaniclastic layers in the slabs are post-depositional silica veins.

Scientists supported in part by the NASA Astrobiology Program have provided new details of how the Hooggeneoeg Formation in South Africa was formed. The Hooggeneoeg Formation is found in the Barberton Greenstone Belt, and holds some of the best-preserved examples of supracrustal rocks from the mid-Archean (3.5 to 3.2 billion years ago).

Astrobiologists have long been interested in the geology of the region because it provides a window into Earth's ancient history. During the mid-Archean, Earth was like an 'alien world,' with environmental conditions that were vastly different than today. However, life was present on the Earth during this time. Studying the mid-Archean can provide clues about how life evolved alongside our planet, and can also help astrobiologists understand the range of conditions that can make a planet habitable for life as we know it.

Recently the Hooggeneoeg Formation has been the focus of scientific scrutiny,. Some studies have suggested that certain rocks found in the formation were deposited under glacial to periglacial conditions, and that these rocks also contain eroded debris from older, granitic continental crust. If true, this would represent a fundamental re-interpretation of the geological history of the Hooggeneoeg Formation. The new study disputes these conclusions, suggesting that floods and storm-driven water flows helped shaped the formation, and that there is no evidence that glaciers influenced sedimentation.

The study, "The non-glacial and non-cratonic origin of an early Archean felsic volcaniclastic unit, Barberton Greenstone Belt, South Africa," was published in the journal Precambrian Research. The work was supported by NASA Astrobiology through the Exobiology Program. This newly-revealed science is also a critical part of NASA's work to understand the Universe, advance human exploration, and inspire the next generation. As NASA's Artemis program moves forward with human exploration of the Moon, the search for life on other worlds remains a top priority for the agency.

The non-glacial and non-cratonic origin of an early Archean felsic volcaniclastic unit, Barberton Greenstone Belt, South Africa. Precambrian Research Volume 341, June 2020, 105647

Astrobiology

Please follow Astrobiology on Twitter.


  • submit to reddit