Application of Grain Size Analysis to Study Sedimentary Environment of Sand Dune in the Vicinity of Tumen River

The average size of the sand of dune in the vicinity of Tumen River is 0.12～0.30 mm, its standard deviation is 0.45～0.99 φ and the frequency cumulative distribution curve is divided into the single peak and the double peak. The Ski of the single peak is negative and the double peak is positive. There are two different areas in the plot of the Ski versus σi* It is shown that the sedimentary environment of the dunes is neritic deposit by the expressions of the grain-size parameters. All of the characters show that the sand dunes in Estuary of Tumen River may be the dunes of sea facies which were changed again by weathering and fluvialaction.

The reverse sediment transport trend between abandoned Huanghe River(Yellow River) Delta and radial sand ridges along Jiangsu coastline of China——an evidence from grain size analysis

To reveal the sediment transporting mechanism between the abandoned Huanghe River （Yellow River） Delta and radial sand ridges, “End Member” Model and grain size trend analysis have been employed to separate the “dynamic populations” in the surficial sediment particle spectra and to determine the possible sediment transporting pathway. The results reveal four “dynamic subpopulations”（EM1 to EM4） and two reverse sediment transporting directions： a northward transport tend from the radial sand ridges to mud patch, and a southward transport trend in deep water area outside the mud patch. Combined with the published hydrodynamic information, the transporting mechanism of dynamic populations has been discussed, and the main conclusion is that the transporting of finer subpopulations EM1 and EM2 is controlled by the “anticlockwise residual current circulation” forming during tidal cycle, which favor a northward transporting trend and the forming of mud patch on the north of radial sand ridges, while the transporting of coarser EM3 is mainly controlled by wind driven drift in winter, which favors a southward transporting direction.

Changes of grain size from peat profile in eastern mountainous area over past 2000 years,Jilin Province,Northeast China

Plenty of high-resolution paleoclimate investigations of the last thousand years were carried out to potentially predict future climate changes.Mountainous ombrotrophic peatland is one of the best recorders for high-resolution paleoclimate studies in the forest area.Grain size analysis was carried out on ombrotrophic peat profile in the eastern mountainous region of Jilin Province,Northeast China.The peat profile lasts the past 2000 a by four radiocarbon(AMS14C)ages.The results showed that the inorganic minerals in the peat profile are mainly silt,with some contribution from clay and a minor amount of sand,which are mainly due to wind dust and suspended transportation.Two paleoclimate stages are found in this peat profile by phytolith analysis,peat cellulose isotope research and historical documents:ca.45–1550 AD,relatively cold period;ca.1550 AD–present,relatively warm period.This finding is important for the initial study of paleoclimatic changes over the last 2000 a in the mountainous area of eastern mountainous area,Jilin Province,Northeast China.

The application of geostatistics in grain size trend analysis： A case study of eastern Beibu Gulf

There are 71 surface sediment samples collected from the eastern Beibu Gulf. The moment parameters （i.e. mean size, sorting and skewness） were obtained after applying grain size analysis. The geostatistical analysis was then applied to study the spatial autocorrelation for these parameters; while range, a parameter in the semivariogram that meters the scale of spatial autocorrelation, was estimated. The results indicated that the range for sorting coefficient was physically meaningful. The trend vectors calculated from grain size trend analysis model were consistent with the annual ocean circulation patterns and sediment transport rates according to previous studies. Therefore the range derived from the semivariogram of mean size can be used as the characteristic distance in the grain size trend analysis, which may remove the bias caused by the traditional way of basing on experiences or testing methods to get the characteristic distance. Hence the results from geostatistical analysis can also offer useful information for the determination of sediment sampling density in the future field work.

Assessment of sediment connectivity using modelling and field-based approaches in the Slavíč River catchment(MoravskoslezskéBeskydy Mts,Czech Republic)

Mountain streams act as conveyors of sediments within the river continuum,where the physical transport of sediments between river reaches through the catchment or between individual parts(e.g.,between hillslopes and channels)of the catchment is assumed.This study focused on sediment connectivity analysis in the SlavíčRiver catchment in the MoravskoslezskéBeskydy Mts in the eastern part of the Czech Republic.The connectivity index and connectivity index target modelling were combined with an analysis of anthropogenic interventions.Additionally,field mapping,grain size of bed sediments and stream power analysis were used to obtain information about connectivity in the catchment.Based on the analysis and obtained results,terrain topography is the current main driving factor affecting the connectivity of sediment movement in the SlavíčRiver catchment.However,the modelling provided valuable information about high sediment connectivity despite different recent land use conditions(highly forested area of the catchment)than those in historical times from the 16th to 19th centuries when the SlavíčRiver catchment was highly deforested and sediment connectivity was probably higher.The analysis of anthropogenic interventions,field mapping,grain size of bed sediments and stream power analysis revealed more deceleration of sediment movement through the catchment,decreased sediment connectivity with bed erosion,and gradual river channel process transformation in some reaches.Field mapping has identified various natural formations and human-induced changes impacting the longitudinal and lateral connectivity in the SlavíčRiver.For instance,embankments along 48%of the river's length,both on the right and left banks,significantly hinder lateral sediment supply to the channel.Stream power index analysis indicates increased energy levels in the flowing water in the river's upper reaches(up to 404.8 W m^(-2)).This high energy is also observed in certain downstream sections(up to 337.6 W m^(-2)),where it is influenced by human activities.These conditions lead to intensified erosion processes,playing a crucial role in sediment connectivity.Similar observations were described in recent studies that pointed out the long-term human interventions on many streams draining European mountains,where a decrease in sediment connectivity in these streams is linked with sediment deficits and the transformation of processes forming channels.

An Improved Method of Laser Particle Size Analysis and Its Applications in Identification of Lacustrine Tempestite and Beach Bar：An Example from the Dongying Depression

Grain size analysis is a common method in the study of sedimentology. For the consolidated sedimentary rocks, the traditional methods are rock slice observation and image analysis. In recent years, laser particle size analyzer is used widely in particle size analysis of sedimentary rock. Unlike the pretreatment of loose samples, the rock samples must be crushed, added acid to wipe out cement, and washed. However, in the step of washing, most of the fines component（less than 63 μm） in the suspended state should be inevitably lost. It will significantly affect the accuracy of particle size analysis, especially for siltstone. This paper presents a siltstone sample pretreatment method which core step is washing acid by centrifuge. Compared with traditional decantation method, the results show that the median particle size reduced 33.2 μm on average. Compared with the precipitation method which is commonly used for handling loose samples, the change of solid-liquid separation time is from 12 h to 10 min, while the average reduction of median particle size is about 15 μm. The grain size value corresponded to the cumulative volume of 10%/90% reduced 2.5 μm/20.3 μm on average. The percentage of the clay component less than 2 μm increased 2.88% on average. The fine particle（2–4 μm） and silt component（4–63 μm） increased 1.71% and 5.56% on average. Based on this method, two kinds of similar lacustrine siltstone were analyzed. They are tempestite and beach bar which are difficult to identify in the Lijin sub-depression, Dongying depression, Shengli oilfield, China. The final grain-size probability plot of tempestite is the type of “one saltation component and three suspension components”. The content of suspension components can reach to 80%–90%. The beach bar is the type of “one saltation component and two suspension components”. The content of suspension components can reach to 40%–45%. They both have the characteristics of high slope which means well sorting. But they can be distinguished based on the suspension sedimentary characteristics which were preserved by maximum degree in this kind of sample pretreatment method.

Three Gorges Dam Controls Sediment Coarsening of the Mud Patch on the Inner East China Sea Shelf

The well-known Three Gorges Dam(TGD) within the Yangtze catchment launched its operation in 2003. The effect of the TGD operation on the sediment size on the East China Sea shelf is rarely known. High resolution(0.5 cm sampling) grain size analysis and 137 Cs and 210 Pb dating of the DH8-1 core were conducted with core collected from the distal part of a main sink for the modern Yangtze sediment entering the sea, the Min-Zhe Coastal Mud Deposits(MZCMD) on the inner East China Sea shelf. The 137 Cs dating results show that the core DH8-1 formed during 1946–2012 with a mean deposition rate of 0.65 cm yr^(-1), indicating that the 0.5 cm sampling for grain size analysis in this local area could reflect environmental changes generally on a one-year time scale. The mean grain size of DH8-1 core sediment that deposited after 2003 is significantly larger than that deposited during 1988–2002. After ruling out other possible factors, we infer that the sediment coarsening of DH8-1 core after 2003 is attributed to the TGD operation which causes the erosion of the Yangtze subaqueous delta. Specifically, the TGD operation significantly intensifies the declining trend of the Yangtze sediment loads to the sea despite no decreased water discharge, which results in extensive erosion of the Yangtze subaqueous delta. The relatively coarse sediment of the subaqueous delta is eroded and resuspended by ocean dynamics and then transported by coastal current, finally depositing on the MZCMD area. In addition, the general sediment fining of core DH8-1 that deposited during 1988–2002, comparing with 1946–1987, is mainly caused by dam construction and soil and water conservation within the Yangtze catchment. Our findings are helpful for better understanding the effects of such a huge dam as the TGD on a sediment sink like the MZCMD of such a large river as the Yangtze River.

Evolution of Quaternary Depositional Environments in Lop Nor,Xinjiang:Sedimentary Records from LDK01 Drilling

Lop Nur is located in the interior of Asian and the lowest part in the eastern Tarim Basin.It is the final destination of major river systems in Tarim Basin and the accumulation center of salt materials(Xia,1987).As

Classifying the sedimentary environments of the Xincun Lagoon,Hainan Island,by system cluster and principal component analyses

An understanding of the sedimentary environment in relation to its controlling factors is of great importance in coastal geomorphology,ecology,tourism and aquaculture studies.We attempt to deal with this issue,using a case study from the Xincun Lagoon,Hainan Island in southern China.For the study,surficial sediment samples were collected,together with hydrodynamic and bathymetric surveys,during August 2013.Numerical simulation was carried out to obtain high-spatial resolution tidal current data.The sediment samples were analyzed to derive mean grain size,sorting coefficient,skewness and kurtosis,together with the sand,silt and clay contents.The modern sedimentary environments were classified using system cluster and principal component analyses.Grain size analysis reveals that the sediments are characterized by extremely slightly sandy silty mud（ESSSM） and slightly silty sand（SSS）,which are distributed in the central lagoon and near-shore shallow water areas,respectively.Mean grain size varies from 0 to 8.0Ф,with an average of 4.6Ф.The silt content is the highest,i.e.,52% on average,with the average contents of sand and clay being 43% and 5%,respectively.There exists a significant correlation between mean size and water depth,suggesting that the surficial sediments become finer with increasing water depth.Cluster analyses reveals two groups of samples.The first group is characterized by mean grain size of more than 5.5Ф,whilst the second group has mean grain size of below 3.5Ф.Further,these groups also have different correlations between mean grain size and the other grain size parameters.In terms of the tidal current,the average values of the root mean square velocity（RMSV） are 7.5 cm/s and 6.9 cm/s on springs and neaps,respectively.For the RMSVs that are higher than 4 cm/s,a significant positive correlation is found between the content of the 63–125 μm fraction and the RMSV,suggesting that the RMSV determines the variability of the very fine sand fraction.Based on system cluster and principal component analyses（PCA）,the modern sedimentary environments are classified into three types according to the grain size parameters,RMSVs and water depth data.The results suggest the importance of grain size parameters and high-spatial resolution hydrodynamic data in differentiating the coastal sedimentary environments.