Microfossil-like objects from the Archaean of Greenland: a cautionary note

Bridgwater, D.; Allaart, J.H; Schopf, J. William; Klein, Cornelis; Walter, Malcolm R.; Barghoorn, Elso S.; Strother, Paul K.; Knoll, Andrew H.; Gorman, B.E

doi:10.1038/289051a0

Cited by 81 publications

(18 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Soon, however, the nature of these carbonaceous spherical microstuctures was disputed by Bridgwater et al (1981) and Roedder (1981). Bridgwater et al (1981) put forward two main arguments.…”

Section: History Of Raman Spectroscopy Applied To Archean Carbonaceoumentioning

confidence: 99%

“…Bridgwater et al (1981) put forward two main arguments. First, they asserted that the putative microfossils were indistinguishable from limonite-stained fluid inclusions-microstructures that are demonstrably inorganic and post-depositional in origin (Bridgwater et al, 1981). Notably and despite this first argument, the Raman spectra indicate disordered sp 2 carbon and a younger contaminated source of functionalized carbon.…”

Section: History Of Raman Spectroscopy Applied To Archean Carbonaceoumentioning

confidence: 99%

See 1 more Smart Citation

Understanding the Application of Raman Spectroscopy to the Detection of Traces of Life

Marshall

Edwards²,

Jehlička³

2010

Astrobiology

167

109

View full text Add to dashboard Cite

Investigating carbonaceous microstructures and material in Earth's oldest sedimentary rocks is an essential part of tracing the origins of life on our planet; furthermore, it is important for developing techniques to search for traces of life on other planets, for example, Mars. NASA and ESA are considering the adoption of miniaturized Raman spectrometers for inclusion in suites of analytical instrumentation to be placed on robotic landers on Mars in the near future to search for fossil or extant biomolecules. Recently, Raman spectroscopy has been used to infer a biological origin of putative carbonaceous microfossils in Early Archean rocks. However, it has been demonstrated that the spectral signature obtained from kerogen (of known biological origin) is similar to spectra obtained from many poorly ordered carbonaceous materials that arise through abiotic processes. Yet there is still confusion in the literature as to whether the Raman spectroscopy of carbonaceous materials can indeed delineate a signature of ancient life. Despite the similar nature in spectra, rigorous structural interrogation between the thermal alteration products of biological and nonbiological organic materials has not been undertaken. Therefore, we propose a new way forward by investigating the second derivative, deconvolution, and chemometrics of the carbon first-order spectra to build a database of structural parameters that may yield distinguishable characteristics between biogenic and abiogenic carbonaceous material. To place Raman spectroscopy as a technique to delineate a biological origin for samples in context, we will discuss what is currently accepted as a spectral signature for life; review Raman spectroscopy of carbonaceous material; and provide a historical overview of Raman spectroscopy applied to Archean carbonaceous materials, interpretations of the origin of the ancient carbonaceous material, and a future way forward for Raman spectroscopy.

show abstract

Section: History Of Raman Spectroscopy Applied To Archean Carbonaceoumentioning

confidence: 99%

Section: History Of Raman Spectroscopy Applied To Archean Carbonaceoumentioning

confidence: 99%

Understanding the Application of Raman Spectroscopy to the Detection of Traces of Life

Marshall

Edwards²,

Jehlička³

2010

Astrobiology

167

109

View full text Add to dashboard Cite

show abstract

“…Rather than seeing a microfossil community, Bridgwater et al (1981) interpreted the features as trails of limonitestained, inorganic, fluid inclusions formed during episodes of deformation and recrystallization. Such a conclusion fits well with the known upper amphibolite facies metamorphism that has affected the rocks and the inconclusive organic geochemistry discussed by Nagy et al (1981).…”

Section: Claims For Life In the Isua Greenstone Beltmentioning

confidence: 99%

“…In response to the claims that these spherical objects were unicellular microfossils, Bridgwater et al (1981) examined samples from the same outcrop and drew a substantially different conclusion based on a deeper understanding of the structural and metamorphic events that have profoundly affected the rocks. Rather than seeing a microfossil community, Bridgwater et al (1981) interpreted the features as trails of limonitestained, inorganic, fluid inclusions formed during episodes of deformation and recrystallization.…”

Section: Claims For Life In the Isua Greenstone Beltmentioning

confidence: 99%

“…van Zuilen et al 2002a;Lepland et al 2003). Even the host sediments or volcanic rocks are prone to exchange their compositional information with percolating fluids and surrounding rocks thus masking original composition and texture (Bridgwater et al 1981;Rosing et al 1996;Fedo & Whitehouse 2002a), and biological shapes (e.g. Brasier et al 2002) are subject to tremendous change.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Geological constraints on detecting the earliest life on Earth: a perspective from the Early Archaean (older than 3.7 Gyr) of southwest Greenland

Fedo

Whitehouse

Kamber

2006

Phil. Trans. R. Soc. B

View full text Add to dashboard Cite

At greater than 3.7 Gyr, Earth's oldest known supracrustal rocks, comprised dominantly of mafic igneous with less common sedimentary units including banded iron formation (BIF), are exposed in southwest Greenland. Regionally, they were intruded by younger tonalites, and then both were intensely dynamothermally metamorphosed to granulite facies (the highest pressures and temperatures generally encountered in the Earth's crust during metamorphism) in the Archaean and subsequently at lower grades until about 1500 Myr ago. Claims for the first preserved life on Earth have been based on the occurrence of greater than 3.8 Gyr isotopically light C occurring as graphite inclusions within apatite crystals from a 5 m thick purported BIF on the island of Akilia. Detailed geologic mapping and observations there indicate that the banding, first claimed to be depositional, is clearly deformational in origin. Furthermore, the mineralogy of the supposed BIF, being dominated by pyroxene, amphibole and quartz, is unlike well-known BIF from the Isua Greenstone Belt (IGB), but resembles enclosing mafic and ultramafic igneous rocks modified by metasomatism and repeated metamorphic recrystallization. This scenario parsimoniously links the geology, whole-rock geochemistry, 2.7 Gyr single crystal zircon ages in the unit, an approximately 1500 Myr age for apatites that lack any graphite, non-MIF sulphur isotopes in the unit and an inconclusive Fe isotope signature. Although both putative body fossils and carbon-12 enriched isotopes in graphite described at Isua are better explained by abiotic processes, more fruitful targets for examining the earliest stages in the emergence of life remain within greater than 3.7 Gyr IGB, which preserves BIF and other rocks that unambiguously formed at Earth's surface.

show abstract

Early Life on Earth: The Ancient Fossil Record

Westall

2004

Astrobiology: Future Perspectives

View full text Add to dashboard Cite

Microfossil-like objects from the Archaean of Greenland: a cautionary note

Cited by 81 publications

References 14 publications

Understanding the Application of Raman Spectroscopy to the Detection of Traces of Life

Understanding the Application of Raman Spectroscopy to the Detection of Traces of Life

Geological constraints on detecting the earliest life on Earth: a perspective from the Early Archaean (older than 3.7 Gyr) of southwest Greenland

Early Life on Earth: The Ancient Fossil Record

Contact Info

Product

Resources

About