Grain Size Distribution Characteristics Research Articles

Grain Size Evidence of Multiple Origins of Red Clays in the Jinhua-Quzhou Basin, South China

Six typical red clay profiles were sampled from Tangxi (TX), Langyaz (LYZ), South Shangshanwen (SSW), Xianqiao (XQ), Qijian (QJ) and Huhaitang (HHT) of Jinhua-Quzhou Basin, Zhejiang Province of China to evaluate the characteristics of grain size composition, distribution and parameters of red clays and to reveal the origin of red clays and interpret possible implications for paleoclimate in subtropical China. The results showed that red clays in TX, LYZ and SSW were fine and uniform, with no > 2 mm gravels and little > 63 μm fraction. They had a high content of 10–50 μm fraction, so-called “basic dust fraction”, and showed unimodal distributions, which were very comparable to those of the Xiashu Loess in southeastern China and the loess in North China. All these features reflected marked aeolian characteristics of the red clays in these areas. Red clays in XQ and QJ were much coarser than those in TX, LYZ and SSW, with high contents of > 63 μm fraction and even containing > 2 mm gravels in some layers. The grain size distribution patterns showed significantly progressive trends from the lower profile to the upmost layer and could not be compared with those of the loess in North China or the Xiashu Loess, implying they might be derived from underlying parent rocks and had some inherited properties from bedrock. Red clays in HHT had high contents of > 63 μm fraction and contain many > 2 mm gravels in each layer. The grain size frequency curves showed multiple-peaks and some abrupt variations were also observed on the profile, revealing its alluvial or diluvial origin in HHT. The multiple origins of red clays reflected the diversity and complexity of the Quaternary environment in South China. It can be concluded that grain size is an effective proxy indicator for the origin of most deposits.

Study of Distal Pyroclastic‐flow Stratum from Tianchi Volcano in 1215 (±15) Eruption: Pyroclastic‐flow Over Water

AbstractIn this paper, we describe three strata at the distal part of the pyroclastic‐flow from the Tianchi volcano in 1215 (±15) eruption. One of the strata with crosslayers that are different from typical pyroclastic‐flow strata may come from a ground‐surge. The grain‐size and scanning electron microscopy (SEM) analysis was performed to study the origin of the pyroclastic‐flow. Characteristics of grain‐size distribution show that it is similar with the ash cloud. Through the SEM analyses, we found some quench structures with less damage on the surfaces of the vitric pumices. These phenomena indicate that there has been hydration in the transportation processes at the distal of pyroclastic‐flow. It has partly changed the transportation mechanism of pyroclastic‐flow, which transitions form dense flow to diluted flow. This paper develops a new distal pyroclastic‐flow model in the Tianchi volcano that can be divided into three stages, i.e. the quench stage, expanding stage and depositing stage.

水俣湾における浮遊懸濁物の粒度分布特性について

水俣湾における浮遊懸濁物の粒度分布特性について

Multifractal analysis to characterize urban surface dust volume-size distribution

Abstract The amount of ubiquitous urban environment surface dust with high contaminants is directly correlated with the degree of harm to the human body. This paper discusses the surface dust grain-size distribution characteristics by utilizing the multifractal model. The results indicate that urban surface dust particle distribution is a scattered distribution. Renyi-dimension spectra curves of dust are either nearly sigma shaped (q ≥ 0), or they follow a quasi-linear variation (q > 0). The Renyi dimensions (D(q)) and pH were found to have significance correlation. No relationship was found between D(q) and Arsenic (As). When q > 0, organic matter (OM) and Mercury (Hg) are positively correlated with Renyi dimensions. However, OM and Hg are not correlated with D(q) when q ≥ 0. The use of this multifractal model could be considered a way to express the contaminant level in dust. It may be taken into consideration in environment management strategies.

Influence of grain size distribution characteristics on compaction and deformation-strength characteristics of gravelly fill material

粒径の大きな礫を含んだ実盛土の変形・強度特性を求めるためには，原粒度試料を用いた大型三軸試験の実施が望ましいが，原粒度試料を用いた試験には数多くの制約があるため，粒度調整した小型供試体を用いた室内試験を実施するのが一般的である。一方，盛土の締固め管理には締固め度Dcを用いるが，盛土材の粒度を調整すると試料の変形・強度特性ばかりでなく締固め特性も変化する。したがって，実盛土の変形・強度特性を正しく求めるためには，締固め管理密度に相当する原粒度試料および各種室内粒度調整試料それぞれのせん断特性を明らかにした上で，適切な室内粒度調整法を選定する必要がある。そこで本研究では，兵庫県西宮市の宅地造成現場から採取した粒子形状が角張った砂礫盛土材および兵庫県南西端部を流れる千種川より採取した円礫が卓越した砂まじり礫盛土材のそれぞれについて，原粒度および異なる3通りの方法で粒度調整した試料を用いた一連の排水三軸圧縮試験を実施し，締固め特性およびせん断時の変形・強度特性に及ぼす粒度特性の影響を明らかにしている。

Grain-size characteristics of sediment in Daniugou peatland in Changbai Mountains, Northeast China: Implications for atmospheric dust deposition

The grain-size distribution characteristics and grain-size parameters of sediment in two vertical sections of Daniugou peatland in the Changbai Mountains were systematically investigated. A comparative analysis of the sediment granularity using a discriminative function with Hongyuan peat, red clay, loess-paleosol, fluvial deposit as well as lacustrine deposit was also conducted. It turns out that the vertical section of Daniugou peat ash is primarily constituted by clay and silt particles, and the content of sand is relatively small. Grain-size frequency curves generally show a single-peak modality while a bimodal pattern is detected in the upper layer. The grain-size component and peak pattern of grain-size frequency curves also illustrate that peat ash materials were transported to the peatland by long-range aeolian dust during the deposition process, while there existed short-distance dust influence in peat deposition of the upper layer. Comparisons of grain-size parameters and the discriminative Y-value of Daniugou peat ash with those of typical aeolian sediments show close similarities, suggesting the possibility that atmospheric dust transport processes were involved in the accumulation of peat again. Moreover, the variations of grain-size distribution suggest the local environmental deterioration which is just the driving force of local dust elevation. Grain-size analysis of peatland sediment is demonstrated to be one effective method to extract information about regional and global environmental evolution, and more attention should be paid to current local ecological environment and to seeking a balance between economic development and environmental protection in Northeast China.

Refinement of the geological model of the Verkhnesalat oil field (Tomsk district) based on lithofacies investigations of the middle-upper Jurassic productive bed

The Verkhnesalat oil field is confined to the Middle Vasyugan megaswell located in the southeastern part of the West Siberian Plate. Callovian‐Oxfordian rocks of this region are productive. The purpose of our study is to refine the geological structure of the Verkhnesalat oil field, in particular, to elaborate indexation of sand beds‐reservoirs. The necessity of such investigations stems from the following fact. Although the oil field was discovered in 1967, there is no agreement regarding the indexation of productive beds so far. At the same time, localization of the industrial object in well sections and its extension over the area should be established for putting the oilfield into operation. This study was based on geological‐geophysical materials (GIS data, results of core examination and description, assessment of capacitance‐filtration properties of rocks, and others) related to wells 21, 30, 31, 33, as well as comprehensive lithological‐petrographic study of the Well 28 section. Quantitative characteristics of grain size distribution, mineralogy, cement, pore space, and secondary processes in 42 thin sections were established based on the method suggested in [3]. Thin sections were prepared from samples preliminarily impregnated with resin under pressure. The Vasyugan Formation, which hosts the majority of petroliferous fields in the southeastern West Siberian Plate, is subdivided into the lower (clayey) and upper (silty‐sandy) units. In elevated areas (in particular, the Verkhnesalat local structure), lower parts of the Lower Vasyugan Subformation are enriched in sand. This fact was established by geologists of the Western Petroleum Exploration Expedition in 1991 who assigned index to productive beds at the base of the Lower Vasyugan J1 Subformation in wells 30 (interval 2490.0‐2503.0 m), 31 (2475.0‐2485.6 m), and 21 (2480.0‐2491.0 m). At the same time, Bed also included a sandy interlayer separated from the main bed by a clayey or clayey‐silty layer 2.4‐3.0 m thick. The author of the present communication believes that the interlayer should be

Evaluation of Various Pedo-Transfer Functions for Developing Soil-Water Characteristic Curve of a Silty Soil

Abstract This paper describes development of the soil-water characteristic curve (SWCC) of a silty soil by measuring its matric suction _m, corresponding to different gravimetric water contents w. To achieve this, a field tensiometer and a dew point potentiameter (WP4) were employed. For this soil, the SWCC was determined indirectly using the estimation algorithms known as pedo-transfer functions (PTFs), which are based on volume-mass properties and the grain-size distribution characteristics, and are available in a commercial database SoilVision. In addition to this, experimental results were used for developing the SWCC of the soil, using various fitting functions cited in the literature and available in the database. An attempt has been made in this technical note to demonstrate the usefulness of these three methods for obtaining the SWCC of the silty soil. The study reveals that the PTFs developed previously to estimate SWCCs match very well with the experimental results.

岡山県細池湿原にみられる過去３万年間の堆積環境

This study aims to reconstruct paleo-environments since 30 ka from the viewpoint of the characteristics of eolian dust and fluvial materials at Hosoike moor in the Chugoku Mountains, western Japan. We collected 2 boring cores 3 meters deep from the moor, which is located at 960 meters asl., on the Chugoku mountain ridge. The moor deposits, which have accumulated for 30 ka, consist of peat, silt, silt with organic matter, sand and gravel, and 4 tephras K-Ah, SUk, DHg, and AT. These deposits can be classified as fluvial material and eolian dust on the basis of the characteristics of ESR oxygen vacancy and grain size distribution. The fluvial material consists of coarse grain of more than 30 μm, while eolian dust consists of a finer material of less than 20μm. Peaks of lithogenic matter density, which consists of fluvial material, may be correlated with Interstadials 1 to 4, as indicated by the GRIP climate record. Fluvial materials were deposited during warmer, wetter periods such as the interstadial periods, whereas eolian dust was deposited during the drier colder periods of MIS 2 and 3. As Hosoike moor was located north of the polar front during MIS 2 and 3, eolian dust was transported from the pre-Cambrian rock areas of north Asia by northwesterly winds. During MIS 1, eolian dust is transported from the Chinese inland deserts by westerly winds.

Bimodal grain-size distribution of Chinese loess, and its palaeoclimatic implications

Grain-size analysis indicates that Chinese loess generally shows a bimodal distribution with a coarse and a fine component. The coarse component, comprising the main part of the loess, has pronounced kurtosis and is well sorted, which is interpreted to be the product of dust storms generated by low-altitude northwesterly winds. Its grain-size reflects the strength of the low-altitude circulation in the dust seasons of the year, and its percentage provides an indicator of the source area aridity and the frequency of dust storms. Conversely, the fine component has a wide grain-size range and is poorly sorted. Sedimentary illustrations based on the grain-size distribution characteristics of bulk samples and of detrital quartz suggest that the fine component probably represents the background dust load of the atmosphere and is mainly transported by high-altitude westerly airstreams. Its grain-size provides an estimate of the westerly air stream intensity. The coarse and fine components of a loess sample can be mathematically separated by fitting a designated mathematical distribution function to the measured grain-size data, and this procedure constitutes an approach for reconstructing the palaeowind system of Northern China.

Paleoenvironment and Period of The “Edoma” Formation in High Arctic Eastern Siberia

There exists large scale ground ice, which locally called “Edoma”, in plains along the Arctic coasts of eastern Siberia and the New Siberian Islands. The Edoma is mainly composed of massive ground ice with pillar-shaped frozen soil. The massive ice is considered as syngenetic ice-wedge origin, which develops alternative accumulations of ice-wedge and sedimentation on ground surface. The soil pillars are arranged in regular intervals of several meters in the massive ice, and contain a lot of ice lenses and several peat layers.A geological and geochemical survey was carried out in the Bykovsky Peninsula near the Lena Delta (Loc. 1), Bolshoi Lyakhovsky Island, the southern part of the New Siberian Islands (Loc. 2) and Oiyagosky Yar facing the Arctic Sea in middle of eastern Siberia (Loc. 3). Results of grain size analysis and determinations of radiocarbon datings of the Edoma in these surveyed sites were summarized as follows : 1) Sediments of the Edoma in Loc. 1 are composed of dark gray silt to fine sand with a lot of organic matters. Compositional ratio of grain size varies vertically, and is characterized by bimodality in the grain size distribution. This suggests that the sediments were formed under two different transportation agents. Sediments of the Edoma both at Loc. 2 and Loc. 3 characterized by dark gray to brown silt, and also contains abundant organic matter. Grain-size distribution of these sediments is similar to the finer population in Loc. 1. Judging from the characteristics of grain size distribution, these sediments are considered as aeolian deposits.2) Radiocarbon ages at Loc. 1 scatter within a range from about 30, 000 to 20, 000 yr BP in upper part and about 11, 000 yr BP in uppermost. The ages at Loc. 2 are resulted in about 30, 000 to 40, 000 yr BP in case of the most parts and about 7, 000 yr BP at uppermost part in permafrost just under the active layer. At Loc. 3, most of the ages of the Edoma are determined over 40, 000 yr BP and that of uppermost is determined as about 22, 000 yr BP.Based on the results of radiocarbon dating mentioned above, it is suggested that the Edoma in eastern Siberia might have formed during Karginkiy Interstadial to Sartan Stadial in the Last Glacial stage, and especially main parts of the Edoma developed during Karginkiy Interstadial, in which period climate was more unstable than Sartan Stadial. Grain size distribution of sediments also suggest that the Edoma have accumulated under the sedimental condition at water flood plain or marsh, which were favorable locations to growth of syngenetic ice wedge as well as loess accumulation. Supply of sediments in Loc. 1 may have been stable because the main transport of sediments have been performed by fluvial activities of the Lena River and the wind action. On the other hand, since the sediments in Loc. 2 and Loc. 3 is probably derived from aeolian loess, the amounts of supplied sediments might have been less than Loc. 1. Therefore, flux of sedimentation, forming the Edoma in Loc. 1 maintained longer than those at Loc. 2 and Loc. 3.