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).
The oxygen isotope record in sedimentary chert and the compelling case for a near constant isotopic oxygen composition of seawater over geologic time support thermophilic surface temperatures prevailing in the Archean, with some support for hot conditions lasting until about 1.5 billion years ago, aside from lower temperatures including glacial episodes at 2.1-2.4 Ga and possibly an earlier one at 2.9 Ga.
Understanding the atmosphere's composition during the Archean eon is a fundamental issue to unravel ancient environmental conditions.
An international team of researchers, including Scripps Institution of Oceanography, UC San Diego, geochemist James Day, has found new evidence that material contained in oceanic lava flows originated in Earth's ancient Archean crust. These findings support the theory that much of the Earth's original crust has been recycled by the process of subduction, helping to explain how the Earth has formed and changed over time.