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Laser-Raman imagery of Earth's earliest fossils
Abstract
Unlike the familiar Phanerozoic history of life, evolution during the earlier and much longer Precambrian segment of geological time centred on prokaryotic microbes. Because such microorganisms are minute, are preserved incompletely in geological materials, and have simple morphologies that can be mimicked by nonbiological mineral microstructures, discriminating between true microbial fossils and microscopic pseudofossil 'lookalikes' can be difficult. Thus, valid identification of fossil microbes, which is essential to understanding the prokaryote-dominated, Precambrian 85% of life's history, can require more than traditional palaeontology that is focused on morphology. By combining optically discernible morphology with analyses of chemical composition, laser--Raman spectroscopic imagery of individual microscopic fossils provides a means by which to address this need. Here we apply this technique to exceptionally ancient fossil microbe-like objects, including the oldest such specimens reported from the geological record, and show that the results obtained substantiate the biological origin of the earliest cellular fossils known.
... Contradicting observations and interpretations invigorated the debate on the biogenicity of the carbonaceous filaments and their putative inclusion in the phylum cyanobacteria. Laser-Raman imagery of carbonaceous filaments (Schopf et al. 2002;Brasier et al. 2002) and of disseminated carbonaceous (kerogenous) matter in the Apex Chert gave controversial results. Schopf et al. (2002) interpreted the carbon as of biological origin. ...
... Laser-Raman imagery of carbonaceous filaments (Schopf et al. 2002;Brasier et al. 2002) and of disseminated carbonaceous (kerogenous) matter in the Apex Chert gave controversial results. Schopf et al. (2002) interpreted the carbon as of biological origin. Brasier et al. (2002) proposed that it rather could be amorphous carbon reorganized in the form of filamentous strains after devitrification processes of the chert veins. ...
... The carbon isotopic composition of the rocks and microfossils is also controversial. The in situ, on single microfossil, measured δ 13 C values from À27‰ to À34‰ versus PDB could be related to photosynthesis (δ 13 C ¼ À25‰ -À10‰; Schopf et al. 2002), methanogenesis (Brasier et al. 2002), or abiotic FTT reactions (e.g., McCollom and Seewald 2006. Buick (1984) suggested that carbonaceous filaments in the silica swarm dykes of the North Pole and Marble Bar, including Apex Chert, were contaminants introduced in the microfracturing of the silica veins during tectonic uplift of the region 2750 myr ago. ...
... Raman spectroscopy has been successfully utilized for diagnostics regarding fossilized remains in multiple studies. For example, Schopf et al. [51] applied micro Raman spectroscopy to the identification of Precambrian fossil microbes. They demonstrated that the valid identification of fossil microbes, via a combination of optical microscopy and Raman spectroscopy imaging, provides a new way to prove the biological origin of the earliest cellular fossils known. ...
... A broad band at 300-700 cm −1 contained broad bands; this can be attributed to the fluorescence, but also the presentation of the Raman scattering peaks. The spectra obtained from the fossilized plants ( Figure 7) were similar to the Raman data acquired for the microbial fossil, with the most informative "D" and "G" bands attributed to the organic matter presented in the fossils in concentrations much greater than for the kerogen embedded in rock [51,56]. We have not observed any Raman bands for chlorophyll or its derivatives (pheophytin, pheoporphyrin, phylloerythrin etc.), compared to the fluorescence spectroscopy measurements discussed above. ...
... A broad band at 300-700 cm −1 contained broad bands; this can be attributed to the fluorescence, but also the presentation of the Raman scattering peaks. The spectra obtained from the fossilized plants (Figure 7) were similar to the Raman data acquired for the microbial fossil, with the most informative "D" and "G" bands attributed to the organic matter presented in the fossils in concentrations much greater than for the kerogen embedded in rock [51,56]. We have not observed any Raman bands for chlorophyll or its derivatives (pheophytin, pheoporphyrin, phylloerythrin etc.), compared to the fluorescence spectroscopy measurements discussed above. ...
Fossilized plant remains have been studied simultaneously by laser induced fluorescence and Raman spectroscopies, to reveal the prospective methods for onsite or/and laser remote sensing in future extraterrestrial missions. A multiwavelength instrument, capable of fluorescence and Raman measurements, has been utilized for the study of isolated plant fossils, as well as fossils associated with sedimentary rocks. Laser-induced fluorescence spectroscopy revealed that plant fossils and rocks’ luminosity differed significantly due to chlorophyll derivatives (chlorin, porphyrins, lignin components etc.); therefore, fossilized plants can be easily detected at rock surfaces onsite. Raman spectroscopy highly altered the fossilized graphitic material via the carbon D and G bands. Our results demonstrated that combined laser-induced fluorescence and Raman spectroscopy measurements can provide new insights into the detection of samples with biogenicity indicators such as chlorophyll and its derivatives, as well as kerogenous materials. The prospects of multiwavelength LIDAR instrument studies under fieldwork conditions are discussed for fossils diagnostics. The method of laser remote sensing can be useful in geological exploration in the search for oil, coal-bearing rocks, and rocks with a high content of organic matter.
... Before this, simple anaerobic life forms emerged and developed on the Earth for a long time. These forms appeared very early (3.6-3.8 billion years ago), which is evidenced by the biogenic nature of the earliest layered stromatolites found in north-western Australia [5][6][7][8][9][10]. Their appearance was preceded and accompanied by the transformation of inorganic to organic matter and formation of prebiotic molecules. ...
... The action of γ-ray and high-energy β-particles (fast electrons with energy of ≥1 MeV) gives rise to radical fragments of the water molecule which are highly reactive: hydrated electron eaq − , hydrogen atom • H, and hydroxide radical • OH; as well as molecular products: hydrogen H2, and hydrogen peroxide H2O2. The values given in parentheses in Equation (3) are the radiation chemical yields of products for the indicated types of radiation (рН [4][5][6][7][8][9]. They are expressed in µmol J −1 , that is, they are equal to the concentration of particles (in µmol) formed upon the absorption of 1 Joule of radiation energy in 1 kg of water. ...
... The formation of organic compounds via transformation of inorganic matter of the Earth contributed to the same goal. The fact that the first signs of simple organisms were found to exist 4 Ga ago [5][6][7][8][9][10] indicates that the transformation of matter has actively proceeded, even during the planet's formation and then during the formation of the ocean, i.e., in the first 500 million years (Hadean). Unfortunately, there are virtually no reliable data on the geochemical state of the early Earth. ...
It is generally recognized that the evolution of the early Earth was affected by an external energy source: radiation from the early Sun. The hypothesis about the important role of natural radioactivity, as a source of internal energy in the evolution of the early Earth, is considered and substantiated in this work. The decay of the long-lived isotopes 232Th, 238U, 235U, and 40K in the Global Ocean initiated the oxygenation of the hydro- and atmosphere, and the abiogenesis. The content of isotopes in the ocean and the kinetics of their decay, the values of the absorbed dose and dose rate, and the efficiency of sea water radiolysis, as a function of time, were calculated. The ocean served as both a “reservoir” that collected components of the early atmosphere and products of their transformations, and a “converter” in which further chemical reactions of these compounds took place. Radical mechanisms were proposed for the formation of simple amino acids, sugars, and nitrogen bases, i.e., the key structures of all living things, and also for the formation of oxygen. The calculation results confirm the possible important role of natural radioactivity in the evolution of terrestrial matter, and the emergence of life.
... The carbonaceous composition of rock-embedded organic matter can be readily determined by the characteristic kerogen peaks in its Raman spectrum (Kudryavtsev et al., 2001;Schopf et al., 2002Marshall et al., 2010). In addition to providing diagnostic molecular information, Raman spectroscopy is also useful for measuring the thermal maturity of ancient organic matter (Beyssac et al., 2002;Pasteris and Wopenka, 2003;. ...
... As a result, further geochemical maturation of kerogen produces a set of stable compounds containing numerous interlinked PAHs, which become increasingly carbon-rich and graphitized under high pressure and temperature conditions as the kerogen becomes more regularly ordered. Raman spectroscopy is also routinely used to document the organic composition and degree of thermal maturity of Precambrian microfossils, and to thereby help assess their biogenicity (Kudryavtsev et al., 2001;Schopf et al., 2002Schopf et al., , 2017Allwood et al., 2006;Marshall et al., 2007;Sugitani et al., 2007). Nevertheless, and despite the value of such analyses, it is worth noting that Raman spectroscopy by itself is incapable of establishing the biological origin of fossilized organic matter or putative microfossils in the absence of supporting morphological and geochemical (e.g., isotopic) data (Pasteris and Wopenka, 2003;Marshall et al., 2010;Bower et al., 2013;Flannery et al., 2018). ...
... The current strategy for exploring and identifying the presence of fossilized microorganisms (and biogenic textures) in ancient martian sedimentary rocks is based largely on knowledge of Precambrian life and microbial evolution on Earth, and of its preservation in the early rock record (Cady et al., 2003). However, in contrast to most Raman studies of Precambrian microfossils on Earth, which typically utilize laser excitation wavelengths in the visible region (*380-700 nm) (Kudryavtsev et al., 2001;Schopf et al., 2002Guo et al., 2018), the Raman spectrometer of the SHERLOC instrument will feature a deep-UV (248.6 nm) laser excitation wavelength to map and characterize various minerals, organic molecules, and potential biosignatures that might be detected in martian rocks and regolith (Beegle et al., 2015;Abbey et al., 2017;Razzell Hollis et al., 2020;Bhartia et al., 2021). ...
The current strategy for detecting evidence of ancient life on Mars-a primary goal of NASA's ongoing Mars 2020 mission-is based largely on knowledge of Precambrian life and of its preservation in Earth's early rock record. The fossil record of primitive microorganisms consists mainly of stromatolites and other microbially influenced sedimentary structures, which occasionally preserve microfossils or other geochemical traces of life. Raman spectroscopy is an invaluable tool for identifying such signs of life and is routinely performed on Precambrian microfossils to help establish their organic composition, degree of thermal maturity, and biogenicity. The Mars 2020 rover, Perseverance, is equipped with a deep-ultraviolet (UV) Raman spectrometer as part of the SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) instrument, which will be used in part to characterize the preservation of organic matter in the ancient sedimentary rocks of Jezero crater and therein search for possible biosignatures. To determine the deep-UV Raman spectra characteristic of ancient microbial fossils, this study analyzes individual microfossils from 14 Precambrian cherts using deep-UV (244 nm) Raman spectroscopy. Spectra obtained were measured and calibrated relative to a graphitic standard and categorized according to the morphology and depositional environment of the fossil analyzed and its Raman-indicated thermal maturity. All acquired spectra of the fossil kerogens include a considerably Raman-enhanced and prominent first-order Raman G-band (∼1600 cm-1), whereas its commonly associated D-band (∼1350 cm-1) is restricted to specimens of lower thermal maturity (below greenschist facies) that thus have the less altered biosignature indicative of relatively well-preserved organic matter. If comparably preserved, similar characteristics would be expected to be exhibited by microfossils or ancient organic matter in rock samples collected and cached on Mars in preparation for future sample return to Earth.
... Figure 2 shows the most representative images of the biomorphs obtained using scanning electron microscopy ( Figure 2A) and optical microscopy ( Figure 2B), while Figure 2C corresponds to the Raman spectrum (the inset shows the mapping of one of the biomorphs; Figure 2D). Both Raman and IR peaks were identified as corresponding to the kerogen signal, which has been proposed as a marker of biogenicity [35][36][37][38], and our research team identified the biogenic kerogen signal for the first time in biomorphs synthetized in the presence of DNA pertaining to the five kingdoms in nature [29]. In the Raman spectrum, the kerogen signal is identified in two bands around 1300 (Band "D") and 1600 (Band "G") cm −1 , and, in the spectrum, there may or may not appear two poorly intense bands between 2600 and 2900 cm −1 [37,38]. ...
... Both Raman and IR peaks were identified as corresponding to the kerogen signal, which has been proposed as a marker of biogenicity [35][36][37][38], and our research team identified the biogenic kerogen signal for the first time in biomorphs synthetized in the presence of DNA pertaining to the five kingdoms in nature [29]. In the Raman spectrum, the kerogen signal is identified in two bands around 1300 (Band "D") and 1600 (Band "G") cm −1 , and, in the spectrum, there may or may not appear two poorly intense bands between 2600 and 2900 cm −1 [37,38]. In biomorphs, bands D and G appear between 1300 and 1700 cm −1 ; generally, one or two poorly intense bands can also be identified between Both Raman and IR peaks were identified as corresponding to the kerogen signal, which has been proposed as a marker of biogenicity [35][36][37][38], and our research team identified the biogenic kerogen signal for the first time in biomorphs synthetized in the presence of DNA pertaining to the five kingdoms in nature [29]. ...
... In the Raman spectrum, the kerogen signal is identified in two bands around 1300 (Band "D") and 1600 (Band "G") cm −1 , and, in the spectrum, there may or may not appear two poorly intense bands between 2600 and 2900 cm −1 [37,38]. In biomorphs, bands D and G appear between 1300 and 1700 cm −1 ; generally, one or two poorly intense bands can also be identified between Both Raman and IR peaks were identified as corresponding to the kerogen signal, which has been proposed as a marker of biogenicity [35][36][37][38], and our research team identified the biogenic kerogen signal for the first time in biomorphs synthetized in the presence of DNA pertaining to the five kingdoms in nature [29]. In the Raman spectrum, the kerogen signal is identified in two bands around 1300 (Band "D") and 1600 (Band "G") cm −1 , and, in the spectrum, there may or may not appear two poorly intense bands between 2600 and 2900 cm −1 [37,38]. ...
The synthesis of nucleic acids in the Precambrian era marked the start of life, with DNA being the molecule in which the genetic information has been conserved ever since. After studying the DNA of different organisms for several decades, we now know that cell size and cellular differentiation are influenced by DNA concentration and environmental conditions. However, we still need to find out the minimum required concentration of DNA in the pioneer cell to control the resulting morphology. In order to do this, the present research aims to evaluate the influence of the DNA concentration on the morphology adopted by biomorphs (barium silica-carbonates) under two synthesis conditions: one emulating the Precambrian era and one emulating the present era. The morphology of the synthetized biomorphs was assessed through scanning electron microscopy (SEM). The chemical composition and the crystalline structure were determined through Raman and IR spectroscopy. Our results showed that DNA, even at relatively low levels, affects the morphology of the biomorph structure. They also indicated that, even at the low DNA concentration prevailing during the synthesis of the first DNA biomolecules existing in the primitive era, these biomolecules influenced the morphology of the inorganic structure that lodged it. On the other hand, this also allows us to infer that, once the DNA was synthetized in the Precambrian era, it was definitely responsible for generating, conserving, and directing the morphology of all organisms up to the present day.
... In fact, some of the vintage chert beds are considered globally significant for containing the direct evidence of > 2 Ga old life forms (Awramik et al., 1983;Barghoorn & Tyler, 1965;Brasier et al., 2002;Buick, 1990;House et al., 2000;Schopf, 1993;Schopf et al., 2002). Very fine siliceous crystals in chert give high resistance to weathering, recrystallization and metamorphism. ...
... Textures are interpreted to indicate both direct crystallization of quartz from a gel and quartz precipitation as cavity fillings. Chert pseudomorphs, which are interpreted as replaced gypsum crystals, are noteworthy in the context of the disputed oldest finding of microfossils from the ~ 3.4 Ga Apex chert in the Pilbara Craton, Australia (Pinti & Altermann, 2015;Schopf, 1993;Schopf & Packer, 1987;Schopf et al., 2002). According to De Gregorio and Sharp (2003), Apex chert does not show in situ biogenic material instead having transported biogenic components interpreted as biogenicity of microfossils which came from a nearby source of microbial community in hydrothermal fluids. ...
The term ‘chert’ ideally refers to fine-grained siliceous (micro/cryptocrystalline) mineral and is also often used for rock with such siliceous mineral aggregate of chemical, biochemical, and organic origin. Petrologically, inorganic non-sedimentary origin or even volcanic derivatives formed by devitrification of metastable felsic volcanic glass can also be included within chert. A new classification scheme for Precambrian cherts is proposed, especially for field workers. Despite several worldwide studies on chert, simple comprehensive classification of chert is not available to date. There are notable differences amongst Archaean, Palaeoproterozoic and Meso-Neoproterozoic cherts. This paper reviews all the Precambrian cherts to divide them into three categories from global context. Archaean and Palaeoproterozoic cherts mostly imply precipitation from silica gel material supplied vide submarine volcanism. This paper also focuses on diagenetic chert concretion, nodules, and geodes in detail. Finally, the Mesoproterozoic Nagari Formation in Cuddapah Basin, India is shown as a case to explain the diagenetic conditions, which could favour chert development by silica supersaturation in the pores. Diagenetic sub-environments are categorized systematically as eogenetic, mesogenetic, and telogenetic types with evidences of each based on photomicrography and outcrop studies. A comprehensive analysis is attempted to understand the development of concretions, nodules and geodes due to diagenesis with respect to the Eastern Ghats Orogeny, which has played a significant role in the prominent development of diagenetic features during mesodiagenetic and telodiagenetic processes.
... Major evolutionary transitions occur when multiple autonomous units (e.g., genes) combine to form an interdependent autonomous unit (e.g., chromosomes) capable of storing and transmitting information in a novel way [1]. Over the past four billion years a relatively small number of such transitions have resulted in a myriad of innovations that have contributed to the diversification of life on Earth [1] [2]. Among the most conspicuous of these is the transition from organisms whose individuals consist of one cell to individuals that consist of many. ...
Background
Throughout its nearly four-billion-year history, life has undergone evolutionary transitions in which simpler subunits have become integrated to form a more complex whole. Many of these transitions opened the door to innovations that resulted in increased biodiversity and/or organismal efficiency. The evolution of multicellularity from unicellular forms represents one such transition, one that paved the way for cellular differentiation, including differentiation of male and female gametes. A useful model for studying the evolution of multicellularity and cellular differentiation is the volvocine algae, a clade of freshwater green algae whose members range from unicellular to colonial, from undifferentiated to completely differentiated, and whose gamete types can be isogamous, anisogamous, or oogamous. To better understand how multicellularity, differentiation, and gametes evolved in this group, we used comparative genomics and fossil data to establish a geologically calibrated roadmap of when these innovations occurred.
Results
Our ancestral-state reconstructions, show that multicellularity arose independently twice in the volvocine algae. Our chronograms indicate multicellularity evolved during the Carboniferous-Triassic periods in Goniaceae + Volvocaceae, and possibly as early as the Cretaceous in Tetrabaenaceae. Using divergence time estimates we inferred when, and in what order, specific developmental changes occurred that led to differentiated multicellularity and oogamy. We find that in the volvocine algae the temporal sequence of developmental changes leading to differentiated multicellularity is much as proposed by David Kirk, and that multicellularity is correlated with the acquisition of anisogamy and oogamy. Lastly, morphological, molecular, and divergence time data suggest the possibility of cryptic species in Tetrabaenaceae.
Conclusions
Large molecular datasets and robust phylogenetic methods are bringing the evolutionary history of the volvocine algae more sharply into focus. Mounting evidence suggests that extant species in this group are the result of two independent origins of multicellularity and multiple independent origins of cell differentiation. Also, the origin of the Tetrabaenaceae-Goniaceae-Volvocaceae clade may be much older than previously thought. Finally, the possibility of cryptic species in the Tetrabaenaceae provides an exciting opportunity to study the recent divergence of lineages adapted to live in very different thermal environments.
... Raman spectroscopy allows non-destructive compositional fingerprinting of complex biological and geological materials. [1][2][3][4][5][6][7][8][9][10] Rapidly generated in situ spectra yield information on covalent, ionic, and non-covalent chemical interactions enabling a comparative search for informative heterogeneities across a diversity of samples, 1 such as modern organismal tissues and their fossilization products. Spectroscopic biosignatures, such as phylogenetic and metabolic signals, represent diagnostic tools in cancer research, [3][4][5][6][7] and a number of signatures present in fresh tissues preserve, occasionally altered but not unrecognizable, in fossilized carbonaceous tissues: in integrative data sets, spectroscopic signatures reflecting the relative abundance of different organic functional groups 1 and organo-mineral interactions 2 encode molecular manifestations of phylogenetic affinity, 2-7,11-13 physiology, [2][3][4][5][6][7][11][12][13][14][15][16][17] and degree and mode of environmental or diagenetic alteration. ...
Raman spectroscopy is a popular tool for characterizing complex biological materials and their geological remains. Ordination methods, such as principal component analysis (PCA), use spectral variance to create a compositional space, the ChemoSpace, grouping samples based on spectroscopic manifestations reflecting different biological properties or geological processes. PCA allows to reduce the dimensionality of complex spectroscopic data and facilitates the extraction of informative features into formats suitable for downstream statistical analyses, thus representing a first step in the development of diagnostic biosignatures from complex modern and fossil tissues. For such samples, however, there is presently no systematic and accessible survey of the impact of sample, instrument, and spectral processing on the occupation of the ChemoSpace. Here, the influence of sample count, unwanted signals and different signal‐to‐noise ratios, spectrometer decalibration, baseline subtraction, and spectral normalization on ChemoSpace grouping is investigated and exemplified using synthetic spectra. Increase in sample size improves the dissociation of groups in the ChemoSpace, and our sample yields a representative and mostly stable pattern in occupation with less than 10 samples per group. The impact of systemic interference of different amplitude and frequency, periodical or random features that can be introduced by instrument or sample, on compositional biological signatures is reduced by PCA and allows to extract biological information even when spectra of differing signal‐to‐noise ratios are compared. Routine offsets ( 1 cm ⁻¹ ) in spectrometer calibration contribute in our sample to less than 0.1% of the total spectral variance captured in the ChemoSpace and do not obscure biological information. Standard adaptive baselining, together with normalization, increases spectral comparability and facilitates the extraction of informative features. The ChemoSpace approach to biosignatures represents a powerful tool for exploring, denoising, and integrating molecular information from modern and ancient organismal samples.
... The observation of microorganism-like silica nanoparticles in GAM indicated that GAM systems might supply targets for recording the process of microorganism biomineralization in a natural water environment. The typical measures for identification of spherical, silicified microorganisms as well as the process of microorganism biomineralization in natural water environment can include: (i) diameter, typically < 200 nm, (ii) distinct cores representing the original microorganism, (iii) levels of microorganism-like silica nanoparticles inside host cells, (iv) chemical biosignatures, such as Fe and S (Laidler and Stedman 2010), similar to those observed in some microfossils (House et al. 2000;Schopf et al. 2002). ...
Relatively little research has been conducted on the preservation of microorganisms and microbial particles in the groundwater of abandoned mines (GAM). In this study, silicified microorganism-like particles, 50-450 nm in diameter, were found to commonly occur outside microbes and their associated extracellular polymers. These particles comprise a cellular core surrounded by a cortex essentially of silica and are similar in morphology to certainly known microorganisms. The studied samples suggest the preservation of microorganisms through silicification and add to understanding about how microorganisms in natural water systems undergo biomineralization. Finally, the silicified microorganism-like particles were surrounded by many silica nanoparticles. This study identified a new mode of silica transport in the GAM.
... Raman spectroscopy allows non-destructive compositional fingerprinting of complex biological and geological materials [1][2][3][4][5][6][7][8][9][10] . Rapidly generated in situ spectra yield information on covalent, ionic, and noncovalent bioinorganic interactions enabling a comparative search for informative heterogeneities across a diversity of samples 1 , such as modern organismal tissues and their fossilization products. ...
Raman spectroscopy is a popular tool for characterizing complex biological materials and their geological remains ¹⁻¹⁰ . Ordination methods, such as Principal Component Analysis (PCA), rely on spectral variance to create a compositional space ¹ , the ChemoSpace, grouping samples based on spectroscopic manifestations that reflect different biological properties or geological processes ¹⁻⁷ . PCA allows to reduce the dimensionality of complex spectroscopic data and facilitates the extraction of relevant informative features into data formats suitable for downstream statistical analyses, thus representing an essential first step in the development of diagnostic biosignatures. However, there is presently no systematic survey of the impact of sample, instrument, and spectral processing on the occupation of the ChemoSpace. Here the influence of sample count, signal–to–noise ratios, spectrometer decalibration, baseline subtraction routines, and spectral normalization on ChemoSpace grouping is investigated using synthetic spectra. Increase in sample size improves the dissociation of sample groups in the ChemoSpace, however, a stable pattern in occupation can be achieved with less than 10 samples per group. Systemic noise of different amplitude and frequency, features that can be introduced by instrument or sample 11,12 , are eliminated by PCA even when spectra of differing signal–to–noise ratios are compared. Routine offsets (± 1 cm ⁻¹ ) in spectrometer calibration contribute to less than 0.1% of the total spectral variance captured in the ChemoSpace, and do not obscure biological information. Standard adaptive baselining, together with normalization, increase spectral comparability and facilitate the extraction of informative features. The ChemoSpace approach to biosignatures represents a powerful tool for exploring, denoising, and integrating molecular biological information from modern and ancient organismal samples.
... L'identification des premières formes de vie se focalise beaucoup sur la recherche de biomorphes dans des formations carbonatées ou silicifiées (Nutman et al., 2016;Dodd et al., 2017;Alleon et al., 2018), ce qui a pu conduire à des controverses (Schopf et al., 2002;Brasier et al., 2002;Wacey et al., 2016) qu'elles privilégiaient l'utilisation des isotopes légers ce qui conduisait à des fractionnements pouvant aller jusqu'à 66 ‰ (pour le rapport 34 S/ 32 S) entre le sulfure d'hydrogène produit et les sulfates résiduels (Harrison et Thode, 1958;Kaplan et Rittenberg, 1964;Kemp et Thode, 1968;Rees, 1973;Chambers et al., 1975;Canfield, 2001a;Johnston, 2005;Leavitt et al., 2014;Antler et al., 2017). Ces expériences ont par ailleurs mis en évidence l'importance de différents paramètres influençant les fractionnements isotopiques comme la température, la disponibilité des sulfates dissous, la nature du donneur d'électrons ou principalement, la cinétique de la réaction (Kaplan et Rittenberg, 1964;Habicht, 2002;Canfield et al., 2006;Sim et al., 2011b;Leavitt et al., 2015;Antler et al., 2017). ...
Les sulfures de fer sont omniprésents dans les roches sédimentaires et se sont révélés particulièrement utiles pour reconstruire l'évolution des paléoenvironnements terrestres. Leur propension à receler des biosignatures, en particulier celles des micro-organismes sulfato-réducteurs, est également utilisée pour tracer l'évolution de la biogéosphère mais reste souvent débattue. En effet, dans les environnements modernes, les bactéries sulfato-réductrices (SRB) jouent un rôle clé dans la réduction des sulfates en sulfures qui peuvent, en présence de métaux, précipiter des minéraux comme la pyrite (FeS2). Cependant, l'implication directe des SRB dans la formation de pyrite sédimentaire est encore mal comprise en raison des échecs à obtenir cette réaction dans des cultures monospécifiques en laboratoire. L'étude en laboratoire est pourtant une étape essentielle pour pouvoir préciser les mécanismes de formation des sulfures de fer, le rôle des SRB et en extraire des biosignatures robustes. Au cours de ce travail de thèse, plusieurs approches expérimentales ont été explorées afin de caractériser les processus de biominéralisation de sulfures de fer par les SRB ainsi que leur évolution diagénétique. Une première approche s'est appuyée sur des enrichissements bactériens (plurispécifiques) réalisés à partir des eaux anoxiques et ferrugineuses du lac Pavin (Massif Central). Elle a montré que les SRB pouvaient se développer dans des milieux pauvres en sulfates et avoir un rôle important dans la biominéralisation des phases porteuses de fer grâce aux interactions avec d'autres métabolismes microbiens et à la mise en place d'un cycle cryptique du soufre. Une seconde approche s'est focalisée sur des cultures monospécifiques d'une souche modèle de SRB (Desulfovibrio desulfuricans) en présence de différentes sources de fer (ferreux dissous ou nanoparticules de phosphate ferrique). Les deux conditions ont conduit à la formation rapide (une semaine) de monosulfures de fer (FeS) présentant cependant des différences morphologiques. En effet, en présence de fer dissous, les sulfures de fer précipitaient sous forme de particules micrométriques rappelant des bactéries encroûtées alors qu'en présence de phosphate de fer, ils ont pris la forme d'un biofilm minéralisé. Après un mois, des pyrites sont apparues au sein de ce biofilm tandis que les cultures en présence de fer dissous n'ont pas évolué. Ces résultats, qui comptent parmi les rares synthèses de pyrites biogéniques, ont permis de préciser les mécanismes de formation des pyrites en lien avec l'activité des SRB. Dans les mêmes conditions de culture, les compositions isotopiques des sulfates, FeS et pyrites ont été mesurées afin de préciser les fractionnements isotopiques liés à la production de sulfures de fer par les SRB, là où les études précédentes s'étaient arrêtées à la formation de sulfure d'hydrogène. Nos résultats ont montré que la sulfato-réduction microbienne détermine le fractionnement majeur par rapport à la précipitation des sulfures de fer. Par ailleurs, des résultats préliminaires en multi-isotopie du soufre ont révélé des signatures distinctes sur la masse 36 selon la source de fer utilisée dans les cultures. Finalement, la diagenèse expérimentale des sulfures de fer abiotiques et biogéniques précédemment obtenus a conduit dans les deux cas à la formation de pyrite mais une nouvelle fois, une dichotomie majeure a été observée concernant leur morphologie. Là où les pyrites obtenues à partir des sulfures de fer abiotiques formaient des cristaux euhédriques semblables à ceux observés dans les sédiments pauvres en matière organique, celles obtenues à partir des produits des cultures ressemblaient à des agrégats sphérulitiques. Ces agrégats, distincts des framboïdes, pourraient avoir été négligés jusqu'à présent dans les environnements sédimentaires et leur recherche permettrait d'ouvrir une nouvelle voie vers l'identification des pyrites biogéniques dans les environnements naturels.
... In comparison, the applications of organic geochemical information derived from carbonate concretions are limited. The oldest fossil of a prokaryotic microorganism on Earth is preserved in the concretions of the Varauna group in the Archaeozoic Pilbara supergroup in Western Australia (Schopf, 1993(Schopf, , 2002. In recent years, some researchers have detected specific and semi-specific biomarkers, including methylhopanes, in concretions and discussed the biochemical action of sulfatereducing bacteria and methanogens in the diagenetic stage (Plet et al., 2016). ...
Paleoenvironmental information is better preserved in carbonate concretions. In this study, carbonate concretions in the Cretaceous Nenjiang shale, Songliao Basin, were examined to determine whether molecular fossils reflective of the paleoenvironment were better preserved at these sites. Organic and inorganic geochemical characteristics of the concretions and surrounding rocks were analyzed using a series of techniques, including SEM, LA-ICP-MS, GC-MS-MS, and GC-IRMS. The concretions are composed of high content microcrystalline dolomite. The δ¹³Ccarb and δ¹⁸Ocarb values of the concretionary dolomite were significantly higher than those of the surrounding rocks. The dolomite show enrichment in the LREEs and have a negative Eu anomaly. The concretion biomarkers showed distribution characteristics similar to those of surrounding rocks. This suggested that the molecular fossils preserved in concretions were mainly inherited from surrounding rocks. However, the concretions contained more C27 sterane and hopanes, with the hopane/sterane ratio being significantly higher than that of surrounding rocks (1.49 v. 0.86). Moreover, the relative content of 2-methylhopane was 2.4–6.6 times that of the surrounding rocks. This indicated changes in the biological equilibrium of source organisms within and outside the concretions. It was possible that the unstable organic matter at the core increased the bacterial concentration and activity inside the concretions. Both the hydrogen index and biomarker-derived indicators implied that the transformation of organic matter in concretions was minimized when compared with their host rock. The isotope δ13C16-30 was 1‰–3‰ more prevalent in individual N-alkane hydrocarbons in the concretions than in surrounding rocks, likely owing to differences in lithology, bacterial action, and degree of weathering. The study concluded that carbonate concretions could preserve molecular fossils better than the surrounding rocks, and the in-depth organic geochemical analysis of concretions could provide a valuable reference for research into early life forms.
... It is from within one of the patchy vein-like deposits that Schopf (1993) reported the presence of eleven putative microfossil taxa, including filamentous microbes, however the biogenicity of these microscopic features has been debated over the last two decades (Brasier et al. 2002;Schopf et al. 2002;De Gregorio and Schopf, 2006;De Gregorio et al., 2009;Schopf et al. , 2018Wacey et al., 2019). These vein-dykes and their associated basaltic flows host hydrothermal minerals such as barite, alunite, jarosite, hyallosite, and potassic phyllosilicates (produced by alteration of feldspars) (Pinti et al., 2009) and minor levels of Fe, Ni, Cu, Zn, and Sn as indications for high hydrothermal temperatures (~ 250-350 °C) (Brasier et al., 2002). ...
Chemically oscillating reactions (COR) are abiotic processes that generate self-repeating circularly concentric morphologies during decarboxylation of organic acids. The geometry and millimetre to centimetre size dimensions of laminated quartz botryoids recorded in the Palaeoarchean Apex and Strelley Pool chert horizons in Western Australia simulate the self-similar fractal patterns arising in vitro from COR using classical and modified reactants of the Belousov-Zhabotinsky (B-Z) reaction. The botryoidal patterns akin to those developed by the COR include circular concentric laminae, open-book features, microbialite- and stromatolite-like laminations, wavy and domal structures, and rosettes. The mineral composition and organic matter (OM) distribution of these objects indicates an origin from the early diagenetic decarboxylation of carboxylic acids. Pore-water alkalinity decrease is likely due to the decomposition of OM, the generation of carbonic acid, and the cessation of chemical wave diffusion. The chemical waves developed from primary circular oxidation spots, under solubility equilibrium with respect to silica could trigger diagenetic precipitation of quartz. The presence of Fe2+-bearing hematite in various botryoidal geometries in the Apex chert is an analogue of ferroin-derived Fe in B-Z solutions, whereas the presence of Fe and Zn sulphides in the Strelley Pool quartz botryoids is akin to sulphur redox intermediates in B-Z experiments. Correlated microscopy and Raman spectral analysis corroborate that the metamorphosed OM associated with these Palaeoarchean botryoids is indigenous and syngenetic with the host chert. OM in botryoidal quartz displays circular concentric laminations as well as gradients of its density. Accordingly, an abiotic model of COR for the diagenetic growth of the studied Apex and Strelley Pool quartz botryoids is proposed. Comparisons with the chemical compositions, geometric morphology and range of size dimensions of self-similar patterns have been the criteria for development of this model expression. The explored ancient botryoids can thus represent abiotic sedimentological signatures of carbon cycling.
... Kerogen has been proposed as a biogenicity marker because the carbon isotopic composition of biogenic kerogen and carbonate carbon coexist since the Precambrian era; and kerogen has been identified in Apex cherts. [1][2][3]93,94 In the Raman spectrum, the presence of kerogen is typically identified in two bands around 1300 (Band "D") and 1600 (Band "G") cm −1 , as well as in poorly intense bands of 2600−2900 cm −1 . 1,94 In biomorphs, bands D and G appear between 1300 and 1700 cm −1 , and generally, one band or the two poorly intense bands are identified from 2600 to 2900 cm −1 . ...
The origin of life on Earth is associated with the Precambrian era, in which the existence of a large diversity of microbial fossils has been demonstrated. Notwithstanding, despite existing evidence of the emergence of life many unsolved questions remain. The first question could be as follows: Which was the inorganic structure that allowed isolation and conservation of the first biomolecules in the existing reduced conditions of the primigenial era? Minerals have been postulated as the ones in charge of protecting theses biomolecules against the external environment. There are calcium, barium, or strontium silica-carbonates, called biomorphs, which we propose as being one of the first inorganic structures in which biomolecules were protected from the external medium. Biomorphs are structures with different biological morphologies that are not formed by cells, but by nanocrystals; some of their morphologies resemble the microfossils found in Precambrian cherts. Even though biomorphs are unknown structures in the geological registry, their similarity with some biological forms, including some Apex fossils, could suggest them as the first "inorganic scaffold" where the first biomolecules became concentrated, conserved, aligned, and duplicated to give rise to the pioneering cell. However, it has not been documented whether biomorphs could have been the primary structures that conserved biomolecules in the Precambrian era. To attain a better understanding on whether biomorphs could have been the inorganic scaffold that existed in the primigenial Earth, the aim of this contribution is to synthesize calcium, barium, and strontium biomorphs in the presence of genomic DNA from organisms of the five kingdoms in conditions emulating the atmosphere of the Precambrian era and that CO2 concentration in conditions emulating current atmospheric conditions. Our results showed, for the first time, the formation of the kerogen signal, which is a marker of biogenicity in fossils, in the biomorphs grown in the presence of DNA. We also found the DNA to be internalized into the structure of biomorphs.
... An example of a promising MeO with an antimicrobial effect is nanostructured La2O3 which has been found to inhibit the growth of bacteria, fungi, and yeast, and for this reason it was investigated in safety and biomedical applications [51]. Lanthanum is a rare-earth element possessing unique physical and chemical properties such as high density, high melting point, high thermal conductance, and conductivity, which provides the potential for enhancing the useful properties of the coating [52,53]. ...
This article deals with the simple preparation of environmentally friendly acrylic latex binders, which are functionalized with nanoparticles of metal oxides, namely MgO, ZnO, La2O3 and combinations of MgO and ZnO, serving as functional components to achieve antimicrobial properties, but also to improve physical–mechanical properties and chemical resilience. The incorporation of uncoated powder nanoparticles was performed during the synthesis, using the two-stage semi-continuous emulsion radical polymerization technique, to obtain latexes containing 0.5–1.3% nanoparticles relative to the polymer content. Changes in latex performance due to nanoparticles were compared from the point of view of the type and concentration of metal oxide nanoparticles in latex. The results of the tests showed that all types of nanoparticles showed very promising properties, while with increasing concentration of nanoparticles there was an improvement in properties. The nanoparticles in latex provided interfacially crosslinked transparent smooth coating films with high gloss and good physical–mechanical properties. Latexes containing the highest concentration of nanoparticles provided coatings with significant antimicrobial activity against all tested bacterial and fungal strains, but also in-can preservative stability of liquid latex. Furthermore, the coatings were resistant to solvents, and in addition, latexes with MgO nanoparticles showed a significant decrease in the minimum film-forming temperature, and latex with a concentration of about 1.3% MgO did not show any flash corrosion under the coating film cast on a steel substrate. The latexes containing MgO and La2O3 nanoparticles provided coatings that were very resistant to water bleaching.
... EDS analyses show that electron-dark laminae are dominated by C with lower relative concentrations of O, Fe, Ca, and Si ( Fig. 4C spots 1 & 3), while electron-bright laminae are dominated by O, Fe, C, Ca, and lower relative concentrations of Si and Mg ( Fig. 4C spot 2). Raman analysis of the electron-dark laminae yield vibrational bands at 1350 cm −1 and~1600 cm −1 , corresponding to disordered "D" and graphitic "G" bands characteristic of macromolecular carbonaceous material 66,67 (Fig. 4). NanoSIMS ion maps of these laminated Frutexites-like structures corroborates the presence of C and additionally show the presence of nitrogen, measured as the 12 C 14 N ion (Fig. 4D), which forms as clearly distinguishable laminae visible in the NanoSIMS ion maps. ...
Serpentinization is a geological process involving the interaction of water and ultramafic rock, the chemical byproducts of which can serve as an energy source for microbial communities. Although serpentinite systems are known to host active microbial life, it is unclear to what extent fossil evidence of these communities may be preserved over time. Here we report the detection of biosignatures preserved in a mineralized fracture within drill cores from the Samail Ophiolite in Oman. Two varieties of filamentous structures were identified in association with iron oxide precipitates. The first type are interpreted as likely microbial remains, while the second type are recognized as potentially microbiological dubiofossils. Additionally, laminated structures composed of carbon and nitrogen rich material were identified and interpreted as having a microbially-associated origin. Our observations affirm the potential to detect subsurface microbial communities within serpentinizing environments and highlight a unique taphonomic window to preserve evidence of rock-hosted life.
... Life on Earth is thought to have emerged in hot environments, with LUCA being either a thermophile or a hyperthermophile 36 . Specifically, the analyses of minerals [38][39][40] and resurrected enzymes [41][42][43] suggests that Earth's surface has gradually cooled down from 75°C about 3 billion years ago, to 35°C about 420 million years ago, with a further decrease to 14°C today. It is therefore likely that-if the metalbinding residues pre-existed in LUCA due to their requirement for protein folding at high temperatures-organisms invading colder environments could gradually mutate these residues to endow proteins with the flexibility required in colder environments [44][45][46] . ...
A bstract
Ribosomal genes are widely used as “molecular clocks” to infer the evolutionary relatedness of species. It is unclear, however, whether these genes can also serve as “molecular thermometers” to precisely estimate an organism’s optimal growth temperature. Previously, some estimations were made using the average nucleotide content in ribosomal RNA, but the universal application of this approach was prevented by numerous outliers. Here, seeking to bypass this problem, we asked whether ribosomal genes contain additional markers of thermal adaptations, aside from their nucleotide composition. To answer this, we analyzed site-specific variations in sequences of ribosomal proteins from 2,021 bacteria with known optimal growth conditions. We found that ribosomal proteins comprise a few “mutational hotspots”—residues that vary in a temperature-dependent manner and distinguish heat- and cold-adapted bacteria. Most of these residues coordinate metal ions that support protein folding at high temperatures. Using these residues, we then showed that the upper and lower limits of an organism’s optimal growth temperatures can be estimated using just 0.001% of the genome sequence or just two amino residues in the cellular proteome. This finding illustrates that laboratory-independent estimation of optimal growth temperatures can be simplified if we abandon the traditional use of rRNA and protein sequences to assess their content and instead focus on those few residues that are most critical for protein structure. This finding may simplify the analysis of unculturable and extinct species by helping bypass the need for laborious, costly, and at times impossible laboratory experiments.
... The successful data validation presented here demonstrates that biological residues can survive millions of years. These results corroborate with the recent findings of biomarkers in fossils [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] . Fluorescence microscopes 44 and examination under UV illumination 45,46 have been used in the past to investigate fossils. ...
The “Search for life”, which may be extinct or extant on other planetary bodies is one of the major goals of NASA planetary exploration missions. Finding such evidence of biological residue in a vast planetary landscape is an enormous challenge. We have developed a highly sensitive instrument, the “Compact Color Biofinder”, which can locate minute amounts of biological material in a large area at video speed from a standoff distance. Here we demonstrate the efficacy of the Biofinder to detect fossils that still possess strong bio-fluorescence signals from a collection of samples. Fluorescence images taken by the Biofinder instrument show that all Knightia spp. fish fossils analysed from the Green River formation (Eocene, 56.0–33.9 Mya) still contain considerable amounts of biological residues. The biofluorescence images support the fact that organic matter has been well preserved in the Green River formation, and thus, not diagenetically replaced (replaced by minerals) over such a significant timescale. We further corroborated results from the Biofinder fluorescence imagery through Raman and attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopies, scanning electron microscopy, energy dispersive X-ray spectroscopy (SEM–EDS), and fluorescence lifetime imaging microscopy (FLIM). Our findings confirm once more that biological residues can survive millions of years, and that using biofluorescence imaging effectively detects these trace residues in real time. We anticipate that fluorescence imaging will be critical in future NASA missions to detect organics and the existence of life on other planetary bodies.
... The biogenic origin of the putative microfossils and organic materials in Archean rocks is a major subject of debate (e.g., Bower et al., 2016;Brasier et al., 2002;Dodd et al., 2019;Moorbath, 2005;Papineau et al., 2011;Schopf et al., 2007). Several workers established the biological origin of the Archean carbonaceous material in shallow marine condition (as in stromatolites) and in hydrothermal settings (included in the hydrothermal quartz veins) by means of various tools such as carbon isotope geochemistry, micro-Raman spectroscopy and Fourier transform infrared spectroscopy (e.g., Schidlowski, 2001;Schopf et al., 2002Schopf et al., , 2005Ueno et al., 2001Ueno et al., , 2004. Recently, Dodd et al. (2019) extensively studied on the graphite associated with apatite in banded iron formations from several localities spanning from Eoarchean to Paleoproterozoic and stated that fluid deposited poorly crystalline graphite is abiotic in origin, whereas syngenetic crystalline graphite is biogenic origin. ...
... The biogenic origin of the putative microfossils and organic materials in Archean rocks is a major subject of debate (e.g., Bower et al., 2016;Brasier et al., 2002;Dodd et al., 2019;Moorbath, 2005;Papineau et al., 2011;Schopf et al., 2007). Several workers established the biological origin of the Archean carbonaceous material in shallow marine condition (as in stromatolites) and in hydrothermal settings (included in the hydrothermal quartz veins) by means of various tools such as carbon isotope geochemistry, micro-Raman spectroscopy and Fourier transform infrared spectroscopy (e.g., Schidlowski, 2001;Schopf et al., 2002Schopf et al., , 2005Ueno et al., 2001Ueno et al., , 2004. Recently, Dodd et al. (2019) extensively studied on the graphite associated with apatite in banded iron formations from several localities spanning from Eoarchean to Paleoproterozoic and stated that fluid deposited poorly crystalline graphite is abiotic in origin, whereas syngenetic crystalline graphite is biogenic origin. ...
The changes in the physicochemical conditions of the carbonaceous material during progressive metamorphism in metapelitic rocks is widely used as a geothermometer with the aid of Raman spectroscopy. However, the application of this technique in carbonate rocks has not been established yet. Here, we compare Raman spectroscopy of carbonaceous material thermometry and carbon isotope thermometry in low- to medium-grade metacarbonate rocks from the Archean Chitradurga Schist Belt in the Dharwar Craton, India. The carbonates in the lowermost Bababudan Group have metamorphosed under lower amphibolite facies metamorphic conditions giving consistent estimates for both Raman spectra of carbonaceous material thermometry (460–592 °C) and carbon isotope thermometry (450–560 °C). Contrastingly, in the Vanivilas Formation, the carbonaceous material with very fine flaky morphology in the grain boundary has slightly lower crystallinity, when compared to the coarse-grained ones near the vein boundary. Nevertheless, the carbon isotope thermometry estimated a lower temperature around 400 °C. The inconsistencies between the temperature estimates are ascribed to the pervasive post-metamorphic aqueous hydrothermal fluid infiltration indicated by the presence of numerous criss crossing quartz veins. This is also corroborated by the lowering of the oxygen isotope ratio of the carbonates near the vein boundary by 2.3‰, but without much difference in the carbon isotope ratios. The coarsening of the carbonaceous material near the vein boundary signifies fluid assisted recrystallisation, that enhanced the crystallinity as evidenced in the Raman spectra. Moreover, the negative δ¹³C shift in the carbonaceous material (c. –8.5 to –13‰) was possibly due to recrystallization following partial CO2 degassing. In the Chitradurga Schist Belt, the Bababudan Group and the Vanivilas Formation have regionally metamorphosed under lower amphibolite facies condition, possibly related to the widespread granitic intrusion at c. 2.61 Ga and later affected by hydrothermal event at c. 2.5 Ga.
... Evaluating the chemical signatures of individual Precambrian microfossils is important for understanding their physiological and phylogenetic characteristics as well as their biogenicity. Recently, spectroscopic and geochemical analyses have enabled the spatially differential examination of the elemental, isotopic, and molecular compositions of micrometer-sized fossils and surrounding minerals preserved in thin sections at the nanometer-to-micrometer scale (e.g., Alleon et al., 2016Alleon et al., , 2018Alleon and Summons, 2019;House et al., 2000House et al., , 2013Igisu et al., 2006Igisu et al., , 2009Igisu et al., , 2014Igisu et al., , 2019Kudryavtsev et al., 2001;Loron et al., 2019;Marshall et al., 2005;Oehler et al., 2006Oehler et al., , 2009Oehler et al., , 2010Pang et al., 2020;Schopf et al., 2002Schopf et al., , 2005Schopf et al., , 2018Ueno et al., 2001;Wacey et al., 2011Wacey et al., , 2017Williford et al., 2013). Transmission Fourier-transform infrared (FTIR) microspectroscopy is a technique used to provide information on the molecular structures in organic-walled microfossils, and has often been used to determine the taxonomy of Proterozoic organic-walled microfossils, morphologically interpreted as cyanobacteria, acritarchs, and other types (e.g., Arouri et al., 1999Arouri et al., , 2000Cornet et al., 2019;Igisu et al., 2009Igisu et al., , 2014Igisu et al., , 2017Igisu et al., , 2019Loron et al., 2019;Marshall et al., 2005;Qu et al., 2015Qu et al., , 2017. ...
Raman and Fourier-transform infrared (FTIR) microspectroscopic analyses were performed to examine the chemical signatures and their spatial distribution of organic-walled microfossils together with organic matter (OM) in a black chert nodule from the Ediacaran (635–551 Ma) Doushantuo Formation in China. Raman spectral parameters (I-1350/1600 values) reveal that the acritarchs, bundled filaments, and OM have different degrees of structural order, and that there is no significant difference in I-1350/1600 values among the different portions of individual acritarchs (i.e., inner structure, inner membrane, and outer wall). The IR mapping reveals portion-specific chemical signatures within the individual acritarch specimens. The inner membrane of Tianzhushania contains aliphatic C-H bonds. The acritarchs, including Tianzhushania, show chemically four types of inner structures: (1) aromatic C-H-rich type, (2) aliphatic C-H-rich type, (3) aromatic/aliphatic C-H-poor type, or (4) heterogeneous. All of the examined acritarchs have aromatic C-H rich outer wall, irrespective of the presence/absence of processes. These features support a eukaryotic cyst origin, although it is difficult to determine whether the acritarchs correspond to the cysts of Protista or Metazoa. The bundled filaments also consist of an aromatic C-H bond, but its origin is uncertain. The OM shows a high degree of variation in Raman spectral I-1350/1600 values, as does the IR spectral intensity ratio of asymmetric aliphatic CH3/CH2, alongside a heterogeneous spatial distribution of aromatic and aliphatic C-H bands. This suggests the contribution of various precursors derived from dead microbial cell debris and extracellular organic compounds. Overall, these results confirm the presence of diverse microorganisms in the Doushantuo microbiota. Furthermore, the spatial distribution of organic functional groups in individual microfossils could provide clues about the taxonomy of microfossils of unknown origin.
... Raman spectroscopy has also been applied to the detection of organic materials for astrobiological purposes ( Jones et al., 1985;Dickensheets et al., 2000;Schopf et al., 2002;Pasteris and Wopenka, 2003;Marshall et al., 2010;Eshelman et al., 2014;Jehlička et al., 2014;Beegle et al., 2015;Lalla et al., 2016Lalla et al., , 2019Stromberg et al., 2019). These capabilities make it a favorable technique to use in planetary exploration. ...
The Mars 2020 Perseverance rover landed on February 18, 2021, and has started ground operations. The ExoMars Rosalind Franklin rover will touch down on June 10, 2023. Perseverance will be the first-ever Mars sample caching mission-a first step in sample return to Earth. SuperCam and Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC) on Perseverance, and Raman Laser Spectrometer (RLS) on Rosalind Franklin, will comprise the first ever in situ planetary mission Raman spectroscopy instruments to identify rocks, minerals, and potential organic biosignatures on Mars' surface. There are many challenges associated when using Raman instruments and the optimization and quantitative analysis of resulting data. To understand how best to overcome them, we performed a comprehensive Raman analysis campaign on CanMars, a Mars sample caching rover analog mission undertaken in Hanksville, Utah, USA, in 2016. The Hanksville region presents many similarities to Oxia Planum's past habitable conditions, including liquid water, flocculent, and elemental compounds (such as clays), catalysts, substrates, and energy/ food sources for life. We sampled and conducted a complete band analysis of Raman spectra as mission validation analysis with the RLS ExoMars Simulator or RLS Sim, a breadboard setup representative of the ExoMars RLS instrument. RLS Sim emulates the operational behavior of RLS on the Rosalind Franklin rover. Given the high fidelity of the Mars analog site and the RLS Sim, the results presented here may provide important information useful for guiding in situ analysis and sample triage for caching relevant for the Perseverance and Rosalind Franklin missions. By using the RLS Sim on CanMars samples, our measurements detected oxides, sulfates, nitrates, carbonates, feldspars, and carotenoids, many with a higher degree of sensitivity than past results. Future work with the RLS Sim will aim to continue developing and improving the capability of the RLS system in the future ExoMars mission. Key Words: Rover simulation mission—Mars—Raman spectroscopy—Planetary exploration.
Paleoarchean carbonates in the Pilbara Craton (Western Australia) are important archives for early life and environment on early Earth. Amongst others, carbonates occur in interstitial spaces of ca. 3.5–3.4 Ga pillow basalts (North Star-, Mount Ada-, Apex-, and Euro Basalt, Dresser Formation) and associated with bedded deposits (Dresser- and Strelley Pool Formation, Euro Basalt). This study aims to understand the formation and geobiological significance of those early Archean carbonates by investigating their temporal-spatial distribution, petrography, mineralogy, and geochemistry (e.g., trace elemental compositions, δ13C, δ18O). Three carbonate factories are recognized: (i) an oceanic crust factory, (ii) an organo-carbonate factory, and (iii) a microbial carbonate factory. The oceanic crust factory is characterized by carbonates formed in interspaces between pillowed basalts (“interstitial carbonates”). These carbonates precipitated inorganically on and within the basaltic oceanic crust from CO2-enriched seawater and seawater-derived alkaline hydrothermal fluids. The organo-carbonate factory is characterized by carbonate precipitates that are spatially associated with organic matter. The close association with organic matter suggests that the carbonates formed taphonomically via organo-mineralization, that is, linked to organic macromolecules (either biotic or abiotic) which provided nucleation sites for carbonate crystal growth. Organo-carbonate associations occur in a wide variety of hydrothermally influenced settings, ranging from shallow marine environments to terrestrial hydrothermal ponds. The microbial carbonate factory includes carbonate precipitates formed through mineralization of extracellular polymeric substances (EPS) associated with microbial mats and biofilms. It is commonly linked to shallow subaquatic environments, where (anoxygenic) photoautotrophs might have been involved in carbonate formation. In case of all three carbonates factories, hydrothermal fluids seem to play a key-role in the formation and preservation of mineral precipitates. For instance, alkaline earth metals and organic materials delivered by fluids may promote carbonate precipitation, whilst soluble silica in the fluids drives early chert formation, delicately preserving authigenic carbonate precipitates and associated features. Regardless of the formation pathway, Paleoarchean carbonates might have been major carbon sinks on the early Earth, modulating the carbon cycle and, hence, climate variability.
In the last 5 decades, paleontological research has exploded where fossils have enabled robust dating of rocks, improved understanding of origination/extinction rates or mass extinction events, biogeography, adaptive strategies, and many more. New molecular technologies have enabled intensive analyses of vertebrates and invertebrates, plant fossils, fossilized microbes, trace fossils, and fossil molecules, alike. Paleontological research has become interdisciplinary with inputs from geology, chemistry, biology, astronomy, and archaeology. Herein, we review the principles of promising molecular technologies and explore their applications and limitations vis-à-vis paleontological research. This review will attempt to provide a roadmap that can be used for future research directions. Advanced chemical imaging provides the ability to identify and quantify chemical characteristics to evaluate taphonomic damage, original biological structures, or fossils microbes. Molecular methods (e.g., molecular clock, DNA barcode, racemization dating, and biomarkers) offer a unique source of information and provide robust clues into the co-evolution of life in modern and past environments. Two main limitations are noted and include an exceptional preservation of the organic material, which is not always the case, and the complexity and cost of the instruments involved in the analyses. These difficulties are limiting the factual applications in paleontological analysis. Although very little research has been carried out on the aforementioned methods, they however, provide improved answers to highly debated and unsolved biological and climatic issues and a window to better understanding the origin of life. Biomarker proxies will be further developed and refined to answer emerging questions in the Quaternary Period.
Minerals are the fundamental record of abiotic processes over time, while biominerals are one of the most common records of life due to their easy preservation and abundance. However, distinguishing between biominerals and abiotic minerals is challenging due to the superimposi-tion and repetition of geologic processes and the interference of ubiquitous and diverse life on Earth's surface and crust. Mineral dubiofossils, being potential outcomes of both abi-otic and biotic environments, emerge as valuable entities that can contribute significantly to the understanding of this issue, facilitating the testing and refinement of biogenicity criteria.
The Pilbara craton of northwestern Australia is known for what were, when reported, the oldest known microfossils and paleosols on Earth. Both interpretations are mired in controversy, and neither remain the oldest known. Both the microfossils and the paleosols have been considered hydrothermal artefacts: carbon films of vents and a large hydrothermal cupola, respectively. This study resampled and analyzed putative paleosols within and below the Strelley Pool Formation (3.3 Ga), at four classic locations: Strelley Pool, Steer Ridge, Trendall Ridge, and Streckfuss, and also at newly discovered outcrops near Marble Bar. The same sequence of sedimentary facies and paleosols was newly recognized unconformably above the locality for microfossils in chert of the Apex Basalt (3.5 Ga) near Marble Bar. The fossiliferous Apex chert was not a hydrothermal vein but a thick (15 m) sedimentary interbed within a sequence of pillow basalts, which form an angular unconformity capped by the same pre-Strelley paleosol and Strelley Pool Formation facies found elsewhere in the Pilbara region. Baritic alluvial paleosols within the Strelley Pool Formation include common microfossil spindles (cf. Eopoikilofusa ) distinct from marine microfossil communities with septate filaments ( Primaevifilum ) of cherts in the Apex and Mt Ada Basalts. Phosphorus and iron depletion in paleosols within and below the Strelley Pool Formation are evidence of soil communities of stable landscapes living under an atmosphere of high CO 2 (2473 ± 134 ppmv or 8.8 ± 0.5 times preindustrial atmospheric level of 280 ppm) and low O 2 (2181 ± 3018 ppmv or 0.01 ± 0.014 times modern).
Throughout its nearly four-billion-year history, life has undergone evolutionary transitions in which simpler subunits have become integrated to form a more complex whole. Many of these transitions opened the door to innovations that resulted in increased biodiversity and/or organismal efficiency. The evolution of multicellularity from unicellular forms represents one such transition, one that paved the way for cellular differentiation, including differentiation of male and female gametes. A useful model for studying the evolution of multicellularity and cellular differentiation is the volvocine algae, a clade of freshwater green algae whose members range from unicellular to colonial, from undifferentiated to completely differentiated, and whose gamete types can be isogamous, anisogamous, or oogamous. To better understand how multicellularity, differentiation, and gametes evolved in this group, we used comparative genomics and fossil data to establish a geologically calibrated roadmap of when these innovations occurred. Our results, presented as ancestral-state reconstructions, show that multicellularity arose independently twice in this clade. Our chronograms indicate multicellularity evolved during the Carboniferous-Triassic periods in Goniaceae + Volvocaceae, and possibly as early as the Cretaceous in Tetrabaenaceae. Using divergence time estimates we inferred when, and in what order, specific developmental changes occurred that led to differentiated multicellularity and oogamy. We find that in the volvocine algae the temporal sequence of developmental changes leading to differentiated multicellularity is much as proposed by David Kirk, and that multicellularity is correlated with the acquisition of anisogamy and oogamy. Lastly, morphological, molecular, and divergence time data suggest the possibility of cryptic species in Tetrabaenaceae.
Ribosomal genes are widely used as 'molecular clocks' to infer evolutionary relationships between species. However, their utility as 'molecular thermometers' for estimating optimal growth temperature of microorganisms remains uncertain. Previously, some estimations were made using the nucleotide composition of ribosomal RNA (rRNA), but the universal application of this approach was hindered by numerous outliers. In this study, we aimed to address this problem by identifying additional indicators of thermal adaptation within the sequences of ribosomal proteins. By comparing sequences from 2021 bacteria with known optimal growth temperature, we identified novel indicators among the metal-binding residues of ribosomal proteins. We found that these residues serve as conserved adaptive features for bacteria thriving above 40°C, but not at lower temperatures. Furthermore, the presence of these metal-binding residues exhibited a stronger correlation with the optimal growth temperature of bacteria compared to the commonly used correlation with the 16S rRNA GC content. And an even more accurate correlation was observed between the optimal growth temperature and the YVIWREL amino acid content within ribosomal proteins. Overall, our work suggests that ribosomal proteins contain a more accurate record of bacterial thermal adaptation compared to rRNA. This finding may simplify the analysis of unculturable and extinct species.
Life's origin is an enigma. Mankind has been pondering as to how it all began for millennia, yet are we any closer to uncovering the answer to this enigma? It would seem not, but we are slowly and surely edging towards discovery of the processes and mechanics by which life emerged on Earth. There are more than a couple of dozen hypotheses which claim to have the answer, but in reality, there is no absolute front runner. We have categorised these hypotheses under the following four banners: metabolism, genetic, proteins and vesicles first. In this chapter we strive to demonstrate how they conflict with one another and to this effect we have brought into focus both the top‐down and bottom‐up approaches to the question of the origin of life in general, as well as answering the question as to which came first, chemolithoautotrophs and photolithoautotrophs? In addition, the part played by viruses (in particular the RNA ones) during the origin of life is addressed.
Knowledge of evolutionary history is based extensively on relatively rare fossils that preserve soft tissues. These fossils record a much greater proportion of anatomy than would be known solely from mineralized remains and provide key data for testing evolutionary hypotheses in deep time. Ironically, however, exceptionally preserved fossils are often among the most contentious because they are difficult to interpret. This is because their morphology has invariably been affected by the processes of decay and diagenesis, meaning that it is often difficult to distinguish preserved biology from artifacts introduced by these processes. Here we describe how a range of analytical techniques can be used to tease apart mineralization that preserves biological structures from unrelated geological mineralization phases. This approach involves using a series of X-ray, ion, electron and laser beam techniques to characterize the texture and chemistry of the different phases so that they can be differentiated in material that is difficult to interpret. This approach is demonstrated using a case study of its application to the study of fossils from the Ediacaran Doushantuo Biota.
Where did we come from? Are we alone? Where are we going? These are the questions that define the field of astrobiology. New discoveries about life on Earth, the increasing numbers of extrasolar planets being identified, and the technologies being developed to locate and characterize Earth-like planets around other stars are continually challenging our views of nature and our connection to the rest of the universe. In this book, philosophers, historians, ethicists, and theologians provide the perspectives of their fields on the research and discoveries of astrobiology. A valuable resource for graduate students and researchers, the book provides an introduction to astrobiology, and explores subjects such as the implications of current origin of life research, the possible discovery of extraterrestrial microbial life, and the possibility of altering the environment of Mars.
Where did we come from? Are we alone? Where are we going? These are the questions that define the field of astrobiology. New discoveries about life on Earth, the increasing numbers of extrasolar planets being identified, and the technologies being developed to locate and characterize Earth-like planets around other stars are continually challenging our views of nature and our connection to the rest of the universe. In this book, philosophers, historians, ethicists, and theologians provide the perspectives of their fields on the research and discoveries of astrobiology. A valuable resource for graduate students and researchers, the book provides an introduction to astrobiology, and explores subjects such as the implications of current origin of life research, the possible discovery of extraterrestrial microbial life, and the possibility of altering the environment of Mars.
Where did we come from? Are we alone? Where are we going? These are the questions that define the field of astrobiology. New discoveries about life on Earth, the increasing numbers of extrasolar planets being identified, and the technologies being developed to locate and characterize Earth-like planets around other stars are continually challenging our views of nature and our connection to the rest of the universe. In this book, philosophers, historians, ethicists, and theologians provide the perspectives of their fields on the research and discoveries of astrobiology. A valuable resource for graduate students and researchers, the book provides an introduction to astrobiology, and explores subjects such as the implications of current origin of life research, the possible discovery of extraterrestrial microbial life, and the possibility of altering the environment of Mars.
Where did we come from? Are we alone? Where are we going? These are the questions that define the field of astrobiology. New discoveries about life on Earth, the increasing numbers of extrasolar planets being identified, and the technologies being developed to locate and characterize Earth-like planets around other stars are continually challenging our views of nature and our connection to the rest of the universe. In this book, philosophers, historians, ethicists, and theologians provide the perspectives of their fields on the research and discoveries of astrobiology. A valuable resource for graduate students and researchers, the book provides an introduction to astrobiology, and explores subjects such as the implications of current origin of life research, the possible discovery of extraterrestrial microbial life, and the possibility of altering the environment of Mars.
Where did we come from? Are we alone? Where are we going? These are the questions that define the field of astrobiology. New discoveries about life on Earth, the increasing numbers of extrasolar planets being identified, and the technologies being developed to locate and characterize Earth-like planets around other stars are continually challenging our views of nature and our connection to the rest of the universe. In this book, philosophers, historians, ethicists, and theologians provide the perspectives of their fields on the research and discoveries of astrobiology. A valuable resource for graduate students and researchers, the book provides an introduction to astrobiology, and explores subjects such as the implications of current origin of life research, the possible discovery of extraterrestrial microbial life, and the possibility of altering the environment of Mars.
Where did we come from? Are we alone? Where are we going? These are the questions that define the field of astrobiology. New discoveries about life on Earth, the increasing numbers of extrasolar planets being identified, and the technologies being developed to locate and characterize Earth-like planets around other stars are continually challenging our views of nature and our connection to the rest of the universe. In this book, philosophers, historians, ethicists, and theologians provide the perspectives of their fields on the research and discoveries of astrobiology. A valuable resource for graduate students and researchers, the book provides an introduction to astrobiology, and explores subjects such as the implications of current origin of life research, the possible discovery of extraterrestrial microbial life, and the possibility of altering the environment of Mars.
Where did we come from? Are we alone? Where are we going? These are the questions that define the field of astrobiology. New discoveries about life on Earth, the increasing numbers of extrasolar planets being identified, and the technologies being developed to locate and characterize Earth-like planets around other stars are continually challenging our views of nature and our connection to the rest of the universe. In this book, philosophers, historians, ethicists, and theologians provide the perspectives of their fields on the research and discoveries of astrobiology. A valuable resource for graduate students and researchers, the book provides an introduction to astrobiology, and explores subjects such as the implications of current origin of life research, the possible discovery of extraterrestrial microbial life, and the possibility of altering the environment of Mars.
Where did we come from? Are we alone? Where are we going? These are the questions that define the field of astrobiology. New discoveries about life on Earth, the increasing numbers of extrasolar planets being identified, and the technologies being developed to locate and characterize Earth-like planets around other stars are continually challenging our views of nature and our connection to the rest of the universe. In this book, philosophers, historians, ethicists, and theologians provide the perspectives of their fields on the research and discoveries of astrobiology. A valuable resource for graduate students and researchers, the book provides an introduction to astrobiology, and explores subjects such as the implications of current origin of life research, the possible discovery of extraterrestrial microbial life, and the possibility of altering the environment of Mars.
Where did we come from? Are we alone? Where are we going? These are the questions that define the field of astrobiology. New discoveries about life on Earth, the increasing numbers of extrasolar planets being identified, and the technologies being developed to locate and characterize Earth-like planets around other stars are continually challenging our views of nature and our connection to the rest of the universe. In this book, philosophers, historians, ethicists, and theologians provide the perspectives of their fields on the research and discoveries of astrobiology. A valuable resource for graduate students and researchers, the book provides an introduction to astrobiology, and explores subjects such as the implications of current origin of life research, the possible discovery of extraterrestrial microbial life, and the possibility of altering the environment of Mars.
Where did we come from? Are we alone? Where are we going? These are the questions that define the field of astrobiology. New discoveries about life on Earth, the increasing numbers of extrasolar planets being identified, and the technologies being developed to locate and characterize Earth-like planets around other stars are continually challenging our views of nature and our connection to the rest of the universe. In this book, philosophers, historians, ethicists, and theologians provide the perspectives of their fields on the research and discoveries of astrobiology. A valuable resource for graduate students and researchers, the book provides an introduction to astrobiology, and explores subjects such as the implications of current origin of life research, the possible discovery of extraterrestrial microbial life, and the possibility of altering the environment of Mars.
Where did we come from? Are we alone? Where are we going? These are the questions that define the field of astrobiology. New discoveries about life on Earth, the increasing numbers of extrasolar planets being identified, and the technologies being developed to locate and characterize Earth-like planets around other stars are continually challenging our views of nature and our connection to the rest of the universe. In this book, philosophers, historians, ethicists, and theologians provide the perspectives of their fields on the research and discoveries of astrobiology. A valuable resource for graduate students and researchers, the book provides an introduction to astrobiology, and explores subjects such as the implications of current origin of life research, the possible discovery of extraterrestrial microbial life, and the possibility of altering the environment of Mars.
A checklist of Cyanobacteria (Blue-green algae) has been made by reviewing available literature in order to contribute to the knowledge of biodiversity of algae in the Punjab state of India. The list records 317 taxa of the phylum Cyanobacteria distributed among 74 genera, 32 families, and six orders. The order Oscillatoriales has 115 taxa, followed by Nostocales (84), Synechococcales (60), Chroococcales (49), Spirulinales (8), and Pleurocapsales (1). The family Nostocaceae has the maximum number of genera followed by Microcoleaceae, Chroococcaceae, Oscillatoriaceae and other reported families. The genera with the highest number of species were Phormidium (39 species), Lyngbya (15 species), Oscillatoria (14 species), and Leptolyngbya & Scytonema (13 species each). The checklist revealed a high degree of species richness within phylum Cyanobacteria found in Punjab. This checklist can provide a baseline for future floristic studies with taxonomically updated/accepted name of genera/species of cyanobacteria.
It is generally recognized that the evolution of early Earth was affected by an external energy source: radiation from the early Sun. We also propose and substantiate the hypothesis of important role of natural radioactivity, as an internal energy source, in the evolution of early Earth. Radioactive isotopes have been present on Earth since its formation. The decay of long-lived ²³²Th, ²³⁸U, ²³⁸U, and ⁴⁰K was an important source of energy and, together with accretion of interplanetary matter and the action of gravitational forces, it promoted melting and differentiation of matter and tectonic activity of early Earth. At the same time, radioactive isotopes initiated radiation-chemical transformations of the Earth's matter and contributed to the chemical evolution of the planet. The initial content of radioactive isotopes in the World Ocean of the early Earth and the kinetics of their decay, the values of the absorbed dose and dose rate, as well as the efficiency of seawater radiolysis as a function of time are calculated. It is shown that the decay of long-lived isotopes initiated radiation chemical reactions of compounds dissolved in the ocean and gave rise to oxygen. The ocean served as a “reservoir” that collected components of the early atmosphere and products of their transformations and simultaneously as a “converter” in which further chemical reactions of these compounds took place. The chemical transformations of dissolved inorganic compounds boosted interrelated processes important for evolution: formation of organic matter, including prebiotic molecules, purification of the ocean, and oxygenation of hydro- and atmosphere of Earth. As a result, ocean became the “cradle” for the emergence of life. Radical mechanisms for the formation of simple amino acids, sugars, and nitrogen bases, i.e., the key structures of all living matter, were proposed. The amounts of organic matter and oxygen accumulated with time were calculated; the results confirmed the role of natural radioactivity in the evolution of Earth's matter and the emergence of life. We expect that this hypothesis would become the starting point for considering the important role of natural radioactivity and radiation-chemical processes in the general picture of Earth's evolution and emergence of life.
Fifteen years after the discovery of major glacial/interglacial cycles in the CO2 concentration of the atmosphere, it seems that all of the simple mechanisms for lowering pCO2 have been eliminated. We use a model of ocean and sediment geochemistry, which includes new developments of iron limitation of biological production at the sea surface and anoxic diagenesis and its effect on CaCO3 preservation in the sediments, to evaluate the current proposals for explaining the glacial/interglacial pCO2 cycles within the context of the ocean carbon cycle. After equilibration with CaCO3 the model is unable to generate glacial pCO2 by increasing ocean NO3- but predicts that a doubling of ocean H4SiO4 might suffice. However, the model is unable to generate a doubling of ocean H4SiO4 by any reasonable changes in SiO2 weathering or production. Our conclusions force us to challenge one or more of the assumptions at the foundations of chemical oceanography. We can abandon the stability of the ``Redfield ratio'' of nitrogen to phosphorus in living marine phytoplankton and the ultimate limitation of marine photosynthesis by phosphorus. We can challenge the idea that the pH of the deep ocean is held relatively invariant by equilibrium with CaCO3. A third possibility, which challenges physical oceanographers, is that diapycnal mixing in ocean circulation models exceeds the rate of mixing in the real ocean, diminishing the model pCO2 sensitivity to biological carbon uptake.
Structures resembling remarkably preserved bacterial and cyanobacterial microfossils from about 3,465-million-year-old Apex cherts of the Warrawoona Group in Western Australia currently provide the oldest morphological evidence for life on Earth and have been taken to support an early beginning for oxygen-producing photosynthesis. Eleven species of filamentous prokaryote, distinguished by shape and geometry, have been put forward as meeting the criteria required of authentic Archaean microfossils, and contrast with other microfossils dismissed as either unreliable or unreproducible. These structures are nearly a billion years older than putative cyanobacterial biomarkers, genomic arguments for cyanobacteria, an oxygenic atmosphere and any comparably diverse suite of microfossils. Here we report new research on the type and re-collected material, involving mapping, optical and electron microscopy, digital image analysis, micro-Raman spectroscopy and other geochemical techniques. We reinterpret the purported microfossil-like structure as secondary artefacts formed from amorphous graphite within multiple generations of metalliferous hydrothermal vein chert and volcanic glass. Although there is no support for primary biological morphology, a Fischer--Tropsch-type synthesis of carbon compounds and carbon isotopic fractionation is inferred for one of the oldest known hydrothermal systems on Earth.
First published in 1992, The Proterozoic Biosphere was the first major study of the paleobiology of the Proterozoic Earth. It is a multidisciplinary work dealing with the evolution of the Earth, the environment and life during the forty percent of Earth's history that extends from the middle of the Precambrian eon (2500 Ma) to the beginning of the Paleozoic era (550 Ma). The book includes a vast amount of data on Proterozoic organisms and their analogs. Prepared by the Precambrian Paleobiology Research Group, a multidisciplinary consortium of forty-one scientists from eight countries, this monograph was a benchmark in the development of the science of the biochemistry and the organic chemistry of Proterozoic sediments. The study aimed to generate data and analyses based on the re-examination of previous studies and on newer investigations and to build towards the future by placing special emphasis on neglected aspects of paleobiologic study and unsolved problems in the field.
First published in 1992, The Proterozoic Biosphere was the first major study of the paleobiology of the Proterozoic Earth. It is a multidisciplinary work dealing with the evolution of the Earth, the environment and life during the forty percent of Earth's history that extends from the middle of the Precambrian eon (2500 Ma) to the beginning of the Paleozoic era (550 Ma). The book includes a vast amount of data on Proterozoic organisms and their analogs. Prepared by the Precambrian Paleobiology Research Group, a multidisciplinary consortium of forty-one scientists from eight countries, this monograph was a benchmark in the development of the science of the biochemistry and the organic chemistry of Proterozoic sediments. The study aimed to generate data and analyses based on the re-examination of previous studies and on newer investigations and to build towards the future by placing special emphasis on neglected aspects of paleobiologic study and unsolved problems in the field.
The paper deals with the degradation of organic matter at the seawater-sediment interface which plays an important role in the pattern of calcium carbonate preservation in the deep sea. A model developed to quantify this effect shows that the amount of calcium carbonate dissolved by metabolic CO//2 at the sediment-water interface is dependent upon the rain ratio of organic carbon and calcium carbonate, and the rates of organic matter degradation and calcite dissolution.
Dissimilarity coefficients measure the difference between multivariate samples and provide a quantitative aid to the identification of modern analogs for fossil pollen samples. How eight coefficients responded to differences among modern pollen samples from eastern North America was tested. These coefficients represent three different classes: (1) unweighted coefficients that are most strongly influenced by large-valued pollen types, (2) equal-weight coefficients that weight all pollen types equally but can be too sensitive to variations among rare types, and (3) signal0to-noise coefficients that are intermediate in their weighting of pollen types. The studies with modern pollen allowed definition of critical values for each coefficient, which, when not exceeded, indicate that two pollen samples originate from the same vegetation region. Dissimilarity coefficients were used to compare modern and fossil pollen samples, and modern samples so similar to fossil samples were found that most of three late Quaternary pollen diagrams could be “reconstructed” by substituting modern samples for fossil samples. When the coefficients indicated that the fossil spectra had no modern analogs, then the reconstructed diagrams did not match all aspects of the originals. No modern analogs existed for samples from before 9300 yr B.P. at Kirchner Marsh, Minnesota, and from before 11,000 yr B.P. at Wintergreen Lake, Michigan, but modern analogs existed for almost all Holocene samples from these two sites and Brandreth Bog. New York.
The goals of this study were to: (1) digest available sedimentary data into a format appropriate for validating models of oceanic calcium carbonate (CaCO{sub 3}) dynamics, (2) estimate the inventory of deep sea CaCO{sub 3} available for neutralization of fossil fuel carbon dioxide, and (3) determine the variability of CaCO{sub 3} preservation relative to local saturation conditions. CaCO{sub 3} concentrations in global deep sea sediments were compiled from published data and compared to a gridded field of seawater carbonate ion concentration to determine regional variations in the calcite lysocline. The thicker calcite lysocline in the Atlantic, as compared to the Pacific, is attributed to the delivery rate of terriginous material. A gradient in calcite preservation with latitude was found to be smaller than the glacial/interglacial shift, implying that a rain ratio type of model requires a uniform application of perturbation conditions during glacial time which do not correspond to current conditions. Therefore, a whole ocean change in silicon content would be required to account for glacial conditions. An estimated inventory of 1600 G tons carbon in fossil fuel carbon dioxide can be neutralized by existing carbonates in the deep sea; this quantity may be exceeded by fossil fuel release over several centuries. 46 refs., 13 figs., 2 tabs.
The Proterozoic Biosphere is the first major study of the paleobiology of the Proterozoic Earth. It is a multidisciplinary work dealing with the evolution of the Earth, the environment, and life during the forty percent of Earth's history that extends from the middle of the Precambrian Eon (2500 Ma) to the beginning of the Paleozoic Era (550 Ma.). The Proterozoic Biosphere includes a vast amount of new data on Proterozoic organisms and their modern analogs. Prepared by the Precambrian Paleobiology Research Group, a multidisciplinary consortium of forty-one scientists from eight countries, this monograph will serve as a benchmark in the development of the science of the biochemistry and the organic chemistry of Proterozoic sediments. The three main goals of this study are: (1) to amass, evaluate, and synthesize the large body of paleobiologic data available from previous studies, eliminating mistakes so that future investigations will not be encumbered by them; (2) to generate new data and new analyses based on the reexamination of previous studies and on new investigations within an interdisciplinary framework; (3) to build toward the future by placing special emphasis on new or relatively neglected aspects of paleobiologic study and by highlighting major unsolved problems in the field.
Recent geochemical models invoke ocean alkalinity changes, particularly in the surface Southern Ocean, to explain glacial age pCO2 reduction. In such models, alkalinity increases in glacial periods are driven by reductions in North Atlantic Deep Water (NADW) supply, which lead to increases in deep-water nutrients and dissolution of carbonate sediments, and to increased alkalinity of Circumpolar Deep Water upwelling in the surface Southern Ocean. We use cores from the Southeast Indian Ridge and from the deep Cape Basin in the South Atlantic to show that carbonate dissolution was enhanced during glacial stages in areas now bathed by Circumpolar Deep Water. This suggests that deep Southern Ocean carbonate ion concentrations were lower in glacial stages than in interglacials, rather than higher as suggested by the polar alkalinity model [Broecker and Peng, 1989]. Our observations show that changes in Southern Ocean CaCO3 preservation are coherent with changes in the relative flux of NADW, suggesting that Southern Ocean carbonate chemistry is closely linked to changes in deepwater circulation. The pattern of enhanced dissolution in glacials is consistent with a reduction in the supply of nutrient-depleted water (NADW) to the Southern Ocean and with an increase of nutrients in deep water masses. Carbonate mass accumulation rates on the Southeast Indian Ridge (3200-3800 m), and in relatively shallow cores (
These structurally preserved Precambrian fossils from Ontario are the most ancient organisms known.
Some of the subjects discussed are related to the early biogeologic history, the nature of the earth prior to the oldest known rock record, the early earth and the Archean rock record, the prebiotic organic syntheses and the origin of life, Precambrian organic geochemistry, the biochemical evolution of anaerobic energy conversion, the isotopic inferences of ancient biochemistries, Archean stromatolites providing evidence of the earth's earliest benthos, Archean microfossils, the geologic evolution of the Archean-Early Proterozoic earth, and the environmental evolution of the Archean-Early Proterozoic earth. Other topics examined are concerned with geochemical evidence bearing on the origin of aerobiosis, biological and biochemical effects of the development of an aerobic environment, Early Proterozoic microfossils, the evolution of earth's earliest ecosystems, and geographic and geologic data for processed rock samples. Attention is given to a processing procedure for abiotic samples and calculation of model atmospheric compositions, and procedures of organic geochemical analysis.
Raman spectra are reported from single crystals of graphite and other graphite materials. Single crystals of graphite show one single line at 1575 cm−1. For the other materials like stress‐annealed pyrolitic graphite, commercial graphites, activated charcoal, lampblack, and vitreous carbon another line is detected at 1355 cm−1. The Raman intensity of this band is inversely proportional to the crystallite size and is caused by a breakdown of the k‐selection rule. The intensity of this band allows an estimate of the crystallite size in the surface layer of any carbon sample. Two in‐plane force constants are calculated from the frequencies.
Sixteen deep-sea cores from the central equatorial Pacific are used to
reconstruct a continuous 800,000-year (800-kyr) record of bathymetric
variations in carbonate preservation as measured by calcium carbonate
(CaCO3) content. The depth of the sedimentary lysocline has
fluctuated markedly in conjunction with late Pleistocene climate cycles
while the carbonate critical depth (CCrD), which is the water depth
where the sediments contain 10% CaCO3, has remained
relatively constant. As a result, the depth of the lysocline controls
the bathymetric position and thickness of the CaCO3
transition zone, defined as the depth from the lysocline to the CCrD.
Modern and interglacial-aged sediments show poor CaCO3
preservation and thick CaCO3 transition zones. Glacial-aged
sediments show good preservation and deep, thin zones due to the
deepening of the lysocline. Detailed comparison of the CaCO3
preservation and oxygen isotope records from the central equatorial
Pacific confirms the observation that preservation maxima and minima
tend to occur during the latter half of glacial and interglacial stages
and on climate transitions rather than during the middle of climatic
stages. During the nine major glacial stages of the last 800 kyr, the
lysocline deepened by at least 400 to 800 m. This deepening indicates an
increase in the abyssal carbonate ion concentration ([CO3=])
and a depression of the calcite saturation horizon best explained by the
deeper presence of a more carbonate-saturated water mass. The bottom of
the transition zone has remained at a relatively constant depth during
the Brunhes Chron, indicating a balance between CaCO3
sedimentation and dissolution in the deepest waters of the central
equatorial Pacific.
Describes the "coral reef hypothesis" for CO2 drawdown during glacial intervals. This theory predicts CO2 removal via redistribution of calcite to the pelagic realm and alkalinity increases due to lower sea-level. The authors run a model that suggests this may have a significant effect, however, cannot account for entire shift recorded in ice cores. A 40% decrease of carbonate burial relative to organic burial can account for entire CO2 shift. Works this way: Higher rain rate of Corg allows for increase of total CO2 in sedimentary pore water. This leads to increased alkalinity via carbonate dissolution. Alter ocean pH.
A sample of chert from North Pole in the Archaean Pilbara block of Western Australia contains carbonaceous filaments that resemble microfossils. These occur in alternating light and dark laminae that look stromatolitic. However, the filaments are too simple in form for their origin to be determined, so they should be regarded as dubiofossils, perhaps biogenic, perhaps inorganic. Their host laminae were inorganically precipitated in a concordant fissure and thus cannot be stromatolitic. This fissure is younger than the surrounding silicified sediments of the ca. 3500 Ma old Warrawoona Group and possibly formed towards the end of the uplift and associated fracturing of the North Pole Dome, perhaps ca. 2750 Ma ago. The filaments are therefore contaminants in secondary chert.The filament-bearing rock was collected less than a metre from one of the localities (B) from which Awramik et al. reported early Archaean microfossils and possible microfossils. Their filaments from this locality were almost identical to those described here and were found in similar laminae. This suggests that their locality B filaments may also be contaminants in secondary chert. Other filaments found by Awramik et al. at North Pole come from an imprecisely located sample site (locality A) where the rock relationships are unknown. Since the host laminae of these filaments are not demonstrably primary and as cryptic concordant fissures filled with secondary minerals are common in locality A rocks, the filaments from this sample site could be contaminants too. Those that were assigned to Archaeotrichion should be treated as dubiofossils. Thus, the filaments described by Awramik et al. may not be fossil bacteria in ca. 3500 Ma old stromatolites, as they proposed, and are not necessarily the oldest known fossil organisms, as has been claimed.
The Swaziland Supergroup, Barberton Mountain Land, South Africa, has long been regarded as a promising location for the Earth's oldest fossils because it includes some of the most ancient well-preserved sedimentary rocks, many of which contain carbonaceous matter. Although there have been numerous reports of microfossils from Swaziland Group rocks1-7, the biogenicity of most of the structures has been questioned8-10. Although some of the organic spheroids are probably biogenic10,11, the best early Archaean simple spheroids are generally regarded as `possible microfossils'10 because organic spheroids may form abiotically in several ways12. The discovery of less-simple biological morphologies is therefore important in establishing the existence of early life forms in the early Archaean. Uniformly-sized curving filaments, especially tubular ones, are difficult to explain as anything other than the fossil remains of filamentous organisms. Here we report the discovery of numerous filaments from two different stratigraphical positions in the 3,500-Myr-old Onverwacht Group of the Swaziland Supergroup. Their morphologies and abundance provide convincing evidence for the existence of bacteria- or cyanobacteria-like organisms on the Earth during the early Archaean. This supports recent reports of similar filamentous microfossils from 3,500-Myr-old rocks from Western Australia13.
OF the four dozen fossiliferous Precambrian sediments now known1, only a very few contain diverse microfossil assemblages preserved in situ on which inferences of ecologic setting and evolutionary status can be based reliably. The time gaps between these deposits are enormous, commonly approaching or exceeding a duration equivalent to that of the entire Palaeozoic. Present inferences regarding the course of early evolutionary development are therefore highly speculative. There is obvious need for the detection of additional evidence with which to evaluate such inferences and to fill in the skeletal picture that has emerged in recent years. We report here the discovery of a well preserved, Stromatolitic microbiota from the late Precambrian of Boorthanna, South Australia, that should contribute measurably toward this goal.
Laser-Raman imagery is a sensitive, noninvasive, and nondestructive technique that can be used to correlate directly chemical composition with optically discernable morphology in ancient carbonaceous fossils. By affording means to investigate the molecular makeup of specimens ranging from megascopic to microscopic, it holds promise for providing insight into aspects of organic metamorphism and biochemical evolution, and for clarifying the nature of ancient minute fossil-like objects of putative but uncertain biogenicity.
Eleven taxa (including eight heretofore undescribed species) of cellularly preserved filamentous microbes, among the oldest fossils known, have been discovered in a bedded chert unit of the Early Archean Apex Basalt of northwestern Western Australia. This prokaryotic assemblage establishes that trichomic cyanobacterium-like microorganisms were extant and morphologically diverse at least as early as approximately 3465 million years ago and suggests that oxygen-producing photoautotrophy may have already evolved by this early stage in biotic history.
Cellularly preserved filamentous and colonial fossil microorganisms have been discovered in bedded carbonaceous cherts from
the Early Archean Apex Basalt and Towers Formation of northwestern Western Australia. The cell types detected suggest that
cyanobacteria, and therefore oxygen-producing photosynthesis, may have been extant as early as 3.3 billion to 3.5 billion
years ago. These fossils are among the oldest now known from the geologic record; their discovery substantiates previous
reports of Early Archean microfossils in Warrawoona Group strata.
Ion microprobe measurements of carbon isotope ratios were made in 30 specimens representing six fossil genera of microorganisms petrified in stromatolitic chert from the approximately 850 Ma Bitter Springs Formation, Australia, and the approximately 2100 Ma Gunflint Formation, Canada. The delta 13C(PDB) values from individual microfossils of the Bitter Springs Formation ranged from -21.3 +/- 1.7% to -31.9 +/- 1.2% and the delta 13C(PDB) values from microfossils of the Gunflint Formation ranged from -32.4 +/- 0.7% to -45.4 +/- 1.2%. With the exception of two highly 13C-depleted Gunflint microfossils, the results generally yield values consistent with carbon fixation via either the Calvin cycle or the acetyl-CoA pathway. However, the isotopic results are not consistent with the degree of fractionation expected from either the 3-hydroxypropionate cycle or the reductive tricarboxylic acid cycle, suggesting that the microfossils studied did not use either of these pathways for carbon fixation. The morphologies of the microfossils suggest an affinity to the cyanobacteria, and our carbon isotopic data are consistent with this assignment.
in The Carbon Cycle and Atmospheric Carbon Dioxide: Natural Variations Archean to Present
- L C Peterson
- W L Prell
Peterson, L. C. & Prell, W. L. in The Carbon Cycle and Atmospheric Carbon Dioxide: Natural Variations Archean to Present (eds Sundquist, E. T. & Broecker, W. S.) 251±269 (American Geophysical Union, Washington DC, 1985).
Laser±Raman imagery of Earth's earliest fossils Czaja* * Department of Earth & Space Sciences, and Institute of Geophysics & Planetary Physics (Center for the Study of the Evolution and Origin of Life)
- ................................................................ J William
- Schopf
- B Anatoliy
- David G Kudryavtsev²
- Thomas J Agresti²
- Wdowiak²
- Andrew
................................................................. Laser±Raman imagery of Earth's earliest fossils J. William Schopf*, Anatoliy B. Kudryavtsev², David G. Agresti², Thomas J. Wdowiak² & Andrew D. Czaja* * Department of Earth & Space Sciences, and Institute of Geophysics & Planetary Physics (Center for the Study of the Evolution and Origin of Life), University of California, Los Angeles, California 90095-1567, USA ² Astro and Solar System Physics Program, Department of Physics, University of Alabama at Birmingham, Birmingham, Alabama 35294-1170, USA
Sigman for helpful suggestions. Correspondence and requests for materials should be addressed to D
- Acknowledgements We
- D Lea
- S Lehman
- R Toggweiler
Acknowledgements We thank D. Lea, S. Lehman, R. Toggweiler and D. Sigman for helpful suggestions. Correspondence and requests for materials should be addressed to D.M.A. (e-mail: dma@ngdc.noaa.gov).
- CV Mendelson
The Renishaw Raman Database of Gemological and Mineralogical Materials. (Renishaw Tranducers Systems Division
- K P J Williams
- J Nelson
- S Dyer
- KPJ Williams