Isotopic evidence for source of diagenetic carbonates formed during burial of organic-rich sediments
TL;DR: In this article, the relative dominance of different burial diagenesis processes within specific depth intervals is given by the isotopic composition of incorporated oxygen which is temperature dependent (1) 0 to −2‰, (2) −1.5 to −5'
Abstract: Organic matter is modified by several processes operating at different depths during burial diagenesis: (1) sulphate reduction; (2) fermentation; (3) thermally-induced decarboxylation, and so on. CO2, one common product of each, can be distinguished by its carbon isotope composition: approximately (1) −25‰, (2) +15‰, (3) −20‰ relative to PDB. These values are preserved in diagenetic carbonates of the Upper Jurassic Kimmeridge Clay. Independent corroboration of the relative dominance of each process within specific depth intervals is given by the isotopic composition of incorporated oxygen which is temperature dependent (1) 0 to −2‰, (2) −1.5 to −5‰,(3) −3.5 to −7.0‰.
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TL;DR: For example, in this article, the main component is dense, clotted or peloidal micrite resulting from calcification of bacterial cells, sheaths and biofilm, and from phytoplankton-stimulated whiting nucleation.
Abstract: Summary
Deposits produced by microbial growth and metabolism have been important components of carbonate sediments since the Archaean. Geologically best known in seas and lakes, microbial carbonates are also important at the present day in fluviatile, spring, cave and soil environments. The principal organisms involved are bacteria, particularly cyanobacteria, small algae and fungi, that participate in the growth of microbial biofilms and mats. Grain-trapping is locally important, but the key process is precipitation, producing reefal accumulations of calcified microbes and enhancing mat accretion and preservation. Various metabolic processes, such as photosynthetic uptake of CO2 and/or HCO3– by cyanobacteria, and ammonification, denitrification and sulphate reduction by other bacteria, can increase alkalinity and stimulate carbonate precipitation. Extracellular polymeric substances, widely produced by microbes for attachment and protection, are important in providing nucleation sites and facilitating sediment trapping.
Microbial carbonate microfabrics are heterogeneous. They commonly incorporate trapped particles and in situ algae and invertebrates, and crystals form around bacterial cells, but the main component is dense, clotted or peloidal micrite resulting from calcification of bacterial cells, sheaths and biofilm, and from phytoplankton-stimulated whiting nucleation. Interpretation of these texturally convergent and often inscrutable fabrics is a challenge. Conspicuous accumulations are large domes and columns with laminated (stromatolite), clotted (thrombolite) and other macrofabrics, which may be either agglutinated or mainly composed of calcified or spar-encrusted microbes. Stromatolite lamination appears to be primary, but clotted thrombolite fabrics can be primary or secondary. Microbial precipitation also contributes to hot-spring travertine, cold-spring mound, calcrete, cave crust and coated grain deposits, as well as influencing carbonate cementation, recrystallization and replacement. Microbial carbonate is biologically stimulated but also requires favourable saturation state in ambient water, and thus relies uniquely on a combination of biotic and abiotic factors. This overriding environmental control is seen at the present day by the localization of microbial carbonates in calcareous streams and springs and in shallow tropical seas, and in the past by temporal variation in abundance of marine microbial carbonates. Patterns of cyanobacterial calcification and microbial dome formation through time appear to reflect fluctuations in seawater chemistry.
Stromatolites appeared at ∼3450 Ma and were generally diverse and abundant from 2800 to 1000 Ma. Inception of a Proterozoic decline variously identified at 2000, 1000 and 675 Ma, has been attributed to eukaryote competition and/or reduced lithification. Thrombolites and dendrolites mainly formed by calcified cyanobacteria became important early in the Palaeozoic, and reappeared in the Late Devonian. Microbial carbonates retained importance through much of the Mesozoic, became scarcer in marine environments in the Cenozoic, but locally re-emerged as large agglutinated domes, possibly reflecting increased algal involvement, and thick micritic reef crusts in the late Neogene. Famous modern examples at Shark Bay and Lee Stocking Island are composite coarse agglutinated domes and columns with complex bacterial–algal mats occurring in environments that are both stressed and current-swept: products of mat evolution, ecological refugia, sites of enhanced early lithification or all three?
1,273 citations
TL;DR: Studies of sediments related to a decomposing methane hydrate provide strong evidence that methane is being consumed by archaebacteria that are phylogenetically distinct from known methanogens.
Abstract: Large amounts of methane are produced in marine sediments but are then consumed before contacting aerobic waters or the atmosphere1. Although no organism that can consume methane anaerobically has ever been isolated, biogeochemical evidence indicates that the overall process involves a transfer of electrons from methane to sulphate and is probably mediated by several organisms, including a methanogen (operating in reverse) and a sulphate-reducer (using an unknown intermediate substrate)2. Here we describe studies of sediments related to a decomposing methane hydrate. These provide strong evidence that methane is being consumed by archaebacteria that are phylogenetically distinct from known methanogens. Specifically, lipid biomarkers that are commonly characteristic of archaea are so strongly depleted in carbon-13 that methane must be the carbon source, rather than the metabolic product, for the organisms that have produced them. Parallel gene surveys of small-subunit ribosomal RNA (16S rRNA) indicate the predominance of a new archael group which is peripherally related to the methanogenic orders Methanomicrobiales and Methanosarcinales.
1,170 citations
TL;DR: In this paper, a correlation scheme for the Neoproterozoic that corroborates radiometric data that indicate that there were three glacial epochs between ca. 750 and 580 Ma was proposed.
Abstract: Glacial deposits of Sturtian and Marinoan age occur in the well-studied Neoproterozoic successions of northern Namibia, South Australia, and northwestern Canada. In all three regions, the Marinoan glaciation is presaged by a large negative δ 13 C anomaly, and the cap carbonates to both glacial units share a suite of unique sedimentological, stratigraphic, and geochemical features. These global chronostratigraphic markers are the bases of a new correlation scheme for the Neoproterozoic that corroborates radiometric data that indicate that there were three glacial epochs between ca. 750 and 580 Ma. Intraregional correlation of Neoproterozoic successions in the present-day North Atlantic region suggests that glacial diamictite pairs in the Polarisbreen Group in northeastern Svalbard and the Tillite Group in eastern Greenland were deposited during the Marinoan glaciation, whereas the younger of a pair of glacials (Mortensnes Formation) in the Vestertana Group of northern Norway was deposited during the third (Gaskiers) Neoproterozoic glaciation. Gaskiers-aged glacial deposits are neither globally distributed nor overlain by a widespread cap carbonate but are associated with an extremely negative δ 13 C anomaly. framework for a new, high-resolution model carbon-isotope record for the Neoproterozoic comprising new δ 13 C (carbonate) data from Svalbard (Akademikerbreen Group) and Namibia (Otavi Group) and data in the literature from Svalbard, Namibia, and Oman. A new U-Pb zircon age of 760 ± 1 Ma from an ash bed in the Ombombo Subgroup in Namibia provides the oldest direct time-calibration point in the compilation, but the time scale of this preliminary δ 13 C record remains
818 citations
Cites background from "Isotopic evidence for source of dia..."
...The process that can alter carbonate δ13C compositions most severely is the incorporation of 13C-depleted carbon from the oxidation of organic matter or methane during diagenesis (e.g., Irwin et al., 1977)....
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Book•
01 Jan 1993
TL;DR: In this paper, the authors investigated the long-term fate of organic matter in the geosphere and its role in sedimentary organic matter preservation and degradation in the geological timescale.
Abstract: Preface 1 Carbon, the Earth and life: 11 Carbon and the basic requirements of life12 Chemical elements, simple compounds and their origins13 The origin of life14 Evolution of life and the atmosphere15 Major contributors to sedimentary organic matter 2 Chemical composition of biogenic matter: 21 Structure of natural products22 Carbohydrates23 Amino acids and proteins24 Lipids25 Lignins, tannins and related compounds26 Nucleotides and nucleic acids27 Geochemical implicatiions of compositional variation 3 Production, preservation and degradation of organic matter: 31 How and why organic-rich deposits form32 Controls on primary production33 Preservation and degradation of organic matter34 Depositional environments associated with accumulation of organic matter 4 Long-term fate of organic matter in the geosphere: 41 Diagenesis42 Humic material43 Coal44 Kerogen45 Catagenesis and metagenesis46 Temporal and geographical distribution of fossil organic carbon 5 Chemical stratigraphy 51 Biologically mediated transformations52 Examples of source indicators in recent sediments53 Diagenesis at the molecular level54 Source and environment indicators in ancient sediments and oil55 Thermal maturity and molecular transformations56 Palaeotemperature and age measurement57 Maturity of ancient sedimentary organic matter58 Isotopic palaeontology 6 The carbon cycle and climate 61 Global carbon cycle62 Changes in carbon reservoirs over geological time63 Palaeoclimatic variations64 Isotopic excursions at period boundaries65 Human influence on the carbon cycle 7 Anthropogenic carbon and the environment 71 Introduction72 Halocarbons73 Hydrocarbon pollution in aquatic environments74 Endocrine disrupting chemicals75 Environmental behaviour of selected xenobiotic compounds76 Factors affecting the rate of anthropogenic components Appendix 1: SI units usedAppendix 2: SI unit prefixesAppendix 3: Geological timescaleReferencesIndex
814 citations
Cites background from "Isotopic evidence for source of dia..."
...Postdepositional diagenetic alteration of carbonates can alter the d13C value significantly by exchange with the CO2 produced from oxidation of organic matter (Irwin et al. 1977)....
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TL;DR: Significant short-term carbon isotope fluctuations are present in Cretaceous pelagic limestones from widely distributed onshore sections in the Circum-Atlantic-western Tethyan region as discussed by the authors.
Abstract: Significant short-term carbon isotope fluctuations are present in Cretaceous pelagic limestones from widely distributed onshore sections in the Circum-Atlantic-western Tethyan region. More than 1,000 closely spaced samples were analyzed during this study. At least seven major ^dgr13C excursions can be correlated from section to section. The most important "heavy events" occur near the Aptian-Albian and Cenomanian-Turonian boundaries, whereas "light events" are near the Jurassic-Cretaceous, Albian-Cenomanian, Turonian-Coniacian, and Cretaceous-Tertiary boundaries. The association of "events" with stage boundaries and the consistent correlation of "events" between stratigraphic sections provides a significant new tool for time-rock correlation independent of stan ard biostratigraphic techniques. The temporal association of these carbon isotope events with stage boundaries (faunal and floral events), global eustatic sea-level variations, and oceanic "anoxic events" demonstrates the potential usefulness of carbon isotope studies in interpreting variations in paleo-oceanic circulation. Furthermore, the association of carbon isotope variations with anoxic events is potentially useful for evaluation of the precise timing and the magnitude of preservation of organic matter in deep-sea and continental-margin sediments. Thus, isotopic studies may aid in estimating potential hydrocarbon resources in largely unexplored oceanic basins or along continental margins.
796 citations
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4,094 citations
TL;DR: In this paper, Niee's and Solenhofen standards were compared to the Chicago PDB standard for carbon and oxygen isotope ratios, and the correction factors for instrumental effects and for the nature of the mass spectra were derived.
4,071 citations
TL;DR: In this paper, the temperature variation of the fractionation of oxygen in exchange reactions between dissolved carbonate and water and between calcite and water was calculated on theoretical grounds, and checked experimentally.
Abstract: The temperature variation of the fractionation of oxygen in exchange reactions between dissolved carbonate and water and between calcite and water and calculated on theoretical grounds, and checked experimentally. In the course of the experiments it was necessary to investigate several methods of decomposing calcium carbonate to carbon dioxide for mass spectrometer analysis. A method was developed for growing calcium carbonate from solution with the same isotopic composition as the carbonate shells of organisms produced at the same temperature from water of the same isotopic composition, and the results of these experiments at various temperatures are expressed in an equation relating the temperature of formation with the isotopic composition of the calcium carbonate and of the water.
3,579 citations
TL;DR: The relationship between temperature and O(18) content relative to that for a Cretaceous belemnite of the Pee Dee formation previously reported (Epstein, Buchsbaum, Lowenstam, and Urey, 1951) has been re-determined using modified procedures for removing organic matter from shells, and is found to be 16.5 - 4.3 δ + 0.14 δ^2
Abstract: The relationship between temperature and O^(18) content relative to that for a Cretaceous belemnite of the Pee Dee formation previously reported (Epstein, Buchsbaum, Lowenstam, and Urey, 1951) has been re-determined using modified procedures for removing organic matter from shells, and is found to be
t(°C) = 16.5 - 4.3δ + 0.14δ^2
where δ is the difference in per mil of the O^(18) to O^(16) ratio between the sample and reference gas. The new relationship agrees with that determined by McCrea (1950) for inorganically precipitated calcium carbonate. Carbonate-carbon dioxide exchange experiments were done to determine the direct and indirect effects of organic matter in the shell on the mass spectrometer analyses.
2,109 citations
TL;DR: Investigation of carbon isotope fractionation in a variety of photosynthetic and nonphotosynthetic organisms, including some grown in the laboratory under controlled conditions and some that had grown in a natural environment finds the effect of isotopic substitution on the physicochemical properties of molecules interesting.
Abstract: When inorganic carbon is converted to living matter during photosynthesis, there is an isotope effect and the carbon-containing compounds of cells have a slightly lower C13 concentration than the carbonate and carbon dioxide of the environment.' Craig2 has reviewed the existing data on carbon isotope abundances in nature. Park and Epstein3 4 have recently reported on some carbon isotope fractionations in plants grown in the laboratory. The effect of isotopic substitution on the physicochemical properties of molecules has been well studied for inorganic and nonbiological organic systems.5 The relative rates of photosynthesis of the C13and C'2-containing molecules are of a similar order of magnitude as observed for reactions involving formation or rupture of carbon bonds. Although it may be difficult to achieve precise understanding of the carbon isotope effect in living systems, the more qualitative and descriptive features are interesting and have already been the subject of geochemical speculation. Thus, Epstein and Silverman6 have made extensive measurements on petroleum and petroleum fractions. Since marine organisms tend to have a slightly higher concentration of C13 than nonmarine forms, carbon isotope measurements may be important to investigations of the origin and migration of petroleum. In a study of a Finnish Precambrian formation, Rankama7 observed that a problematic fossil, Coryecium enigmaticum (probable age >1.4 X 109 years) has carbon which is depleted in C13 similar to present organic carbon. Rankama's conclusion concerning early life obtained from this evidence has been discussed by Craig.8 Detailed study of this effect might produce information relevant to photosynthesis, biosynthesis, and comparative biochemistry. Accordingly, we have investigated carbon isotope fractionation in a variety of photosynthetic and nonphotosynthetic organisms, including some grown in the laboratory under controlled conditions and some that had grown in a natural environment. A typical experiment consisted of (1) culturing the organisms, (2) extracting the lipides, (3) hydrolyzing the proteins, (4) separating pure amino acids by ion-exchange chromatography, (5) combusting a portion of the amino acids to carbon dioxide, (6) decarboxylating a portion of the amino acids with ninhydrin and purifying the liberated carbon dioxide, and (7) performing an isotopic analysis on the
458 citations