Microfossils of the Early Archean Apex Chert: New Evidence of the Antiquity of Life

Schopf, J. William

doi:10.1126/science.260.5108.640

Cited by 1,232 publications

(696 citation statements)

References 27 publications

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“…The oldest sedimentary rocks in the Greenland Isua formation have been heated to 500°C, so the evidence on the conditions at that time has been largely destroyed. The sediments in the Australian Warrawoona formation 3.5 x 10 9 years old contain very convincing cyanobacteria-like microfossils (Schopf 1993).…”

Section: What Was the Physical Setting Of The Origin Of Life?mentioning

confidence: 99%

The origin of life?did it occur at high temperatures?

1995

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Abstract.A high-temperature origin of life has been proposed, largely for the reason that the hyperthermophiles are claimed to be the last common ancestor of modern organisms. Even if they are the oldest extant organisms, which is in dispute, their existence can say nothing about the temperatures of the origin of life, the RNA world, and organisms preceding the hyperthermophiles. There is no geological evidence for the physical setting of the origin of life because there are no unmetamorphosed rocks from that period. Prebiotic chemistry points to a low-temperature origin because most biochemicals decompose rather rapidly at temperatures of 100°C (e.g., half-lives are 73 rain for ribose, 21 days for cytosine, and 204 days for adenine). Hyperthermophiles may appear at the base of some phylogenetic trees because they outcompeted the mesophiles when they adapted to lower temperatures, possibly due to enhanced production of heat-shock proteins.

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Section: What Was the Physical Setting Of The Origin Of Life?mentioning

confidence: 99%

The origin of life?did it occur at high temperatures?

1995

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“…Marine microbialites have been abundantly reported in the fossil record: in the Precambrian, which bears the earliest microfossils at the Earth's surface [43], and throughout the Phanerozoic until Quaternary times [13,14]. Based on the similarities between the microfossils included in Precambrian stromatolites and cyanobacteria, it has been suggested that oxygenic photosynthesis was carried out by cyanobacteria 3.5 billion years ago [24].…”

Section: Introductionmentioning

confidence: 99%

Irradiance Regulation of Photosynthesis and Respiration in Modern Marine Microbialites Built by Benthic Cyanobacteria in a Tropical Lagoon (New Caledonia)

2005

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Microbialites are organosedimentary deposits that have built up as a result of the growth and binding of detrital sediment by a benthic microbial community. This study focuses on microbialites built by monospecific populations of cyanobacteria in the south-west lagoon of New Caledonia, where they have been observed down to 20-25 m depth. The aim was to study their photosynthetic and respiratory responses to various light intensities. The Phormidium sp. TK1 microbialite was collected at 19 m depth and the P. crosbyanum (Tilden) microbialite was collected at 0.5 and 13 m depth. Phormidium sp. TK1 showed all the characteristic features of a low-light adapted species. The initial slope of the Photosynthesis versus Irradiance curve for this microbialite was close to the maximum quantum yield indicating an efficient light absorption and utilization at low light. The photosynthesis maximum was located 0.2-0.4 mm below the surface and did not shift with changing light intensity. Respiration rates were low and not enhanced by light; photoinhibition was observed at higher light intensities. In Phormidium crosbyanum (Tilden) microbialites, the photosynthesis maximum shifted downward to lower depths with increasing light, probably as a result of phototactic migration of cyanobacterial filaments, and light-enhanced respiration was observed at light intensities above light saturation. The photosynthetic parameters measured in P. crosbyanum indicate that P. crosbyanum is capable of photo-acclimation at high light intensities. The gross productivity of the different microbialites was comparable to values measured in cyanobacterial stromatolites observed in other shallow environments. However, the microbialites studied here were characterized by a lower respiration / production ratio which indicates a higher growth efficiency.

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“…Sedimentary deposits of the Palaeoarchaean greenstones of the East Pilbara Craton, Western Australia, are of particular geological significance for hosting the oldest putative microfossils (Schopf, 1993;Schopf et al 2002), the oldest stromatolites (Allwood et al 2006;Van Kranendonk, 2006) and preserving evidence of the environmental conditions of the Early Earth (Robert & Chaussidon, 2006;Hoashi et al 2009;van den Boorn et al 2010). Among these rocks, the c. 3460 Ma Marble Bar Chert Member of the Duffer Formation (Warrawoona Group) is a typical Archaean red-white-grey banded chert remarkably exposed at the Marble Bar Pool and Chinaman Pool localities ( Fig.…”

Section: Introductionmentioning

confidence: 99%

A deep subaqueous fan depositional model for the Palaeoarchaean (3.46 Ga) Marble Bar Cherts, Warrawoona Group, Western Australia

et al. 2012

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International audienceThe 3.46 Ga Marble Bar Chert Member of the East Pilbara Craton, Western Australia, is one of the earliest and best-preserved sedimentary successions on Earth. Here, we interpret the finely laminated thin-bedded cherts, mixed conglomeratic beds, chert breccia beds and chert folded beds of the Marble Bar Chert Member as the product of low-density turbidity currents, high-density turbidity currents, mass transport complexes and slumps, respectively. Integrated into a channel-levee depositional model, the Marble Bar Chert Member constitutes the oldest documented deep-sea fan on Earth, with thin-bedded cherts, breccia beds and slumps composing the outer levee facies tracts, and scours and conglomeratic beds representing the channel systems

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Microfossils of the Early Archean Apex Chert: New Evidence of the Antiquity of Life

Cited by 1,232 publications

References 27 publications

The origin of life?did it occur at high temperatures?

The origin of life?did it occur at high temperatures?

Irradiance Regulation of Photosynthesis and Respiration in Modern Marine Microbialites Built by Benthic Cyanobacteria in a Tropical Lagoon (New Caledonia)

A deep subaqueous fan depositional model for the Palaeoarchaean (3.46 Ga) Marble Bar Cherts, Warrawoona Group, Western Australia

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