What Type Of Particles/sediment Makeup Limestone? What Type Of Particles Make Up Limestone

Rock Fracture and Rock Strength

Zong-Xian Zhang , in Rock Fracture and Blasting, 2016

three.1.3 Sedimentary Stone

Sedimentary rock is formed by sedimentation of cloth at the Earth's surface and inside bodies of water. Particles that class a sedimentary rock past accumulating are called sediment. Before being deposited, sediment was formed by weathering and erosion in a source area, and so transported to the place of deposition past water, wind, mass movement, or glaciers. Some examples of sedimentary rocks are limestone, sandstone, siltstone, shale, conglomerate, and breccia. Most sedimentary rocks contain either quartz or calcite. In contrast with igneous and metamorphic rocks, a sedimentary rock usually contains very few different major minerals, and it has lower strengths and college porosity.

Most sedimentary rocks are considered to be of anisotropy in their physical and mechanic properties due to marked bedding structure, equally shown in Fig. iii.ic. The term anisotropy refers to a measure out of the directional backdrop of a material. However, some sedimentary rocks such as sandstone and limestone can exist considered to exist isotropy. In full general, the physical and mechanical properties in the horizontal direction to a bedding plane are largely dissimilar from those in the vertical direction to the bedding plane. The cement or matrix between grains often determines the mechanical properties of sedimentary rocks. The sedimentary rocks containing clay minerals are especially sensitive to pressure and water. Therefore, h2o can cause a large problem in the stability of a tunnel or an underground structure that is surrounded past sedimentary rock containing some clay minerals.

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Sediments, Diagenesis, and Sedimentary Rocks

W.B.N. Berry , in Treatise on Geochemistry, 2003

vii.13.1 Introduction

Sedimentary rocks are usually organized into detached strata. The strata are composed of materials, diverse particles of inorganic and/or organic origin, that reflect aspects of the environmental weather condition under which they got accumulated. Sequences of sedimentary-rock layers were seen and studied initially in cliffs, man-made exposures, and sites where the vegetation was not thick enough to obscure the stone layers. Information technology was in mines, even so, that sequences of strata came to be examined closely. Miner'southward observations of the succession of sedimentary rock layers they saw and quarried below the Globe's surface gave nativity to a domain, viz. stratigraphy, and an understanding of sedimentary rocks. Berry (1968, 1987) discusses—from a historical perspective, the geological timescale—how an economic imperative became a significant force in the evolution of chronometry of sedimentary rocks.

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The Oceans and Marine Geochemistry

H.D. Kingdom of the netherlands , in Treatise on Geochemistry, 2007

6.21.four.ii The Mesoproterozoic (1.8–i.2   Ga)

Sedimentary rocks of the McArthur Basin in Northern Australia provide one of the best windows on the chemistry of the Mesoproterozoic bounding main. Some ten  km of 1.7–1.6   Ga sediments accumulated in this intracratonic basin (Southgate et al., 2000). In certain intervals, they contain giant strata-bound Pb–Zn–Ag mineral deposits (Jackson et al., 1987; Jackson and Raiswell, 1991; Crick, 1992). The sediments accept experienced only low-grade metamorphism.

Shen et al. (2002) have reported data for the isotopic composition of sulfur in carbonaceous shales of the lower part of the 1.73–i.72   Ga Wollogorang Formation and in the lower part of the i.64–1.63   Ga Reward Germination of the McArthur Basin. These shales were probably deposited in a euxinic intracratonic basin connected to the open body of water. The δ³⁴S of pyrite in black shales of the Wollogorang Germination ranges from −1‰ to +six.3‰ with a hateful and standard derivation of iv.0±i.9‰ (n=fourteen). Donnelly and Jackson (1988) reported similar values. The δ³⁴Southward values of pyrite in the Lower Reward Formation range from +18.2‰ to +23.4‰ with an boilerplate and standard divergence of 18.4±i.8‰ (n=10). The spread of δ³⁴S values within each formation is relatively small. The sulfur is quite ³⁴South enriched compared to compositions expected from the reduction of seawater sulfate with a δ³⁴Southward of +twenty−25‰ (Strauss, 1993). This is especially true of the sulfides in the Reward Formation. Shen et al. (2002) propose that the Reward data are best explained if the concentration of sulfate in the gimmicky seawater was betwixt 0.five and 2.4   mmol   kg⁻¹. Sulfate concentrations in the Mesoproterozoic ocean well beneath those of the present oceans take also been proposed on the footing of the rapid modify in the value of δ³⁴S in carbonate-associated sulfate of the 1.2   Ga Bylot Supergroup of northeastern Canada (Lyons et al., 2002). Withal, the value of in Mesoproterozoic seawater is still rather uncertain.

Somewhat of a cross-check on the SO_four ²⁻ concentration of seawater can be obtained from the evaporite relics in the McArthur Group (Walker et al., 1977). Up to 40% of the measured sections of the Amelia Dolomite consists of such relics in the class of carbonate pseudomorphs after a variety of morphologies of gypsum and anhydrite crystals, chert pseudomorphs after anhydrite nodules, halite casts, and microscopic remnants of original, unaltered sulfate minerals. Muir (1979) and Jackson et al. (1987) have pointed out the similarity of this germination to the recent sabkhas along the Farsi Gulf coast. The pseudomorphs crosscut sedimentary features such as bedding and laminated microbial mats, suggesting that the original sulfate minerals crystallized in the host sediments during diagenesis.

Pseudomorphs after halite are common throughout the McArthur Group. The halite appears to have formed by near complete evaporation of seawater in shallow marine environments and probably represents ephemeral salt crusts. The full general lack of association of halite and calcium sulfate minerals in these sediments probably resulted in part from the dissolution of previously deposited halite during surface flooding, but too indicates that evaporation did not always proceed beyond the calcium sulfate facies.

This observation allows a crude check on the reasonableness of Shen et al.'s (2002) estimate of the sulfate concentration in seawater during the deposition of the McArthur Group. On evaporating modernistic seawater, gypsum begins to precipitate when the caste of evaporation is ca. 3.8. As shown in Effigy thirteen, the onset of gypsum and/or anhydrite precipitation occurs at progressively greater degrees of evaporation as the product ${\mathrm{1000}}_{{\text{Ca}}^{2+}}{m}_{{\text{Then}}_4^{\mathrm{two}-}}$ in seawater decreases. Today, ${\mathrm{1000}}_{{\text{Ca}}^{2+}}{\mathrm{one\; thousand}}_{{\text{SO}}_4^{2-}}$ =280 (mmol   kg^−one)². If this product is reduced to 23 (mmol   kg⁻ⁱ)^two, anhydrite begins to precipitate simultaneously with halite at a degree of evaporation of 10.viii. The presence of gypsum casts without halite in the sediments of the McArthur Group indicates that in seawater at that time ${\mathrm{yard}}_{{\text{Ca}}^{\mathrm{ii}+}}{m}_{{\text{And then}}_4^{\mathrm{two}-}}$ >23 (mmol   kg⁻¹)², provided the salinity of seawater was the aforementioned as today. If $m_{{\text{So}}_4^{2-}}$ was 2.4   mmol   kg⁻¹, the upper limit suggested by Shen et al. (2002), $m_{{\text{Ca}}^{2+}}$ must so have been >10   mmol   kg⁻ⁱ the concentration of Caⁱⁱ⁺ in modern seawater. An And then₄ ²⁻ concentration of 2.4   mmol   kg⁻¹ is therefore permissible. Sulfate concentrations as low as 0.v   mmol   kg⁻¹ require what are probably unreasonably high concentrations of Caⁱⁱ⁺ in seawater to account for the precipitation of gypsum before halite in the McArthur Grouping sediments.

Figure 13. The relationship between the value of the production ${\mathrm{one\; thousand}}_{{\text{Ca}}^{\mathrm{two}}}+\cdot m_{{\text{SO}}_{\mathrm{four}}^{2-}}$ in seawater and the concentration cistron at which seawater becomes saturated with respect to gypsum at 25   °C and ane   atm (Holland, 1984; Eugster et al., 1980). Reprinted by permission of Princeton University Press from Kingdom of the netherlands (1984). © 1984 Princeton University Press.

The common occurrence of dolomite in the McArthur Group indicates that the $m_{{\text{Mg}}^{2+}}/m_{{\text{Ca}}^{2+}}$ ratio in seawater was >one (see below). This is also indicated by the common occurrence of aragonite as the major principal CaCO₃ phase of sediments on Archean and Proterozoic carbonate platforms (Grotzinger, 1989; Winefield, 2000). Although these hints regarding the composition of Mesoproterozoic seawater are welcome, they demand to be confirmed and expanded by analyses of fluid inclusions in marine calcite cements.

Maybe the most interesting implication of the close association of gypsum, anhydrite, and halite relics in the McArthur Group is that the temperature during the degradation of these minerals was non much higher up 18   °C, the temperature at which gypsum, anhydrite, and halite are stable together (Hardie, 1967). At higher temperatures, anhydrite is the stable calcium sulfate mineral in equilibrium with halite. The coexistence of gypsum and anhydrite with halite suggests that the temperature during their degradation was possibly lower, only probably no higher than in the modern sabkhas of the Western farsi Gulf, where anhydrite is the dominant calcium sulfate mineral in association with halite (Kinsman, 1966).

In their newspaper on the carbonaceous shales of the McArthur Basin, Shen et al. (2002) comment that euxinic weather condition were common in marine-continued basins during the Mesoproterozoic, and they propose that low concentrations of seawater sulfate and reduced levels of atmospheric oxygen at this time are compatible with euxinic deep ocean waters. Anbar and Knoll (2002) echo this sentiment. They betoken out that biologically of import trace metals would and so have been scarce in almost marine environments, potentially restricting the nitrogen bike, affecting primary productivity, and limiting the ecological distribution of eukaryotic algae. However, some of the before long available evidence does not support the notion of a Mesoproterozoic euxinic body of water flooring. Figure 14 shows that the redox-sensitive elements Mo, U, and Re are well correlated with the organic carbon content of carbonaceous shales in the McArthur Basin. The slope of the correlation lines is close to that in many Phanerozoic black shales, suggesting that the concentration of these elements in McArthur Basin seawater was comparable to their concentration in modern seawater. Preliminary data for the isotopic composition of Mo in the Wollogorang Germination of the McArthur Basin (Arnold et al., 2002) propose somewhat more extensive sulfidic deposition of Mo in the Mesoproterozoic than in the modern oceans. Their data may, nevertheless, reflect a greater extent of shallow water euxinic basins rather than an entirely euxinic ocean flooring. Additional information for the concentration of redox-sensitive elements in carbonaceous shales and more data for the isotopic limerick of Mo and perhaps of Cu in carbonaceous shales will probably analyze and peradventure settle the questions surrounding the redox state of the deep body of water during the Mesoproterozoic (Poulson et al., 2006).

Figure 14. The concentration of Mo, U, and Re in carbonaceous shales: McArthur Bowl, Australia, 1.half dozen   Ga; Finland and Gabon, ii.15–2.0   Ga; South Africa, ≥2.3   Ga.

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Sedimentary: Phosphates☆

Shamim A. Dar , ... W.D. Birch , in Reference Module in Earth Systems and Environmental Sciences, 2017

Distinguishing Characteristics

Phosphate-rich sedimentary rocks may occur in layers ranging from thin laminae a few millimeters thick to beds a few meters thick. Some phosphate successions such as the Phosphoria Germination of the Idaho-Wyoming area may reach several hundred meters in thickness, although such successions are non composed entirely of phosphate-rich rocks. Phosphorites are more often than not interbedded with shales, cherts, limestones, dolomites, and, more rarely, sandstones. Phosphatic rocks commonly course regionally into nonphosphatic sedimentary rocks of the same age. Phosphorites take textures that resemble those in limestones. Thus, they may exist fabricated upwards of peloids, ooids, fossils (bioclasts), and clasts that are at present composed of apatite. Some phosphorites lack distinctive granular textures and are equanimous instead of fine, micrite-like, textureless collophane. The phosphatic grains may incorporate inclusions of organic matter, clay minerals, silt-size detrital grains, and pyrite. Peloidal or pelletal phosphorites are specially common; oolitic phosphorites are somewhat less and so. Phosphatized fossils or fragments of original phosphatic shells are important constituents of some deposits. Virtually phosphorite grains are sand size, although particles greater than 2  mm may be present. These larger grains, referred to as nodules, tin can range in size to several tens of centimeters. Considering the textures of phosphorites have such close resemblance to those of limestones, some geologists suggest using modified limestone classifications to distinguish unlike kinds of phosphorites. For example, Slansky (1986) advocates using a classification system based to some extent on Folk'south (1962) limestone classification, and Cook and Shergold (1986b) and Trappe (2001) suggest adapting Dunham's 1962 carbonate classification (modified by Embry and Klovan, 1971) for employ in describing phosphorites. Using these modified classifications thus yields names such as wackestone phosphorite (Cook and Shergold) and phosdast wackestone (Trappe).

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The Oceans and Marine Geochemistry

T.I. Eglinton , D.J. Repeta , in Treatise on Geochemistry, 2003

6.06.2.2.1 Terrigenous organic matter fluxes to the oceans

OC fluxes from sedimentary rock weathering on state are not well constrained just on geological timescales are believed to match OC burial in sediments (Berner, 1989). Superimposed on this background of relict OC from sedimentary rock weathering are fluxes associated with terrestrial primary production. The global rate of net terrestrial photosynthesis is estimated to be in the range of 60   Gt   twelvemonth⁻¹ (Mail service, 1993). Approximately two-thirds of the resulting full plant litter is oxidized rapidly to CO₂ (Post, 1993), while the remainder enters the soil cycle and is subject to further oxidation. Organic matter pools inside soils exhibit different reactivities and turnover times that range from decades to millenia (Torn et al., 1997). Over geologic timescales, all the same, the pervasive and continuous oxidative degradation and leaching and erosion processes on the continents event in little long-term storage of organic matter on the continents (Hedges et al., 1997). All the same, some fraction of this terrestrial (vascular plant-derived) OC and sedimentary rock-derived (relict) OC escapes oxidation and is delivered to the oceans. The delivery of terrigenous OC to the oceans is primarily via riverine or atmospheric (eolian) processes.

Riverine fluxes. Approximately 0.2   Gt each of dissolved and particulate OC are carried from land to sea annually by rivers (Ludwig et al., 1996). Much of this riverine organic matter appears to be soil derived based on its chemical characteristics (Meybeck, 1982; Hedges et al., 1994), although autochthonous sources may be of import for the dissolved fraction (Repeta et al., 2002). It is now recognized that, on a global basis, riverine belch is dominated past low-latitude tropical rivers. This non but includes major systems such as the Amazon, and Congo, but also includes the numerous smaller rivers draining mountainous tropical regions (Nittrouer et al., 1995), most notably in Papua New Guinea and other parts of Oceania, which are estimated to business relationship for most l% of the global flux of river sediment to the oceans (Milliman and Syvitski, 1992). During the present-day high sea-level stand, much of the particulate OC associated with riverine discharge is trapped and buried on continental shelves (Berner, 1982; Hedges, 1992). Nevertheless, some rivers discharge much of their terrestrial OC load across the shelf due either to turbidity flows down submarine canyons (e.g., Congo, Ganges, Brahmaputra), to the presence of a narrow shelf (east.g., on the eastern flank of Papua New Guinea), or the influence of ice-rafting equally an additional mode of sediment entrainment and export on polar margins (e.g., Macdonald et al., 1998).

Eolian fluxes.Eolian fluxes of organic matter from country to ocean are much less well constrained than riverine inputs. They have been estimated to be <0.one   Gt   year⁻¹ (Romankevich, 1984). While these flux estimates imply lesser importance of eolian inputs compared to riverine OC contributions, this way of delivery may be pregnant in a regional context. In detail, marine locations downwind from major grit sources (principally in eastern asia and western Africa) are influenced greatly by eolian inputs of OC and other detrital components. In improver, eolian ship can deliver terrigenous materials to remote locations of the oceans, far from the influence of rivers. For such regions (eastward.g., primal equatorial Pacific Ocean) eolian OC fluxes may exist important both in terms of POM in the water cavalcade and underlying sediments (Gagosian and Peltzer, 1986; Zafiriou et al., 1985; Prospero et al., 2003; Eglinton et al., 2002).

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Microbial transformations of organic matter in blackness shales and implications for global biogeochemical cycles

South.T. Petsch , ... T.I. Eglinton , in Geobiology: Objectives, Concepts, Perspectives, 2005

2 Clay Metropolis, Kentucky: the field site

Late Devonian marine sedimentary rocks outcrop as a v- to 10-km-wide band extending ~300 km around the edge of the Jessamine Dome in cardinal Kentucky. Amongst these rocks are successions of finely laminated pyritic black shales upwardly of thirty g thick, termed the New Albany, Chattanooga and Ohio Shales (in the w, s, and northeast portions of Kentucky, respectively). In Powell Canton, approximately 50 km ESE of Lexington (KY), a suite of road cuts through these Late Devonian black shales is located almost the town of Clay City. One particular road cut has been the focus of much attention due to the obvious and well-developed weathering profile exposed ( Fig. 1). A well-developed, vertical weathering forepart into this black shale was exposed ~40 years ago (individual landowner, personal advice) when the hillside was excavated to enlarge the roadway and provide fill for construction. The exposed weathering profile exhibits a distinctly lighter brown colour and a friable unconsolidated physical texture compared with unweathered rock in the center of the roadcut. This weathered fabric is not the upshot of degradation of soil from upslope considering individual stone strata are discernibly continuous in horizontal layers extending from unweathered rock through the weathering profile. Our efforts have focused on evaluating the chemical and microbiological variations associated with color and textural changes within this and other black shale weathering profiles.

Fig. 1. Exposure of ~iv m thick black shale weathering profile in roadcut through L. Devonian black shale well-nigh Clay City, Kentucky, U.s.a..

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Lime

Robert 50. Zimdahl , in Six Chemicals That Inverse Agriculture, 2015

Agronomical Lime

Limestone is a sedimentary rock composed of different crystal forms of calcium carbonate (CaCO₃). It is virtually 10% of all sedimentary rock. Near besides contains skeletal fragments of marine organisms. Historic uses of limestone included mortar and pulverized limestone used to neutralize acidic soils. Burnt lime (CaO, quicklime) is made by the thermal decomposition of naturally occurring things that incorporate CaCO₃ (e.g., limestone, seashells), When calcium carbonate is heating above 825°C (1517°F), calcination or lime-burning liberates carbon dioxide and producing quicklime. ¹

CaCO₃(s) → CaO(s)   +   CO_ii(thou)

The chief agronomical employ was and is to raise soil pH. There is no reliable record of when lime was kickoff used as a soil amendment. Lime mortar dated 15,000 to 7000   years BCE has been recovered from terrazzo floors in Turkey. Limestone was used to build portions of the Cracking Wall of China and the Great Pyramid of Giza, Egypt. Lime has many other uses:

calcium supplement for brute feeds;

structure amass every bit a roadway base;

manufacturing of some kinds of glass;

additive to paper, plastics, paint, tiles, and other materials every bit both white pigment and a cheap filler;

toothpaste;

food supplement every bit a source of calcium; and an

condiment to some pharmaceuticals and cosmetics.

The world's soils vary in color, texture, structure, and chemical, concrete, and biological composition. It is reasonable to claim that soil is 1 of the most important things on the earth. It is unquestionably essential to agronomics. Soil is the medium in which food is grown. It is not, as many think, just clay. Soils are not compatible, although they may appear to be, particularly at the local level, but in reality they tin be very different within a few anxiety. The multifariousness of soils is the result of five soil-forming factors. ^two Each spans a continuum, which results in their beingness thousands of different soils in the world.

ane.

Climate. The amount, intensity, and timing of precipitation influence soil formation. Seasonal and daily changes in temperature bear on moisture, weathering, and leaching. Air current (erosion) redistributes sand and other particles. Seasonal and daily changes in temperature determine rainfall's role, its effects, the rate of biological action and chemic reactions, and the resulting vegetation.

2.

Biology. Plants, animals, microorganisms, and humans, independently and collectively, affect soil formation. Plant roots open up channels in soil, taproots penetrate deeply gristly roots near the surface easily decompose and add organic affair. Animals and microorganisms mix soils. Microorganisms bear on chemical exchanges between roots and soil. Humans mix soil, oft extensively, and abound the plants they want.

3.

Landscape position, topography. Slope and directional orientation touch soil moisture and temperature. Steep slopes facing the sun are warmer. Slopes may lose topsoil equally they form and exist thinner than well-nigh level soils that receive deposits from areas higher up.

iv.

Parent cloth. Well-nigh soil has been created from materials that have moved in from miles or only a few feet abroad. Loess, an aeolian (windblown) sediment, is common in the good soils of the midwestern United States and some parts of China. It is formed by the gradual accumulation of air current-diddled silt (20–50   μm particles) and has 20% or less clay. Loess soils are typically near neutral pH.

5.

Time. Soil formation is continuous. Over time, soils exhibit features that reflect the other forming factors.

The primary, if non the only, reason agricultural lime (CaCO_iii) is added to soil is to raise soil pH toward neutrality (7.0), thereby reducing soil acerbity, increasing food availability, and permitting successful growth of many crops that are pH sensitive. pH is an abbreviation for potential hydrogen. It is the negative logarithm (base 10) of the reciprocal of the hydrogen ion concentration in gram atoms/liter of water. It indicates hydrogen ion activeness. It defines acerbity or basicity (pH aq) of a solution on a scale from 0 to 14. Seven is neutral; below is acidic and above is bones. That means that for each unit pH increases or decreases, basicity or acidity changes by 10 times. A pH of 5 is 10 times more acidic than pH 6 and 100 times more acidic than pH 7.

Because pH controls many soil chemical processes and the chemical form of nutrients, it may enable or inhibit their uptake. Acid soils (below pH v.5) have greatly reduced microbial activeness, but release many nutrients, notably atomic number 26, which is much less bachelor above pH 7.v. Soils with pH lower than 4.half-dozen are besides acidic for virtually plants. Many soils are naturally calcareous ⁱⁱⁱ (pH to a higher place seven). In some cases, sulfur can be added to brand them more acidic through formation of sulfuric acrid (H_twoSO₄), hydrogen sulfite (HSO₃), and hydrogen sulfide (H_iiS). At a pH above 7, carbonates and oxides are formed and can react with many metallic nutrient elements (e.g., atomic number 26, copper, molybdenum), which renders them insoluble and therefore unavailable to plants. Most crops exercise non grow well in acidic soil or soil with a pH above eight. Raising the pH of acidic soil improves plant growth, may ameliorate h2o penetration, and reduce aluminum toxicity. Lime is a source of calcium and magnesium for plants. Because it is high in calcium, it tin can likewise be beneficial to bone growth of foraging animals.

Soils in high rainfall areas become acidic through leaching. Crop growth and livestock grazing remove essential nutrients over time and soil may gradually go acidic. Chemical fertilizers required to accomplish maximum yield are major contributors to soil acerbity. Therefore, liming acidic soil is essential to attain maximum yield of nutrient crops grown in acidic soils.

In areas of extreme rainfall and high temperature, ⁴ clays and humus may be leached away, which further reduces soil's buffering capacity (i.due east., resistance to changes in pH). In low-rainfall areas, unleached calcium may raise pH to 8.5 and if exchangeable sodium levels are high, soil pH may reach x. To a higher place pH 9, about food crops will non grow or their growth and yield will exist severely reduced. High pH also results in low micronutrient mobility and availability.

The desirable (optimum) pH range for most food crops is v–7. Every ingather has an optimum pH range within which production potential peaks. No important food crops take an optimum pH less than five. Rye, oats, and lupins are acid-tolerant. The optimum for corn and soybeans is 5–seven.5. The almost important food crops (beans, rice, and wheat) take an optimum pH between five and 7. They are acrid sensitive. The ten virtually important nutrient crops—the plants that feed the world—all grow best between pH v.5 and 6.5 (see Table 3.1). Potatoes, an exception, grow when soil pH is 4.8–v.5, although they grow well above pH five.five. Many plants, but not the important food crops, accept adapted to thrive at pH values outside the optimum range, merely do best within the optimum.

Table three.1. Optimum pH Range for Some Food Plants ^a

pH Range
5.0–5.5	5.eight–half-dozen.5	6.5–7.0
Blueberries	Edible bean X	Alfalfa
White potato 10	Cassava X	Barley X
Sweetness white potato X	Corn/maize 10	Carmine
Grasses Ten	Grapes
Millet X	Soybean Ten
Oats	Sugarbeet
Rice X	Wheat Ten
Rye
Some clovers
Sorghum X
Tomato plant
Watermelon

a

12 of the globe's most of import nutrient crops are indicated with X.

Well-nigh xxx% as much phosphorus is available when pH is beneath 6 versus above 6.5. Nitrogen and potassium become less bachelor beneath six. Availability of both decreases by about thirty% at pH 5.5 and 70% at five. Below pH 5, soil nitrogen, phosphorus, and potassium concentrations may exist acceptable to support plant growth, but, because of formation of insoluble minerals, they are unavailable and of piffling use to plants. In contrast, iron, copper, manganese, and zinc are most available when pH is acidic. It seems contradictory, but when pH is effectually four, other nutrient levels may exist high considering lack of plant uptake leads to their aggregating in soil.

The nearly effective mode to raise pH is to use proficient-quality, finely ground agronomical lime. Lime'due south calcium and/or magnesium carbonate content and the fineness of grinding decide quality. Finely ground lime will enhance soil pH more apace. Incorporating information technology in soil is more efficient than surface application. Change in pH is more rapid when soil is moist from irrigation or rainfall; water is required for the chemical reaction. Action (pH change) may have a twelvemonth or more in dry out soil. However, with good soil moisture, a response may be observed within weeks if pH is extremely low. When pH is low, information technology is important to apply lime immediately afterwards the growing flavor to allow sufficient reaction time before the side by side crop is planted.

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Meteorites, Comets, and Planets

R.Due north. Clayton , in Treatise on Geochemistry, 2003

1.06.2.ii.1 Primitive nebular materials

Chondritic meteorites are sedimentary rocks composed primarily of chondrules, typically sub-millimeter-sized spherules believed to take been molten aerosol in the solar nebula, formed by melting of dust in a brief, local heating event. During the high-temperature stage, with a duration of some hours, the droplets could interact chemically and undergo isotopic exchange with the surrounding gas. Thus, isotopic analyses of individual chondrules tin can provide information about both the dust and gas components of the nebula. Figure 2 shows oxygen isotopic compositions of chondrules from the three major groups—ordinary (O), carbonaceous (C), and enstatite (Eastward) chondrites—and i minor group—Rumuruti-blazon (R)-chondrites. The 3-isotope graph has two useful backdrop: (i) samples related to one another by ordinary mass-dependent isotopic fractionation prevarication on a line of gradient=0.52, similar the line labeled terrestrial fractionation (TF), and (ii) samples that are 2-component mixtures lie on a direct line connecting the compositions of the end-members.

Figure 2. Oxygen isotopic compositions of chondrules from all classes of chondritic meteorites: ordinary (O), enstatite (E), carbonaceous (C), and Rumuruti-type (R). The TF line and carbonaceous chondrite anhydrous mineral (CCAM) line are shown for reference in this and many subsequent figures. Equations for these lines are: TF—δ¹⁷=0.52δ^xviii and CCAM—δ¹⁷=0.941δ¹⁸−four.00 (sources Clayton et al., 1983, 1984, 1991; Weisberg et al., 1991).

Figure 2 shows that chondrule compositions do non prevarication on a mass-dependent fractionation line, thus indicating isotopic heterogeneity in the nebula. Chondrules from dissimilar chondrite classes occupy different regions of the diagram, and for each course, they class near-linear arrays that are considerably steeper than a mass-dependent fractionation line. For comparison, it tin can be noted that coordinating three-isotope graphs for fe in diverse meteorite types are strictly mass dependent, and prove no evidence for nebular heterogeneity (Zhu et al., 2001).

Another grouping of primitive objects with a direct link to the solar nebula are the calcium–aluminum-rich inclusions (CAIs), that range in size from a few μm to >i cm (see Chapter one.08). They are found in all types of primitive chondrites just are rare in all but the CV carbonaceous chondrites. Their bulk chemical compositions correspond to the most refractory five% of condensable solar affair (Grossman, 1973). They may represent direct condensates from the nebular gas, followed, in many cases, past further chemical and isotopic interaction with the gas. Their radiometric ages have been measured with high precision (Allègre et al., 1995), and signal solidification earlier than any other solar arrangement rocks (excluding the presolar dust grains). Thus, the oxygen isotope abundances in CAIs may provide the best guide to the composition of the nebular gas.

CAIs exhibit a specific, characteristic pattern of oxygen isotope abundances. Within an individual CAI, different minerals have dissimilar isotopic compositions, with all data points falling on a straight line in the three-isotope graph. This beliefs is illustrated in Effigy three, based on analyses of physically separated minerals from the Allende (CV3) carbonaceous chondrite (Clayton et al., 1977). Each analysis represents a large number of grains. Effigy 4 shows data obtained by ion microprobe analysis, where each bespeak represents only one grain (Aléon et al., 2002; Fagan et al., 2002; Itoh et al., 2002; Jones et al., 2002; Krot et al., 2002). The line labeled "CCAM" is the same in Figures three and 4. Although the ion microprobe data take larger analytical uncertainties, leading to greater scatter in the data, information technology is clear that the aforementioned blueprint exists at both the microscopic and macroscopic level. Within private CAIs, the sequence of isotopic composition, in terms of ^xviO-enrichment, is spinel≧pyroxene>olivine>melilite=anorthite. A straight line on the three-isotope graph is indicative of some sort of 2-component mixture. The fact that the range of variation in the individual-grain studies is well-nigh the same as the range in the bulk-sample studies shows that the end-members do non lie much across the observed range of variation. All studies, every bit of early 2003, reveal an ¹⁶O-rich end-member nearly −45‰ for both δ¹⁷O and δ¹⁸O, frequently represented by spinel, the most refractory of the CAI phases. The virtually obvious interpretation is that this cease-fellow member represents the limerick of the primary nebular gas, from which the CAIs originally condensed. Subsequent reaction and isotopic exchange with an isotopically modified gas could then yield the observed heterogeneities on a micrometer to millimeter calibration (Clayton et al., 1977; Clayton, 2002).

Effigy 3. Oxygen isotopic compositions of physically separated minerals from several Allende CAIs. These points were used to define the CCAM line (source Clayton et al., 1977).

Figure 4. Ion microprobe oxygen isotope analyses of single grains in several carbonaceous chondrites. Belittling uncertainties are typically well-nigh ±2‰. The CCAM line is shown for reference sources: are noted in the figure.

Another argument that the ¹⁶O-rich end-fellow member was a ubiquitous component of primitive solids is that it is plant in many different chemical forms (dissimilar minerals) in many classes of meteorites: CAIs and amoeboid olivine aggregates (AOAs) from Efremovka (CV3) (Aléon et al., 2002; Fagan et al., 2002), AOA from a CO chondrite, Y 81020 (Itoh et al., 2002), and CAI and AOA from CM and CR chondrites (Krot et al., 2002). This isotopic composition tin can too serve as an terminate-member for the chondrule mixing line in Figure 2.

If the ¹⁶O-rich composition is indeed the isotopic composition of the primordial solar nebula, the consequences for solar organization germination are profound. As noted above, materials with the ¹⁶O-rich composition are ubiquitous, simply they are also rather rare, never amounting to more than than a few per centum of the host meteorite. The implication is that all the other material in the inner solar organisation has undergone some process that changed its ¹⁶O-abundance by four–5%. This must have been a major chemical or concrete process that must leave evidence in forms other than the isotopic limerick of oxygen.

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Cetacean Fossil Record

R. Ewan Fordyce , in Encyclopedia of Marine Mammals (Second Edition), 2009

II Occurrence, Surround, and Historic period

Fossil cetaceans occur in sedimentary rocks. Originally, remains accumulated in mud, silt, sand, or gravel which, equally mankind decayed, was cached and turned to rock through compaction and/or deposition of cementing minerals. Sedimentary rocks are recognized as detached formations (genetically unified bodies of strata), and are named formally, e.g., the Calvert Formation, Maryland. Marine mammals come from strata including sandstone, mudstone, limestone, greensand, and phosphorite, most of which are marine rocks at present exposed on land. Rare fossils have been recovered from the sea floor. Because broadly similar rock types may form at different times and places, sedimentary rocks must be dated to found their fourth dimension relationships.

2 correlated timescales, relative and accented, are used for the fossil record. The relative timescale has named intervals (epochs; Fig. 1) in an agreed international sequence: Eocene, Oligocene, Miocene, Pliocene, and Pleistocene. These epochs are usually subdivided into early, middle, and late. Stages (e.g., Aquitanian of Fig. ane) may provide finer subdivision. Typically, distinct historic period-diagnostic fossils are used to recognize time intervals. The most reliable dates are based on oceanic microfossils with short-time ranges, such every bit foraminifera, which permit correlation between sea basins. Because of compounded errors of long-distance correlation, ages are rarely authentic to within ane 1000000 years, and many fossils tin can be placed but roughly within a stage. Across the relative timescale, absolute dates in millions of years are needed to understand rates of processes in phylogeny (involving, e.1000., molecular clocks) and in geology (involving, e.chiliad., rates of sediment accumulation or of climatic change). Absolute dates are usually obtained from radiometric analysis of grains of volcanic rock interbedded with fossiliferous strata.

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The Crust

A.I.Southward. Kemp , C.J. Hawkesworth , in Treatise on Geochemistry, 2003

3.11.5.3 Relevance for Crustal Differentiation

The fractionated igneous and sedimentary rocks in Figure 20 have Rb/Sr and Eu/Sr ratios that are much higher than those in current estimates for the upper continental chaff. The latter can be constrained past the strontium isotope ratios of continental run-off (∼0.712), and its model neodymium age (∼1.8   Ga). According to this method, a minimum time-integrated upper crustal Rb/Sr ratio of 0.14 is indicated.

Another striking feature of the data in Figure xx is that the upper, lower and bulk continental crust compositions all accept like Eu/Sr ratios and thus define a distinct, near-vertical trend that is separate from the igneous and sedimentary arrays. There are several potential interpretations for this. It might only reflect the methods employed to estimate the upper and lower crustal averages. The upper crust represents a mixture between sediments and intermediate to felsic igneous rocks (note how close the upper crustal composition plots to the reference suite array in Effigy 20), whereas the lower crust inevitably combines xenolith information from both intraplate and destructive margin settings, not necessarily in representative proportions; the bulk crustal composition is constrained to prevarication betwixt these extremes. The dispersion in crustal compositions on Figure 20 could therefore exist constructed and petrogenetically meaningless. Alternatively, if the chemic variation between the crustal components results from the differentiation or "unmixing" of a bulk starting composition, the data suggests that neither igneous fractionation nor weathering processes tin be wholly responsible for such differentiation, since strongly increasing Eu/Sr is a signature of those processes. In any case, it is clear from Figure 20 that the upper crustal limerick has sufficiently low Rb/Sr and Eu/Sr to preclude a pregnant contribution from the continental sediments, in dissimilarity to the implications drawn from the granite and upper crust trace-chemical element patterns in Figure 5.

One resolution to this conundrum could be related to a shift in the oxidation state of europium (i.due east., the proportion of European union²⁺ to Eu³⁺) either through time, or in different tectonic settings (Carmichael, 1991). The marked increase in Eu/Sr in igneous suites indicates that D_Sr was much larger than D_Eu in the fractionating plagioclase. Nonetheless, D_{European union} in plagioclase is sensitive to oxygen fugacity (f _O2 ), and it is very low in oxidizing conditions where europium exists as European union³⁺ (Drake, 1974). The igneous rocks plotted in Figure 20 can be inferred to take formed under reasonably oxidizing conditions, since many of them originate above subduction zones, where the drape has been modified by the introduction of hydrous fluids from the subducted slab, or they derive from, or have interacted with, recycled sedimentary rocks in the deep crust.

However, in reducing conditions, D_Eu increases until, at f _O2 ∼10^–12.fiveconfined, it approaches values similar to that of D_Sr. Plagioclase formed under these conditions volition therefore non fractionate europium from strontium, and its removal results in vertical arrays on Effigy 20, as is shown by the continental chaff. This raises the intriguing possibility that the differentiation of the continental crust was primarily accomplished nether relatively reducing weather condition, such as existed in the Archean period where a CO₂-rich atmosphere prevailed, or in intraplate settings. The latter would be marked by magmas with distinctive trace-elements patterns, and in item no negative Nb–Ta anomalies. Such magmas did contribute to the generation of new chaff, they cannot be the dominant component, and and then the credible lack of Eu/Sr fractionation in the crustal compositions may largely reflect processes in the Archean. Independent evidence for a reducing environment at this time includes the presence of banded iron formations, uranium placer deposits, high Th/U ratios in igneous rocks, non-mass dependent sulfur isotope fractionations (Farquhar et al., 2000; encounter also Affiliate 4.04) and the atomic number 82 isotope limerick of the mantle (run into Elliott et al., 1999). Under such reducing atmospheric condition, intracrustal melting can generate the observed differentiation of the continents, the important point being that the residual plagioclase contained substantially more than europium than that of the magmatic reference array in Figure xx. Recycling of small amounts of the residues of melting, approximated by the estimated lower crustal composition, tin explain the displacement of the bulk crust from the magmatic assortment on Figure xx. The fundamental implication from this reasoning is that melting and weathering processes operating in the outer function of the post-Archean Globe take contributed relatively picayune to the bulk differentiation of the continental crust, consequent with its average age of ∼1.eight   Ga.

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