The most ancient structures described from the Onverwacht Group are mineralized microtubes from the formerly glassy margins of pillow basalts and inter-pillow ->■
Figure 3. (continued) Research, Volume 106. Westall, F. de Witt, M.J., Dann, J., van der Gaast, S., de Ronde, and Gerneke, D. Early Archean fossil bacteria and biofilms in hydrothermally-influenced sediments from the Barberton greenstone belt, South Africa, pp. 93-116. Copyright (2001), with permission from Elsevier. Figure 3d and f are reprinted from Precambrian Research, Volume 54. Walsh, M.M. Microfossils and possible microfossils from the early Archean Onverwacht Group, Barberton Mountain Land, South Africa, pp. 271-293. Copyright (1992), with permission from Elsevier.
Figure 3. Putative biogenic structures from the Barberton greenstone belt (BGB), South Africa. (a) Location of the BGB on the South Africa-Swaziland border; (b) stratigraphy of the -3,500-3,200 Ma Onverwacht Group; (c) etched fracture surface of chert from the -3,400 Ma Kromberg Formation showing short rod-shaped bateriomorph structures embedded in quartz (Westall et al., 2001); (d) petrographic thin section of spindle structure in chert from the base of the Kromberg Formation (Walsh, 1992); (e) petrographic thin section of putative microbial mat layer from the 3,416 Ma Buck Reef Chert; (f) petrographic thin section of solid filaments in chert from the -3,450 Ma upper Hooggenoeg Formation (Walsh, 1992); (g) pet-rographic thin section of mineralized microtubular structures within the formerly glassy margin of pillow basalt from the -3,450 Ma upper Hooggenoeg Formation. Figure 3c is reprinted from Precambrian
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