Mass occurrence of benthic coccoid cyanobacteria and their role in the production of Neoarchean carbonates of South Africa

Abstract

a b s t r a c tThe sparse Archean fossil record is based almost entirely on carbonaceous remnants of microorganisms cellularly preserved due to their early post-mortem silicification. Hitherto as an exception, sedimentary carbonate rocks from the Neoarchean Nauga Formation of South Africa contain calcified microbial mats composed of microbiota closely resembling modern benthic colonial cyanobacteria (Chroococcales and Pleurocapsales). Their remains, visible under the scanning electron microscope (SEM) after etching of polished rock samples, comprise capsular envelopes, mucilage sheaths, and groups of cells mineralized by calcium carbonate with an admixture of Al-K-Mg-Fe silicates. The capsular organization of the mucilaginous sheaths surrounding individual cells and cell clusters forming colonies and the mode of mineralization are the characteristic common features of the Neoarchean microbiota described and their modern analogues. The new findings indicate massive production of calcium carbonates by benthic coccoid cyanobacteria in the Neoarchean, and offer a solution to the problem of the origin of Archean carbonate platforms, stromatolites and microbial reefs.

Large tufa mounds, Searles Lake, California

“…, 1999; Folk & Chafetz, 2000; Folk & Lynch, 2001; Benzerera et al. , 2003, 2006; Pentecost, 2003; Kazmierczak et al. , 2009; Zhou & Chafetz, 2009).…”

LateDevonian marine anoxia challenged by benthic cyanobacterial mats

“…As shown in the examples of modern permineralized coccoidal cyanobacterial mats from Lake Van, Turkey composed predominantly of entophysalidacean and pleurocapsalean cyanobacteria (Gessner, ; López‐Garcia et al ., ) (Figs I–K and A,B), and in pleurocapsalean biofilms from the Sulejów Reservoir, central Poland (Fig. B), the web‐like or ‘pits and walls’ organization of the Devonian mats is analogous in shape and size to the organization of the common mucilage sheaths (glycocalyx) in living benthic mats built of such microbiota (see also: Horodyski & Vonder Haar, ; Horodyski, ; Krumbein & Swart, ; Scott et al ., ; Kazmierczak et al ., , ). As in recent mats composed of colonial coccoidal cyanobacteria (Horodyski, ; Horodyski & Vonder Haar, ), the postmortem degradation of the Kellwasser and Hangenberg mats removed progressively first the cells and the thinner mucilage sheaths enveloping them, leaving almost intact the thicker, more resistant sheaths, which, as modern example from Lake Van shows (Fig.…”

“…C). Web‐like textures with similar morphology, size, and mineral (elemental) composition were described from Early Silurian (Kremer & Kazmierczak, ; Kremer, ) and Late Archean (Kazmierczak & Altermann, ; Kazmierczak et al ., ) deposits and interpreted as remnants of benthic coccoidal cyanobacterial mats. Comparative studies of variously degraded fossil (particularly Proterozoic) and modern entophysalidacean and pleurocapsalean cyanobacteria from marine, freshwater and hypersaline settings showed explicitly that identification of fossil colonial coccoidal cyanobacteria is possible basing on the preserved remains of their glycocalyx (e.g., Knoll et al ., ; Hofmann, ; Golubic & Hofmann, ; Oehler, ; Knoll & Golubic, ; Knoll et al ., ).…”

Hydrochemistry and microbialites of the alkaline crater lake Alchichica, Mexico

“…The process of their formation significantly influenced the chemical evolution of atmosphere and hydrosphere, and, consequently, biosphere evolution (e.g., Holland 1984; Kempe and Degens 1985;Kempe and Kazmierczak 1994;Lowe and Tice 2004;Ohmoto 2004). Archean carbonate deposits enclose only few remains of microorganisms, which nevertheless indicate that microbial ecosystems, for example cyanobacterial mats, were involved in their origin (e.g., Walter 1983; Kazmierczak and Altermann 2002;Altermann and Kazmierczak 2003;Kazmierczak et al , 2009Altermann et al 2006). However, due to the lack of relevant modern analogues, the genesis of such deposits remains unclear.…”

“…However, due to the lack of relevant modern analogues, the genesis of such deposits remains unclear. This concerns particularly the origins of diverse microstructurally laminated Precambrian biosedimentary structures called ''stromatolites'' and non-laminated finegrained (micritic) carbonates known as ''thrombolites' ' (e.g., Bertrand-Sarfati 1976;Semikhatov et al 1979;Buick et al 1981;Kennard and James 1986;Grotzinger and Rothman 1996;Riding 2000;Kazmierczak et al 2009). Papers presenting potential modern analogues of Precambrian microbialites (e.g., Fairchild 1991; Kazmierczak and Kempe 2006) are still rare, and, in spite of intensive efforts, far from solving the basic problems of stromatolite morphogenesis.…”