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1
Monkul, Mehmet Murat, e Jerry A. Yamamuro. "Influence of silt size and content on liquefaction behavior of sands". Canadian Geotechnical Journal 48, n. 6 (giugno 2011): 931–42. http://dx.doi.org/10.1139/t11-001.
Testo completoAbstract (sommario):
This study investigates the fines content influence on liquefaction potential of a single base sand mixed with three different essentially nonplastic silts through strain-controlled monotonic undrained triaxial compression tests. Confining stress (30 kPa) and deposition method (dry funnel deposition) were kept the same, while fines content was varied, to solely focus on how different silts and their contents influence the undrained response of the sand under comparable conditions. It was found that if the mean grain diameter ratio (D50-sand/d50-silt) of the sand grains to silt grains is sufficiently small, the liquefaction potential of the sand increases steadily with increasing fines content for the studied range (0%–20%). As D50-sand/d50-silt increases, the liquefaction potential of the silty sand might actually be less than the liquefaction potential of the clean sand. Test results also revealed that commonly used comparison bases (i.e., void ratio, intergranular void ratio, relative density) are not sufficient for assessing the influence of fines on liquefaction potential of silty sands. Finally, relative size of the silt grains should also be considered in geotechnical engineering practice in addition to content and plasticity of fines to characterize the influence of silt on liquefaction potential of sands.
2
Catto, N. R. "Hydrodynamic distribution of palynomorphs in a fluvial succession, Yukon". Canadian Journal of Earth Sciences 22, n. 10 (1 ottobre 1985): 1552–56. http://dx.doi.org/10.1139/e85-163.
Testo completoAbstract (sommario):
Investigation of a sequence of alternating sand and silt deposits formed in an ephemeral braided stream channel adjacent to the modem Caribou River, Yukon, revealed differences in the palynological spectra of the sediment types. Picea, Betula, Alnus, and Gramineae are more concentrated in the silt units, whereas Cyperaceae, Chenopodium, Lycopodium, and Ericaceae are preferentially concentrated in the sand strata. These distribution patterns reflect the hydrodynamic properties of the grains, in addition to environmental differences. Grains of Picea, Betula, and Alnus settle through still water at the same rates as silt-sized quartz particles and are therefore concentrated in the portion of the deposit derived from the stream's suspended load. Thus, increases in percentages of these palynomorphs with decreasing grain size may not reflect vegetation changes or climatic alterations but may be consequences of the hydrodynamic situation.
3
Crouvi, Onn, Rivka Amit, Yehouda Enzel, Naomi Porat e Amir Sandler. "Sand dunes as a major proximal dust source for late Pleistocene loess in the Negev Desert, Israel". Quaternary Research 70, n. 2 (settembre 2008): 275–82. http://dx.doi.org/10.1016/j.yqres.2008.04.011.
Testo completoAbstract (sommario):
AbstractGrain size analyses of three hilltop, primary eolian loess sequences in the Negev desert, southern Israel, show a bimodal grain-size distribution at 50–60 μm and 3–8 μm. Using analyses of mineralogy and OSL ages we demonstrate that the coarse mode is composed mostly of quartz grains and its relative magnitude increases regionally with time, suggesting an enhancement of a time-transgressive proximal dust source compared to a distal, Saharan fine-grain dust. The only proximal dust source for large amount of coarse silt quartz grains is the sands that advanced into Sinai and the Negev concurrently with the loess accretion during the late Pleistocene as a result of the exposure of the Mediterranean shelf. We therefore propose that the coarse silt quartz grains were formed through eolian abrasion within the margins of an advancing sand sea. This relationship between desert sand seas as a source for proximal coarse dust and desert margin loess deposits can be applicable to other worldwide deserts such as Northern Africa, China and Australia.
4
Lamirande, I., B. Lauriol, A. E. Lalonde e I. D. Clark. "La production de limon sur des terrasses de cryoplanation dans les monts Richardson, Canada". Canadian Journal of Earth Sciences 36, n. 10 (1 ottobre 1999): 1645–54. http://dx.doi.org/10.1139/e99-072.
Testo completoAbstract (sommario):
The production of silt on cryoplanation terraces in the Richardson Mountains was documented by a sedimentological study. Geochemical, grain-size, and petrographic analyses of the Jurassic Bug Creek sandstone were done. Results show that in the unaltered rock the detrital quartz grains are solidly held by a siliceous cement. In the altered and strongly altered sandstone, there is a marked increase in intergranular porosity and fracturing of the grains. The disaggregation and weathering of the sandstone releases mainly material in the silt-size fraction, with lesser amounts of sand and clay. This material covers the tread of the terraces and constitutes a potential source of loess in glacial time. Runoff water has a PCO2 value two orders of magnitude greater than the atmosphere yet is weakly mineralized, with only amorphous silica approaching saturation. However, the weathering of sandstones is probably accelerated by the chemical action of water which, by attacking the cement that forms the diagenetic overgrowth of the quartz grains, facilitates their release.
5
Jonczak, Jerzy, Marek Degórski e Bogusława Kruczkowska. "Comparing quartz silt surface microstructures in two sandy soils in young-glacial landscape of northern Poland". Soil Science Annual 67, n. 3 (1 settembre 2016): 131–39. http://dx.doi.org/10.1515/ssa-2016-0016.
Testo completoAbstract (sommario):
AbstractThe studies on quartz silt surface microstructures using scanning electron microscopy (SEM) were performed in Brunic Arenosol and Gleyic Ortsteinic Podzol, as major components of soil cover of the lower supra-flood terrace of the Słupia River, N Poland. Brunic Arenosols have developed from coarse- and medium-grained fluvioglacial sands, whereas Podzols from aeolian sands of mid-Holocene age, which in some places were covered with younger aeolian deposits. A group of at least 100 randomly selected grains from each soil horizon have been analyzed. The grains were classified into one of the following groups: fresh (type A), grains with the features of chemical weathering (type B), grains coated with scaly-grain incrustations (type C), grains coated with bulbous incrustations (type D), and cracked grains (type E). Parent materials of the investigated soils did not differ significantly in terms of contribution of grain types and type C predominated in both soils. Significant differences were noted in soil solums. Grains covered by scaly-grained incrustations predominated in Brunic Arenosol, which constituted 62–89%. In the profile of Gleyic Ortsteinic Podzol grains type B predominated in AE and E horizons (65–82%), whereas in the remaining horizons grains type C (54–77%).
6
Delage, Pierre, Martine Audiguier, Yu-Jun Cui e Michael D. Howat. "Microstructure of a compacted silt". Canadian Geotechnical Journal 33, n. 1 (25 marzo 1996): 150–58. http://dx.doi.org/10.1139/t96-030.
Testo completoAbstract (sommario):
This paper presents a qualitative and quantitative study of the microstructure of a compacted silt, carried out using a scanning electron microscope and mercury intrusion pore size distribution measurements. Samples have been statically compacted at three water contents: on the dry side of the standard Proctor optimum water content, at the optimum, and on the wet side. The wet sample has a matrix type structure, with a clayey fraction filling the voids and adhering to the silt-sized grains, whereas the other samples display a structure characterized by a skeleton made of silt grain aggregates linked together by clayey bidges. The distribution of water and air within the microstructure of the compacted soil is described for each of the three compaction states. Key words: compacted soil, microstructure, scanning electron microscope, pore size distribution, mercury intrusion, clay hydration.
7
Ryan, Adrienne L., e Stephen R. Cattle. "Do sand dunes of the lower Lachlan floodplain contain the same dust that produced parna?" Soil Research 44, n. 8 (2006): 769. http://dx.doi.org/10.1071/sr06051.
Testo completoAbstract (sommario):
Æolian dust deposits are known to be widespread in south-eastern Australia, with the dominant model being that of ‘parna’, an aggregated material comprising clay, calcium carbonate, and silt-sized quartz. Despite a general acceptance of the parna model, there is surprisingly little evidence of silt-sized clay aggregates remaining in parna profiles. To investigate a relatively pure æolian dust deposit within the proposed zone of parna distribution, we examined the various phases of 3 source-bordering sand dunes on the lower Lachlan River floodplain of south-western NSW. In each dune exists an upper-slope phase of coarse brown sand, a mid-slope layer of reddish, clay-enriched sand, and a lower-slope phase of coarse sand dominated by an accumulation of carbonate glaebules. Granulometric analyses of the clay-enriched phase(s) of each dune identified a conspicuous particle population in the 20–60 μm range, and another in the fine-silt/clay range (<10 μm). Mineralogical characterisation revealed an abundance of illite and kaolinite in the upper 2 dune phases, coupled with a minor amount of smectite, further suggesting an allochthonous æolian origin, as the surrounding floodplain is smectite-rich and relatively poor in illite. Micromorphological features within the clay-enriched phase, including abundant argillans and laminar bands of well-sorted fine quartz grains, indicate that this clay is a depositional feature, illuviated from surface horizons and re-deposited at depth. A similar illuvial origin is suggested by the fine crystalline nature of the calcium carbonate accumulation, ubiquitously coating the matrix mineral grains of the lower dune phase. No discrete clay aggregates were identified; however, all the assumed components of parna (silt-sized quartz grains, clay, and calcium carbonate) were identified, spatially separated within each dune. The consistency of these features among the 3 dunes indicates an analogous æolian dust accession, but it is not clear whether the clay component of this dust was transported as coatings on quartz grains, or as silt-sized clay aggregates accompanied by silt-sized quartz grains.
8
Setiady, Deny, e Ediar Usman. "MINERAL CONTENT OF SURFICIAL SEDIMENT OF THE RANGSANG ISLAND AND ITS SURROUNDING AREA, MERANTI REGENCY, ARCHIPELAGO RIAU PROVINCE". BULLETIN OF THE MARINE GEOLOGY 30, n. 2 (15 febbraio 2016): 67. http://dx.doi.org/10.32693/bomg.30.2.2015.76.
Testo completoAbstract (sommario):
According to the regulation No 4 of 2009 of Mineral and Coal Mining Management stated that the requirement of an inventory for mineral resources data was created to support the establishment of mining area. This study is intended to obtain mineral resources content and surficial sediment data, Geographically the study area belongs to Meranti Archipelago Regency, Riau Province. it is located between 102o00'00" - 103o 15'00" E and 00o35'00" - 01o28'00" N. Grain size analyses result show that surficial sediment in the study area consists of silt, silty sand and sand which is dominated by silt. Based on the mineral identification, some of the minerals such as quartz, cassiterite, magnetite, hematite, dolonite, biotite and zircon have been found. Silt distribution is very wide started from estuarine southeast part northen part of Rangsang Island toward southeast of rangsang island. Sandy silt only found at the southeast of Rangsang Island, while sand sediment is found at the south and southeast of Rangsang Island. The presence of silt and sand grains is influenced by moderate to strong currents and wave patterns, so that the silt and sand grains sediment was transported along coastal to offsore area, while the fine grained (clay - silt) are deposited in the valley at the western part of Rangsang Island.Keywords: mineral, surficial sediment, Rangsang Island Berdasarkan Undang Undang Nomor 4 tahun 2009 tentang Pengelolaan Pertambangan Mineral dan Batubara, disebutkan bahwa inventarisasi data sumber daya mineral diperlukan dalam rangka mendukung penetapan Wilayah Pertambangan (WP). Penelitian ini dimaksudkan untuk memperoleh data kandungan sumber daya mineral dan sedimen dasar laut. Daerah penelitian, secara geografis termasuk dalam Kabupaten Kepulauan Meranti, Provinsi Riau, dan terletak pada koordinat antara 102o00'00" - 103o15'00" BT dan 00o35'00" - 01o28'00" LU. Hasil analisis besar butir menunjukkan sedimen permukaan dasar laut di daerah penelitian terdiri atas lanau, lanau pasiran dan pasir yang didominasi oleh lanau. Berdasarkan identifikasi mineral pada sedimen permukaan dasar lautnya menunjukkan kehadiran mineral kasiterit, magnetit, hematit, dolomit, biotit, zirkon dan kuarsa. Penyebaran lanau sangat luas dimulai dari daerah estuari barat laut dan bagian utara Pulau Rangsang, hingga ke sebelah tenggara Pulau Rangsang. Lanau pasiran hanya terdapat di tenggara Pulau rangsang, sedangkan pasir hanya terdapat di daerah di bagian selatan - tenggara Pulau Rangsang. Adanya butiran lanau - pasir dipengaruhi oleh pola arus dan gelombang yang sedang sampai kuat, sehingga butiran berukuran lanau - pasir dapat terangkut ke arah lepas pantai, sedangkan butiran halus (lempung) mengendap di daerah lembah di bagian barat Pulau Rangsang. Kata kunci: mineral, sedimen permukaan dasar laut, Pulau Rangsang
9
Davidson, Donald. "Balneaves: Soil Thin Sections". Proceedings of the Prehistoric Society 58, S2 (1992): 23–25. http://dx.doi.org/10.1017/s0079497x00079172.
Testo completoAbstract (sommario):
1. Structure: partially accommodated channels (0.16 to 0.80mm in width) above the pan; no aggregates; fewer channels below the pan; channel pattern - straight to curved; vughs (spherical to elongate, not normally connected) 0.4 to 0.8mm in diameter and are not orientated and have random pattern: above pan channels and vughs partially connected; pellicular grain microstructure - weakly developed.2. Mineral components: coarse fraction: quartz grains range in size from silt to fine/medium sand (<lmm). One large quartz (200mm). Dominance of single and compound quartz grains; instances of biotite and plagioclase; quartz grains -angular/subangular and smooth. Fine fraction: brown, optically amorphous iron oxides, isotropic.
10
Velbel, Michael. "Phoenix first to see silt grains on Mars". Nature 481, n. 7379 (gennaio 2012): 29. http://dx.doi.org/10.1038/481029c.
Testo completo
11
Cattle, Stephen R., e Carol M. S. Smith. "Fabric of soil derived from parna and the riddle of transported pellets". Soil Research 56, n. 3 (2018): 219. http://dx.doi.org/10.1071/sr16343.
Testo completoAbstract (sommario):
It is generally accepted that large areas of southern New South Wales (NSW) and northern Victoria are mantled by soils derived from clayey loess deposits called parna. These parna deposits are believed to have formed during arid phases of the Pleistocene and the mineral constituents are assumed to have been transported as silt- and fine sand-sized pellets of calcareous clay, with some companion quartz grains of a similar size. A common property of parna-derived soils is subplasticity, where the apparent field texture grade becomes more clayey with increasing mechanical working of the bolus. This propensity for subplastic behaviour suggests that parna-derived soils contain stable silt- and fine sand-sized pellets of clay, yet there has been little direct micromorphological evidence of these pellets ever published. In the present study, thin section samples from several parna type-sites in southern NSW were examined micromorphologically to reveal the presence of very well size-sorted quartz grain populations (companion grains) and identifiable prolate clay aggregations of a similar silt to fine sand size. These prolate pellets, comprised of quartz, illite, kaolinite and chlorite, have a very distinctive mosaic-speckled b-fabric and are more widely distributed throughout the soil than the similarly sized and shaped faunal faecal pellets. Where these pelletal aggregations are not evident, such as in the deeper parna deposits, abundant illuviation features suggest that clay particles deposited within the parna, whether as pellets or coatings on grains, have subsequently undergone considerable weathering and a range of pedogenic processes.
12
Crompton, Jeff W., Gwenn E. Flowers e Brendan Dyck. "Characterization of glacial silt and clay using automated mineralogy". Annals of Glaciology 60, n. 80 (dicembre 2019): 49–65. http://dx.doi.org/10.1017/aog.2019.45.
Testo completoAbstract (sommario):
AbstractGlacial erosion produces vast quantities of fine-grained sediment that has a far-reaching impact on Earth surface processes. To gain a better understanding of the production of glacial silt and clay, we use automated mineralogy to quantify the microstructure and mineralogy of rock and sediment samples from 20 basins in the St. Elias Mountains, Yukon, Canada. Sediments were collected from proglacial streams, while rock samples were collected from ice marginal outcrops and fragmented using electrical pulse disaggregation. For both rock fragments and sediments, we observe a log-normal distribution of grain sizes and a sub-micrometer terminal grain size. We find that the abrasion of silt and clay results in both rounding and the exploitation of through-going fractures. The abundance of inter- versus intragranular fractures depends on mineralogy and size. Unlike the relatively larger grains, where crushing and abrasion are thought to exploit and produce discrete populations of grain sizes, the comminution of fines leads to a grain size, composition and rounding that is continuously distributed across size, and highly dependent on source-rock properties.
13
McClung, J. E., e J. D. Mollard. "Predicting settlement at a damsite on a tunnel valley deposit in Alberta". Canadian Geotechnical Journal 24, n. 1 (1 febbraio 1987): 45–57. http://dx.doi.org/10.1139/t87-005.
Testo completoAbstract (sommario):
During investigations for a damsite on the Sand River, Alberta, an 80 m thick silt deposit in a valley some 500 m across was encountered. The most distinctive feature of the deposit is the uniformity of the silt, with thicknesses of up to 50 m occurring as a single layer uninterrupted by seams of significantly different material. The silt unit is believed to be the result of very uniform, prolonged depositional conditions in a subglacial river. The silt consists largely of silica grains between 10 and 60 μm, and although it contains clay, in some aspects its behaviour is close to that of sand.Evidence suggests that the present valley is a tunnel valley formed by meltwaters flowing through the underside of a glacier. The implications for the engineering geology of the damsite investigated are discussed and some geotechnical properties of this unusual silt deposit are presented, particularly as they affect settlement prediction. Key words: tunnel valley, glacial silt, earth dam, settlement, airphoto interpretation.
14
Milliken, Kitty L., Ying Shen, Lucy T. Ko e Quansheng Liang. "Grain composition and diagenesis of organic-rich lacustrine tarls, Triassic Yanchang Formation, Ordos Basin, China". Interpretation 5, n. 2 (31 maggio 2017): SF189—SF210. http://dx.doi.org/10.1190/int-2016-0092.1.
Testo completoAbstract (sommario):
The role of the primary detrital grain assemblage as a control on diagenetic pathways is reasonably well-understood in sandstones and limestones, but less so in mudrocks. We have documented diagenesis in mudstones from the Triassic Yanchang Formation that are dominated ([Formula: see text] by volume) by grains derived from outside the basin of deposition (terrigenous-argillaceous mudstones or tarls). Major extrabasinal grains are K-rich clay, quartz, plagioclase, K-feldspar, lithic fragments, and micas. In terms of the quartz-feldspar-lithic grain compositions, the silt fraction in these samples is classified as arkose. Grains of intrabasinal derivation include particulate organic matter, phosphatic debris, and rare carbonate allochems. The principal chemical diagenetic components in these mudrocks have strongly localized spatial distributions at micrometer to centimeter scales. Chemical diagenetic components include cone-in-cone structures, replacements of detrital feldspar, pore-filling precipitates within anomalously large pores, pore-filling solid hydrocarbon, and very minor quartz overgrowths associated with local packing flaws around silt-size detrital quartz grains. Matrix-dispersed intergranular cementation, as observed in well-known organic-rich marine mudstones, such as the Barnett Shale and the Eagle Ford Formation, is not observed in Yanchang Formation lacustrine mudstones. The authigenic features present are consistent with the thermal maturity of the units ([Formula: see text]) and are broadly similar to features observed in other mudstones that contain grain assemblages dominated by particles of extrabasinal derivation. The low porosity and the absence of significant amounts of intergranular cement indicate that compactional porosity loss and in-filling by migrated solid hydrocarbon were the major causes of porosity decline during diagenesis of Yanchang Formation mudrocks. Although the mudstones of the Yanchang Formation have a relatively high content of organic carbon and serve as source rocks in the Ordos Basin, the depositional grain assemblage is not conducive to creation of porosity, permeability, and mechanical properties that would make these mudrocks effective unconventional reservoirs.
15
Song, Min, Ian Baker e David M. Cole. "The effect of particles on dynamic recrystallization and fabric development of granular ice during creep". Journal of Glaciology 51, n. 174 (2005): 377–82. http://dx.doi.org/10.3189/172756505781829287.
Testo completoAbstract (sommario):
AbstractThe mechanical behavior and microstructural evolution of laboratory-prepared, particle-free fresh-water ice and ice with 1 wt.% (~0.43 vol.%) silt-sized particles were investigated under creep with a stress level of 1.45 MPa at −10°C. The particles were present both within the grains and along the grain boundaries. The creep rates of specimens with particles were always higher than those of particle-free ice. Dynamic recrystallization occurred for both sets of specimens, with new grains nucleating along grain boundaries in the early stages of creep. The ice with particles showed a higher nucleation rate. This resulted in a smaller average grain-size for the ice with particles after a given creep strain. Fabric studies indicated that ice with particles showed a more random orientation of c axes after creep to ~10% strain than the particle-free ice.
16
Lancaster, Nicholas. "On the formation of desert loess". Quaternary Research 96 (29 aprile 2020): 105–22. http://dx.doi.org/10.1017/qua.2020.33.
Testo completoAbstract (sommario):
AbstractSequences of quartz-rich coarse (20−63 μm) silt occur in many low- and midlatitude unglaciated arid and semiarid areas and have been termed “desert loess.” The processes by which these deposits are generated have been debated for decades. All hypotheses to explain their origin seek to provide mechanisms for the generation of silt-sized material without glacial grinding, which is the main process involved in the production of coarse silt at high latitudes. Possible mechanisms for the formation of coarse silt in arid regions include derivation from preexisting siltstones, mechanical weathering of silicate rocks, and abrasion of sand grains in active dune environments during intense transport events. Examination of the characteristics of desert loess and field and laboratory experiments to assess the role of dune areas as a source of coarse silt by abrasion and/or resuspension of residual fines suggests that many loess sequences are dominated by locally derived coarse silt. Improvements in the characterization of desert loess particle size, mineralogy, and geochemistry are needed, however, to identify sources and sinks of coarse silt, especially when combined with climatic back-trajectory analysis. Properly scaled experiments and modeling of particle collisions will also help to better quantify the effectiveness of abrasion in the generation of coarse silt in support of field observations.
17
Polito, Carmine P., e Erin L. D. Sibley. "Threshold fines content and behavior of sands with nonplastic silts". Canadian Geotechnical Journal 57, n. 3 (marzo 2020): 462–65. http://dx.doi.org/10.1139/cgj-2018-0698.
Testo completoAbstract (sommario):
The threshold fines content of a sand with nonplastic fines represents the silt content where the soil transitions from being a sand matrix, with silt particles entirely contained in the voids between the sands, to being a silt matrix that contains isolated sand grains. A laboratory testing program was performed on a series of mixtures of sand and silt, with silt contents ranging from 0% to 45%, to determine if the friction angle, cyclic resistance, and normalized dissipated energy per unit volume required to initiate liquefaction changed based upon the silt content of the soil relative to the threshold fines content. These data were evaluated with respect to whether the silt content of the specimens was below the lower-bound threshold fines content or above the upper-bound threshold fines content. It was determined that soils above the upper-bound threshold fines content had lower friction angles, lower cyclic resistances, and required less normalized dissipated energy per unit volume to initiate liquefaction than soils below the lower-bound threshold fines content. It was also shown that under the larger strains experienced during monotonic testing, the friction angle did not reach a constant value until it was well above the upper-bound limiting silt content.
18
Helland, P. E., Pei-Hua Huang e R. F. Diffendal. "SEM Analysis of Quartz Sand Grain Surface Textures Indicates Alluvial/Colluvial Origin of the Quaternary “Glacial” Boulder Clays at Huangshan (Yellow Mountain), East-Central China". Quaternary Research 48, n. 2 (settembre 1997): 177–86. http://dx.doi.org/10.1006/qres.1997.1916.
Testo completoAbstract (sommario):
AbstractGeomorphic features and Pleistocene deposits on Huangshan have been attributed to glaciation. Recent reassessment questions this interpretation. As part of the reassessment, quartz sand grains from deposits identified as glacial boulder clays (till composed of boulders in a clay or silt matrix) were analyzed by scanning electron microscope for evidence of their sedimentary history. Surface textures found on the boulder-clay grains were compared with those on grains with known sedimentary histories including glacial, grus, colluvial, and alluvial grains. The analysis shows that the grains lack typical glacial textures. The surface textures present indicate a complex history. Nonuniformly weathered grain surfaces point to chemical weathering of the source rock. This is supported by the deep weathering of the nonquartz clasts in the sand-sized fraction as well as in boulders at the outcrops. The close correspondence in surface-texture frequencies with those of the alluvial grains indicates an alluvial component to the grains’ history. The similarity with the colluvial grains and the outcrops’ structures suggest an alluvial/colluvial origin for the deposits. The history indicated by the surface textures agrees with the recent reassessment of the geomorphic features and points to warm climatic conditions in east-central China for at least part of the Pleistocene.
19
Alexanderson, Helena. "Residual Osl Signals from Modern Greenlandic River Sediments". Geochronometria 26, n. -1 (1 gennaio 2007): 1–9. http://dx.doi.org/10.2478/v10003-007-0001-6.
Testo completoAbstract (sommario):
Residual Osl Signals from Modern Greenlandic River SedimentsRipple-laminated sandy deposits at shallow water depths in four rivers on Jameson Land, East Greenland were sampled for optically stimulated luminescence (OSL) dating. Silt-sized grains have significantly higher equivalent doses (~1.1 Gy) than sand grains (~0.1 Gy). This suggests that coarse grain-size fractions are better bleached and more suitable than fine grains for OSL dating of glaciofluvial/fluvial sediments. A sample from a sidebar deposited during the spring flood yielded 1.0 Gy (~500 years) while a subaerial deposit was completely zeroed. The spring flood deposit is considered to be most similar to deglacial conditions and incomplete bleaching of this amount (1 Gy) is generally not a significant source of error for sediments of Pleistocene age. Most samples have rather poor luminescence characteristics and are affected by thermal transfer if preheat temperatures at or above 260°C are used.
20
Amit, Rivka, Yehouda Enzel e Onn Crouvi. "Quaternary influx of proximal coarse-grained dust altered circum-Mediterranean soil productivity and impacted early human culture". Geology 49, n. 1 (11 settembre 2020): 61–65. http://dx.doi.org/10.1130/g47708.1.
Testo completoAbstract (sommario):
Abstract The carbonate mountainous landscape around most of the Mediterranean is karstic, is almost barren, and has thin soils. Erosion of preexisting thicker soils is a common hypothesis used to explain this bare terrain. An alternative hypothesis is that in the Mediterranean region, thin soils are attributed to long-distance transport of very fine, silty clay dust, resulting in low mass accumulation rates. Even if accreted over millennia, such dust cannot produce thick, highly productive soils. A pronounced anomaly in the Mediterranean is the thick, more productive soil of the semiarid southern Levant (SL). These soils contain order-of-magnitude coarser grains than the characteristic thin soils in the Mediterranean and a high proportion (>70%) of coarse silt quartz sourced from the nearby Sinai-Negev erg, the primary contributor of the Negev loess. This proximal intense dust supply produced greatly thicker soils. However, influx of coarse silt quartz loess is a geologically recent phenomenon in the SL. Pre-loess (i.e., older than 200 ka, pre-coarse-silt influx) SL soils are much finer and were generated by long-distance dust from the Sahara and Arabia like most other Mediterranean soils. Thus, we hypothesize that the geologically recent Negev Desert loess interval caused a drastic change in mountainous soil properties within the SL, enriching the Levant’s ecology and affecting early human development. The high amounts of coarse silt deposited on the landscape have contributed to the unique sustainable agriculture in the SL, which assisted in transforming the Levant into “the land of milk and honey” and a cradle of civilizations.
21
Hamid Al-Jaberi, Mohanad. "Clay Minerals Variations in Quaternary Sediments of Basrah City-Iraq". Earth Science Research 6, n. 2 (8 aprile 2017): 41. http://dx.doi.org/10.5539/esr.v6n2p41.
Testo completoAbstract (sommario):
Mineralogical and chemical analysis of two well cutting in quaternary sediments at Basrah city. This study have been focused on the quaternary clay minerals variations which give a clear indication to marine transgression and or / regression in Hammar formation. Kaolinite, Illite, Palygoreskite, Illite-Palygorestike mixed layer, Chlorite, Montmorillonite, Vermiculte, and mixed layers of Illite- Smectite are the most quantitatively important phyllosilicates in soil studies in both boreholes. The mineralogical composition of cutting sediments shows significant variability in the different size fractions and depth distribution. Chlorite and kaolinite minerals were increase in the fine grain size especially in the clayey silt, whereas montmoriolllinite and vermiculite minerals were increase in coarse grains especially in silty sand texture. Kaolinite decrease in abundance with depth, which give indicative of a transition from non-marine in quaternary recent sediment ( fresh or brackish water silt) to marine facies in quaternary Hammar formation ( marine shelly silt) during last transgression of quaternary. Palygoreskite mineral percentages increasing at depths 27 and 28 meter , after decreased at 30, 32, 35 , and 40 m respectively , which give data indication that early quaternary marine transgression happened in 32m , and center of quaternary marine transgression detected in 27 and 28 meters , while late marine transgression detected in 17 m , and all of these represent by Hammar formation. Soil ageing also caused to downward increase of montmorillonite suggest to climate became more arid during the early quaternary. Variations ratio of montmorillonite versus kaolinite can be indicated to climatic fluctuation. Illite-Semectite featured indicates changes in both sediment source and paleoclimate. Illite transformation for Illite-Palygoreskite mixed layers with ageing. Vermiculite has strong susceptibility to increase with age. SiO₂, Al₂O₃, CaO, MgO, K₂O, and Fe₂O₃ were the major oxides that identified in present study and used as indicated of clay minerals in studied sediments.
22
Schuiling, R. D., e P. L. de Boer. "Rolling stones; fast weathering of olivine in shallow seas for cost-effective CO<sub>2</sub> capture and mitigation of global warming and ocean acidification". Earth System Dynamics Discussions 2, n. 2 (6 dicembre 2011): 551–68. http://dx.doi.org/10.5194/esdd-2-551-2011.
Testo completoAbstract (sommario):
Abstract. Human CO2 emissions may drive the Earth into a next greenhouse state. They can be mitigated by accelerating weathering of natural rock under the uptake of CO2. We disprove the paradigm that olivine weathering in nature would be a slow process, and show that it is not needed to mill olivine to very fine, 10 μm-size grains in order to arrive at a complete dissolution within 1–2 year. In high-energy shallow marine environments olivine grains and reaction products on the grain surfaces, that otherwise would greatly retard the reaction, are abraded so that the chemical reaction is much accelerated. When kept in motion even large olivine grains rubbing and bumping against each other quickly produce fine clay- and silt-sized olivine particles that show a fast chemical reaction. Spreading of olivine in the world's 2% most energetic shelf seas can compensate a year's global CO2 emissions and counteract ocean acidification against a price well below that of carbon credits.
23
Chaolu, Yi. "Subglacial comminution in till — evidence from microfabric studies and grain-size distributions". Journal of Glaciology 43, n. 145 (1997): 473–79. http://dx.doi.org/10.1017/s0022143000035073.
Testo completoAbstract (sommario):
Abstract Quartz, feldspar and chlorite, the principal minerals in a basal till from the Halasi River catchment in the Altay Mountains, northwestern China, are present in approximately equal concentrations in the coarse fraction of the till, 1.0-0.125 mm. Quartz concentrations are significantly higher than those of the other two minerals in the 0.125-0.016 mm size range. Feldspar and chlorite concentrations are higher than those of quartz in the finest fraction. Quartz has a strong preferred mode at 0.063-0.032 mm. Feldspar and chlorite have two weak modes in the silt-size range, one between 0.063 and 0.032 mm and the other between 0.016 and 0.004 mm. Thin sections of oriented impregnated samples were used to study crushing and abrasion. Over 2700 daughter particles were identified as products of comminution of 925 parent grains. Quartz and feldspar are most likely to be broken into two particles of roughly equal size, as are fine chlorite grains. However, owing to their weakness and cleavage, larger grains of chlorite tend to he split into more than two daughter particles. Sizes of the daughter grains were measured and sizes of the original parent grains were estimated. Mean parent grain-sizes for quartz, feldspar and chlorite are 0.129, 0.078 and 0.059 mm, respectively, whereas mean daughter grain-sizes are 0.068,0.041 and 0.024 mm, respectively. The greater percentage reduction in the size of chlorite reflects its tendency to break into more than two daughter particles. Most grains tend to be crushed. Only a few large particles seem to have suffered from abrasion.
24
Chaolu, Yi. "Subglacial comminution in till — evidence from microfabric studies and grain-size distributions". Journal of Glaciology 43, n. 145 (1997): 473–79. http://dx.doi.org/10.3189/s0022143000035073.
Testo completoAbstract (sommario):
AbstractQuartz, feldspar and chlorite, the principal minerals in a basal till from the Halasi River catchment in the Altay Mountains, northwestern China, are present in approximately equal concentrations in the coarse fraction of the till, 1.0-0.125 mm. Quartz concentrations are significantly higher than those of the other two minerals in the 0.125-0.016 mm size range. Feldspar and chlorite concentrations are higher than those of quartz in the finest fraction. Quartz has a strong preferred mode at 0.063-0.032 mm. Feldspar and chlorite have two weak modes in the silt-size range, one between 0.063 and 0.032 mm and the other between 0.016 and 0.004 mm.Thin sections of oriented impregnated samples were used to study crushing and abrasion. Over 2700 daughter particles were identified as products of comminution of 925 parent grains. Quartz and feldspar are most likely to be broken into two particles of roughly equal size, as are fine chlorite grains. However, owing to their weakness and cleavage, larger grains of chlorite tend to he split into more than two daughter particles.Sizes of the daughter grains were measured and sizes of the original parent grains were estimated. Mean parent grain-sizes for quartz, feldspar and chlorite are 0.129, 0.078 and 0.059 mm, respectively, whereas mean daughter grain-sizes are 0.068,0.041 and 0.024 mm, respectively. The greater percentage reduction in the size of chlorite reflects its tendency to break into more than two daughter particles.Most grains tend to be crushed. Only a few large particles seem to have suffered from abrasion.
25
Iverson, Neal R., Thomas S. Hooyer e Roger Leb Hooke. "A laboratory study of sediment deformation: stress heterogeneity and grain-size evolution". Annals of Glaciology 22 (1996): 167–75. http://dx.doi.org/10.3189/1996aog22-1-167-175.
Testo completoAbstract (sommario):
In shearing sediment beneath glaciers, networks of grains may transiently support shear and normal stresses that are larger than spatial averages. Consistent with studies of fault-gouge genesis, we hypothesize that crushing of grains in such networks is responsible for surrounding larger grains with smaller grains. At sufficiently large strains, this should minimize stress heterogeneity, favor intergranular sliding and abrasion rather than crushing, and result in a self-similar grain-size distribution.This hypothesis is tested with a ring-shear device that slowly shears a large annular sediment sample to high strains. Shearing and comminution of weak equigranular (2.0–3.3 mm) sediment resulted in a self-similar grain-size distribution with a fractal dimension that increased with shear strain toward a steady value of 2.85. This value is significantly larger than that of gouges produced purely by crushing, 2.6, but it is comparable to values for tilts thought to be deforming beneath modern glaciers, 2.8 to nearly 3.0. At low strains, under a steady mean normal stress of 84 kPa, variations in normal stress measured locally ranged in amplitude from 50 to 300 kPa with wavelengths that were 100 times larger than the initial grain diameter. Crushing of grains, observed through the transparent walls of the device, apparently caused the failure of grain networks. At shearing displacements ranging from 0.7 to 1.0 m, the amplitude of local stress fluctuations decreased abruptly. This change is attributed to fine sediment that distributed stresses more uniformly and caused grain networks to fail primarily by intergranular sliding rather than by crushing of grains. Sliding between grains apparently produced silt by abrasion and resulted in a fractal dimension that was higher than if there had been only crushing.A size distribution with a fractal dimension greater than 2.6 is probably a necessary but not sufficient condition for determining whether a basal till has been highly deformed. Stress heterogeneity in subglacial sediment that is shearing through its full thickness should contribute to the erosion of underlying rock.
26
Iverson, Neal R., Thomas S. Hooyer e Roger Leb Hooke. "A laboratory study of sediment deformation: stress heterogeneity and grain-size evolution". Annals of Glaciology 22 (1996): 167–75. http://dx.doi.org/10.1017/s0260305500015378.
Testo completoAbstract (sommario):
In shearing sediment beneath glaciers, networks of grains may transiently support shear and normal stresses that are larger than spatial averages. Consistent with studies of fault-gouge genesis, we hypothesize that crushing of grains in such networks is responsible for surrounding larger grains with smaller grains. At sufficiently large strains, this should minimize stress heterogeneity, favor intergranular sliding and abrasion rather than crushing, and result in a self-similar grain-size distribution.This hypothesis is tested with a ring-shear device that slowly shears a large annular sediment sample to high strains. Shearing and comminution of weak equigranular (2.0–3.3 mm) sediment resulted in a self-similar grain-size distribution with a fractal dimension that increased with shear strain toward a steady value of 2.85. This value is significantly larger than that of gouges produced purely by crushing, 2.6, but it is comparable to values for tilts thought to be deforming beneath modern glaciers, 2.8 to nearly 3.0. At low strains, under a steady mean normal stress of 84 kPa, variations in normal stress measured locally ranged in amplitude from 50 to 300 kPa with wavelengths that were 100 times larger than the initial grain diameter. Crushing of grains, observed through the transparent walls of the device, apparently caused the failure of grain networks. At shearing displacements ranging from 0.7 to 1.0 m, the amplitude of local stress fluctuations decreased abruptly. This change is attributed to fine sediment that distributed stresses more uniformly and caused grain networks to fail primarily by intergranular sliding rather than by crushing of grains. Sliding between grains apparently produced silt by abrasion and resulted in a fractal dimension that was higher than if there had been only crushing.A size distribution with a fractal dimension greater than 2.6 is probably a necessary but not sufficient condition for determining whether a basal till has been highly deformed. Stress heterogeneity in subglacial sediment that is shearing through its full thickness should contribute to the erosion of underlying rock.
27
Nemecz, Ernö, Márton Pécsi, Zsuzsa Hartyáni e Timea Horváth. "The origin of the silt size quartz grains and minerals in loess". Quaternary International 68-71 (giugno 2000): 199–208. http://dx.doi.org/10.1016/s1040-6182(00)00044-6.
Testo completo
28
Chang, Ching S., e Mehrashk Meidani. "Dominant grains network and behavior of sand-silt mixtures: stress-strain modeling". International Journal for Numerical and Analytical Methods in Geomechanics 37, n. 15 (24 ottobre 2012): 2563–89. http://dx.doi.org/10.1002/nag.2152.
Testo completo
29
Srivastava, Pradeep, George A. Brook, Eugene Marais, P. Morthekai e Ashok K. Singhvi. "Depositional environment and OSL chronology of the Homeb silt deposits, Kuiseb River, Namibia". Quaternary Research 65, n. 3 (maggio 2006): 478–91. http://dx.doi.org/10.1016/j.yqres.2006.01.010.
Testo completoAbstract (sommario):
AbstractPrevious studies suggest that the Homeb silts of the Kuiseb valley, Namibia (i) accumulated in a dune-dammed lake, (ii) are end-point deposits, (iii) represent an aggrading river bed, and (iv) are slackwater deposits. Thus, they have been used alternatively as evidence of past drier conditions or past wetter conditions. Lithostratigraphic analysis of two sediment sequences at Homeb indicates sedimentation by aggradation of the Kuiseb River triggered by a transition from an arid to humid climate. OSL ages for the sequences were obtained by the SAR protocol on aliquots of 9.6-mm and 4.0-mm diameter and on single grains. Four-millimeter aliquot minimum ages closely approximate the single-grain minimum ages and are younger than 9.6-mm aliquot minimum and central ages. Based on these results, the small-aliquot (4-mm) approach appears to provide ages comparable to those obtained by the more laborious and time-consuming single-grain method. Minimum ages indicate rapid deposition of the Homeb Silts in at least two episodes centered at ∼15 ka and ∼6 ka during climate transitions from arid to humid. Flash floods eroded the valley fills during slightly more arid conditions.
30
Ubeid, Khalid. "The nature of the Pleistocene-Holocene palaeosols in the Gaza Strip, Palestine". Geologos 17, n. 3 (1 settembre 2011): 163–73. http://dx.doi.org/10.2478/v10118-011-0009-2.
Testo completoAbstract (sommario):
The nature of the Pleistocene-Holocene palaeosols in the Gaza Strip, PalestineThe Pleistocene to Holocene succession in the Gaza Strip, Palestine, consists of an alternation of calcareous sandstones and reddish fine-grained deposits (palaeosols). The palaeosols can be subdivided into two main groups based on the sand-sized versus clay- to silt-sized grains: (1) the sandy hamra palaeosols, and (2) the loess and loess-derived palaeosols. The hamra palaeosols can, in turn, also be subdivided into two main types according to their colour and grain size: (1) light brown loamy to sandy hamra palaeosols, and (2) dark brown sandy clay hamra palaeosols. The hamra palaeosols are polygenetic and originated in humid environments. Their red colour results from ferric oxides coating the sand grains, but also by illuviation. The various pedogenitic units and their gradual transition to loess palaeosols are due to different phases of dust accretion. Both groups of palaeosols developed during the last glacial. They are considered to represent different climate environments: hamra palaeosols represent humid climates, whereas the loess and loess-derived palaeosols represent dry and semi-dry climates.
31
Berger, G. W. "Thermoluminescence dating applied to a thin winter varve of the late glacial South Thompson silt, south-central British Columbia". Canadian Journal of Earth Sciences 22, n. 11 (1 novembre 1985): 1736–39. http://dx.doi.org/10.1139/e85-182.
Testo completoAbstract (sommario):
The partial bleach (R–Γ) procedure of thermoluminescence (TL) dating of unheated sediments has been applied to the 2–4 μm sized feldspar-dominated grains from two components of a 10–11 ka BP glaciolacustrine silt. A previous TL study of the 4–11 μm sized feldspars from a ~12 cm thick summer layer of this varved deposit did not produce the correct age. Here it is shown that the 2–4 μm feldspar grains from a contiguous, 5 mm thick clay-rich winter varve give a satisfactory TL apparent age of 14.2 ± 2.3 ka. On the other hand, and consistent with the previous results, the 2–4 μm feldspar grains from the thicker summer layer yield an incorrect high apparent age of 55 ± 13 ka. These results have implications for general TL dating of waterlaid sediments.
32
Han, Tongcheng, Roman Beloborodov, Marina Pervukhina, Matthew Josh, Yanlin Cui e Pengyao Zhi. "Theoretical Modeling of Dielectric Properties of Artificial Shales". Geofluids 2018 (2018): 1–12. http://dx.doi.org/10.1155/2018/2973181.
Testo completoAbstract (sommario):
Accurately modeling the anisotropic dielectric properties of shales is important for the interpretation of dielectric data acquired from shales as source rocks and unconventional reservoirs. We have developed a multiphase incremental model for the frequency dependent anisotropic dielectric properties of sedimentary rocks and presented an approach based on the developed model to simulate the measured anisotropic dielectric behaviors of artificial shales. The new model was built based on the theoretical basis of differential effective medium models for any number of mineral grain components aligned in any direction and was shown to be independent of the mixing order. The model incorporates the measured orientation distribution function of the clay particles to determine the shale dielectric anisotropy, and the frequency dependent dielectric behaviors of the wet clay minerals are obtained by inverting the dielectric properties of the artificial sample composed of clay and the same brine as in other artificial shales. The modeling technique combined important polarization mechanisms in the intermediate frequency range and was shown to give satisfactory fit to the measured frequency dependent anisotropic relative permittivity and conductivity of the artificial shales with varying silt contents by using a reasonable aspect ratio and constant dielectric parameters for the silt grains.
33
Maksimova, Ekaterina, e Evgeny Abakumov. "Micromorphological characteristics of sandy forest soils recently impacted by wildfires in Russia". Solid Earth 8, n. 2 (25 aprile 2017): 553–60. http://dx.doi.org/10.5194/se-8-553-2017.
Testo completoAbstract (sommario):
Abstract. Two fire-affected soils were studied using micromorphological methods. The objective of the paper is to assess and compare fire effects on the micropedological organisation of soils in a forest-steppe zone of central Russia (Volga Basin, Togliatti city). Samples were collected in the green zone of Togliatti city. The results showed that both soils were rich in quartz and feldspar. Mica was highly present in soils affected by surface fires, while calcium carbonates were identified in the soils affected by crown fires. The type of plasma is humus–clay, but the soil assemblage is plasma–silt with a prevalence of silt. Angular and subangular grains are the most dominant soil particulates. No evidence of intensive weathering was detected. There was a decrease in the porosity of soils affected by fires as a consequence of soil pores filled with ash and charcoal.
34
Balagurunathan, Yoganand, Edward R. Dougherty, Stanislav Frančišković-Bilinski, Halka Bilinski e Neda Vdović. "MORPHOLOGICAL GRANULOMETRIC ANALYSIS OF SEDIMENT IMAGES". Image Analysis & Stereology 20, n. 2 (3 maggio 2011): 87. http://dx.doi.org/10.5566/ias.v20.p87-99.
Testo completoAbstract (sommario):
Sediments are routinely analyzed in terms of the sizing characteristics of the grains of which they are composed. Via sieving methods, the grains are separated and a weight-based size distribution constructed. Various moment parameters are computed from the size distribution and these serve as sediment characteristics. This paper examines the feasibility of a fully electronic granularity analysis using digital image processing. The study uses a random model of three-dimensional grains in conjunction with the morphological method of granulometric size distributions. The random model is constructed to simulate sand, silt, and clay particle distributions. Owing to the impossibility of perfectly sifting small grains so that they do not touch, the model is used in both disjoint and non-disjoint modes, and watershed segmentation is applied in the non-disjoint model. The image-based granulometric size distributions are transformed so that they take into account the necessity to view sediment fractions at different magnifications and in different frames. Gray-scale granulometric moments are then computed using both ordinary and reconstructive granulometries. The resulting moments are then compared to moments found from real grains in seven different sediments using standard weight-based size distributions.
35
McKissock, I., R. J. Gilkes e W. van Bronswijk. "The relationship of soil water repellency to aliphatic C and kaolin measured using DRIFT". Soil Research 41, n. 2 (2003): 251. http://dx.doi.org/10.1071/sr01091.
Testo completoAbstract (sommario):
In general, water repellency by soil increases with the increase of total organic matter and decreases as the clay and silt contents of the soil increase. The prediction of water repellency from soil organic carbon (OC) content may be improved by examining the types of carbon associated with water repellency. This paper examines the hypothesis that measurement of aliphatic C can provide a better prediction of water repellency than measurement of total OC and also looks at the effects of soil texture on water repellency and the amount of aliphatic C in the soil. DRIFT (diffuse reflectance infrared fourier transform) spectra were measured on sandy soils from the West Midland Sandplains north of Perth in Western Australia. The areas of the aliphatic CH stretching signal (3000–2800/cm) and the OH stretching signal due to kaolin (3750–3570/cm) were used as relative measures of aliphatic carbon and kaolin contents. The relationships of aliphatic C and kaolin to water repellency have been examined and compared with the relationships of water repellency to total OC and clay contents of soil.Hydrophobic organic C as measured by DRIFT gave a better prediction of soil water repellency (r2 = 0.45) than did the total OC (r2 = 0.36). The specific hydrophobicity of organic matter (aliphatic C/OC ratio) increased as sand content increased. However, the direct influence of soil texture on water repellency was of more significance than its indirect influence on the amounts and forms of soil organic matter. A multivariate model including aliphatic C and clay + silt content was the best model for describing water repellency (r2 = 0.58). DRIFT is an effective, rapid method for screening soils for water repellent properties.For individual sand grains there was a weak positive relationship (r2 = 0.26) between the size of the aliphatic CH peak measured from surfaces of sand grains and the water repellency of the grains. A discontinuous aliphatic surface layer was present on the surface of individual sand grains.
36
Anand, RR, e RJ Gilkes. "Muscovite in Darling Range bauxitic laterite". Soil Research 25, n. 4 (1987): 445. http://dx.doi.org/10.1071/sr9870445.
Testo completoAbstract (sommario):
Darling Range bauxitic laterite contains 0-17% silt size, Na-rich, 2M1 muscovite which is most abundant in laterite developed from granitic parent rocks. Muscovite grains show evidence of dissolution, but there has been no formation of dioctahedral vermiculite. Muscovite is clearly a much more resistant mineral than the feldspar, biotite and chlorite in the parent materials that have completely altered to secondary minerals. Muscovite is therefore a significant constituent of Darling Range bauxitic laterite and consequently poses problems in bauxite processing.
37
Sim, Ho, Yungoo Song, Jaehun Kim, Eomzi Yang, Tae Sup Yun e Jae-Hong Lim. "Measurement of 3D-Shape Preferred Orientation (SPO) Using Synchrotron μ-CT: Applications for Estimation of Fault Motion Sense in a Fault Gouge". Minerals 10, n. 6 (9 giugno 2020): 528. http://dx.doi.org/10.3390/min10060528.
Testo completoAbstract (sommario):
We propose a 3D-shape preferred orientation (SPO) measurement method of rigid grains using synchrotron micro-computational tomography (μ-CT). The method includes oriented sampling, 3D μ-CT imaging, image filtering, ellipsoid fitting, and SPO measurement. After CT imaging, all processes are computerized, and the directions of thousands of rigid grains in 3D-space can be automatically measured. This method is optimized for estimating the orientation of the silt-sized rigid grains in fault gouge, which indicates P-shear direction in a fault system. This allows us to successfully deduce fault motion sense and quantify fault movement. Because this method requires a small amount of sample, it can be applied as an alternative to study fault systems, where the shear sense indicators are not distinct in the outcrop and the fault gouge is poorly developed. We applied the newly developed 3D-SPO method for a fault system in the Yangsan fault, one of the major faults in the southeastern Korean Peninsula, and observed the P-shear direction successfully.
38
Papanicolaou, E. P., C. G. Apostolakis, V. Skarlou, C. Nobeli e P. Kritidis. "Ratio of plant to soil concentrations of strontium-85 and its relation to properties of Greek soils". Journal of Agricultural Science 116, n. 2 (aprile 1991): 275–79. http://dx.doi.org/10.1017/s0021859600077686.
Testo completoAbstract (sommario):
SUMMARYPlant:soil ratios (CRs) of 85Sr concentration were studied in wheat, lucerne, lettuce, radish, string bean (Phaseolus vulgaris), and cucumber grown in pots in eight Greek soil types in a glasshouse pot experiment in 1989.The CRs of the crops and of the plant parts studied differed according to soil type. They ranged from 0·034–1·39 for wheat grains to 7·6–36·5 for cucumber stems and leaves. The CRs of the edible parts were much lower than those of the other plant material.The correlation between CRs and clay content was negative and, in most cases, significant (P = 0·05–0·01) or highly significant (P < 0·01). The negative correlation improved (higher absolute value of r, lower variability) if clay plus silt content or cation exchange capacity was used instead of clay content.The correlation between CRs and soil properties was greatest for soil pH (r = –0·89) and decreased in the order: pH > total clay plus silt ≃ cation exchange capacity > total clay.
39
Jozefaciuk, Grzegorz, Kamil Skic, Agnieszka Adamczuk, Patrycja Boguta e Krzysztof Lamorski. "Structure and Strength of Artificial Soils Containing Monomineral Clay Fractions". Materials 14, n. 16 (19 agosto 2021): 4688. http://dx.doi.org/10.3390/ma14164688.
Testo completoAbstract (sommario):
Structure and strength are responsible for soil physical properties. This paper determines in a uniaxial compression test the strength of artificial soils containing different proportions of various clay-size minerals (cementing agents) and silt-size feldspar/quartz (skeletal particles). A novel empirical model relating the maximum stress and the Young’s modulus to the mineral content basing on the Langmuir-type curve was proposed. By using mercury intrusion porosimetry (MIP), bulk density (BD), and scanning electron microscopy (SEM), structural parameters influencing the strength of the soils were estimated and related to mechanical parameters. Size and shape of particles are considered as primary factors responsible for soil strength. In our experiments, the soil strength depended primarily on the location of fine particles in respect to silt grains and then, on a mineral particle size. The surface fractal dimension of mineral particles played a role of a shape parameter governing soil strength. Soils containing minerals of higher surface fractal dimensions (rougher surfaces) were more mechanically resistant. The two latter findings appear to be recognized herein for the first time.
40
Wright, Janet S. "Glacial comminution of quartz sand grains and the production of loessic silt: A simulation study". Quaternary Science Reviews 14, n. 7-8 (gennaio 1995): 669–80. http://dx.doi.org/10.1016/0277-3791(95)00048-8.
Testo completo
41
Smalley, Ian, e Samson Ng’ambi. "Problems with collapsible soils: Particle types and inter-particle bonding". Open Geosciences 11, n. 1 (16 novembre 2019): 829–36. http://dx.doi.org/10.1515/geo-2019-0064.
Testo completoAbstract (sommario):
Abstract A collapsible soil is composed essentially of a packing of mineral particles and a set of interparticle bonds holding the system together. Failure requires the bond system to fail and the soil structure to collapse. A natural hazard is presented. The soil structure may collapse inwards (consolidate), as in loess failure, or it may collapse outwards (disperse, disintegrate), as in the failure of quick-clays, some collapsing sands, some silty estuarine deposits, and in wind erosion of silty soils by saltating sand grains. Generalising about bonding systems allows two types of interparticle bond to be recognized: long range bonds and short range bonds. Long range bonds are found in clay mineral systems and allow the occurrence of plasticity. They are represented by c in the standard Coulomb equation. Short range bonds are found in inactive particle systems. These are soil systems where the constituent particles do not have a significant electrical charge. A slight deformation of a short-range bonded system causes much loss of strength. It is short range bonds which tend to dominate in collapsing soil systems, although in the complex case of loess the bond failure is initially mediated by long range bonds at the interparticle contact regions. A collapse failure involves a large scale remaking of the soil structure, and thus total failure of the bonding system. Generalising again- it can be claimed that five types of particle make up engineering soils: A active clay mineral particles (the smectites), B inactive clay mineral particles (e.g. kaolinite, illite), C very small inactive primary mineral particles (close to the comminution limit in size- mostly in the quick-clays), D silt (usually quartz silt), and E sand (usually quartz sand). The nature of type D particles contributes to the collapse of loess soils, the most widespread of the collapsing soil phenomena. The nature of type C particles controls the behaviour of quick-clays. C and D systems are essentially dominated by short-range bonds.
42
Afifah, Rohima Sera, Karmila Karmila e Nuruddin Kafy El-Ridlo. "KAJIAN MATERIAL SEDIMEN PANTAI BALIKPAPAN UNTUK MENGETAHUI VARIASI UKURAN BUTIR PARTIKEL PASIR (SAND) SEDIMEN". INFO-TEKNIK 22, n. 2 (5 gennaio 2022): 173. http://dx.doi.org/10.20527/infotek.v22i2.12391.
Testo completoAbstract (sommario):
Along the Balikpapan Beach, there are abundant sand-sized sediment particles. Sand is one of the unconsolidated sediment grains based on fractions on the Wentworth Scale. Unconsolidated Sediment is defined as Loose Material and/or sedimentary rocks that is not yet solid. Balikpapan Beach, based on the Regional Geological Map of Balikpapan sheet, formed the Alluvium Formation (abbreviated as Qa) of the Holocene Epoch, Quaternary. Alluvium formation (Qa) has an arrangement of rocks in the form of pebbles, gravel, sand, and clay. Samples of Unconsolidated Sediment or loose material and sedimentary rocks that is not yet solid are determined for grain size variations using the Sieving method.
The Seiving method or Sieve Test is a method for determining the size of the grains which will then be viewed on a scale and followed by the amount of grain size data that will be presented in graphical form to facilitate the type of grain size that dominates. The research focused on how the grain size on Balikpapan Beach based on the Wentworth Scale and Sorting data after the Sieve Test.
Sieve Test results measured Mesh#10, Mesh#20, Mesh#40, Mesh#60, Mesh#120, Mesh#200 and Filter Analysis of the relationship between Filter Diameter and Retained Percentage as follows: Granule by 3.53%, Sand (Very Coarse Sand by 3.53%, Coarse Sand by 4.75%, Medium Sand by 13.26%, Fine Sand by 66.26%, Very Fine Sand by 5.15%) and Coarse Silt by 3.35%. Therefore, particles in the area of research with the Sieve Test were dominated by Fine Sand particles. Fine Sand with grain size 0.125 – 0.25 mm tested with a filter diameter of 0.125 mm got a Retained Weight of 331.29 gr, Retained Weight Precentage of 66.26%.
43
Afifah, Rohima Sera, Karmila Karmila e Nuruddin Kafy El-Ridlo. "KAJIAN MATERIAL SEDIMEN PANTAI BALIKPAPAN UNTUK MENGETAHUI VARIASI UKURAN BUTIR PARTIKEL PASIR (SAND) SEDIMEN". INFO-TEKNIK 22, n. 2 (5 gennaio 2022): 173. http://dx.doi.org/10.20527/infotek.v22i2.12391.
Testo completoAbstract (sommario):
Along the Balikpapan Beach, there are abundant sand-sized sediment particles. Sand is one of the unconsolidated sediment grains based on fractions on the Wentworth Scale. Unconsolidated Sediment is defined as Loose Material and/or sedimentary rocks that is not yet solid. Balikpapan Beach, based on the Regional Geological Map of Balikpapan sheet, formed the Alluvium Formation (abbreviated as Qa) of the Holocene Epoch, Quaternary. Alluvium formation (Qa) has an arrangement of rocks in the form of pebbles, gravel, sand, and clay. Samples of Unconsolidated Sediment or loose material and sedimentary rocks that is not yet solid are determined for grain size variations using the Sieving method.
The Seiving method or Sieve Test is a method for determining the size of the grains which will then be viewed on a scale and followed by the amount of grain size data that will be presented in graphical form to facilitate the type of grain size that dominates. The research focused on how the grain size on Balikpapan Beach based on the Wentworth Scale and Sorting data after the Sieve Test.
Sieve Test results measured Mesh#10, Mesh#20, Mesh#40, Mesh#60, Mesh#120, Mesh#200 and Filter Analysis of the relationship between Filter Diameter and Retained Percentage as follows: Granule by 3.53%, Sand (Very Coarse Sand by 3.53%, Coarse Sand by 4.75%, Medium Sand by 13.26%, Fine Sand by 66.26%, Very Fine Sand by 5.15%) and Coarse Silt by 3.35%. Therefore, particles in the area of research with the Sieve Test were dominated by Fine Sand particles. Fine Sand with grain size 0.125 – 0.25 mm tested with a filter diameter of 0.125 mm got a Retained Weight of 331.29 gr, Retained Weight Precentage of 66.26%.
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Haines, John, e Jim Mazzullo. "The original shapes of quartz silt grains: A test of the validity of the use of quartz grain shape analysis to determine the sources of terrigenous silt in marine sedimentary deposits". Marine Geology 78, n. 3-4 (gennaio 1988): 227–40. http://dx.doi.org/10.1016/0025-3227(88)90111-9.
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Limantseva, Oxana A., e E. G. Potapov. "Thermodynamic Simulation of Essentuki Type Mineral Water Formation". E3S Web of Conferences 98 (2019): 05012. http://dx.doi.org/10.1051/e3sconf/20199805012.
Testo completoAbstract (sommario):
Thermodynamic models of Essentuki and Nagutsky fields of Caucasian Mineral Waters deposits (KMW) are developed. The models are based on laboratory studies of core samples of aptian-albian lower Cretaceous rock dissolution. The rock samples were disintegrated up to 0.25 mm grains. The rock grains were mixed with distilled or mineral waters and the mixtures were kept at 20-25°С and 65-70°С, carbon dioxide pressure of 4.04 MPa. The results of experimental and thermodynamic modeling are showed that aqueous solution composition formed, in particular, microcomponent concentrations, depends on the rock cement composition (clayey, calcic, siliceous, ferriferous, chloritic, zeolitic phosfatic, sulfatic or mixed) and on the percentage of the microelement mineral-bearing in the water-bearing rock. Also the aqueous solution composition depends on temperature and CO2 partial pressure in the silt - rain water CO2 system. Thermodynamic modeling of the system confirmed gypsum dominant role in sulfate type water formation against pyrite role.
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Demuro, Martina. "Initial OSL dating results for sedimentary silt-sized quartz grains from Galeria archaeological site, Atapuerca, Spain: observations on multi-grain and single-grain datasets". Quaternary International 279-280 (novembre 2012): 115. http://dx.doi.org/10.1016/j.quaint.2012.07.510.
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Kasprzak, Marek, e Michał Łopuch. "Sand: A Critical Component for Beach Volleyball Courts". Applied Sciences 12, n. 14 (10 luglio 2022): 6985. http://dx.doi.org/10.3390/app12146985.
Testo completoAbstract (sommario):
Beach volleyball is growing in popularity. However, the construction of beach sports courts away from the seashore requires the use of the right quality sand, the desired characteristics of which are defined by FIVB standards. We decided to test sand from 11 volleyball courts in Wrocław, Poland and sand from the Central Sport Centre-Olympic Preparation Centre (CSC-OPC) in Spała, the main training facility for Polish beach volleyball players. Laboratory tests showed that too coarse sand containing admixtures of dark minerals was used for most of the courts in Wrocław. The sand containing the properties most similar to FIVB standards is that at CSC-OPC. Even a small amount of silt found does not guarantee that a sandy surface will be dust-free. Silt can adhere to larger mineral grains and separate from them by mechanical impact or from crushing aggregates. In addition, we surveyed volleyball players. The players unequivocally interpreted the ease of play on finer-grained sands and the reduction of movement dynamics on courts with coarse-grained sand. Nevertheless, these are not the only factors determining their preference for their favourite court. Compliance with FIVB standards, however, guarantees comparable playing conditions.
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Marot, Didier, Fateh Bendahmane e Jean-Marie Konrad. "Multichannel optical sensor to quantify particle stability under seepage flow". Canadian Geotechnical Journal 48, n. 12 (dicembre 2011): 1772–87. http://dx.doi.org/10.1139/t11-074.
Testo completoAbstract (sommario):
An optical sensor was designed to measure the fine solid particles concentration contained in a fluid flow. This sensor is composed of four light-emitting diodes and four associated light-dependent resistors, allowing the measurement of fluid transparency. Given the small device dimensions, it can be placed close to the particles exit from the specimen. The optical sensor is able to instantaneously measure a large range of clay or silt concentrations in the effluent, without a significant influence of flow rate. The presence of sand grains in fluid flow can be detected. The use of this sensor with a specific triaxial device allows precise characterization of the initiation and development of the suffusion process on clayey sand specimens. It is shown that suffusion of clay particles induces a decrease of hydraulic conductivity, which is due to a diffuse process of eroded particles filtration. Clay suffusion and filtration processes are influenced by grain-size distribution and also by grain shape of the coarse fraction. Under a high hydraulic gradient, clay suffusion can be accompanied by sand erosion. The critical value of mean pore velocity to initiate clay suffusion was determined for the types of soils.
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Watanuki, T., A. S. Murray e S. Tsukamoto. "A comparison of OSL ages derived from silt-sized quartz and polymineral grains from Chinese loess". Quaternary Science Reviews 22, n. 10-13 (maggio 2003): 991–97. http://dx.doi.org/10.1016/s0277-3791(03)00053-2.
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Lacelle, Denis, Véronique Juneau, André Pellerin, Bernard Lauriol e Ian D. Clark. "Weathering regime and geochemical conditions in a polar desert environment, Haughton impact structure region, Devon Island, Canada". Canadian Journal of Earth Sciences 45, n. 10 (ottobre 2008): 1139–57. http://dx.doi.org/10.1139/e08-063.
Testo completoAbstract (sommario):
This study examines the physical and geochemical properties of near-surface sediments, as well as the geochemical and stable O–H–C isotope composition of (ground)surface waters in and around the Haughton impact structure region (Devon Island, Nunavut) to determine the types of weathering (mechanical, (bio)chemical) and their relative contribution in this polar desert environment. The surface sediments collected from the Allen Bay and Thumb Mountain formations surrounding the impact crater are dominated by sand-sized particles; whereas the impact melt breccias inside the crater have a greater abundance of silt-sized particles. The subsurface sediments in the Allen Bay formation show a near equal amount of sand- and silt-sized particles. However, the micromorphologies of the sand-sized particles collected at the surface revealed that these grains, irrespective of the local geology, were heavily fractured. By contrast, fractures and rounded pits are observed on the surface of the sand grains located within the active layer; whereas those located just above the permafrost table have only rounded cavities on their surface. The (ground)waters also show variations in their solute concentration with depth; the highest concentrations being found in the groundwaters near the top of permafrost. Taken together, these observations suggest that there is a progressive evolution from a mechanically dominated weathering regime near the surface, to increasing chemical weathering with depth. The transition from mechanical weathering near the surface to increasing chemical weathering with depth can be attributed to the decreasing frequency and intensity of mechanical weathering processes (i.e., frost action, wetting–drying, thermal dilation) with depth, and to the presence of permafrost, which allows a greater availability of water for chemical aqueous reactions at the base of the active layer.