Stromatolites formation

Biogenic forsterite and opal as a product of biodeterioration and lichen stromatolite formation in table mountain systems (tepuis) of Venezuela. Geomicrobiology Journal, 18, 117-32. 

Harder EC (1919) Iron-depositing bacteria and their geologic relations. US Geol Surv Prof Pap 113 Hartman H (1984) The evolution of photosynthesis and microbial mats a speculation on banded iron formations. In Microbial Mats Stromatolites. Cohen Y, Castenholz RW, Halvorson HO (eds) Alan Liss Pub, New York, p 451-453... 

The time period in which prebiotic synthesis of organic compounds took place is frequently misunderstood. The earth is 4.5 x 109 years old, and the earliest fossil organisms known, the Warrawoona microfossils and stromatolites, are 3.5 x 109 years old.10 The difference is 1.0 x 109 years, but the time available for life to arise was probably shorter. It probably took a few hundred million years for organisms to evolve to the level of those found in the Warrawoona formation. In addition, if the earth completely melted during its formation, then the time available would be further shortened by the time needed for the earth to cool down sufficiently for organic compounds to be stable. 

The find is associated with other specimens of the same kind and together with non-structured carbonaceous debris of similar chemical composition. The assemblages are arranged along bedding planes or other primary patterns of the sediment which is a chert, stromatolite, banded iron formation, shale or related rock. 

Occurences union years Cell-like morpholo- gies Organic Materials Cell encrustations indicating photosynthesis Organic carbon (C-lsotope ana lysis) Organic Molecules Organic debris Stromatolites Banded iron formations... 

Simonson B. M. and Lanier W. P. (1987) Early silica cementation and microfossil preservation in cavities in iron-formation stromatolites. Early Proterozoic of Canada. In Precambrian Iron-formations (eds. A. Uitterdijk, W. Peter, and L. L. Gene). Theophrastus Publ. and Pty. Co., Athens, Greece, pp. 187-213. 

Figure 4 Stromatolitic limestone, Cheshire Formation, Belingwe belt, Zimbabwe (2.6-2.7 Ga old) (a) outcrop surface—structures occur on a variety of scales, from microscopic to metre relief (b) detail of one outcrop (from Nisbet, 1987) and (c) shallow-water shale associated with Cheshire stromatolites.

Carbonate precipitation by cyanobacteria has been extensively reviewed by Golubic (1973) and the role of these organisms in the formation of stromatolites is discussed in Walter (1976). 

Shallow marine environments include coral and algal reefs as well as other bioherms and many favour calcification by benthic fauna. Stromatolites and stromatolitic environments are also typical shallow marine formations. The shallow marine carbonate environment may be subdivided into more or less agitated waters with dominantly benthic fauna, calm shallow areas with carbonate muds (e.g. Bahama Banks) with ooids as typical forms of deposits and reef areas with their complicated patterns of calcification and deposition (Bathurst, 1975 Kinsey and Davies, Chapter 2.5). 

Most of the discussions relating organic activity to the origin of banded iron formations have centered on three areas (1) the presence of fossil microorganisms in cherts from banded iron formations (2) the similarities between laminations in banded iron formations and modem algal and bacterial stromatolites and (3) role of photosynthesis in the evolution of oxygen in the ocean and atmosphere, and consequently in the origin of banded iron formations. 

Additional evidence of the existence of microorganisms in the Precambrian BIF s is provided by the occurrence of stromatolites within the iron formations. 

The masses of laminated chert characteristic of all Precambrian BIF s occur in a wide variety of external forms comprising just about every form type described for modem and ancient stromatolites. Hofmann (1969) devised a complex form taxonomy of stromatolites from the Gunflint Formation of the Lake Superior region, and has tied this classification into those of Logan et al. (1964), Rezak (1957), and Soviet geologists (e.g. Korolyuk, 1960 Krylov, 1963 Komar, 1966) which are based mainly on carbonate stromatolites. 

Unfortunately, most so-called stromatolites do not contain micro-structures which can be identified as organic, and consequently an organic interpretation rests mainly on the laminations and external morphology. However, comparison of true stromatolites in Precambrian iron formations (e.g. Barghoorn and Tyler, 1965 Cloud, 1965 Glaessner et al., 1969 Walter et al., 1976) with recognizable unequivocal organic remains leaves little doubt that most of the lamination in the BIF s and other Precambrian strata are indeed tme stromatolites. 

Direct organic control on the formation of stromatolites, often difficult... 

Walter, M.R., Goode, A.D.T. and Hall, W.D.M., 1976. Microfossils from a newly discovered Precambrian stromatolitic iron formation in Western Australia. Nature, 261 221—223. 

The carbonate horizons of the Cheshire and Manjeri Formations contain extensive well-preserved stromatolites. These were formed in shallow or intertidal waters, as demonstrated by interbedded ripple-marked and mud-cracked silts. Texturally, the limestones show many indications of organic activity and gas release structures (Martin et al. 1980). The simplest uni-formitarian explanation is that the structures were built by cyanobacteria. Isotopically, carbon from kerogen in the stromatolites typically has 6 C = -25 to -30%o. This implies but does not prove fractionation by rubisco of carbon captured from the atmosphere-ocean system. Carbonate in Cheshire limestones is typically close to 0%o, suggesting that carbon in the atmosphere-ocean system was modulated by rubisco and dominated by oxygenic photosynthesis on a planetary scale (Fig. 1) at least by this date. It should be noted that the c. 3 Ga Steep Rock stromatolites are similar (work by Abell, Grassineau and Nisbet). 

Carbon isotope compositions of organic carbon in the stromatolites of the Macgregor Member of the Cheshire Formation are variable, but... 

To summarize, the most probable explanation of the C isotope spread in the shallow-water facies of the Manjeri Formation (Spring Valley and Shavi sediments and Rupemba (Spring Valley) stromatolites), and in the Cheshire Formation stromatohtes and black shales is thus that carbon isotope fractionation records a diverse ecology that existed based primarily on oxygenic photosynthesis, but with associated organisms... 

Klappa, C.F. (1979) Lichen stromatolites criterion for subaerial exposure and a mechanism for the formation of laminar calcrete (caliche). Journal of Sedimentary Petrology 49, 387-400. 

Late Archaean stromatolites Younger stromatolites have been described from 3.0 Ga rocks at Steep Rock in Canada (Wilks St Nisbet, 1985), from the 2.7 Ga Cheshire formation of the Belingwe Greenstone belt (Martin et al., 1980) and from 2.52 Ga shelf carbonate sediments in the Campbellrand subgroup, South Africa. In this latter locality there are also well-documented calcified microfossils of cyanobacteria (Kazmierczak St Altermann, 2002). It is also possible that at this locality the mineralization of the dead bacteria was the result of the action of het-erotrophic bacteria. 

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