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The mean flow depth h (cm), water surface slope Se, flow stress t0 (dynes/cm2) and bedload transport rate q (milligram!
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The heavy minerals are highly concentrated close to the river, reaching 60 to 70% of bulk samples from the summer beach. The concentrations decrease systematically with longshore distance, being reduced to less than 2% after 20 km of longshore transport from the river mouth. The median grain sizes of the principal minerals generally become finer wi...
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... Presently, similar hydraulic sorting processes are noticed on other recent deltas, in which heavy minerals or placers are highly concentrated on opposite shores of the modern river mouths, where physical processes could have potentially concentrated these denser minerals. Examples occur at the Rosetta and Damietta Nile delta promontories [17], and comparable ones have been noted at the fluvial mouths of other deltas elsewhere, such as that of the Columbia River [71,72]. ...
... This landward shoreline retreat, corresponding to Phase III, was defined by Stanley and Clemente [41] and is shown in Figure 4. Hence, we interpret the considerable local concentrations of heavy minerals observed along the Nile shelf as markers of ancient Nile estuaries at or near the mouths of the former delta's fluvial branches. This phenomenon has also been noted in the modern marine settings of continental margins elsewhere [71][72][73]. ...
The most extensive coverage of surficial sediment samples collected to date on Egypt’s Nile Delta coast and shelf is needed to better define sediment dispersal patterns across this setting’s rapidly eroding margin. Changes in time are now induced by River Nile sediment cutoff by dams, sea level rise, marked shelf subsidence, and regional climate changes, which have altered the amounts and components of sediments; these require replacement, along with the implementation of more effective coastal protection measures. Multiple computer-generated offshore maps depict the distributions and proportions of sand, silt, and mud; the mean grain size and standard deviation (sorting); heavy mineral concentrations; and carbonate content. Heavy mineral lobes at the coast and offshore identify former Nile branch sites. Channel lobes extending seaward resulted from their progradational phase and from the delta’s altered sedimentation from the early to late Holocene. The progressive deposition and erosion of these fossil fluvial lobes, and of two active Nile channels, selectively removed their quartz and less dense minerals, thus concentrating heavy minerals on the coast and inner shelf. The prolonged dispersal of original sediment effluence from relict and recent Nile tributaries induced variable depositional patterns on the present shelf. These coastal depocenters, along with extensive sand, silt, and mud from shelf sediments, were reworked further seaward and dispersed by bottom currents, thus masking most previous onshore-to-offshore transport patterns. The major surficial features document long-term responses to the diverse dispersal that influenced the shoreline to the outer shelf deposits from the Pleistocene to the present.
... The dried sediment samples have been placed in the uppermost sieve as suggested by Lewis (1984). The sieve set (18,25,35,45, 60, 80, 120, 170, +230 and -230 mesh) was placed on Ro-Tap sieve shaking machine. Sieving of sand is carried out in the ASTM (American Society for Testing Materials) sieving sets at ½ φ interval using Ro-Tap sieve shaker continuously for about 15 minutes. ...
... The sediments transported along straight shoreline tend to become fine grain in the direction of transportation (Li and Komar, 1992;Frihy and Dewidar, 1993;and Ergin et al.2007). The study area is almost straight coastline and medium sands have been noticed in the mouths of rivers indicate that the sediments are transported from drainage network and mixing to the existing sediments in the foreshore, which will cause for local variation of mean grain size of the sediments. ...
The texture of a rock or sediment is the size, shape, and arrangement of the grains. The microgeometry of sediments deals with intergranular relationship of grains, their size and shape. In the present study, a total of sixty surficial sediment samples were collected from the study area (foreshore-20, berm-7, backshore-13, and dunes-20) with an interval of 1 km. The geology, geomorphology, drainage pattern, climate, waves, and currents are discussed. The grain size parameters viz., mean grain size, standard deviation, skewness, and kurtosis are discussed extensively. Sand is the predominant component in all the sediment samples (99.82–99.93%) whereas silt and clay contents are less than 1% from the four environments. The mean grain size of the sediment samples shows that medium grained sands are followed by fine grained sands indicating a low energy environment of deposition. The standard deviation values reveal that the sediments are well to moderately sorted. The average values of skewness indicate that all the sediment samples are negatively skewed to positively skewed representing an environment of deposition of low to moderate energy conditions. Most of the kurtosis values indicate that the sediments are of platykurtic to leptokurtic in nature. The platykurtic nature of sediments indicates the sorting of tail portions of sediment populations.
... The beach placer is formed through the process of chemical weathering or mechanical bulk rock and their reformatting along a continental shelf [7]. Across the coastal shorelines/beaches or river channels, these heavy minerals gather in placer deposits formed by chemical or mechanical concentrations of mineral particles from the debris storm [8]. It is deposited by a hydraulic process that occurs in very low concentrations in different types of fiery and transformed rocks, but also through the physicochemical process, the heavy minerals are concentrated by hindering the weathering process. ...
Abstract: Hatiya is the second largest island of Bangladesh and is situated near the Meghna River estuary in the central coastal zone of Bangladesh. This island hosts a few scenic beaches with a huge deposit of mineral sands. Representative mineral sand samples from various beaches of this island were collected during the year 2019, and analyzed for different mineralogical contents using state-of-the-art techniques, such as WD-XRF, XRD, SEM and EDX. This study determined various mineralogical contents, such as SiO2 (73.58%), micas (40.30%), Al2O3 (12.13%), TiO2 (0.56%), MgO (1.31%), Fe2O3
(4.71%), K2O (3.1%), Na2O (1.92%), CaO (3.16%), some earth metals, and heavy minerals, such as ilmenite (14.77%), garnet (11.02%), rutile (14.94%), magnetite (15.26%), andzircon
(13.63%), were identified in the analyzed samples. It is suggested that the studied sand can be utilized as a raw material in the glass industry, due to its high SiO2 content. The approximate prices of heavy and light minerals, such as garnet (USD 75–USD 210/mt), ilmenite (USD 110/mt), magnetite (USD 84/mt), rutile (USD 840/mt), zircon (USD 1050/mt) and micas (USD 109/mt), some oxides such as K2O (USD 350–400/mt), CaO (USD 350–450/mt), Al2O3 (USD 1000-USD 1300/mt), TiO2 (USD 4000–4500/mt), and Fe2O3 (USD 650–1500/mt), and some other heavy metals (Rb, Th, Ba, V, Cr, Cs, Ni and Co), indicates a great economic value of the sand of the Hatiya Island beaches. This study recommends that Hatiya Island’s minerals should be mined responsibly and used effectively, to enhance the nation’s economy.
... Further, it is known that selective entrainment of mineral grains by Cowing water might be the most important process involved in the development of these placers. It was shown by earlier workers Li and Komar 1991) that during entrainment, due to their lower densities and larger diameters, the grains of quartz and feldspars are more easily moved than the heavy minerals leading to the highest enrichment of placers. ...
The occurrence of workable beach placer deposits of garnet and ilmenite along the coastal region of southern Tamil Nadu is known for long. Though the adjoining rivers like Kallar, Vaippar and Vembar are generally thought to be the major contributors of placer minerals, especially garnet, to their respective beaches, none of the river basins has yet been explored. The present paper discusses the distribution, resource potential and geomorphic controls of garnet placer in the Vaippar basin using ArcGIS. Analysis of sediment samples collected from the Vaippar River and its tributaries shows that the concentration of garnet is up to 20 wt.% and predominantly localized in river alluvium, coastal alluvium and pediment. A distribution map of garnet for the entire basin (5508 km2) portrays three zones of enrichment: zone I: 0.06–1.0 million tonnes (Mt); zone II: 1.0–1.1 Mt; zone III: 1.1–1.21 Mt. It is estimated that in zone III (942 km2) for every 100 km2, about 17 km2 area has an average garnet reserve of 1 Mt and this could be profitably mined.
... In this area, foreshore micro-environment is considered as a high energy zone. The sediments that are transported along the straight coastline tend to have finer sand population, authenticate the trend of transport explained (Li and Komar, 1992). The sediments of this area are winnowed out the fine particles towards the berm by the actions of waves, which are very active in this zone, especially during the SW monsoon period. ...
Pre and post monsoonal changes in the environment have led to a noticeable variation in sediment characteristics, heavy mineral concentrations and their distribution. The current study aimed to find out the effect of seasonal fluctuations on the concentration of heavy minerals along the coast and the variations in sediment textures and distribution. The study has revealed the effect of seasons on the sediments supply and its distribution along coast in the study area. The total heavy minerals concentrations are more in post monsoon than in pre monsoon and the concentration also increases from south to north in parts of the study area because of seasonal circulation of currents from south to north along the shore. The micro textural study of the heavy mineral grains from different locations in the study area revealed the mechanical and chemical erosions on the grain surfaces.
... These heavy or dense minerals, both in modern and relict sands, are widely used as tracers of sand-transport paths and depositional patterns. This is because their concentration results in a large part from the selective sorting due to differences in size and density (Garzanti et al., 2009;Komar & Wang, 1984;Li & Komar, 1992). In the beach and nearshore sands of the Nile delta, heavy minerals have been successfully used for analyzing sediment sources, grain sorting processes, energy levels of transporting agents, and sediment provenance (Frihy, 2007;Komar, 2007;Stanley, 1989). ...
Surficial sediment samples collected from the recently formed fluvial delta in Lake Nasser/Nubia (Egypt and Sudan) in conjunction with data on bottom current and depth soundings are examined to interpret hydraulic-sorting processes and transport/depositional patterns. The ~500 km long northeastward trending lake, lies within Egypt and Sudan, is created as a result of the construction of the Aswan High Dam in 1964. The original grain-size distribution and heavy mineral compositions of these samples help to characterize the classical depositional features of the recently formed underwater delta-front and prodelta depocenters. Starting from the south, those delta-front deposits, which floor most of the narrow-shallow basin of Lake Nubia, are characterized by thick coarse-grained sandy deposits, rich in heavy minerals (averaged 12.8%). This delta-front is followed to the northeast by thin layers of prodelta mud, poor in heavy mineral contents (averaged 0.6%). These layers cover the entire broad basin of Lake Nasser. The northeasterly downslope fining-trend, along with a continuous decrease in heavy mineral composition, along the length of the lake, are attributable to processes of grain sorting, which take place due to contrasting densities and grain sizes. These processes lead to the concentration of heavy mineral placer, mostly in the delta-front samples. The sorting mechanism, in turn, is controlled by the interplay of unidirectional-directed northeastward current, physiographic characteristics of the lake, including topographic configuration, geometry (cross-section), and floor topography (slope gradient). In terms of mineral exploration, the highest proportion of mineral grades in the delta-front sediments is likely to be considered as a viable source for economic placers that require more planning initiatives for industrial and commercial evaluation
... The precise sorting mechanism separating the heavy and light minerals is still unclear and several hypotheses have been proposed including suspension sorting (Slingerland and Smith, 1986), selective entrainment sorting (Komar and Wang, 1984), transport sorting (Steidtmann, 1982) and shear sorting (Bagnold, 1954). On dissipative beaches with very broad swash zones (ca. 100 m or more) dominated by infragravity swash, for example, in Oregon, United States, selective entrainment and transport have been proposed as the most likely mechanisms (Komar and Wang, 1984;Li and Komar, 1992). On a steeper reflective beach with narrow swash zone (ca. ...
This chapter describes the morphological features and key processes related to the swash zone, situated at the landward edge of the inundated part of the beach system. It is where incoming surf zone waves force oscillatory motion of the shoreline at a variety of frequencies. Morphological features addressed include the beach face slope, beach berms, beach steps and beach scarps. Sediment sorting across the beach face profile and the formation of heavy mineral deposits are also discussed. In the recent literature, swash flow kinematics/dynamics and sediment transport mechanics have received more attention than the morphology. This research is discussed in the context of its relevance to an improved understanding of swash zone morphodynamics. Rather than presenting a detailed review of the available literature, the authors present their perspective on current research directions and outstanding issues still to be resolved.
... This unconsolidated sediment contains different types of minerals which are classified as valuable minerals (such as, barium, chromium, gold, iron, rare earth elements, tin, thorium, tungsten, and zirconium), and rock-form minerals (such as, feldspar, garnet, silica, etc.) (Sharma & Ram, 1964). Finding and extracting these valuable minerals poses a big challenge for countries and companies because the concentration of the typical heavy mineral sand ore deposit is usually found in low amounts (Berquist et al., 1990;Brown et al., 2009;Gent et al., 2005;Lenoble et al., 1995;Li & Komar, 1992;Noakes, 1977;Perissoratis et al., 1987;Praditwan, 1988;Roy, 1999). Modern sediment forms a stretch of varying width adjacent to marine water bodies all over the world. ...
The current study aimed to describe textural characteristics, heavy mineral composition, and grain microtextures of the sediment from three micro-environments (foreshore, berm, and dune). A total of forty-one (41) representative surficial sediment samples have been collected from fifteen (15) locations along the beach area between the Sarada and Gosthani rivers on the east coast of India, where the length of the stretch is more than 100 km. The study reveals that most of the coastal sediment is medium to fine sand with relatively high ratios of coarse sand at Yarada beach, and the nature of the sediment is moderately to well sorted. These characteristics indicate a high energy environment. The heavy mineral analysis of the sediment in the current study was done for coarse (þ60#) and fine (þ230#) size fractions. Studying the weight percentage (WT%) reveals that a high percentage of heavy minerals is associated with fine fractions. Ilmenite, sillimanite, garnet, zircon, and rutile are the major heavy minerals identified in the current investigation. The concentrations of these heavy minerals show great variations from south to north of the study area. From an economic point of view, a considerable amount of heavy minerals (average 48.41%) are present on both sides (north and south) of the Gosthani River mouth. In the Sarada Estuary, the concentration of the economic heavy minerals was found under the minimum economic range. The grain microtextures of the major heavy minerals from the different locations along the study area demonstrate the variation in grain microtextures, which is controlled by the chemical and mechanical processes. These microtextures reflect moderate to high wave energy on the beach area, in addition to high mechanical impact on the grains from the estuary point.
... Beach placers are formed when the mechanical or chemical weathering of rock masses and their redistribution along a continental shelf [14]. The sediments are sorted by gradual movement of the sea water, directing the coarser materials towards the shore and the finer materials into deep water [15]. The heavy minerals are gradually resistant to weathering and hence become concentrated. ...
Sea beaches are always a good source of heavy minerals around the world. Cox's Bazar has 120 km of unbroken sandy sea beach. The study includes the sea beaches of 5 upazilas (Moheshkhali, Kolatoli, Ramu, Ukhia, Teknaf) in Cox's bazaar district for studying the concentration, identification and investigation of heavy mineral deposits along the sandy beaches. This study has concentrated on the physical properties, identification, and abundance of the heavy minerals fraction in sediments collected from the study area. Satellite imagery Landsat-8 OLI was used for remote sensing verifications. The image processing and crucial analysis carried out using Environment for Visualizing Images (ENVI), Arc GIS and Erdas Imagine software. Coastal areas adjacent to Teknaf upazila has a very significant amount of heavy mineral reserves, almost 16%. The study has identified around nineteen variety of heavy minerals from the collected samples in the study area. Ilmenite, Kyanite, Garnet, Rutile, Zircon, Magnetite, Augite, Hornblende, Enstatite, Epidote, Andalusite, Hypersthene, Diopside and Cassiterite have been found the most abundant in the entire study area. The Coastline of Bangladesh was surveyed completely to map the heavy minerals which are potential resources for our national economy.
... In fact, the simultaneous high concentration of heavy minerals and fine sands in unvegetated shores together with the direct relationship between fine sand content and bulk density suggests a relatively high density of fine sands. Similarly, other studies have shown that coarser sediments associated with light minerals occur in relatively low erosive shores, where there are inverse relationships between the size and density of minerals (Li and Komar 1992;Frihy 1994). On the other hand, the volume of prop roots appears to influence the binding of coarse sediments and to restrict the transport of coarse sands within the swash zone. ...
Fringe mangroves face waves daily and are thought to protect against erosion in low wave energy sites and undergo erosion if exposed to high wave energy. We aimed to understand the effects of fringe mangroves on erosion and sediment dynamics and of wave exposure on seedling density at three sites of increasing wave energy. Sediment properties (mean grain size, sorting, and bulk density) were assessed within each site in unvegetated and mangrove-vegetated shores in wet and dry seasons. In addition, we estimated seasonal erosion/accretion rates for 2.4 years and seedling density in two zones from the forest edge with contrasting wave exposure. Regression analysis was carried out to explain sediment properties and erosion rate variance in response to the vegetation volume that opposes wave energy and to explain erosion rates in response to wave energy. Mangrove-vegetated shores reduced erosion rates from 3 to 15 times in the two sites with higher wave energy, while the vegetated site with the lowest wave energy experienced accretion compared to minor erosion along the unvegetated shore. Shores with greater Rhizophora mangle basal areas and vegetation volumes favored deposition of particles with low settling rates, different sediment classes, reduced erosion rates, and increased shoreline stability. Mangrove seedling density decreased between 2 and 43 times from the low wave exposure zone to the high wave exposure zone at the forest edge in studied sites. In order to increase vegetation volume, coastal adaptation based on mangroves must limit human disturbances and facilitate epiphytic relationships with oysters.
