The Experts below are selected from a list of 198 Experts worldwide ranked by ideXlab platform
J. D. Hudson - One of the best experts on this subject based on the ideXlab platform.
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Stable isotopes and limestone Lithification
Journal of the Geological Society, 2007Co-Authors: J. D. HudsonAbstract:Data on the carbon and oxygen isotopic composition of carbonate sediments, limestones and calcite cements are compiled and reviewed, and an elementary exposition of the factors that control them is given. Typical compositions and diagenetic trends are displayed on 8OXs-sc 13 scatter diagrams, and an attempt is made at an isotopic categorization of environments of car- bonate Lithification. Many limestones pass through through several diagenetic environments, which are recorded isotopically by cement gen- erations of distinct isotopic composition. Most limestones contain essentially 'marine' carbon, but extreme compositions can result from organic reactions, especially those involving methane; some of these may be important in petroleum exploration, but their volumetric abundance is probably quite small.
Robert Riding - One of the best experts on this subject based on the ideXlab platform.
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late miocene halimeda alga microbial segment reefs in the marginal mediterranean sorbas basin spain
Sedimentology, 1997Co-Authors: José M. Martín, Juan C. Braga, Robert RidingAbstract:A ∼6 Ma Messinian (late Miocene) Bioherm Unit on the southern slope of the Sorbas Basin, SE Spain, contains numerous biotically diverse lensoid patch reefs that formed on a shelf to basin slope during a cycle of relative sea-level change. Halimeda reefs are the largest and most complex of the patch reefs and are divisible into core, cap, and flank facies. On the upper and midslope they are up to 40 m thick and 400 m long. They become smaller downslope. The core consists of jumbled Halimeda segments, released by spontaneous disaggregation of the alga. The segments were stabilized close to their sites of growth and rapidly lithified by micritic and peloidal microbial crusts. Residual cavities were further veneered by isopachous marine cements. Flank facies, consisting of bedded packstones to rudstones, form wedge-shaped units lateral to the mounds. Cap facies consist of bioclastic calcarenites/calcirudites and microbial carbonates. Synsedimentary Lithification assisted rapid accretion and inhibited off-mound export of sediment. Allochthonous reef-derived blocks on the mid-slope reflect penecontemporaneous rigidity of the Halimeda bioherms. Proximal Porites coral frame patch reefs associated with calcarenites were located near the shelf margin during the initial lowstand stage. Halimeda segment reefs associated with calcarenites and silty marls developed on the midslope and bivalve-bryozoan-serpulid reefs formed on the lower slope in silty marls with occasional turbidites. During the transgressive stage, coral patch reefs near the shelfbreak were overgrown by Halimeda. During highstand progradation, cap facies spread basinward as a sheet connecting many of the midslope patch reefs. These ancient analogues differ from most modern Halimeda reefs in being discrete laterally restricted patch reefs, surrounded by marly sediment, and located on a slope. They are, however, broadly comparable in biota, thickness, and depositional depth. Intense early Lithification by microbial crusts and marine cements is an important feature of these Messinian segment reefs. It has not been reported from modern examples.
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internal structure of segment reefs halimeda algal mounds in the mediterranean miocene
Geology, 1996Co-Authors: Juan C. Braga, José M. Martín, Robert RidingAbstract:Halimeda reefs in the upper Miocene strata (∼6 Ma) of the Sorbas basin, southeastern Spain, shed light on the internal structure of more extensive but less accessible Holocene counterparts, and challenge conventional reef concepts. Coarse discoid segments, released by Halimeda during life or immediately after death, dominate the lenslike mounds. Their chaotic, loose appearance disguises the reefal nature of the mounds. Segments, accumulating at or very close to sites of growth, were quickly stabilized by microbial and cement crusts that bound them into distinctive rigid gravel fabrics. This early Lithification generated relief but inhibited off-mound export of sediment, although large blocks detached locally and moved downslope. Encrustation of parautochthonous Halimeda gravel created a unique reef type: segment reefs.
Hengchao Xu - One of the best experts on this subject based on the ideXlab platform.
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macrofaunal burrowing enhances deep sea carbonate Lithification on the southwest indian ridge
Biogeosciences, 2018Co-Authors: Hengchao Xu, Xiaotong Peng, Shun Chen, Jiwei Li, S Dasgupta, Kaiwen Ta, Mengran DuAbstract:Abstract. Deep-sea carbonates represent an important type of sedimentary rock due to their effect on the composition of the upper oceanic crust and their contribution to deep-sea geochemical cycles. However, the role of deep-sea macrofauna in carbonate Lithification remains poorly understood. A large lithified carbonate area, characterized by thriving benthic faunas and a tremendous amount of burrows, was discovered in 2008, blanketing the seafloor of the ultraslowly spreading Southwest Indian Ridge (SWIR). Benthic inhabitants – including echinoids, polychaetes, gastropods and crustaceans – are abundant in this carbonate lithified area. The burrowing features within these carbonate rocks, as well as the factors that may influence deep-sea carbonate Lithification, were examined. We suggest that burrowing in these carbonate rocks enhances deep-sea carbonate Lithification. We propose that active bioturbation may trigger the dissolution of the original calcite and thus accelerate deep-sea carbonate Lithification on mid-ocean ridges. Macrofaunal burrowing provides a novel driving force for deep-sea carbonate Lithification at the seafloor, illuminating the geological and biological importance of bioturbation in global deep-sea carbonate rocks.
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endolithic boring enhance the deep sea carbonate Lithification on the southwest indian ridge
Biogeosciences Discussions, 2018Co-Authors: Hengchao Xu, Xiaotong Peng, Shun Chen, Jiwei Li, Kaiwen Ta, Mengran DuAbstract:Abstract. Deep-sea carbonates represent an important type of sedimentary rock due to their effect on the composition of upper oceanic crust and their contribution to deep-sea geochemical cycles. However, the Lithification of deep-sea carbonates at the seafloor has remained a mystery for many years. A large lithified carbonate area, characterized by thriving benthic faunas and tremendous amount of endolithic borings, was discovered in 2008, blanketed on the seafloor of ultraslow spreading Southwest Indian Ridge (SWIR). Macrofaunal inhabitants including echinoids, polychaetes, gastropods as well as crustaceans, are abundant in the sample. The most readily apparent feature of the sample is the localized enhancement of density around the borings. The boring features of these carbonate rocks and factors that may enhance deep-sea carbonate Lithification are reported. We suggest that active boring may trigger the dissolution of the original calcite and thus accelerate deep-sea carbonate Lithification on mid-ocean ridges. Our study reports an unfamiliar phenomenon of non-burial carbonate Lithification and interested by the observation that it is often associated with boring feature. These carbonate rocks may provide a novel mechanism for deep-sea carbonate Lithification at the deep-sea seafloor and also illuminate the geological and biological importance of deep-sea carbonate rocks on mid-ocean ridges.
Austin J W Hendy - One of the best experts on this subject based on the ideXlab platform.
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taphonomic overprints on phanerozoic trends in biodiversity Lithification and other secular megabiases
2011Co-Authors: Austin J W HendyAbstract:Taphonomic biases introduce heterogeneity into the quality of the fossil record and can skew paleontologists’ perception of biodiversity. This paper reviews the temporal extent and consequences of major taphonomic biases, including Lithification of sediments, skeletal replacement through silicification and phosphatization, concentration of skeletal hard-parts, and the exceptional preservation of soft-bodied faunas. The frequency of occurrence of particular biases, and their effects of fossil faunas is identified using occurrence-based datasets, such as the Paleobiology Database.
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the influence of Lithification on cenozoic marine biodiversity trends
Paleobiology, 2009Co-Authors: Austin J W HendyAbstract:Recent research has corroborated the long-held view that the diversity of genera within benthic marine communities has increased from the Paleozoic to the Cenozoic as much as three-to fourfold, after mitigating for such biasing influences as secular variation in time-averaging and environmental coverage. However, these efforts have not accounted for the considerable increase in the availability of unlithified fossiliferous sediments in strata of late Mesozoic and Cenozoic age. Analyses presented here on the Cenozoic fossil record of New Zealand demonstrate that unlithified sediments not only increase the amount of fossil material and hence the observed diversity therein, but they also preserve a pool of taxa that is compositionally distinct from lithified sediments. The implication is that a large component of the difference in estimates of within-community diversity between Paleozoic and Cenozoic assemblages may relate to the increased availability of unlithified sediments in the Cenozoic.
Pieter T Visscher - One of the best experts on this subject based on the ideXlab platform.
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microbial species richness and metabolic activities in hypersaline microbial mats insight into biosignature formation through Lithification
Astrobiology, 2009Co-Authors: Laura K Baumgartner, Christophe Dupraz, Daniel H Buckley, John R Spear, Norman R Pace, Pieter T VisscherAbstract:Abstract Microbial mats in the hypersaline lake of Salt Pan, Eleuthera, Bahamas, display a gradient of Lithification along a transect from the center to the shore of the lake. These mats exist unde...
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microbial Lithification in marine stromatolites and hypersaline mats
Trends in Microbiology, 2005Co-Authors: Christophe Dupraz, Pieter T VisscherAbstract:Lithification in microbial ecosystems occurs when precipitation of minerals outweighs dissolution. Although the formation of various minerals can result from microbial metabolism, carbonate precipitation is possibly the most important process that impacts global carbon cycling. Recent investigations have produced models for stromatolite formation in open marine environments and Lithification in shallow hypersaline lakes, which could be highly relevant for interpreting the rock record and searching for extraterrestrial life. Two factors that are controlled by microbial processes and physicochemical characteristics determine precipitation: exopolymeric substances and the saturation index, the latter being determined by the pH, {Ca 2+ } and {CO 3 2− }. Here, we evaluate community metabolism in microbial mats and hypothesize why these organosedimentary biofilms sometimes lithify and sometimes do not.