AGGREGATE SIZE DISTRIBUTION OF SELECTED TERENGGANU BEACH AREA

2015 ◽  
Vol 77 (32) ◽  
Author(s):  
Noraisyah Sapon ◽  
Rosnan Yaacob ◽  
Mohd-Lokman Husain ◽  
Mohd-Zaini Mustapa ◽  
Rokiah Suriadi
Keyword(s):  
Grain Size ◽  
High Tide ◽  
Size Fraction ◽  
River Mouth ◽  
Aggregate Size ◽  
Coarse Grained ◽  
Northeast Monsoon ◽  
Sediment Size ◽  
Mean Size ◽  
One Year

In general, the Terengganu beaches consist mainly of medium- to coarse-grained sand. Grain sizes were determined by dry sieving sediments; samples represent the upper 15 cm of surficial sediment, collected from the three main geomorphological tidal units during one year observation periods, covering the southwest and northeast monsoon seasons. The result demonstrates a good relationship between the monsoonal processes and the corresponding geomorphological elements. There are some differences between the various geomorphological tidal units, with a subtle trend from the low tide to high tide zone. Grain size decreases slightly from the low tide to the high tide. The sediment size fraction averaging from -0.48phi to 1.87phi. The most fine material was found at Kuala Besut (northernmost Terengganu) while the coarsest particle was found at Seberang Takir. However, the grain size parameters at different beach locations do not suggest a general trend of long-shore variations, except on the beach close to the river mouth. The differences between the seasons were larger than those between the geomorphological tidal units. During the northeast monsoon the mean size was coarser, sorting was worse and the distribution was more positively skewed.

scholarly journals ANNUAL CHANGES OF BEACH PROFILE AND NEARSHORE SEDIMENT DISTRIBUTION OFF DUNGUN-KEMAMAN,TERENGGANU, MALAYSIA

2018 ◽  
Vol 80 (5) ◽  
Author(s):  
Rosnan Yaacob ◽  
Hasrizal Shaari ◽  
Noraisyah Sapon ◽  
Mohd Fadhli Ahmad ◽  
Effi Helmi Arifin ◽  
...  
Keyword(s):  
Surf Zone ◽  
River Mouth ◽  
Coarse Sand ◽  
Sediment Distribution ◽  
Proper Understanding ◽  
Sediment Size ◽  
Dominant Component ◽  
Beach Processes ◽  
Mean Size ◽  
One Year

A proper understanding of beach processes must include the adjacent shallow marine waters or nearshore environment. This paper focused on the sedimentological and morphological investigation of Terengganu coastal area stretch lies between Dungun and Kemaman. The study area comprised five beaches and 36 nearshore stations. The present investigation attempts to study the time variation of the grain-size along the coast and in order to observe one-year cycle of the perpendicular profile of the beach. Teluk Lipat beach faced a huge modification compared to other beaches. The severely-eroded beaches in the study area characterized by coarse sand. Sediments from backshore and upper beach zone decreased in mean size and became poorly sorted towards surf zone area. Meanwhile, superficial sediment distribution of nearshore area revealed that silt is the most dominant component and the sediment size became coarser towards the shoreline. The results favor an alternative explanation, indicating that the river is the main source for the coastal sands, which are probably reworked by longshore currents on opposite directions apart from the river mouth, resulting on coastal propagation.

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

2001 ◽  
Vol 73 (1) ◽  
pp. 121-133 ◽  
Author(s):  
MARCIA DE MELO FARIA ◽  
BRAZ A. SANCHEZ
Keyword(s):  
Heavy Metal ◽  
Grain Size ◽  
Clay Minerals ◽  
Bottom Sediments ◽  
River Sediments ◽  
Size Fraction ◽  
River Mouth ◽  
Guanabara Bay ◽  
Metal Contents ◽  
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 Consideration of modern sendimentary processes of the Evros river delta front and prodelta, NE Aegean sea

2018 ◽  
Vol 34 (2) ◽  
pp. 709 ◽  
Author(s):  
Θ. Δ. ΚΑΝΕΛΛΟΠΟΥΛΟΣ ◽  
Β. ΚΑΨΙΜΑΛΗΣ ◽  
Μ. Ο. ΑΓΓΕΛΙΔΗΣ ◽  
Ε. ΚΑΜΠΕΡΗ ◽  
Α. ΚΑΡΑΓΕΩΡΓΗΣ
Keyword(s):  
Grain Size ◽  
Sedimentary Cover ◽  
River Mouth ◽  
River Delta ◽  
Coarse Grained ◽  
Delta Front ◽  
Long Distance ◽  
Sediment Distribution ◽  
Eastern Area ◽  
Evros River

Gravity cores data from the Evros River delta front and prodelta confirm the aspect that the Evros River deltaic deposits tend to west-northwest, along the main direction of the local hydrodynamic regime, preventing the construction of a symmetrical Holocene prism. In the delta front, the terrigenous sediment consists mostly of fine-grained material. Its vertical succession is monotonous with slight differences in grain size or colour, and lack of internal structure or current-produced laminae, indicating almost immutable sedimentary processes as well as long-term discharge fluctuations. The river-borne sand is limited because of its entrapment in the river mouth but sometimes, during extreme conditions (periods of high river discharge, short-lived catastrophic events etc.), can be transported seawards covering an extensive area of the Alexandroupolis Gulf. The negligible biogenic content and the absence of bioturbation effects are attributed to the high rates of deposition. Some bioturbated horizons are produced when sedimentation rates decrease temporarily. The prodelta sediment distribution patterns occur a distinctive zonation along an east-southeast to westnorthwest trend. In the central part, mud dominates, while on both sides of this area, the content of sand gradually increases and becomes the prevalent facies near the coast and in the outer plateau of the gulf. The vertical facies sequences of the upper sedimentary cover are complicated, with many variations in grain size, colour and biogenic content reflecting a complicated manner of deposition. The major feeder of this area is the Evros River providing great amounts of suspended load. Another remarkable source of sand is derived from the coastline, which during storm conditions provides coarse-grained material in the shoreface area. Finally, a sediment supplier of local importance, Loutros River, affects the eastern area of Alexandroupolis building up a small subaqueous fan. In the open sea, the consequences of the modern sedimentation are negligible. The sandy character of the surface and sub-surface sediments, the analysis of biogenic fragments, the long distance from the present-day terrigenous sources are some evidences which lead to the view that the upper sediment body of the southwestern part of the study area has a presumable relict origin. 210Pb profiles are, more of less, consistent showing a sedimentation rate more than 2 cm/yr in the delta front, which decreases to 0.2 cm/yr at about 8 km seaward.

Three-Dimensional Morphological and Mineralogical Characterization of Testate Amebae

2013 ◽  
Vol 19 (6) ◽  
pp. 1511-1522 ◽  
Author(s):  
Eric Armynot du Châtelet ◽  
Catherine Noiriel ◽  
Maxence Delaine
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Three Dimensional ◽  
Size Fraction ◽  
Environmental Scanning Electron Microscopy ◽  
Mineralogical Composition ◽  
Mineralogical Characterization ◽  
Sediment Size ◽  
Morphological Studies

AbstractTestate amebae are unicellular shelled protozoa commonly used as indicators in ecological and paleoecological studies. We explored the potential application of three-dimensional (3D) X-ray micro-tomography used in addition to 2D techniques (environmental scanning electron microscopy, electron probe micro-analysis, and cathodoluminescence) for detailed characterization of agglutinated shells of protozoa. We analyzed four specimens of the aquatic testate ameba Difflugia oblonga (Arcellinida), to test whether size distribution and mineral composition of shell grains diverged from sediment size distribution and mineralogical composition. From the 3D images, the geometry of the specimens (size and mass) and of the individual grains forming the specimen (grain size distribution and volume) were calculated. Based on combined chemical, mineralogical, and morphological analyses we show that D. oblonga is able to selectively pick up the small size fraction of the sediment with a preference for low-density silicates close to quartz density (~2.65). The maximum size of the grains matches the size of the pseudostome (shell aperture), suggesting the existence of a physical limit to grain size used for building the shell. This study illustrates the potential of this combined approach to characterize agglutinated shells of protozoa. This data can be useful for detailed morphological studies with applications in taxonomy and ecology.

scholarly journals Submarine lava deltas of the 2018 eruption of Kīlauea volcano

2021 ◽  
Vol 83 (4) ◽  
Author(s):  
S. Adam Soule ◽  
Michael Zoeller ◽  
Carolyn Parcheta
Keyword(s):  
Grain Size ◽  
Pore Pressure ◽  
Mechanistic Model ◽  
Large Fraction ◽  
Volcanic Hazards ◽  
Lava Flows ◽  
Coarse Grained ◽  
Fine Grained ◽  
Fine Grain ◽  
Delta Formation

AbstractHawaiian and other ocean island lava flows that reach the coastline can deposit significant volumes of lava in submarine deltas. The catastrophic collapse of these deltas represents one of the most significant, but least predictable, volcanic hazards at ocean islands. The volume of lava deposited below sea level in delta-forming eruptions and the mechanisms of delta construction and destruction are rarely documented. Here, we report on bathymetric surveys and ROV observations following the Kīlauea 2018 eruption that, along with a comparison to the deltas formed at Pu‘u ‘Ō‘ō over the past decade, provide new insight into delta formation. Bathymetric differencing reveals that the 2018 deltas contain more than half of the total volume of lava erupted. In addition, we find that the 2018 deltas are comprised largely of coarse-grained volcanic breccias and intact lava flows, which contrast with those at Pu‘u ‘Ō‘ō that contain a large fraction of fine-grained hyaloclastite. We attribute this difference to less efficient fragmentation of the 2018 ‘a‘ā flows leading to fragmentation by collapse rather than hydrovolcanic explosion. We suggest a mechanistic model where the characteristic grain size influences the form and stability of the delta with fine grain size deltas (Pu‘u ‘Ō‘ō) experiencing larger landslides with greater run-out supported by increased pore pressure and with coarse grain size deltas (Kīlauea 2018) experiencing smaller landslides that quickly stop as the pore pressure rapidly dissipates. This difference, if validated for other lava deltas, would provide a means to assess potential delta stability in future eruptions.

scholarly journals Mudrock Microstructure: A Technique for Distinguishing between Deep-Water Fine-Grained Sediments

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 653
Author(s):  
Shereef Bankole ◽  
Dorrik Stow ◽  
Zeinab Smillie ◽  
Jim Buckman ◽  
Helen Lever
Keyword(s):  
Grain Size ◽  
Deep Water ◽  
Sedimentary Facies ◽  
X Ray Diffraction ◽  
Weak Current ◽  
Large Area ◽  
Fine Grained ◽  
Mean Size ◽  
The Mean ◽  
Water Facies

Distinguishing among deep-water sedimentary facies has been a difficult task. This is possibly due to the process continuum in deep water, in which sediments occur in complex associations. The lack of definite sedimentological features among the different facies between hemipelagites and contourites presented a great challenge. In this study, we present detailed mudrock characteristics of the three main deep-water facies based on sedimentological characteristics, laser diffraction granulometry, high-resolution, large area scanning electron microscopy (SEM), and the synchrotron X-ray diffraction technique. Our results show that the deep-water microstructure is mainly process controlled, and that the controlling factor on their grain size is much more complex than previously envisaged. Retarding current velocity, as well as the lower carrying capacity of the current, has an impact on the mean size and sorting for the contourite and turbidite facies, whereas hemipelagite grain size is impacted by the natural heterogeneity of the system caused by bioturbation. Based on the microfabric analysis, there is a disparate pattern observed among the sedimentary facies; turbidites are generally bedding parallel due to strong currents resulting in shear flow, contourites are random to semi-random as they are impacted by a weak current, while hemipelagites are random to oblique since they are impacted by bioturbation.

The Effect of Grain Size on Superplastic Deformation of Ti-6Al-4V Alloy

2007 ◽  
Vol 551-552 ◽  
pp. 387-392 ◽  
Author(s):  
Wen Juan Zhao ◽  
Hua Ding ◽  
D. Song ◽  
F.R. Cao ◽  
Hong Liang Hou
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Superplastic Deformation ◽  
Initial Strain Rate ◽  
Deformation Mode ◽  
Tensile Tests ◽  
Optical Microscope ◽  
Coarse Grained ◽  
Transmission Electron ◽  
Grain Growth Model

In this study, superplastic tensile tests were carried out for Ti-6Al-4V alloy using different initial grain sizes (2.6 μm, 6.5μm and 16.2 μm) at a temperature of 920°C with an initial strain rate of 1×10-3 s-1. To get an insight into the effect of grain size on the superplastic deformation mechanisms, the microstructures of deformed alloy were investigated by using an optical microscope and transmission electron microscope (TEM). The results indicate that there is dramatic difference in the superplastic deformation mode of fine and coarse grained Ti-6Al-4V alloy. Meanwhile, grain growth induced by superplastic deformation has also been clearly observed during deformation process, and the grain growth model including the static and strain induced part during superplastic deformation was utilized to analyze the data of Ti-6Al-4V alloy.

Structure of Low Cobalt Alloy for Permanent Magnets of Basis System Fe-Cr-Co at Complex Two-Level Loading in Isothermal Conditions

2007 ◽  
Vol 539-543 ◽  
pp. 2928-2933 ◽  
Author(s):  
V.S. Yusupov ◽  
A.I. Milyaev ◽  
Galia F. Korznikova ◽  
Alexander V. Korznikov ◽  
J.K. Kovneristii
Keyword(s):  
Grain Size ◽  
Active Zone ◽  
Single Phase ◽  
Permanent Magnets ◽  
Phase Region ◽  
The Body ◽  
Coarse Grained ◽  
Isothermal Conditions ◽  
Basis System ◽  
Level Loading

Results of experimental research into evolution of the structure and microhardness of the hard magnetic Fe-30Cr-8Co-0,7Ti-0,5V-0,7Si alloy during complex two-level loading (compression + torsion) in isothermal conditions at various temperatures in single-phase region are reported. It was revealed that the deformation leads to a strong refinement of initial coarse-grained structure in the whole volume of the sample, however the generated structure is non-uniform through the body of the sample. In an active zone of deformation, near to mobile head, there is a microcrystalline layer with a grain size of about 5 microns which thickness poorly depends on the formation. With removal from the active zone of deformation the grain size increases, and microhardness decreases.

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