scholarly journals Molecular fossils within bitumens and kerogens from the ~ 1 Ga Lakhanda Lagerstätte (Siberia, Russia) and their significance for understanding early eukaryote evolution

PalZ ◽  
2021 ◽  
Author(s):  
Jan-Peter Duda ◽  
Hannah König ◽  
Manuel Reinhardt ◽  
Julia Shuvalova ◽  
Pavel Parkhaev
Keyword(s):  
Organic Matter ◽  
Organic Geochemistry ◽  
Anaerobic Bacteria ◽  
Peak Oil ◽  
Molecular Fossil ◽  
Molecular Fossils ◽  
Eukaryote Evolution ◽  
Organic Biomarkers ◽  
Major Emphasis ◽  
Maturity Parameters

AbstractThe emergence and diversification of eukaryotes during the Proterozoic is one of the most fundamental evolutionary developments in Earth’s history. The ca. 1-billion-year-old Lakhanda Lagerstätte (Siberia, Russia) contains a wealth of eukaryotic body fossils and offers an important glimpse into their ecosystem. Seeking to complement the paleontological record of this remarkable lagerstätte, we here explored information encoded within sedimentary organic matter (total organic carbon = 0.01–1.27 wt.%). Major emphasis was placed on sedimentary hydrocarbons preserved within bitumens and kerogens, including molecular fossils (or organic biomarkers) that are specific to bacteria and eukaryotes (i.e. hopanes and regular steranes, respectively). Programmed pyrolysis and molecular organic geochemistry suggest that the organic matter in the analyzed samples is about peak oil window maturity and thus sufficiently well preserved for detailed molecular fossil studies that include hopanes and steranes. Together with petrographic evidence as well as compositional similarities of the bitumens and corresponding kerogens, the consistency of different independent maturity parameters establishes that sedimentary hydrocarbons are indigenous and syngenetic to the host rock. The possible presence of trace amounts of hopanes and absence of steranes in samples that are sufficiently well preserved to retain both types of compounds evidences an environment dominated by anaerobic bacteria with no or very little inputs by eukaryotes. In concert with the paleontological record of the Lakhanda Lagerstätte, our study adds to the view that eukaryotes were present but not significant in Mesoproterozoic ecosystems.

Biomarkers: Molecular Fossils

1988 ◽  
Vol 1 ◽  
pp. 98-113 ◽  
Author(s):  
Roger E. Summons
Keyword(s):  
Organic Matter ◽  
Organic Compounds ◽  
Recent Progress ◽  
Organic Geochemistry ◽  
New Developments ◽  
Molecular Fossils ◽  
Primary Literature ◽  
History Of ◽  
Biomarker Research ◽  
Made In

Curiosity about the history of life on our planet is a major motivational force for earth scientists. Fossil organic compounds, the components of petroleum and sedimentary organic matter, record aspects of the evolution of the biosphere from as far back as 1.8 billion years and perhaps longer. Elucidation of this record is continually advancing as a result of the concerted interests and efforts of geologists, biologists and chemists. It is also aided by advances in technique and instrumentation. Fascinating new developments and insights abound. In this paper I review some early landmarks and discuss the recent progress made in organic geochemistry, particularly as it applies to biomarker research. The examples of recent work are heavily biased toward my own interests and are not intended to be comprehensive. Because the literature citations are also selective and rely heavily on reviews, readers are advised to seek out the primary literature for accurate detail of specific subjects.

scholarly journals Organic Geochemistry and Thermal Maturity Assessment of Cretaceous Balambo Formation from Selected Sites, Kurdistan, NE Iraq

2021 ◽  
pp. 532-554
Author(s):  
Razawa Hamarashid A. Sarraj ◽  
Ibrahim Mohammed J. Mohialdeen
Keyword(s):  
Organic Matter ◽  
Organic Geochemistry ◽  
Source Rocks ◽  
Gas Chromatography Mass Spectrometry ◽  
Distribution Analysis ◽  
Type Ii ◽  
Thermal Maturity ◽  
Peak Oil ◽  
Northern Iraq ◽  
Marine Organic Matter

The Cretaceous Balambo Formation from three sections in Kurdistan Region of Northern Iraq was studied. The selected sections are located in the Zagros Fold -Thrust Belt. Eleven rock samples were analyzed by means of the organic geochemical method, Bitumen extraction method, and gas chromatography/mass spectrometry to determine the bitumen and hydrocarbon content, kerogen types, origin of organic matter, thermal maturity level, and depositional environment. The analyzed samples are considered to have an excellent potential in Baranan-1.G1 and Sazan sections, with poor to fair potential in Baraw section. The Baranan-1.G1 source rocks are of type II kerogen (oil prone), whereas Sazan and Baraw samples are of type II/III (oil/ gas prone). Detailed distribution analysis of biomarkers such as normal alkane, isoprenoids, sterane and terpane was performed on saturated hydrocarbons. The mode of n-alkanes and isoprenoids distribution in all analyzed samples is similar, with a unimodal distribution that indicates non-biodegraded hydrocarbons, with the same range of alkane compounds between C13-C34 alkanes. The results of n-C17, pristane, n-C18 and phytane, and regular steranes show that the source rocks of Balambo Formation in Baranan-1.G1 are mainly rich with algal marine organic matter deposited under a reducing environment, while Baraw and Sazan sections are composed of mixed marine organic matter that refers to terrestrial land plants input deposited under reducing anoxic/dysoxic environments. Thermal maturation appraisal is deduced from Pristane/n-C17 versus Phytane/n-C18 diagram, Carbon Preference Index (CPI), C29 ββ/ (ββ+αα), C29 20S/ (20S +20R), C32 22S/ (22S+22R), and Ts/ (Ts+Tm). All these parameters indicate that the analyzed samples are mature and have entered the oil window (early to peak oil window). Biomarker ratios of C22/C21, C24/C23 and C26/C25, C31R/C30H show that the Balambo Formation is composed mostly of carbonates with less shale beds.

scholarly journals A Mesoproterozoic iron formation

2018 ◽  
Vol 115 (17) ◽  
pp. E3895-E3904 ◽  
Author(s):  
Donald E. Canfield ◽  
Shuichang Zhang ◽  
Huajian Wang ◽  
Xiaomei Wang ◽  
Wenzhi Zhao ◽  
...  
Keyword(s):  
Organic Matter ◽  
Time Window ◽  
Iron Formation ◽  
The North ◽  
Fe Oxidation ◽  
Organic Biomarkers ◽  
Rock Eval ◽  
Fe Reduction ◽  
Rule Out ◽  
Xiamaling Formation

We describe a 1,400 million-year old (Ma) iron formation (IF) from the Xiamaling Formation of the North China Craton. We estimate this IF to have contained at least 520 gigatons of authigenic Fe, comparable in size to many IFs of the Paleoproterozoic Era (2,500–1,600 Ma). Therefore, substantial IFs formed in the time window between 1,800 and 800 Ma, where they are generally believed to have been absent. The Xiamaling IF is of exceptionally low thermal maturity, allowing the preservation of organic biomarkers and an unprecedented view of iron-cycle dynamics during IF emplacement. We identify tetramethyl aryl isoprenoid (TMAI) biomarkers linked to anoxygenic photosynthetic bacteria and thus phototrophic Fe oxidation. Although we cannot rule out other pathways of Fe oxidation, iron and organic matter likely deposited to the sediment in a ratio similar to that expected for anoxygenic photosynthesis. Fe reduction was likely a dominant and efficient pathway of organic matter mineralization, as indicated by organic matter maturation by Rock Eval pyrolysis combined with carbon isotope analyses: Indeed, Fe reduction was seemingly as efficient as oxic respiration. Overall, this Mesoproterozoic-aged IF shows many similarities to Archean-aged (>2,500 Ma) banded IFs (BIFs), but with an exceptional state of preservation, allowing an unprecedented exploration of Fe-cycle dynamics in IF deposition.

scholarly journals Petrography and Organic Geochemistry Characterizations of Lower Paleozoic Organic-Rich Shale in the Northwestern Upper Yangtze Plate: Niutitang Formation and Longmaxi Formation, Dabashan Foreland Belt

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 439 ◽  
Author(s):  
Delu Li ◽  
Rongxi Li ◽  
Di Zhao ◽  
Feng Xu
Keyword(s):  
Gas Chromatography ◽  
Organic Matter ◽  
Organic Geochemistry ◽  
Source Rocks ◽  
Gas Chromatography Mass Spectrometry ◽  
Mature Stage ◽  
Type I ◽  
Lower Paleozoic ◽  
Longmaxi Formation ◽  
Niutitang Formation

Measurements of total organic carbon, Rock-Eval pyrolysis, X-ray diffraction, scanning electron microscope, maceral examination, gas chromatography, and gas chromatography-mass spectrometry were conducted on the organic-rich shale of Lower Paleozoic Niutitang Formation and Longmaxi Formation in Dabashan foreland belt to discuss the organic matter characteristic, organic matter origin, redox condition, and salinity. The results indicate that the Niutiang Formation and Longmaxi Formation organic-rich shale are good and very good source rocks with Type I kerogen. Both of the shales have reached mature stage for generating gas. Biomarker analyses indicate that the organic matter origin of Niutitang Formation and Longmaxi Formation organic-rich shale are all derived from the lower bacteria and algae, and the organic matter are all suffered different biodegradation degrees. During Niutitang Formation and Longmaxi Formation period, the redox conditions are both anoxic with no stratification and the sedimentary water is normal marine water.

scholarly journals Classical Biomarker and Quantitative Extended Diamondoid Analysis Fingerprints for Crude Oils from Deepwater Developments in Block 17, Lower Congo Basin, Angola

2020 ◽  
Vol 17 (19) ◽  
pp. 7204
Author(s):  
Carlos Boente ◽  
Gonzalo Márquez ◽  
Patricia Marín ◽  
Emilio Romero ◽  
Cristina Rodrigues ◽  
...  
Keyword(s):  
Cluster Analysis ◽  
Organic Geochemistry ◽  
Hierarchical Cluster ◽  
Molecular Data ◽  
Congo Basin ◽  
Hydrocarbon Generation ◽  
Thermal Maturity ◽  
Maturity Level ◽  
Oil Type ◽  
Maturity Parameters

The organic geochemistry of six oil samples from the offshore Block 17 (Lower Congo Basin, northwestern Angola) was studied by a combination of classical biomarker and extended diamondoid analyses to elucidate source rock facies, the extent of biodegradation, and thermal maturity. Based on molecular data, oils are interpreted as depicting a mixture of two pulses of hydrocarbon generation probably from the Bucomazi and Malembo formations. Geochemical results also gave evidence of mixing of a lacustrine siliciclastic-sourced oil charge and a second more terrestrially derived oil type in the samples analyzed. A single genetic oil family was identified through hierarchical cluster analysis; however, two groups of oils were identified on the basis of their biodegradation levels using the Peters/Moldowan scale. Lower and upper Malembo oils have a slight depletion and a notable absence of n-alkanes, suggesting PM levels of 1 and 2, respectively. Most molecular maturity parameters of the oil samples suggest a maturity level equivalent to the onset of the peak of the oil generative window.

scholarly journals Mercury Methylation and Demethylation in Anoxic Lake Sediments and by Strictly Anaerobic Bacteria

1998 ◽  
Vol 64 (3) ◽  
pp. 1013-1017 ◽  
Author(s):  
K.-R. Pak ◽  
R. Bartha
Keyword(s):  
Organic Matter ◽  
Anaerobic Bacteria ◽  
Mercury Methylation ◽  
Strictly Anaerobic ◽  
Anoxic Sediment ◽  
Acetogenic Bacteria ◽  
High Potentials ◽  
High Mercury ◽  
Pure Cultures ◽  
Sediment Ph

ABSTRACT After spiking anoxic sediment slurries of three acidic oligotrophic lakes with either HgCl2 at 1.0 μg/ml or CH3HgI at 0.1 μg/ml, both mercury methylation and demethylation rates were measured. High mercury methylation potentials were accompanied by high demethylation potentials in the same sediment. These high potentials correlated positively with the concentrations of organic matter and dissolved sulfate in the sediment and with mercury levels in fish. Adjustment of the acidic sediment pH to neutrality failed to influence either the methylation or the demethylation rate of mercury. The opposing methylation and demethylation processes converged to establish similar Hg2+-CH3Hg+equilibria in all three sediments. Because of their metabolic dominance in anoxic sediments, mercury methylation and demethylation in pure cultures of sulfidogenic, methanogenic, and acetogenic bacteria were also measured. Sulfidogens both methylated and demethylated mercury, but the methanogen tested only catalyzed demethylation and the acetogen neither methylated nor demethylated mercury.

scholarly journals On oral calcifications: sialoliths, dental calculi and tonsilloliths

2013 ◽  
Vol 19 (S4) ◽  
pp. 23-24 ◽  
Author(s):  
A.J. Anjos ◽  
P. Nolasco ◽  
J.M. Aquino Marques ◽  
F. Cabrita ◽  
M.F.C. Pereira ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Organic Matter ◽  
Calcium Phosphates ◽  
Stone Formation ◽  
Bacterial Species ◽  
Complex Structure ◽  
Anaerobic Bacteria ◽  
Bacterial Cells ◽  
Sulphur Compounds ◽  
Salivary Calculi

The oral cavity is susceptible to several calcifications such as salivary calculi (sialoliths), dental calculus (tartar) and tonsillar concretions (tonsilloliths). Although several individual studies had been already carried out, a comprehensive morphological and elemental comparison between them is still missing.Sialoliths are most commonly found in the submandibular glands and are composed of regions rich in Ca and P minerals, namely hydroxyapatite, whitlockite and brushite, and regions consisting of organic matter with high-sulphur content. These regions are organized in alternating concentric layers. Several bacterial species have also been identified in sialoliths microstructure showing that infection occurs recurrently throughout the stone formation.Generally, tartar presents an inorganic structure rich in Ca and P minerals, such as brushite, octacalcium phosphate, hydroxyapatite and whitlockite, and an organic matrix, mainly constituted by aerobic bacteria and yeast or just anaerobic bacteria.Tonsilloliths occur most commonly on the crypts of the palatal tonsils and are composed of a mixture of organic matter, namely bacterial cells and epithelial debris, as well as inorganic material rich in Ca and P minerals such as hydroxyapatite. Volatile sulphur compounds produced by anaerobic bacteria are usually associated to these, in general, innocuous structures.The current study involved the ultrastructure and chemical characterization of the calcified structures by scanning electron microscopy (SEM) combined with energy dispersive spectroscopy carried out with a JEOL JSM 7001F instrument with an INCA pentaFetx3 Oxford spectrometer operated at 15 kV. Higher resolution characterization has been performed by transmission electron microscopy (TEM) using a H8100 Hitachi instrument operated at 200 kV. SEM samples were prepared following metallographic procedures, whereas TEM samples were obtained following standard biological sample preparation procedures.The results show that sialoliths present the most complex structure, with a central core surrounded by concentric layers, while tartar and tonsilloliths do not have a distinctive architecture (Figures 1 (a), 2 (a) and 3 (a). At higher magnifications, layered structures, as well as crystals could be found in sialoliths and tartar (Figures 1 (b) and 2 (b). Bacteria were common in all the calcified structures, although in tonsilloliths their abundance is higher (Figure 3 (b)). All calcifications have similar elemental constitution, with Ca and P, indicating the presence of calcium phosphates (Figures 1 (c), 2 (c) and 3 (c). Sulphur was also found associated with the organic matter in sialoliths and tonsilloliths, though the amounts found in the latter were much smaller than initially expected.Based on the similarities found, new correlations between these calcification will be available. For instance, the mineralization process described in tartar can help understand the similar processes occurring in sialoliths and tonsilloliths, while the association between bacteria and sulphur in tonsilloliths can be a clue for their presence in sialoliths.The work was carried out with financial support of the Portuguese Foundation for Science and Technology through PTDC/SAU-ENB/111941/2009 and PEst-OE/CTM-UI0084/2011 grants.

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