Journal articles on the topic 'Grains de silt/clastes'
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1
Helland, P. E., Pei-Hua Huang, and 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, no. 2 (September 1997): 177–86. http://dx.doi.org/10.1006/qres.1997.1916.
Abstract:
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.
2
Ubeid, Khalid Fathi, and Khaled Ahmed Ramadan. "Soil types and their relations with radon concentration levels in Middle Governorate of Gaza Strip, Palestine." Polish Journal of Soil Science 53, no. 1 (June 22, 2020): 55. http://dx.doi.org/10.17951/pjss.2020.53.1.55.
Abstract:
<p>Determination of natural radioactivity has been carried out in surface and core agricultural soil samples collected from various sites in the Middle Governorate – Gaza Strip, Palestine. Mechanical and chemical analysis has been done to determine soil characteristics. Radon activity concentration measurements were carried out using solid state nuclear tracks detectors, Cr-39. The mechanical analysis results show that they belong to two classes, sandy loam and loamy sand. The sandy loam soil was observed in the eastern side of the study area, whereas the loamy sand was observed in western and middle parts. The radon concentration levels were higher in core samples and were proportionate to the soil depth. Also they were higher in sandy loam than loamy sand soil samples. The radon concentration levels had a positive correlation with fine grains (clay- to silt-size) of soil sample which translocated from upper to lower horizons of soil during its development. Additionally, there was a positive correlation with pH and water content, whereas a negative correlation was observed with organic matter and potassium contents. The positive correlation referred to a large specific surface of fine grains which were located in lower horizons of soil and were able to adsorb more water and consequently led to high radon concentration levels.</p>
3
Krawczyk, Marcin, and Małgorzata Wieczorek. "New approach of clustering of late Pleni-Weichselian loess deposits (L1LL1) in Poland." Open Geosciences 12, no. 1 (September 23, 2020): 866–75. http://dx.doi.org/10.1515/geo-2020-0044.
Abstract:
AbstractThe results of grain size distribution of loess units are suitable for the study of past climate change. There are many methods for the analysis of the grain size, but clustering methods have not been used before. In this article, a new approach in the sediment research, the k-median method was used. This method separates the grain size classes of the youngest loess units of three loess-soil profiles in Poland: Biały Kościół, Złota and Tyszowce. In the analysis, only the content for the loess silt fraction (range from 4 to 63 µm) was used. This allowed eliminating the admixtures of sandy and clay fraction, considered as secondary material. For the purposes of this analysis, silt fractions were divided into smaller units using a 1/4 phi interval, resulting in 16 new subfractions. The grain size data from three profiles were combined into one data set. As a result, four classes with a similar internal of grain structure were obtained. The separated classes showed the sedimentological variability of the sediment well. It has been shown that the k-median method can be used to classify loess in a fast and objective way.
4
Borromeo, Laura, Sergio Andò, Christian France-Lanord, Giovanni Coletti, Annette Hahn, and Eduardo Garzanti. "Provenance of Bengal Shelf Sediments: 1. Mineralogy and Geochemistry of Silt." Minerals 9, no. 10 (October 18, 2019): 640. http://dx.doi.org/10.3390/min9100640.
Abstract:
This article illustrates a multi-technique frontier approach for the provenance study of silt-size sediments. The mineralogical composition of low-density and heavy-mineral fractions of four samples of fine to very coarse silt deposited on the Bengal shelf was analyzed separately for six different grain-size classes by combining grain counting under an optical microscope, Raman spectroscopy, and X-ray diffraction. The geochemical composition was determined on both bulk-sediment samples and on their <5-μm classes. Such a “multiple-window” approach allowed capturing the full mineralogical information contained in each sample, as well as the size-dependent intra-sample variability of all compositional parameters. The comparison between grain-size distributions obtained by different methods highlighted a notable fallacy of laser granulometry, which markedly overestimated the size of the finest mode represented by fine silt and clay. As a test case, we chose to investigate sediments of the Bengal shelf, where detritus is fed from the Meghna estuary, formed by the joint Ganga and Brahmaputra Rivers and representing the largest single entry point of sediment in the world’s oceans. The studied samples show the typical fingerprint of orogenic detritus produced by focused erosion of collision orogens. Bengal shelf silt is characterized by a feldspatho-quartzose (F-Q) composition with a Q/F ratio decreasing from 3.0 to 1.7 with increasing grain size, plagioclase prevailing over K-feldspar, and rich transparent-heavy-mineral assemblages including mainly amphibole with epidote, and minor garnet and pyroxene. Such a detrital signature compares very closely with Brahmaputra suspended load, but mineralogical and geochemical parameters, including the anomalous decrease of the Q/F ratio with increasing grain size, consistently indicate more significant Ganga contribution for cohesive fine silt. The accurate quantitative characterization of different size fractions of Bengal shelf sediments represents an essential step to allow comparison of compositional signatures characterizing different segments of this huge source-to-sink system, from fluvial and deltaic sediments of the Himalayan foreland basin and Bengal shelf to the Bengal Fan.
5
Monkul, Mehmet Murat, and Jerry A. Yamamuro. "Influence of silt size and content on liquefaction behavior of sands." Canadian Geotechnical Journal 48, no. 6 (June 2011): 931–42. http://dx.doi.org/10.1139/t11-001.
Abstract:
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.
6
Velbel, Michael. "Phoenix first to see silt grains on Mars." Nature 481, no. 7379 (January 2012): 29. http://dx.doi.org/10.1038/481029c.
7
Ryan, Adrienne L., and Stephen R. Cattle. "Do sand dunes of the lower Lachlan floodplain contain the same dust that produced parna?" Soil Research 44, no. 8 (2006): 769. http://dx.doi.org/10.1071/sr06051.
Abstract:
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
Freitas, Rosa, Susana Silva, Victor Quintino, Ana Maria Rodrigues, Karl Rhynas, and William T. Collins. "Acoustic seabed classification of marine habitats: studies in the western coastal-shelf area of Portugal." ICES Journal of Marine Science 60, no. 3 (January 1, 2003): 599–608. http://dx.doi.org/10.1016/s1054-3139(03)00061-4.
Abstract:
Abstract Two single-beam, seabed-classification systems, QTC VIEW Series IV and QTC VIEW Series V, were used to identify and map biosedimentary gradients in a mid-shelf area off Western Portugal. The survey area has a moderate slope, a depth ranging from 30 to 90 m along a 3.5-km axis perpendicular to the shoreline, and is characterized by smooth sedimentary and biological gradients. Ground truth for sediment grain size and macrofaunal communities was based on grab sampling at 20 sites. The sedimentary and biological data were analysed using classification and ordination techniques. The acoustic data were analysed with qtc impact software and classified into acoustic classes. The affinity groups obtained in each data set were mapped using a Geographics Information System. All showed good agreement and identified prevailing gradients along a northwest–southeast direction. Three acoustic classes were identified, corresponding to the predominant sediment types, namely fine sand with low silt and clay content, silty, very fine sand, and mud. A close relationship with benthic communities was also verified, although less marked because benthic communities continuously change along the northwest–southeast gradient. Overall, the acoustic system coupled with ground-truthing data was able to discriminate and characterize the various benthic biotopes in the survey area.
9
Catto, N. R. "Hydrodynamic distribution of palynomorphs in a fluvial succession, Yukon." Canadian Journal of Earth Sciences 22, no. 10 (October 1, 1985): 1552–56. http://dx.doi.org/10.1139/e85-163.
Abstract:
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.
10
McClung, J. E., and J. D. Mollard. "Predicting settlement at a damsite on a tunnel valley deposit in Alberta." Canadian Geotechnical Journal 24, no. 1 (February 1, 1987): 45–57. http://dx.doi.org/10.1139/t87-005.
Abstract:
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.
11
Lamirande, I., B. Lauriol, A. E. Lalonde, and I. D. Clark. "La production de limon sur des terrasses de cryoplanation dans les monts Richardson, Canada." Canadian Journal of Earth Sciences 36, no. 10 (October 1, 1999): 1645–54. http://dx.doi.org/10.1139/e99-072.
Abstract:
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.
12
Delage, Pierre, Martine Audiguier, Yu-Jun Cui, and Michael D. Howat. "Microstructure of a compacted silt." Canadian Geotechnical Journal 33, no. 1 (March 25, 1996): 150–58. http://dx.doi.org/10.1139/t96-030.
Abstract:
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.
13
Jonczak, Jerzy, Marek Degórski, and Bogusława Kruczkowska. "Comparing quartz silt surface microstructures in two sandy soils in young-glacial landscape of northern Poland." Soil Science Annual 67, no. 3 (September 1, 2016): 131–39. http://dx.doi.org/10.1515/ssa-2016-0016.
Abstract:
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%).
14
Demarco, Larissa Felicidade Werkhauser, Antonio Henrique da Fontoura Klein, and Jorge Antonio Guimarães de Souza. "Marine substrate response from the analysis of seismic attributes in CHIRP sub-bottom profiles." Brazilian Journal of Oceanography 65, no. 3 (September 2017): 332–45. http://dx.doi.org/10.1590/s1679-87592017124306503.
Abstract:
Abstract This paper presents an evaluation of the response of seismic reflection attributes in different types of marine substrate (rock, shallow gas, sediments) using seafloor samples for ground-truth statistical comparisons. The data analyzed include seismic reflection profiles collected using two CHIRP subbottom profilers (Edgetech Model 3100 SB-216S), with frequency ranging between 2 and 16 kHz, and a number (38) of sediment samples collected from the seafloor. The statistical method used to discriminate between different substratum responses was the non-parametric Kruskal-Wallis analysis, carried out in two steps: 1) comparison of Seismic Attributes between different marine substrates (unconsolidated sediments, rock and shallow gas); 2) comparison of Seismic Attributes between different sediment classes in seafloors characterized by unconsolidated sediments (subdivided according to sorting). These analyses suggest that amplitude-related attributes were effective in discriminating between sediment and gassy/rocky substratum, but did not differentiate between rocks and shallow gas. On the other hand, the Instantaneous Frequency attribute was effective in differentiating sediments, rocks and shallow gas, with sediment showing higher frequency range, rock an intermediate range, and shallow gas the lowest response. Regarding grain-size classes and sorting, statistical analysis discriminated between two distinct groups of samples, the SVFS (silt and very fine sand) and the SFMC (fine, medium and coarse sand) groups. Using a Spearman coefficient, it was found that the Instantaneous Amplitude was more efficient in distinguishing between the two groups. None of the attributes was able to distinguish between the closest grain size classes such as those of silt and very fine sand.
15
STREEL, Maurice, Jacques THOREZ, Mario V. CAPUTO, Stanislas LOBOZIAK, and José Henrique G. MELO. "Palynology and sedimentology of laminites and tillites from the latest Famennian of the Parnaiba Basin, Brazil." Geologica Belgica 3, no. 1-2 (April 1, 2001): 87–96. http://dx.doi.org/10.20341/gb.2014.025.
Abstract:
Varvelike rhythmites, usually laminated siltstones and shales with scattered clasts, are known from outcrops and well cores of the upper Cabeças Formation in the Parnaíba (Maranhão) Basin, Brazil, with sediments laid down under glacial and periglacial conditions. Palynological study from different lithologies, indicates a latest Famennian age (LN Zone). Sedimentological approach of one rhythmite indicates that the grain-size contrast clearly separate between silt and sand layers but that all layers, even the dark silty ones, show features characteristic of sediment-gravity flows. Lateral influx was permanent during the deposition of the sediment. Clay analyses reveal the predominance of kaolinite probably originated from Middle Devonian rocks. Latest Famennian miospores and acritarchs are present and confirm the marine character of the depositionnal environment but a large part (70%) of the palynological material is reworked from Givetian / Frasnian rocks. No reworked miospores from early to late Famennian can be demonstrated. At least two distinct source-areas of the reworked material, Givetian (or older) and Frasnian, can be recognized. Contemporaneous miospores are significally less present in the tillites and associated shale than in the laminites which suggest that they are produced locally, the glacial tongue, carrying the reworked part of the material, only partially overlapping adjacent environments. The rythmites are presumed to be true varves, the sandy layers being first settled after the local seasonal melting of the ice cover and the rush of fresh water supply into the sea, the silty layers being deposited when the spring water run-off decreases. The Vallatisporites mother-plant, believed to live in a swamp margin environment, might have been the first to produce spores immediately after the melting of the ice cover
16
Lancaster, Nicholas. "On the formation of desert loess." Quaternary Research 96 (April 29, 2020): 105–22. http://dx.doi.org/10.1017/qua.2020.33.
Abstract:
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., and Erin L. D. Sibley. "Threshold fines content and behavior of sands with nonplastic silts." Canadian Geotechnical Journal 57, no. 3 (March 2020): 462–65. http://dx.doi.org/10.1139/cgj-2018-0698.
Abstract:
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
Crouvi, Onn, Rivka Amit, Yehouda Enzel, Naomi Porat, and Amir Sandler. "Sand dunes as a major proximal dust source for late Pleistocene loess in the Negev Desert, Israel." Quaternary Research 70, no. 2 (September 2008): 275–82. http://dx.doi.org/10.1016/j.yqres.2008.04.011.
Abstract:
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.
19
Cattle, Stephen R., and Carol M. S. Smith. "Fabric of soil derived from parna and the riddle of transported pellets." Soil Research 56, no. 3 (2018): 219. http://dx.doi.org/10.1071/sr16343.
Abstract:
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.
20
Davidson, Donald. "Balneaves: Soil Thin Sections." Proceedings of the Prehistoric Society 58, S2 (1992): 23–25. http://dx.doi.org/10.1017/s0079497x00079172.
Abstract:
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.
21
Nemecz, Ernö, Márton Pécsi, Zsuzsa Hartyáni, and Timea Horváth. "The origin of the silt size quartz grains and minerals in loess." Quaternary International 68-71 (June 2000): 199–208. http://dx.doi.org/10.1016/s1040-6182(00)00044-6.
22
Chang, Ching S., and Mehrashk Meidani. "Dominant grains network and behavior of sand-silt mixtures: stress-strain modeling." International Journal for Numerical and Analytical Methods in Geomechanics 37, no. 15 (October 24, 2012): 2563–89. http://dx.doi.org/10.1002/nag.2152.
23
Setiady, Deny, and 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, no. 2 (February 15, 2016): 67. http://dx.doi.org/10.32693/bomg.30.2.2015.76.
Abstract:
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
24
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, no. 11 (November 1, 1985): 1736–39. http://dx.doi.org/10.1139/e85-182.
Abstract:
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.
25
Tita, G., M. Vincx, and G. Desrosiers. "Size spectra, body width and morphotypes of intertidal nematodes: an ecological interpretation." Journal of the Marine Biological Association of the United Kingdom 79, no. 6 (December 1999): 1007–15. http://dx.doi.org/10.1017/s0025315499001241.
Abstract:
Nematode species from three intertidal assemblages (St Lawrence Estuary, Quebec, Canada) were studied in order to form an ecological interpretation of three allometric attributes: body width, size spectra, and morphotypes. The three assemblages were characterized by a very similar sediment grain median (Md) but different silt–clay proportions: A1 (upper-tidal level; Md=122 μm; silt=34.8%), A3 (mid-tidal level; Md=182 μm; silt=12.8%), and A5 (lower-tidal level; Md=122 μm; silt=6.8%). Silt–clay proportions were an influential factor in determining the mean nematode body width, used as a morphological discriminant between burrowing and interstitial organisms. A plot of the number of species vs the body width-classes showed two peaks: between 19.3 and 22.6 μm (interstitial), and between 32.0 and 45.5 μm (burrowers). As for the size spectra, in sandy sediments the mean nematode individual biomass was smaller than in muddy sediments. As a consequence, the estimated mean individual respiration rate was greater in muddy (A1=2.26 nl O2 h−1) than sandy sediments (A3=1.25 nl O2 h−1; A5=1.12 nl O2 h−1). In contrast, estimated metabolic ratios were lower in A1 (2.78 nl O2 h−1 μg−1 dry weight, DW) than in A3 (2.95 nl O2 h−1 μg−1 DW) and A5 (3.01 nl O2 h−1 μg−1 DW) suggesting different productivity and/or physiological adaptations to different lifestyles (burrowing vs interstitial) between species inhabiting muddy or sandy sediments. Morphotypes (body width/body length ratio=w/l ratio) were found to be associated with feeding groups. Small w/l ratios were typical of microvores, while greater ratios were typical of epigrowth feeders and predators. Ciliate-feeders, deposit-feeders and facultative predators had intermediate ratios. A morphotype food-related hypothesis is proposed: the species morphotype reflects the quality of exploited food; a small w/l ratio (i.e. long gut) would favour digestive efficiency and would be an adaptation to low quality food (microvores); inversely, a greater w/l ratio (i.e. short gut) would be an adaptation to high quality food (epigrowth-feeders and predators).
26
Alexanderson, Helena. "Residual Osl Signals from Modern Greenlandic River Sediments." Geochronometria 26, no. -1 (January 1, 2007): 1–9. http://dx.doi.org/10.2478/v10003-007-0001-6.
Abstract:
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.
27
Balagurunathan, Yoganand, Edward R. Dougherty, Stanislav Frančišković-Bilinski, Halka Bilinski, and Neda Vdović. "MORPHOLOGICAL GRANULOMETRIC ANALYSIS OF SEDIMENT IMAGES." Image Analysis & Stereology 20, no. 2 (May 3, 2011): 87. http://dx.doi.org/10.5566/ias.v20.p87-99.
Abstract:
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.
28
Crompton, Jeff W., Gwenn E. Flowers, and Brendan Dyck. "Characterization of glacial silt and clay using automated mineralogy." Annals of Glaciology 60, no. 80 (December 2019): 49–65. http://dx.doi.org/10.1017/aog.2019.45.
Abstract:
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.
29
Maksimova, Ekaterina, and Evgeny Abakumov. "Micromorphological characteristics of sandy forest soils recently impacted by wildfires in Russia." Solid Earth 8, no. 2 (April 25, 2017): 553–60. http://dx.doi.org/10.5194/se-8-553-2017.
Abstract:
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.
30
Schuiling, R. D., and 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, no. 2 (December 6, 2011): 551–68. http://dx.doi.org/10.5194/esdd-2-551-2011.
Abstract:
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.
31
Milliken, Kitty L., Ying Shen, Lucy T. Ko, and Quansheng Liang. "Grain composition and diagenesis of organic-rich lacustrine tarls, Triassic Yanchang Formation, Ordos Basin, China." Interpretation 5, no. 2 (May 31, 2017): SF189—SF210. http://dx.doi.org/10.1190/int-2016-0092.1.
Abstract:
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.
32
McKissock, I., R. J. Gilkes, and W. van Bronswijk. "The relationship of soil water repellency to aliphatic C and kaolin measured using DRIFT." Soil Research 41, no. 2 (2003): 251. http://dx.doi.org/10.1071/sr01091.
Abstract:
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.
33
Anand, RR, and RJ Gilkes. "Muscovite in Darling Range bauxitic laterite." Soil Research 25, no. 4 (1987): 445. http://dx.doi.org/10.1071/sr9870445.
Abstract:
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.
34
Wright, Janet S. "Glacial comminution of quartz sand grains and the production of loessic silt: A simulation study." Quaternary Science Reviews 14, no. 7-8 (January 1995): 669–80. http://dx.doi.org/10.1016/0277-3791(95)00048-8.
35
Amit, Rivka, Yehouda Enzel, and Onn Crouvi. "Quaternary influx of proximal coarse-grained dust altered circum-Mediterranean soil productivity and impacted early human culture." Geology 49, no. 1 (September 11, 2020): 61–65. http://dx.doi.org/10.1130/g47708.1.
Abstract:
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.
36
Sim, Ho, Yungoo Song, Jaehun Kim, Eomzi Yang, Tae Sup Yun, and 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, no. 6 (June 9, 2020): 528. http://dx.doi.org/10.3390/min10060528.
Abstract:
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.
37
Song, Min, Ian Baker, and David M. Cole. "The effect of particles on dynamic recrystallization and fabric development of granular ice during creep." Journal of Glaciology 51, no. 174 (2005): 377–82. http://dx.doi.org/10.3189/172756505781829287.
Abstract:
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.
38
Hejduk, Agnieszka, and Leszek Hejduk. "Variability of suspended sediment grain size distribution in winter floods." Annals of Warsaw University of Life Sciences – SGGW. Land Reclamation 48, no. 2 (June 1, 2016): 141–51. http://dx.doi.org/10.1515/sggw-2016-0011.
Abstract:
Abstract Variability of suspended sediment grain size distribution in winter floods. The work presents the results of research concern variability of suspended sediment grain size, transported during the winter floods in agricultural catchment, in the period of hydrological years 2012-2015. The information about grain size distribution from nine winter flood events were collected over the study period, which allowed to analyze the variability of suspended sediment particle size during the various events. Grain size of sediment was determined using a laser particle size analyzer Mastersizer Microplus from Malvern Instruments Ltd. Variability of individual particle size classes were observed in each flood. Sand fraction dominated in seven of nine measured events. There was no significant increase of suspended sediment size in relation to the maximum of discharge. It can be explain by a relatively low discharge of recorded events. The percentage of material classified as clay (<4 μm) ranged from 0.08 to 1.01%, silt-sized material (>4 and <63 μm) ranged between 9.31 and 67.17% and sand-size material (>63 μm) ranged from 32.01 to 90.61%. The relationship between the particle size and the discharge requires further studies. The diameter d10, d50 and d90 and a standard deviation were calculated for each flood. Mean values of d50 for individual flood ranged between 41.05 and 191.32 μm with average value of 99.01 μm and average standard deviation of 32.57.
39
Chaolu, Yi. "Subglacial comminution in till — evidence from microfabric studies and grain-size distributions." Journal of Glaciology 43, no. 145 (1997): 473–79. http://dx.doi.org/10.1017/s0022143000035073.
Abstract:
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.
40
Chaolu, Yi. "Subglacial comminution in till — evidence from microfabric studies and grain-size distributions." Journal of Glaciology 43, no. 145 (1997): 473–79. http://dx.doi.org/10.3189/s0022143000035073.
Abstract:
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.
41
Watanuki, T., A. S. Murray, and S. Tsukamoto. "A comparison of OSL ages derived from silt-sized quartz and polymineral grains from Chinese loess." Quaternary Science Reviews 22, no. 10-13 (May 2003): 991–97. http://dx.doi.org/10.1016/s0277-3791(03)00053-2.
42
Papanicolaou, E. P., C. G. Apostolakis, V. Skarlou, C. Nobeli, and P. Kritidis. "Ratio of plant to soil concentrations of strontium-85 and its relation to properties of Greek soils." Journal of Agricultural Science 116, no. 2 (April 1991): 275–79. http://dx.doi.org/10.1017/s0021859600077686.
Abstract:
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.
43
Jozefaciuk, Grzegorz, Kamil Skic, Agnieszka Adamczuk, Patrycja Boguta, and Krzysztof Lamorski. "Structure and Strength of Artificial Soils Containing Monomineral Clay Fractions." Materials 14, no. 16 (August 19, 2021): 4688. http://dx.doi.org/10.3390/ma14164688.
Abstract:
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.
44
Limantseva, Oxana A., and 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.
Abstract:
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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Kasprzak, Marek, and Michał Łopuch. "Sand: A Critical Component for Beach Volleyball Courts." Applied Sciences 12, no. 14 (July 10, 2022): 6985. http://dx.doi.org/10.3390/app12146985.
Abstract:
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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Gowan, Evan J., Lu Niu, Gregor Knorr, and Gerrit Lohmann. "Geology datasets in North America, Greenland and surrounding areas for use with ice sheet models." Earth System Science Data 11, no. 1 (March 12, 2019): 375–91. http://dx.doi.org/10.5194/essd-11-375-2019.
Abstract:
Abstract. The ice–substrate interface is an important boundary condition for ice sheet modelling. The substrate affects the ice sheet by allowing sliding through sediment deformation and accommodating the storage and drainage of subglacial water. We present three datasets on a 1 : 5 000 000 scale with different geological parameters for the region that was covered by the ice sheets in North America, including Greenland and Iceland. The first dataset includes the distribution of surficial sediments, which is separated into continuous, discontinuous and predominantly rock categories. The second dataset includes sediment grain size properties, which is divided into three classes: clay, silt and sand, based on the dominant grain size of the fine fraction of the glacial sediments. The third dataset is the generalized bedrock geology. We demonstrate the utility of these datasets for governing ice sheet dynamics by using an ice sheet model with a simulation that extends through the last glacial cycle. In order to demonstrate the importance of the basal boundary conditions for ice sheet modelling, we changed the shear friction angle to account for a weaker substrate and found changes up to 40 % in ice thickness compared to a reference run. Although incorporation of the ice–bed boundary remains model dependent, our dataset provides an observational baseline for improving a critical weakness in current ice sheet modelling (https://doi.org/10.1594/PANGAEA.895889, Gowan et al., 2018b).
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Lo, S. R., and S. PR Wardani. "Strength and dilatancy of a silt stabilized by a cement and fly ash mixture." Canadian Geotechnical Journal 39, no. 1 (February 1, 2002): 77–89. http://dx.doi.org/10.1139/t01-062.
Abstract:
The mechanical behaviour of a weakly cemented silt was studied experimentally. The cementing agent was a cement and fly ash slurry, and the samples so formed were slightly cemented. In triaxial testing, both drained and undrained tests on saturated samples were conducted. Special zero effective stress tests were conducted to measure, directly, the contribution of bonding between grains to the enhanced strength and stiffness. The cemented soils were initially less dilatant than their respective parent soils but eventually became more dilatant than the parent soils. The shear strength data followed a curved failure surface that merged back, at high stress, into that of the parent soil. This feature can be captured by a failure function that models the contribution of cementing agent to strength as two parts, true bonding and increase in dilatancy rate at failure. Both parts degrade with an increase in confining stress, but at different rates.Key words: bonding, cemented soil, dilatancy, strength, triaxial testing.
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Lacelle, Denis, Véronique Juneau, André Pellerin, Bernard Lauriol, and 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, no. 10 (October 2008): 1139–57. http://dx.doi.org/10.1139/e08-063.
Abstract:
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.
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Lamoureux, Scott F. "Catchment and lake controls over the formation of varves in monomictic Nicolay Lake, Cornwall Island, Nunavut." Canadian Journal of Earth Sciences 36, no. 9 (September 1, 1999): 1533–46. http://dx.doi.org/10.1139/e99-040.
Abstract:
On the basis of thin-section sedimentology, 137Cs and 210Pb profiles, and the pronounced seasonality of runoff and sediment delivery, sediments from Nicolay Lake, Cornwall Island, Nunavut (77°46'N, 94°40'W) are interpreted as varves. In thin section, the laminae are conformable, normally graded units of silt and clay. Depending on the location in the lake, the varves frequently contain one or more subannual rhythmites and inclusions of coarse sand and silt grains. Given the unstratified nature of the lake, the rhythmites are interpreted as products of sediment inflow events derived from rainfall, snowmelt, or mass wasting processes. In the most proximal site, these rhythmites may reflect insolation-driven diurnal variations in sediment transport. Isolated coarse grains in the varves are interpreted as eolian sediments washed off the lake ice cover. The lake is currently isothermal, and persistent ice cover and cold inflow prevent the formation of thermal stratification. The high accumulation rate is a critical factor in varve formation and it is probable that increased sediment yield during the past 500 years has led to the formation of varves, compared to the underlying massive mud that accumulated when deposition was focused inland of the lake during higher relative sea level. Evidence in the catchment indicates that high-elevation deglacial deposits have acted as an important fine-grained sediment source throughout the Holocene. These sediments moved progressively downstream through a series of basins by successive degradation and aggradation controlled by glacioisostatic emergence, hence, limiting the progression of this paraglacial sediment wave to areas upstream of the lake until the late Holocene. These results identify the importance of shifting catchment boundary conditions on sediment yield throughout the Holocene, and also indicate the difficulty of interpreting low-frequency yield variations as the direct consequence of changing climate in similar varve records.
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Ubeid, Khalid. "The nature of the Pleistocene-Holocene palaeosols in the Gaza Strip, Palestine." Geologos 17, no. 3 (September 1, 2011): 163–73. http://dx.doi.org/10.2478/v10118-011-0009-2.
Abstract:
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.