19 research outputs found
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Magnetostratigraphic dating: Insights to Late Cenozoic deposition and dolomitization of Little Bahama Bank
Magnetostratigraphic dating of a transect of cores across Little Bahama Bank (LBB) provides refined insight into timing and anatomy of platform deposition since late Miocene. Age-dating of four cores, with biostratigraphic tie-points, shows a gently northward dipping platform from late Miocene to about mid-Pleistocene (0.73 Ma) as a result of higher growth/accumulation of the southwestern platform margin. Magnetostratigraphic dating coupled with Sr-isotope ages from LBB dolomites significantly improves the late Cenozoic depositional/diagenetic framework. Dolomitization episodes at about 2.2-3.4 and 1.6 Ma correspond with a prolonged period of subaerial exposure and formation of large aquifer systems and perhaps providing a mechanism to pump dolomitizing fluids (seawater) through the platform. A distinct northward slope of the dolomite may be explained by either: (1) a northward-dipping platform top, which supported different aquifer levels during fluctuating sea level lowstand events, or (2) the thickness of the freshwater lens which in turn is controlled by differences in permeability and platform slope between the northern and southern margins
The Role of Microorganisms in the Nucleation of Carbonates, Environmental Implications and Applications
Microbially induced carbonate precipitation (MICP) is an important process in the synthesis of carbonate minerals, and thus, it is widely explored as a novel approach with potential for many technological applications. However, the processes and mechanisms involved in carbonate mineral formation in the presence of microbes are not yet fully understood. This review covers the current knowledge regarding the role of microbial cells and metabolic products (e.g., extracellular polymeric substances, proteins and amino acids) on the adsorption of divalent metals, adsorption of ionic species and as templates for crystal nucleation. Moreover, they can play a role in the mineral precipitation, size, morphology and lattice. By understanding how microbes and their metabolic products promote suitable physicochemical conditions (pH, Mg/Ca ratio and free CO32− ions) to induce carbonate nucleation and precipitation, the manipulation of the final mineral precipitates could be a reality for (geo)biotechnological approaches. The applications and implications of biogenic carbonates in areas such as geology and engineering are presented and discussed in this review, with a major focus on biotechnology
The Role of Microorganisms in the Nucleation of Carbonates, Environmental Implications and Applications
Microbially induced carbonate precipitation (MICP) is an important process in the synthesis of carbonate minerals, and thus, it is widely explored as a novel approach with potential for many technological applications. However, the processes and mechanisms involved in carbonate mineral formation in the presence of microbes are not yet fully understood. This review covers the current knowledge regarding the role of microbial cells and metabolic products (e.g., extracellular polymeric substances, proteins and amino acids) on the adsorption of divalent metals, adsorption of ionic species and as templates for crystal nucleation. Moreover, they can play a role in the mineral precipitation, size, morphology and lattice. By understanding how microbes and their metabolic products promote suitable physicochemical conditions (pH, Mg/Ca ratio and free CO32- ions) to induce carbonate nucleation and precipitation, the manipulation of the final mineral precipitates could be a reality for (geo)biotechnological approaches. The applications and implications of biogenic carbonates in areas such as geology and engineering are presented and discussed in this review, with a major focus on biotechnology
Chemostratigraphy of the Upper Albian to mid‐Turonian Natih Formation (Oman) – how authigenic carbonate changes a global pattern
Offshore Carbonate Facies Characterization and Reservoir Quality of Miocene Rocks in the Southern Margin of South China Sea
A fine balance: Accommodation dominated control of contemporaneous cool‐carbonate shelf‐edge clinoforms and tropical reef‐margin trajectories, North Carnarvon Basin, Northwestern Australia
Geochemical fingerprints of dolomitization in Bahamian carbonates: Evidence from sulphur, calcium, magnesium and clumped isotopes
Dolomitization of lower Permian platform facies, Wichita Formation, north platform, Midland basin, Texas
Field geometry, petrography and geochemistry of a dolomitization front (Late Jurassic, central Lebanon)
This contribution describes the field geometry, petrography and geochemistry of a well-exposed dolomitization front in Upper Jurassic carbonates, and attempts to highlight the sedimentological, structural and relative sea-level controls on multiphase dolomitization and related diagenetic events. The data presented reflect the superposition of various diagenetic phases which have resulted in a single dolostone body, whose dimensions are well defined in the field. Local microbial intraclastic dolomites of Late Tithonian age accumulated in a hypersaline lagoon during relative sea-level fall. These pre-date beige hydrothermal dolostones (51 to 55 mol% CaCO3; δ18O: −9·3 to −4·0‰ V-PDB; δ13C: −1·5 to +2·1‰ V-PDB; 87Sr/86Sr: 0·70742; matrix porosity: ≈6%; Klinkenberg permeability: ≈0·5 mD), whose dolomitizing fluid circulated along faults and invaded the nearby facies. First, the burrows were dolomitized, then the bulk rocks, resulting in the investigated 'tongue'-shaped dolomite body. Upon Late Jurassic–Early Cretaceous uplift, near-surface water percolated through – and altered – the underlying beige dolostones. This event was followed by a ferroan dolomite cement phase, which occurred during further burial. This contribution, featuring a well-defined geometric pattern of a dolomitization front with a large petrographic and geochemical data set, may also serve as a case study illustrating the complexity of superimposed diagenetic processes which have to be taken into account in modelling exercises of multiphase hydrothermal dolomitization