La production de limon sur des terrasses de cryoplanation dans les monts Richardson, Canada

10.1139/e99-072 â—½  
1999 â—½  
Vol 36 (10) â—½  
pp. 1645-1654 â—½  
Author(s):  
I Lamirande â—½  
B Lauriol â—½  
A E Lalonde â—½  
I D Clark
Keyword(s):  
Grain Size â—½  
Size Fraction â—½  
Runoff Water â—½  
Chemical Action â—½  
Intergranular Porosity â—½  
Potential Source â—½  
Petrographic Analyses â—½  
Glacial Time â—½  
Richardson Mountains â—½  
Quartz Grains

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.

Measuring Bed Load Transport Rates by Grain-Size Fraction Using the Swiss Plate Geophone Signal at the Erlenbach

2016 â—½  
Vol 142 (5) â—½  
pp. 04016003 â—½  
Author(s):  
Carlos R. Wyss â—½  
Dieter Rickenmann â—½  
Bruno Fritschi â—½  
Jens M. Turowski â—½  
Volker Weitbrecht â—½  
...  
Keyword(s):  
Grain Size â—½  
Size Fraction â—½  
Bed Load â—½  
Load Transport â—½  
Bed Load Transport

scholarly journals Geochemistry and mineralogy of recent sediments of Guanabara Bay (NE sector) and its major rivers - Rio de Janeiro State - Brazil

2001 â—½  
Vol 73 (1) â—½  
pp. 121-133 â—½  
Author(s):  
MARCIA DE MELO FARIA â—½  
BRAZ A. SANCHEZ
Keyword(s):  
Heavy Metal â—½  
Grain Size â—½  
Clay Minerals â—½  
Bottom Sediments â—½  
River Sediments â—½  
Size Fraction â—½  
River Mouth â—½  
Guanabara Bay â—½  
Metal Contents â—½  
Recent Sediments

Geochemical and clay mineralogical studies of bottom sediments collected along the Macacu and Caceribu rivers and Guanabara Bay were carried out in order to investigate the relationship between major source areas and recent sediments of the bay. Clay mineralogy includes different groups with selective distribution conditioned by geomorphic features and depositional settings. Micaceous clay minerals are abundant near parent rock in the upper course, whereas kaolinite derived from varied sources is gradually concentrated towards the estuary. In the Guanabara Bay, kaolinite accumulates near river mouths, while micaceous clay minerals are converted into mixed layers in the estuary. Analyses of heavy metal contents reveal higher levels of Zn and Cu in sediments of the bay than in river sediments. Profiles along rivers indicate a downstream decrease of heavy metals, whereas in the bay geochemical trends display greater variations. In general river mouth sediments present the lowest concentrations. At the north and east of Paquetá Island anomalous areas with the highest heavy metal contents occur. Cu tends to concentrate in < 2mum grain-size fraction and indicates an association with micaceous clay minerals in the upper river course. However, Cu retention seems to be further controlled by other components of bottom sediments due to changes in physical and chemical conditions of the estuarine environment. Zn shows unstable behavior along the rivers and concentrates in the bay. Pb displays small variations from river to bay sediments, and accumulates mainly in the < 63mum grain-size fraction without any association with clay mineral. Geoaccumulation indexes of Cu, Pb and Zn classify the study area as unpolluted in both studied rivers and in the NE sector of the bay, though the enrichment factors are higher in the bay. The study does not indicate those rivers as major sources of heavy metal pollution to the bay.

scholarly journals Historic Lime-Mortar 14C Dating of Santa María La Real (Zarautz, Northern Spain): Extraction of Suitable Grain Size for Reliable 14C Dating

Radiocarbon â—½  
2012 â—½  
Vol 54 (01) â—½  
pp. 23-36
Author(s):  
Luis Angel Ortega â—½  
Maria Cruz Zuluaga â—½  
Ainhoa Alonso-Olazabal â—½  
Xabier Murelaga â—½  
Maite Insausti â—½  
...  
Keyword(s):  
Grain Size â—½  
Size Fraction â—½  
Northern Spain â—½  
14C Dating â—½  
Lime Mortar â—½  
Parish Church â—½  
Slaked Lime â—½  
Lime Mortars â—½  
Santa Maria â—½  
Detrital Carbonate

This paper describes a method for effective separation of the pure binder fraction of lime mortars for reliable radiocarbon dating. The methodology allows removal of the detrital carbonate fraction and the unburnt limestone particles, obtaining particles of under 1 μm. The extracted fraction ensured that all carbonate has been generated by slaked lime carbonation. Consequently, the measured carbon corresponds to atmospheric carbon. The proposed method allows to obtain pure datable binder, simplifying considerably the performance of radiometric measurements because dating other grain-size fraction is unnecessary. In order to prove the effectiveness of binder refining, the extraction method has been applied to 5 lime mortars of different archaeological periods from the perimeter walls of Santa María la Real parish church (Zarautz, northern Spain).

High resolution magnetostratigraphy and deposition cycles in the Nihewan Basin (North China) and their significance for stone artifact dating

Quaternary Research â—½  
2008 â—½  
Vol 69 (2) â—½  
pp. 250-262 â—½  
Author(s):  
Li Huamei â—½  
Yang Xiaoqiang â—½  
Friedrich Heller â—½  
Li Haitao
Keyword(s):  
Grain Size â—½  
Age Determination â—½  
Size Fraction â—½  
Close Relation â—½  
Homo Erectus â—½  
Chinese Loess Plateau â—½  
Chinese Loess â—½  
Susceptibility Data â—½  
Nihewan Basin â—½  
Stone Artifact

Three lacustrine sections in the Nihewan Basin, Xiaodukou, Donggutuo and Xiaochangliang (40.1–40.4°N; 114.6–114.7°E), were closely sampled for magnetostratigraphic and deposition cycle analysis. Rock magnetic investigations show that the characteristic remanent magnetization of the sediments is mainly carried by magnetite and hematite. The Xiaodukou sequence is one of the most complete sections in the basin and has recorded substantial parts of the Brunhes and Matuyama chrons back to the termination of the Olduvai subchron. Several subchrons within the Matuyama period have been documented such as the Jaramillo, the Cobb Mt. and others. The Matuyama/Brunhes boundary, the Jaramillo, as well as the Cobb Mountain events were observed also at Donggutuo. On the basis of grain size and susceptibility data and of field investigations, the sections are divided into two longer lasting lacustrine episodes with a fluvio-lacustrine deposit in between. They are structured by 15 high-frequency deposition sub-cycles. In each cycle, the grain size fines upwards, while magnetic susceptibility decreases. This behavior is due to cyclic water level change of the ancient lake Nihewan. At Xiaodukou, the variations of the 0.2 to 7.5 μm grain size fraction can be correlated with the marine oxygen isotope stages OIS 64–OIS 11. The grey-green clayey to silty Paleolithic stone artifact layers at Xiaochangliang and Donggutuo are located at depths of 55.4 m and 43–38.7 m, respectively. They were buried when the lake-level was rising. The artifact layers have been deposited around the Cobb Mountain event during the sedimentary sub-cycle 6 of the older lacustrine phase corresponding to OIS 35, 36. Thus in contrast to the results of other studies, the estimated age of the Xiaochangliang stone artifact layer does not exceed 1.26 Ma, while the Donggutuo stone artifact layers date back to 1.21–1.15 Ma. This age determination brings the Nihewan hominids in close relation to the findings of Homo Erectus at Lantian on the Chinese Loess Plateau.

scholarly journals Heavy Mineral Variability in the Yellow River Sediments as Determined by the Multiple-Window Strategy

Minerals â—½  
10.3390/min9020085 â—½  
2019 â—½  
Vol 9 (2) â—½  
pp. 85 â—½  
Author(s):  
Bingfu Jin â—½  
Mengyao Wang â—½  
Wei Yue â—½  
Lina Zhang â—½  
Yanjun Wang
Keyword(s):  
Particle Size â—½  
Grain Size â—½  
Yellow River â—½  
River Sediments â—½  
Size Fraction â—½  
Heavy Mineral â—½  
The Yellow River â—½  
Yellow River Sediment â—½  
Yellow River Sediments â—½  
End Members

In this study, heavy mineral analysis was carried out in different size fractions of the Yellow River sediment to extract its end-members. It shows that heavy mineral contents, species, and compositions vary in different grain sizes. Distribution curve of heavy mineral concentration (HMC) and particle size frequency curve are in normal distribution. In most samples, the size fraction of 4.5–5.0 Φ contains the maximum HMC (18% on average). Heavy mineral assemblages of the Yellow River are featured by amphibole + epidote + limonite + garnet. Amphibole content is high in coarse fraction of >3.0 Φ and reaches its peak value in 3.5–4.5 Φ. Epidote is rich in a size fraction of >3.5 Φ, and increase as the particle size becomes fine. Micas content is high in coarse subsamples of <3.0 Φ, but almost absent in fine grains of >4.0 Φ. Metallic minerals (magnetite, ilmenite, hematite, and limonite) increase as the sediment particle size become fine, and reach the peak in silt (>4.0 Φ). Other minerals such as zircon, rutile, tourmaline, garnet, and apatite account for about 15%, and mainly concentrate in fine sediment. Further analysis reveals that similarity value between the most abundant grain size group and wide window grain size group is high (0.978 on average). The grain size of 4.0–5.0 Φ ± 0.5 Φ is suitable to carry out detrital mineral analysis in the Yellow River sediments. Our study helps to eliminate cognitive bias due to narrow grain size strategy, and to provide heavy mineral end-members of the Yellow River sediment for provenance discrimination in the marginal seas of East China.

A Significant middle Pleistocene tephra deposit preserved in the caves of Mulu, Borneo

Quaternary Research â—½  
2012 â—½  
Vol 77 (3) â—½  
pp. 335-343 â—½  
Author(s):  
Joyce Lundberg â—½  
Donald A. McFarlane
Keyword(s):  
Grain Size â—½  
Isotopic Ratio â—½  
The Philippines â—½  
Plinian Eruption â—½  
Middle Pleistocene â—½  
Fall Deposit â—½  
Potential Source â—½  
Tephra Deposit â—½  
Potential Sources â—½  
Ratio Limit

A distinctive white sediment in the caves of Mulu, Sarawak, Borneo is a well-preserved tephra, representing a fluvially transported surface air-fall deposit, re-deposited inside the caves. We show that the tephra is not the Younger Toba Tephra, formerly considered as most likely. The shards are rod-shaped with elongate tubular vesicles; the largest grains ~ 170 μm in length; of rhyolitic composition; and 87Sr/86Sr ratio of 0.70426 ± 0.00001. U–Th dating of associated calcites suggest that the tephra was deposited before 125 ± 4 ka, and probably before 156 ± 2 ka. Grain size and distance from closest potential source suggests an eruption of VEI 7. Prevailing winds, grain size, thickness of deposit, location of potential sources, and Sr isotopic ratio limit the source to the Philippines. Comparisons with the literature give the best match geochemically with layer 1822 from Ku et al. (2009a), dated by ocean core stratigraphy to 189 ka. This tephra represents a rare terrestrial repository indicating a very substantial Plinian/Ultra-Plinian eruption that covered the Mulu region of Borneo with ash, a region that rarely receives tephra from even the largest known eruptions in the vicinity. It likely will be a valuable chronostratigraphic marker for sedimentary, palaeontological and archaeological studies.

Quartz surface microtextures and grain-size characteristics of Quaternary sediments in the Porcupine Strand area of coastal Labrador, Newfoundland, Canada

10.1139/e83-036 â—½  
1983 â—½  
Vol 20 (3) â—½  
pp. 377-387 â—½  
Author(s):  
R. J. Rogerson â—½  
H. M. Hudson
Keyword(s):  
Grain Size â—½  
Distribution Data â—½  
Quartz Surface â—½  
Quaternary Sediments â—½  
Multivariate Statistical â—½  
Surface Textures â—½  
Systematic Fashion â—½  
Statistical Pattern â—½  
Quartz Grains â—½  
Scanning Electron

Sand-sized quartz grains from five Quaternary environments on the coast of Labrador were scrutinized under a scanning electron microscope. Various surface textural characteristics defined in previous literature were noted and "counted" in a systematic fashion. Multivariate statistical analysis of the data reveals that certain groups of surface textures provide for significant environmental identification, but no single surface texture is unique to any one environment. Absolute recognition of a particular environment from the presence of "diagenetic" features on several grains is not recommended for areas such as this. Yet the statistical pattern of scores for some features results in a position of individual samples and groups similar to the patterns obtained from the analysis of grain-size distribution data. The glacial environment appears to be no harder to define than most others in this type of analysis.

scholarly journals The movement of desert sand

1936 â—½  
Vol 157 (892) â—½  
pp. 594-620 â—½  
Keyword(s):  
Grain Size â—½  
Wind Velocity â—½  
Mass Movement â—½  
Mechanical Analysis â—½  
Sand Beach â—½  
Desert Sand â—½  
Eolian Sand â—½  
Percentage Weight â—½  
Surface Sand â—½  
Quartz Grains

It is well known that on a dry sand beach and, on a much larger scale, on sand-strewn desert country the wind, if above a certain strength, will cause the surface sand grains to rise and to travel down-wind as a low-flying cloud. The mechanism, however, by which ( a ) the grains composing this cloud are raised, ( b ) the rate of mass movement of the sand depends upon the wind velocity, or ( c ) the wind velocity close to the surface is affected by the presence of the sand cloud, does not appear to have been previously investigated experimentally. This mutual interaction of wind and sand grains is of interest both in connexion with the problem of the tendency of sand to heap itself up into dunes even in totally flat uniform plains, and also for the light it may throw on certain aspects of the allied problem of the transport of sediment by liquid currents. Sand found in the desert is usually composed of rounded quartz grains whose sizes range from small pebbles 2 to 3 mm. in diameter down to small particles 0∙01 mm. in diameter, which must be regarded as dust. Mechanical analysis of eolian sand for grain size show, when curves of percentage weight are plotted against grain size, that the peaks of such curves never occur on the small side of 0∙15 mm. diameter. Sand having this smallest peak size is found at the crests of dunes. Here the grains approach uniformity of size, so that the diagrams are sharp-peaked. On the other hand, sand deposits clear of the actual dunes give broad, low diagrams with the peak at a larger diameter. In every case the diagrams show only a few per cent by weight at a size of 0∙03 mm. In fact, it is a peculiarity of all sand accumulations that they are practically free from dust.

scholarly journals The Grain Size Influence on the E1' Centre Observed in Quartz of Atmospheric Deposition at Two Japanese Cities: A Preliminary Study

Geochronometria â—½  
2010 â—½  
Vol 37 (-1) â—½  
pp. 9-12 â—½  
Author(s):  
Yuya Yamamoto â—½  
Shin Toyoda â—½  
Kana Nagasima â—½  
Yasuhito Igarashi â—½  
Ryuji Tada
Keyword(s):  
Grain Size â—½  
Atmospheric Deposition â—½  
Oxygen Vacancies â—½  
Size Fraction â—½  
Mixture Ratio â—½  
Taklamakan Desert â—½  
Dust Sources â—½  
Preliminary Study

The Grain Size Influence on the E1' Centre Observed in Quartz of Atmospheric Deposition at Two Japanese Cities: A Preliminary StudyThe grain size influence on the number of oxygen vacancies in quartz was investigated by ESR in atmospheric deposition collected at two Japanese cities, Fukuoka and Akita, in 1969 and 1971. The finer grain size fraction shows the highest value of concentration of oxygen vacancies, most closely resembling dust originating in the Taklamakan desert. Month to month and year to year variation of the dependence was also observed which could possibly be attributed to the variation of the mixture ratio of at least two dust sources in China, A conclusive statement can not be made at this stage.

Sign in / Sign up

Export Citation Format

Share Document