Evidence for 2.0 Ga continental microbial mats in a paleodesert setting

• Microbial mat diverse within the ca. 2.0 Ga Makgabeng Formation.
• Biological soil crusts [BSC], tufted mat, and gas escape structures identified.
• BSCs are ca. 800 Myr older than previously described in literature.
• Microbial communities well established in continental settings by 2.0 Ga.

Early evolved microbial communities characterized the initial biological invasion of Precambrian continental landscapes. In modern arid settings, microbial mats and biological soil crusts are well-developed and stabilize sediment. The Paleoproterozoic Makgabeng Formation in South Africa is one of the oldest and best preserved, dryland systems on Earth. Six types of microbial mat-related structures are now recognized within these depositional systems. This paper presents three newly discovered structures that include tufted microbial mat, biological soil crusts, and gas-escape features, in addition to three previously documented structures that include roll up features, sand cracks, and wrinkled features. These discoveries demonstrate that microbial communities were well-established and inhabited diverse continental settings by 2.0 Ga, approximately 200 million years after the onset of the Great Oxidation Event.

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