Archean Surface Environments, Moodies Group (BASE)

Barberton Greenstone Belt, South Africa

View of part the central Barberton Greenstone Belt. All strata in view are part of the 3.7 km thick, overturned southern limb of the Saddleback Syncline, exposing thick tidal-facies sandstones laced with microbial mats, shales and tuffs. Drilling at Site 4 (holes A, B, C) is taking place in the left foreground, drilling at Site 3 just outside the image to the right. Photo ©: Heubeck

Sedimentary rocks of the Moodies Group in the Barberton Greenstone Belt (BGB), South Africa, are about 3.22 Ga old and represent some of the world’s oldest well-preserved shallow-water strata. They reach almost 4 km in stratigraphic thickness, are lithologically variable and were deposited within ca. 1 to 14 Ma. The metamorphic grade is lower greenschist-facies; widespread early-diagenetic silicification preserved micro- and macrotextures virtually without strain.

Moodies strata represent a very-high-magnification record of Archean surface processes and are probably unique worldwide in allowing the regional and temporal contextualization of micro-scale and high-resolution Archean analytical data, comparable or superior to similar strata in Australia’s Pilbara region. Their coastal depositional environment is ideal to investigate and combine data from both marine and terrestrial settings.

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