Evidence for 2.0 Ga continental microbial mats in a paleodesert setting

Abstract

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