Academic literature on the topic 'Calcareous units'
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Journal articles on the topic "Calcareous units"
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Cuif, J. P., Y. Dauphin, B. Farre, G. Nehrke, J. Nouet, and M. Salomé. "Distribution of sulphated polysaccharides within calcareous biominerals suggests a widely shared two-step crystallization process for the microstructural growth units." Mineralogical Magazine 72, no. 1 (February 2008): 233–37. http://dx.doi.org/10.1180/minmag.2008.072.1.233.
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AbstractSynchrotron-based XANES characterization of sulphated sulphur combined with atomic force microscopy and transmission electron microscopy (imaging and diffraction) allow insights into the crystallization of the calcareous units produced by invertebrates. As a result of a series of converging data, reticulate crystallization of the amorphous Ca-carbonate molecules conveyed to the micron-thick growth layer by the sumicrometric organo-mineral units seems a reasonable hypothesis, providing us with a method of explaining the multiple and taxonomy-linked ‘vital effects’ which have long been recognized among the calcareous biocrystals.
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Li, Guohua, Haigang Li, Peter A. Leffelaar, Jianbo Shen, and Fusuo Zhang. "Dynamics of phosphorus fractions in the rhizosphere of fababean (Vicia faba L.) and maize (Zea mays L.) grown in calcareous and acid soils." Crop and Pasture Science 66, no. 11 (2015): 1151. http://dx.doi.org/10.1071/cp14370.
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The dynamics of soil phosphorus (P) fractions were investigated, in the rhizosphere of fababean (Vicia faba L.) and maize (Zea mays L.) grown in calcareous and acid soils. Plants were grown in a mini-rhizotron with a thin (3 mm) soil layer, which was in contact with the root-mat, and considered as rhizosphere soil. Hedley sequential fractionation was used to evaluate the relationship between soil pH and P dynamics in the rhizosphere of fababean and maize. Soil pH influenced the dynamics of P fractions in both calcareous and acid soils. Fababean and maize roots decreased rhizosphere pH by 0.4 and 0.2 pH units in calcareous soil, and increased rhizosphere pH by 1.2 and 0.8 pH units in acid soil, respectively, compared with the no-plant control. The acid-soluble inorganic P fraction in the rhizosphere of calcareous soil was significantly depleted by fababean, which was probably due to strong rhizosphere acidification. In contrast, maize had little effect on this fraction. Both fababean and maize significantly depleted the alkali-soluble organic P fractions in calcareous soil, but not in acid soil. Fababean and maize utilised different P fractions in soil, which was partly due to their differing abilities to modify the rhizosphere. This study has decoupled successfully the effects of chemically induced pH change from plant growth effects (such as mineralisation and P uptake) on P dynamics. The effect of soil pH on plant exudation response in P-limited soils has been demonstrated in the present study.
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Milosevic, Rajko. "Typological classification and the existing condition of artificially established sycamore maple and Norway maple stands in the protective forest belt." Bulletin of the Faculty of Forestry, no. 104 (2011): 143–54. http://dx.doi.org/10.2298/gsf1104143m.
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The study results on the typological classification of the artificially established sycamore maple and Norway maple stands included in the shelterbelt along the ?Belgrade-Zagreb? highway are presented. The environmental conditions of the sycamore and Norway maple plantation have been typologically defined in specific typological entitities at the ecological level (ecological units). In this context, the specific site conditions were characterised and defined as: a) Forest of common oak (Tilio-Quercetum crassiusculae typicum) on leached chernozem, b) Forest of common oak (Tilio-Quercetum crassiusculae typicum) on moderately deep to deep calcareous chernozem, c) Forest of common oak (Tilio-Quercetum crassiusculae typicum) on shallow to moderately deep calcareous chernozem. The inter-relationship between sycamore maple and Norway maple regarding the ecological and coenological optimum differs within the above ecological units. The diversity reflects the sycamore and Norway maple bioecology and the site typology of the particular ecological units.
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Luitel, Prakash, and Suman Panthee. "Geological study in Tal - Talekhu section of Manang District along the Besisahar – Chame Road." Bulletin of the Department of Geology 22 (December 15, 2020): 25–28. http://dx.doi.org/10.3126/bdg.v22i0.33411.
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The section between Tal to Talekhu of Manang District lacks the detailed geological study. The geological mapping in the scale of 1:50,000 followed by the preparation of geological cross-section and lithostratigraphic column has been done in the present study. The studied area lies partially in the Higher Himalayan Crystalline and the Tibetan Tethys Sequence. The units of the Higher Himalayan Group from Tal to Talekhu consists mainly of vigorous to faintly calcareous gneiss, migmatitic gneiss, quartzite, granite, etc. They are named as the Calc. Silicate Gneiss and Paragneiss and the Orthogneiss and Granite units. The lowermost part of the Tibetan Tethys consisted of metamorphosed calcareous rocks containing silicates and feldspar, so this unit is termed as the Marble and Calc. Gneiss. The section is about 9 km in thickness and is highly deformed with presence of igneous rocks at many places.
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Luitel, Prakash, and Suman Panthee. "Geological study in Tal - Talekhu section of Manang District along the Besisahar – Chame Road." Bulletin of the Department of Geology 22 (December 15, 2020): 25–28. http://dx.doi.org/10.3126/bdg.v22i0.33411.
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The section between Tal to Talekhu of Manang District lacks the detailed geological study. The geological mapping in the scale of 1:50,000 followed by the preparation of geological cross-section and lithostratigraphic column has been done in the present study. The studied area lies partially in the Higher Himalayan Crystalline and the Tibetan Tethys Sequence. The units of the Higher Himalayan Group from Tal to Talekhu consists mainly of vigorous to faintly calcareous gneiss, migmatitic gneiss, quartzite, granite, etc. They are named as the Calc. Silicate Gneiss and Paragneiss and the Orthogneiss and Granite units. The lowermost part of the Tibetan Tethys consisted of metamorphosed calcareous rocks containing silicates and feldspar, so this unit is termed as the Marble and Calc. Gneiss. The section is about 9 km in thickness and is highly deformed with presence of igneous rocks at many places.
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Al-Bahry, S. N., I. Y. Mahmoud, K. Melghit, and I. Al-Amri. "Analysis of Elemental Composition of the Eggshell before and after Incubation in the Loggerhead Turtle (Caretta caretta) in Oman." Microscopy and Microanalysis 17, no. 3 (April 27, 2011): 452–60. http://dx.doi.org/10.1017/s1431927611000298.
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AbstractTo date, there are limited studies on loggerhead turtle (Caretta caretta) eggshell ultrastructure and its elemental composition. Eggs were collected from turtle nests immediately after oviposition and post hatching. Three eggshell layers were recognized. The outer calcareous layer consists of loose nodular units of different shapes and sizes with loose attachment between the units, resulting in numerous spaces and openings. Each unit consists of CaCO3crystals in aragonite (99%) and calcite (1%). The middle layer has several strata with numerous openings connecting the calcareous and the inner shell membrane. Crystallites of the middle layer are a mix of amorphous material with aragonite (62%) and calcite (38%). The inner shell membrane has numerous reticular fibers mixed predominantly with halite (NaCl) and small amounts of sylvite. Thermogravimetry analysis of the calcareous showed a low exothermic peak at 425°C, which corresponds to a transitional phase from aragonite to calcite. A high endothermic peak at 814°C corresponds to decomposition of calcite CaCO3to CaO and CO2. Electron diffraction confirmed the presence of NaCl halite crystal. A significant difference was found in the percentage of elements and crystal configurations in the three layers. This study has value in assessing the emergence success in this endangered species.
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Kilian, Sinah, and Hugo Ortner. "Structural evidence of in-sequence and out-of-sequence thrusting in the Karwendel mountains and the tectonic subdivision of the western Northern Calcareous Alps." Austrian Journal of Earth Sciences 112, no. 1 (January 1, 2019): 62–83. http://dx.doi.org/10.17738/ajes.2019.0005.
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AbstractWe present the results of a field study in the Karwendel mountains in the western Northern Calcareous Alps, where we analysed the boundary between two major thrust sheets in detail in a key outcrop where nappe tectonics had been recognized already at the beginning of the 20th century. We use the macroscopic structural record of thrust sheet transport in the footwall and hanging wall of this boundary, such as folds, foliation and faults. In the footwall, competent stratigraphic units tend to preserve a full record of deformation while incompetent units get pervasively overprinted and only document the youngest deformation.Transport across the thrust persisted throughout the deformation history of the Northern Calcareous Alps from the late Early Cretaceous to the Miocene. As a consequence of transtensive, S-block down strike-slip tectonics, postdating folding of the major thrust, new out-of-sequence thrusts formed that climbed across the step, and ultimately placed units belonging to the footwall of the initial thrust onto its hanging wall.One of these out-of-sequence thrusts had been used to delimit the uppermost large thrust sheet (Inntal thrust sheet) of the western Northern Calcareous against the next, tectonically deeper, (Lechtal) thrust sheet. Based on the structural geometry of the folded thrust and the age of the youngest sediments below the thrust, we redefine the thrust sheets, and name the combined former Inntal- and part of the Lechtal thrust sheet as the new Karwendel thrust sheet and the former Allgäu- and part of the Lechtal thrust sheet as the new Tannheim thrust sheet.
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Baliniak, Weronika. "Paleocene-Eocene calcareous agglutinated foraminifera from slope marl assemblages of the Fore-Magura Thrust Sheet (Polish Outer Carpathian)." Micropaleontology 64, no. 6 (2018): 379–89. http://dx.doi.org/10.47894/mpal.64.6.04.
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Organic-cemented benthic agglutinated foraminifera are a highly dominant component of flysch-type DWAF assemblages, while agglutinated foraminifera that use calcareous cement are rare or almost absent. However, in mixed assemblages, consisting of both benthic and planktonic forms, the agglutinated foraminiferal assemblages usually include calcareous agglutinants and display higher taxonomic diversity than coeval flysch-type agglutinated foraminiferal assemblages. Late Paleocene - Late Eocene mixed foraminiferal assemblages from 45 samples collected from the Fore-Magura Thrust Sheet of the Polish Outer Carpathians, were examined for taxonomic identification of characteristic agglutinated foraminifera with calcareous material in their tests. The following 11 species are reported herein: Vulvulina eocaena Montagne, Plectina elongata Cushman and Bermudez, Gaudryina laevigata Franke, Gaudryina pyramidata Cushman, Arenobulimina d'orbignyi (Reuss), Remesella varians (Glaessner), Dorothia beloides Hillebrandt, Karreriella chapapotensis (Cole), Karreriella subglabra (Gumbel), Clavulinoides havanensis Cushman and Bermudez, Pseudoclavulina clavata (Cushman) and an additional 10 taxa are left in open nomenclature. The species assigned to Vulvulina, Plectina, Gaudryina and Pseudogaudryinella reveal calcareous material within their tests, though the descriptions of these genera do not always specify this feature. The results of this study reveal higher diversity and abundance of calcareous agglutinated foraminifera occurring in themarly deposits of the Fore-Magura Thrust Sheet in comparison with other units of the Polish Outer Carpathians. The studied group of agglutinated foraminifera with calcareous material may be regarded as a characteristic component of DWAF assemblages indicative of the slope marl foraminiferal assemblages.
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Shoval, S., and O. Zlatkin. "Climatic changes during the Pliocene as observed from climate-sensitive rocks and clay minerals of the Sedom formation, the Dead Sea Basin." Clay Minerals 44, no. 4 (December 2009): 469–86. http://dx.doi.org/10.1180/claymin.2009.044.4.469.
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AbstractThe climatic history of the Dead Sea region during the Pliocene and its global connection are observed from climate-sensitive rocks and clay minerals of the Sedom formation. The Sedom formation consists of evaporative halitic rock salt units and calcareous shale units that were deposited in the Dead Sea Basin during the Pliocene. The precipitation of the rock salts took place in the hypersaline sabkha environment of the Sedom Lagoon. The extensive evaporative conditions are related to an extremely dry and warm arid climate at that time. In the arid climate, the influx of meteoric water by the drainage system of the Sedom Lagoon was limited and permitted a large concentration of lagoonal brine as well as a small rate of detritus transportation to the lagoon. Accessory sepiolite found in the rock salt appears to be neoformed from brine enriched with Mg and poor in Al under the extreme salinity condition. The small amounts of Al are in accordance with the small number of detrital minerals in the rock salts. The replacement in the deposition of the rock salt members with the calcareous shale members demonstrates a decrease in the salinity of the brine in the Sedom Basin and an increase in the deposition of detritus. The change in conditions was related to a period of deposition under a more humid climate where the erosion and the transport of detritus by the drainage system to the Sedom Basin was higher, causing the deposition of calcareous shales. Palygorskite found in the calcareous shales appears to be neoformed from brine enriched with Mg and containing Al in conditions of reduced salinity of the Sedom Basin. The larger amounts of Al are in accordance with the abundance of detrital minerals in the calcareous shales.The depositional cycles of the Sedom formation, the cyclic fluctuation of the climatic-hydrologic conditions from an arid to a more humid climate and their correlation with sea-level fluctuations and transgression-regression cycles of the Mediterranean Sea seem to be a response to corresponding global interglacial and glacial periods during the Pliocene.
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Mikuláš, Radek, Petr Skupien, Miroslav Bubík, and Zdeněk Vašíček. "Ichnology of the Cretaceous Oceanic Red Beds (Outer Western Carpathians, Czech Republic)." Geologica Carpathica 60, no. 3 (June 1, 2009): 233–50. http://dx.doi.org/10.2478/v10096-009-0016-1.
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Ichnology of the Cretaceous Oceanic Red Beds (Outer Western Carpathians, Czech Republic)Large differences in the intensity and overall character of bioturbational structures were found in five facies containing hemipelagic red beds. Red beds (CORB) of the Godula facies of the Silesian Unit and their equivalents (mostly not red) in the Kelč facies of the Silesian Unit and the CORB in the non-calcareous sediments of the Rača Unit display a very low degree of bioturbation. The CORB facies of the Rača Unit, containing calcareous intercalations, displays a very high degree of bioturbation as expressed by a high ichnofabric index. They contain trace fossilsChondrites, Zoophycos, Planolites, Thalassinoides, Palaeophycus, TeichichnusandPhycosiphon.The supply of food obviously acted as the controlling factor. The "calcareous" facies of the CORB of the Rača Unit has a considerably higher proportion of sand-dominated interbeds and also carbonates than the non-calcareous facies. This (especially the presence of carbonates) suggests a relative proximity of food-rich environments and an easy transport of nutrition-rich substrate by turbidite currents into the basin directly, not only by periodical fall-out of dead plankton (which is probably responsible for the rhythmicity of poor colonization horizons in weakly bioturbated units).
Book chapters on the topic "Calcareous units"
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Giannetta, Leo G., and Richard J. Behl. "Chemostratigraphic and lithostratigraphic framework of the Eocene Kreyenhagen Formation, Kettleman area, central San Joaquin Basin, California." In Understanding the Monterey Formation and Similar Biosiliceous Units across Space and Time. Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.2556(12).
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ABSTRACT The Eocene Kreyenhagen Formation is a widespread siliceous, organic-rich mudstone within the San Joaquin Basin, but it is less studied than the Monterey Formation. This study characterizes the Kreyenhagen Formation in the Kettleman area to define its vertical and lateral variability on the basis redox conditions (Mo, U, Cr), paleoproductivity (biogenic SiO2, P, Ba), and detrital input (Al2O3, TiO2) to determine the dominant environmental conditions during deposition. The Kreyenhagen Formation was correlated across 72 wells over a 4600 km2 (1776 mi2) area, which revealed an eastward thinning from 335 m (1100 ft) to less than 183 m (600 ft). We identified three informal members on the basis of log response and bulk/trace geochemistry: a lower calcareous silty mudstone, a middle organic-rich clayey mudstone, and an upper siliceous silty mudstone. Spatially, the greatest enrichment of total organic carbon, redox proxies, and biogenic silica occurs along Kettleman North Dome. These properties decrease eastward as clay volume, titanium, and aluminum increase. We interpret the Kreyenhagen Formation to record one transgressive-regressive cycle with contemporaneous climatic cooling: a transgression with initial suboxia and calcareous plankton productivity, a highstand with anoxic-euxinic benthic conditions and clastic starvation, and regression with elevated biogenic silica input. The upward transition from a calcareous to siliceous composition may reflect known cooling and upwelling intensification on the middle Eocene California margin. Mo/U and Th/U patterns suggest variable redox conditions across space and time. Lateral compositional trends indicate that eastern areas were proximal to a Sierran clastic sediment source, while western areas were distal and more anoxic.
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Blake, Gregg H. "Relationship of organic carbon deposition in the Monterey Formation to the Monterey excursion event based on an updated chronostratigraphic framework of the Naples Beach section, California." In Understanding the Monterey Formation and Similar Biosiliceous Units across Space and Time. Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.2556(07).
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ABSTRACT The Monterey Formation, consisting of siliceous and calcareous biogenic sediments, was deposited during the transition from a relatively warm greenhouse climate in the early Miocene to the cooler temperatures of icehouse climatic conditions during the early middle to late Miocene. This cooling event was associated with global paleoclimatic and oceanic changes assumed to be related to the deposition of organic carbon–rich sediments into the marginal basins of California. This chapter introduces an age model for the Miocene strata at Naples Beach based on a composite stratigraphic section and standardized data set, providing the framework for the integration of biostratigraphic zones with a series of astronomically tuned siliceous and calcareous microfossil bioevents, an updated strontium isotope stratigraphy, new tephrochronology ages, and ages from specific magnetostratigraphic units. This multidisciplinary approach, utilizing the integration of microfossil disciplines with independent age controls, is critical to obtaining an age resolution of ~200 k.y. for the majority of the Monterey Formation section. This chronostratigraphic framework improves the age control of the boundaries between the California benthic foraminiferal stages and provides more age refinement for the possible hiatus and condensed interval within the Carbonaceous Marl member of the Monterey Formation. The recalibrated ages for the tops of the Miocene benthic foraminiferal stages are Saucesian (ca. 17.4 Ma), Relizian (15.9 Ma), Luisian (13.1 Ma), and Mohnian (7.7 Ma). Also, the time missing in the hiatus between the Luisian and Mohnian is <200 k.y., and the duration of the condensed interval is from 13.0 to 11 Ma. This refined age model provides a correlation of the organic carbon–rich intervals occurring in the Luisian and lower Mohnian stages within the Naples Beach strata to the deep-sea δ13C maxima events CM5 (ca. 14.7 Ma) and CM6 (ca. 13.6 Ma), suggesting episodic increases in organic carbon deposition along the continental margins coincided with the Miocene carbon isotope excursion found in deep-sea cores. The transition from the Miocene climatic optimum to the icehouse world consisted of four climatic and oceanic phases (from ca. 17.5 to ca. 7 Ma), which are represented in the onshore section by variations in the organic carbon and phosphate contents, the occurrence of calcareous and siliceous lithologic facies, and the distribution of microfossils, especially changes in the benthic foraminiferal assemblages.
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Pörtner, Hans-O., and Magda Gutowska. "Effects of Ocean Acidification on Nektonic Organisms." In Ocean Acidification. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199591091.003.0013.
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The average surface-ocean pH is reported to have declined by more than 0.1 units from the pre-industrial level ( Orr et al. 2005 ), and is projected to decrease by another 0.14 to 0.35 units by the end of this century, due to anthropogenic CO2 emissions (Caldeira and Wickett 2005 ; see also Chapters 3 and 14). These global-scale predictions deal with average surface-ocean values, but coastal regions are not well represented because of a lack of data, complexities of nearshore circulation processes, and spatially coarse model resolution (Fabry et al. 2008 ; Chapter 3 ). The carbonate chemistry of coastal waters and of deeper water layers can be substantially different from that in surface water of offshore regions. For instance, Frankignoulle et al. ( 1998 ) reported pCO2 (note 1) levels ranging from 500 to 9400 μatm in estuarine embayments (inner estuaries) and up to 1330 μatm in river plumes at sea (outer estuaries) in Europe. Zhai et al. (2005) reported pCO2 values of > 4000 μatm in the Pearl River Estuary, which drains into the South China Sea. Similarly, oxygen minimum layers show elevated pCO2 levels, associated with the degree of hypoxia (Millero 1996). These findings suggest that some coastal and mid-water animals, both pelagic and benthic, are regularly experiencing hypercapnic hypercapnic conditions (i.e. elevated pCO2 levels), that reach beyond those projected in the offshore surface ocean. These organisms might, therefore, be preadapted to relatively high ambient pCO2 levels. The anthropogenic signal will nonetheless be superimposed on the pre-existing natural variability. These phenomena lead to the question of whether future changes in the ocean’s carbonate chemistry pose a serious problem for marine organisms. Those with calcareous skeletons or shells, such as corals and some plankton, have been at the centre of scientific interest. However, elevated CO2 levels may also have detrimental effects on the survival, growth, and physiology of marine animals more generally (Pörtner and Reipschläger 1996; Seibel and Fabry 2003; Fabry et al. 2008; Pörtner 2008; Melzner et al. 2009a).
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Bradley, Mark A., L. Page Anderson, Nathan Eck, and Kevin D. Creel. "Chapter 16: Giant Carlin-Type Gold Deposits of the Cortez District, Lander and Eureka Counties, Nevada." In Geology of the World’s Major Gold Deposits and Provinces, 335–53. Society of Economic Geologists, 2020. http://dx.doi.org/10.5382/sp.23.16.
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Abstract The Cortez district is in one of the four major Carlin-type gold deposit trends in the Great Basin province of Nevada and contains three giant (>10 Moz) gold orebodies: Pipeline, Cortez Hills, and Goldrush, including the recently discovered Fourmile extension of the Goldrush deposit. The district has produced >21 Moz (653 t) of gold and contains an additional 26 Moz (809 t) in reserves and resources. The Carlin-type deposits occur in two large structural windows (Gold Acres and Cortez) of Ordovician through Devonian shelf- and slope-facies carbonate rocks exposed through deformed, time-equivalent lower Paleozoic siliciclastic rocks of the overlying Roberts Mountains thrust plate. Juxtaposition of these contrasting Paleozoic strata occurred during the late Paleozoic Antler orogeny along the Roberts Mountains thrust. Both upper and lower plate sequences were further deformed by Mesozoic compressional events. Regional extension, commencing in the Eocene, opened high- and low-angle structural conduits for mineralizing solutions and resulted in gold deposition in reactive carbonate units in structural traps, including antiforms and fault-propagated folds. The Pipeline and Cortez Hills deposits are located adjacent to the Cretaceous Gold Acres and Jurassic Mill Canyon granodioritic stocks, respectively; although these stocks are genetically unrelated to the later Carlin-type mineralization event, their thermal metamorphic aureoles may have influenced ground preparation for later gold deposition. Widespread decarbonatization, argillization, and silicification of the carbonate host rocks accompanied gold mineralization, with gold precipitated within As-rich rims on fine-grained pyrite. Pipeline and Cortez Hills also display deep supergene oxidation of the hypogene sulfide mineralization. Carlin-type mineralization in the district is believed to have been initiated in the late Eocene (>35 Ma) based on the age of late- to postmineral rhyolite dikes at Cortez Hills. The Carlin-type gold deposits in the district share common structural, stratigraphic, alteration, and ore mineralogic characteristics that reflect common modes of orebody formation. Ore-forming fluids were channeled along both low-angle structures (Pipeline, Goldrush/Fourmile) and high-angle features (Cortez Hills), and gold mineralization was deposited in Late Ordovician through Devonian limestone, limy mudstone, and calcareous siltstone. The Carlin-type gold fluids are interpreted to be low-salinity (2–3 wt % NaCl equiv), low-temperature (220°–270°C), and weakly acidic, analogous to those in other Carlin-type gold deposits in the Great Basin. The observed characteristics of the Cortez Carlin-type gold deposits are consistent with the recently proposed deep magmatic genetic model. Although the deposits occur over a wide geographic area in the district, it is possible that they initially formed in greater proximity to each other and were then spatially separated during Miocene and post-Miocene regional extension.
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Beauchamp, Benoit, Charles M. Henderson, Elinda Dehari, Daniela Waldbott Von Bassenheim, Sean Elliot, and Daniel Calvo González. "Carbonate Sedimentology and Conodont Biostratigraphy of Late Pennsylvanian–Early Permian Stratigraphic Sequences, Carlin Canyon, Nevada: New Insights into the Tectonic and Oceanographic Significance of an Iconic Succession of the Basin and Range." In Late Paleozoic and Early Mesozoic Tectonostratigraphy and Biostratigraphy of Western Pangea, 34–71. SEPM (Society for Sedimentary Geology), 2022. http://dx.doi.org/10.2110/sepmsp.113.14.
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The Gzhelian (Upper Pennsylvanian) to Kungurian (Lower Permian) succession around Carlin Canyon, northern Nevada, in the Basin and Range province of the western USA is a relatively undeformed wedge of fossiliferous marine carbonate and fine-grained calcareous and cherty clastic rocks that rests with profound angular unconformity on Mississippian to mid-Pennsylvanian sedimentary rocks that had been uplifted, faulted, folded, and eroded prior to the Late Pennsylvanian transgression. This wedge of sediments, which tapers over less than 2 km from 1341 m in the west to 588 m in the east, comprises the Strathearn, Buckskin Mountain, and lower part of the Beacon Flat formations. These units form a second-order sequence within which five third-order unconformity-bounded transgressive–regressive sequences are nested. These sequences are Gzhelian, early to late Asselian, latest Asselian to late Sakmarian, latest Sakmarian to late Artinskian, and latest Artinskian to late Kungurian in age based on the determination and biostratigraphic interpretation of 26 conodont taxa, including two new species (Adetognathus carlinensis n. sp. and Sweetognathus trexleri n. sp.). Each sequence records sedimentation on a westward-dipping ramp along which significant facies change occurs with inner-ramp coarse-grained algal and bioclastic photozoan grainstone to the east passing westward into mid- to outer-ramp heterozoan carbonate, and ultimately into deep-water fine-grained mixed clastic–carbonate facies with no fossils except sponge spicules, representing deep-water sedimentation in a basinal area that underwent repeated episodes of rapid subsidence associated with each sequence. Accommodation during sedimentation of Gzhelian–Kungurian sequences around Carlin Canyon was repeatedly created in response to flexural subsidence caused by tectonic loading west of the study area. Each sequence recorded the simultaneous foundering of the basinal area in the west and uplift of the basin margin in the east. Individual sequences overlap the underlying sequence to the east, while flexural subsidence from the Gzhelian to the earliest Artinskian led to a basin in the west that became deeper over time. A lull in tectonic activity associated with each sequence allowed carbonates to prograde from east to west, partially filling the basinal area until the early Artinskian, and completely filling it to sea level during the late Artinskian and then again in the late Kungurian. The Gzhelian–Kungurian carbonate succession of the Carlin Canyon area bears much resemblance with the coeval succession that occurs all along the northwest margin of Pangea, from Nevada in the south to the Canadian Arctic islands in the north, and down from the Barents Sea to the central Urals to the east. That broad area was affected by the same oceanographic events, the most significant of which was the earliest Sakmarian closure of the Uralian seaway, which prevented warm water from the Tethys Ocean from reaching the northwestern Pangea margin as it did before; this led to much cooler oceanic conditions all along western North America, even in the low tropical paleolatitudes where northern Nevada was located, in spite of a globally warming climate following the end of the late Paleozoic ice age.
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Sheppard, Charles. "3. The architects of a reef." In Coral Reefs: A Very Short Introduction, 20–41. Oxford University Press, 2021. http://dx.doi.org/10.1093/actrade/9780198869825.003.0003.
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Coral reefs are tropical ecosystems but show global patterns. The Caribbean has about 60 reef-building coral species, while Southeast Asia has nearly 1,000, this number broadly diminishing with distance east and west from the Southeast Asian region. Diversity of corals also diminishes broadly with distance north and south of the equator. While basic patterns exist, there are several kinds of reef in the same sense that there are different kinds of forests, sometimes forming near-monocultures, sometimes with more diverse mixtures of species. Their key to success is that they house vast numbers of captive dinoflagellates that photosynthesize in a close symbiosis, which explains how these complex ecosystems persist in the absence of substantial fields of large, visible seaweeds. All deposit limestone in its aragonite form, in a way characteristic to each species, which has been used for distinguishing between species. The basic unit of a coral, the polyp, reproduces sexually, but more importantly by asexual budding, which allows for the growth of large colonies of polyps, all clones. Numerous other organisms have crucial associations with the coral polyp: bacteria and archaea especially, the whole forming what is now termed the coral holobiont. Aside from photosynthesis, corals have nematocysts in their tentacles to capture zooplankton food. Corals compete for space using these stinging cells also, amongst other methods. On any reef, soft corals are numerous, especially in the Caribbean, though these do not deposit limestone rock. Calcareous algae are crucial reef-building components too, particularly in the shallows.
Conference papers on the topic "Calcareous units"
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Olua, D. T. "Miocene Turbidite Sequence as Potential Reservoir and Source Rock Of Mamberamo Basin: An Insight From Fieldwork in Metaweja Area, Central Mamberamo District, Papua." In Indonesian Petroleum Association 44th Annual Convention and Exhibition. Indonesian Petroleum Association, 2021. http://dx.doi.org/10.29118/ipa21-sg-247.
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The geology of the Metaweja area is characterized by the turbidite sequence which are deposited in the deep-sea environment during the Miocene and exposed to surface due to the latest deformation. The research was conducted to identify the potential source rock and reservoir rock within the turbidite deposits. In the study area, there are three types of rock units, calcareous shale units formed in the Late Miocene, Sandstone unit and interbedded siltstone-sandstone unit that were deposited in Middle Miocene. Measured section was carried out at the several stations in order to analyze the turbid current deposition mechanism. Measured section of the alternating unit of sandstone - siltstone are observed at several places where the unit has intercalation of shale, coal and iron oxide. Some syn-depositional sedimentary structure also found within this unit. The carbonate shale unit has good total organic content (TOC) ranging from 0.51wt% to 2.56wt%. Pyrolysis analysis has S2 value 1.31 mg/g to 1.34 mg/g, Hydrogen Index (HI) 35 mgHC/g to 49 mgHC/g, Oxygen Index (OI) 35 mgHC/g to 49 mgHC/g, Tmax 430 °C to 434 °C and Vitrinite Reflecteance index (Ro) 0.32% to 0.54%. The carbonate shale characterized as the type III kerogen which prone gas source rock and interpreted as immature to early mature source rock. The petrography analysis of alternating rocks of sandstone - siltstone has characteristics of sandstones with 44% of volcanic lithic fragment composition, 20% matrix 10% clay size fragments, secondary porosity reaches 10% and 13% cement carbonate calcite. Based on the petrography analysis, this unit could be interpreted as reservoir rock, although we need further analysis for the Permeability measurement.
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Gaspersz, Gabriela C. N., Vijaya Isnaniawardhani, Santi Dwi Pratiwi, and Lilian C. Rieuwpassa. "Miocene Planktonic Foraminifera of Calcareous Sandstone Unit in Pamutuan Formation West Java, Indonesia." In The International Conference of Geological Engineering Faculty Universitas Padjarajan. The International Institue of Knowledge Management (TIIKM), 2021. http://dx.doi.org/10.17501/27838625.2020.1101.
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Fawzy, Mahmoud, Rasha Al-Morakhi, Riyad Quttainah, Mahmoud Kalawina, Ron Balliet, and Zakaria Swidan. "Unconventional Najmah Reservoir Formation Evaluation in West Kuwait Using an Innovative-Integrated Approach for Productivity and Potential." In SPE Annual Technical Conference and Exhibition. SPE, 2022. http://dx.doi.org/10.2118/210175-ms.
Full textAbstract:
Abstract Abduliyah field is one of the major fields in the West Kuwait asset where the Najmah shale (Kerogen unit) is present. The Najmah shale is a high Kerogen content, calcareous mudstone and is considered the main source rock for shallower depth oil reservoirs in Kuwait, due to the shortage of data especially core data at reservoir condition there is enormous uncertainty in the determination of the unconditional reservoir properties that need to be evaluated to confirm both economic and operational success. An integrated logging approach was implemented using pressurized sidewall rotary coring, magnetic resonance, borehole image logs, conventional logs, and core analysis to assess the Najmah storage volume, and quantify the potential hydrocarbon fluids in place and provide a time and cost-efficient method of reservoir evaluation.
Reports on the topic "Calcareous units"
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Evans, Julie, Kendra Sikes, and Jamie Ratchford. Vegetation classification at Lake Mead National Recreation Area, Mojave National Preserve, Castle Mountains National Monument, and Death Valley National Park: Final report (Revised with Cost Estimate). National Park Service, October 2020. http://dx.doi.org/10.36967/nrr-2279201.
Full textAbstract:
Vegetation inventory and mapping is a process to document the composition, distribution and abundance of vegetation types across the landscape. The National Park Service’s (NPS) Inventory and Monitoring (I&M) program has determined vegetation inventory and mapping to be an important resource for parks; it is one of 12 baseline inventories of natural resources to be completed for all 270 national parks within the NPS I&M program. The Mojave Desert Network Inventory & Monitoring (MOJN I&M) began its process of vegetation inventory in 2009 for four park units as follows: Lake Mead National Recreation Area (LAKE), Mojave National Preserve (MOJA), Castle Mountains National Monument (CAMO), and Death Valley National Park (DEVA). Mapping is a multi-step and multi-year process involving skills and interactions of several parties, including NPS, with a field ecology team, a classification team, and a mapping team. This process allows for compiling existing vegetation data, collecting new data to fill in gaps, and analyzing the data to develop a classification that then informs the mapping. The final products of this process include a vegetation classification, ecological descriptions and field keys of the vegetation types, and geospatial vegetation maps based on the classification. In this report, we present the narrative and results of the sampling and classification effort. In three other associated reports (Evens et al. 2020a, 2020b, 2020c) are the ecological descriptions and field keys. The resulting products of the vegetation mapping efforts are, or will be, presented in separate reports: mapping at LAKE was completed in 2016, mapping at MOJA and CAMO will be completed in 2020, and mapping at DEVA will occur in 2021. The California Native Plant Society (CNPS) and NatureServe, the classification team, have completed the vegetation classification for these four park units, with field keys and descriptions of the vegetation types developed at the alliance level per the U.S. National Vegetation Classification (USNVC). We have compiled approximately 9,000 existing and new vegetation data records into digital databases in Microsoft Access. The resulting classification and descriptions include approximately 105 alliances and landform types, and over 240 associations. CNPS also has assisted the mapping teams during map reconnaissance visits, follow-up on interpreting vegetation patterns, and general support for the geospatial vegetation maps being produced. A variety of alliances and associations occur in the four park units. Per park, the classification represents approximately 50 alliances at LAKE, 65 at MOJA and CAMO, and 85 at DEVA. Several riparian alliances or associations that are somewhat rare (ranked globally as G3) include shrublands of Pluchea sericea, meadow associations with Distichlis spicata and Juncus cooperi, and woodland associations of Salix laevigata and Prosopis pubescens along playas, streams, and springs. Other rare to somewhat rare types (G2 to G3) include shrubland stands with Eriogonum heermannii, Buddleja utahensis, Mortonia utahensis, and Salvia funerea on rocky calcareous slopes that occur sporadically in LAKE to MOJA and DEVA. Types that are globally rare (G1) include the associations of Swallenia alexandrae on sand dunes and Hecastocleis shockleyi on rocky calcareous slopes in DEVA. Two USNVC vegetation groups hold the highest number of alliances: 1) Warm Semi-Desert Shrub & Herb Dry Wash & Colluvial Slope Group (G541) has nine alliances, and 2) Mojave Mid-Elevation Mixed Desert Scrub Group (G296) has thirteen alliances. These two groups contribute significantly to the diversity of vegetation along alluvial washes and mid-elevation transition zones.