Assessment of Natural Enrichment of Heavy Minerals along Coastal Placers of India: Role of Lake and River Mouth Embayment and Its Implications

2021 ◽  
pp. 69-81
Author(s):  
Shayantani Ghosal ◽  
Sudha Agrahari ◽  
Debashish Banerjee ◽  
Debashish Sengupta
Keyword(s):  
River Mouth ◽  
Heavy Minerals ◽  
Natural Enrichment

scholarly journals SEDIMENTATION, TRANSPORT UND EROSION AN DER NORDKÜSTE KOLUMBIENS ZWISCHEN BARRANQUILLA UND DER SIERRA NEVADA DE SANTA MARTA

2016 ◽  
Vol 7 ◽  
Author(s):  
Von Axel Frhr ◽  
Von Erffa
Keyword(s):  
Sierra Nevada ◽  
River Mouth ◽  
Heavy Minerals ◽  
Morphological Evidence ◽  
Second Phase ◽  
Morphological Alterations ◽  
Longshore Drift ◽  
Geological Past ◽  
North Eastern ◽  
Magdalena River

The coast of Northern Colombia between Barranquilla and the Sierra Nevada de Santa Marta has been subject to swift morphological alterations in the near geological past. The Magdalena River mouth into the Caribbean Sea is actually in the western end of the region and has formed deltas in three phases during the recent Quaternary. The two older ones were destroyed by erosion ad can only be detected by submarine morphology. The second phase is represented by a delta, that reached its widest dimensions approximately 2.400 years ago. The then starting destruction continues untill today and is not yet finished. The recent mouth foresets the youngest delta of the Magdalena River. A westbound longshore current along the not always even shoreline is produced by north-eastern tradewinds. This current transports the eroded sediments of the second oldest delta to the mouth of the Magdalena River. Part of them helps to build its new delta, and part of them glides through submarine cañons to the deep sea. Besides the morphological evidence, sedimentary analysis of the shore sands shows: 1. a longshore drift of sediments from east to west. 2. a change in the balance of energy: sedimentation in the east; erosion in the west (placers of heavy minerals). The very important highway from Barranquilla to Santa Marta ist thus endangered by erosion in the near future. 3. the sources of the upper sedimentlayers in the shore area: in the oldest delta their provenance is the Sierra Nevada de Santa Marta; in the younger deltas the area of affluents of the Magdalena River.

scholarly journals Factors Controlling the Extreme Storm Surge Flooding - Insights From Coastal Sedimentary Record of the Southern Baltic Sea

2022 ◽  
Author(s):  
Karolina Leszczyńska ◽  
Karl Stattegger ◽  
Damian Moskalewicz ◽  
Robert Jagodziński ◽  
Mikołaj Kokociński ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Storm Surge ◽  
Heavy Minerals ◽  
Sedimentary Record ◽  
Sea Levels ◽  
Southern Baltic Sea ◽  
Extreme Storm ◽  
Southern Baltic ◽  
Surge Flooding

Abstract Climate change and related sea-level rise pose significant threats to sandy lowland coasts, which account for approximately 30% of the global coastline. However, the role of key controlling factors responsible for the frequency and extent of extreme storm surge of inundation regime is not yet fully understood. Here, we present the longest to date, high-resolution sedimentary record of extreme storm surge flooding from the microtidal southern Baltic Sea, spanning two periods: 3.6-2.9 ka BP and 0.7 ka BP until present. Wetland sediments, including sandy event layers, were analyzed by sedimentological (grain size, loss-on-ignition, micromorphology), geochronological (14C, 210Pb, 137Cs), geochemical (XRF), mineralogical (heavy minerals) and micropaleontological (diatoms) methods. Our results revealed that both periods are characterized by high-frequency storm surge flooding in order of 1.3 – 4.2 events per century. They are correlated to widely recognized enhanced storminess periods in NW Europe and took place during both rising and fluctuating sea levels. The presented results show that the storm surge driven coastal inundation frequency and extent largely depend on the development of coastal barriers (e.g., beach ridges). Thus, in the context of the future coastal storm surge hazard, the protection of existing coastal barriers is essential.

ROLE OF MOUTH PROCESSES IN THE DYNAMICS OF ACCUMULATIVE FORMS IN COASTAL ZONE OF BLACK SEA (WITHIN THE RUSSIAN SECTOR)

2018 ◽  
Author(s):  
М. Исупова ◽  
M. Isupova
Keyword(s):  
Black Sea ◽  
River Mouth ◽  
The Black Sea ◽  
Special Role ◽  
Coastal System ◽  
System A ◽  
Russian Sector ◽  
Mouth Bars ◽  
River Mouths

The processes in the river mouth areas play a special role in the formation and dynamics of coastal accumulative forms. The experience of Russian and foreign specialists on investigations of river mouths shows a modern intensification of sea impact on the river deltas in the world and enhance the abrasion of their delta coastlines. These processes show a trend of transformation of different mouths from the fluvial-dominated objects to the marine-dominated objects. A striking example of this process is the variability of the mouth fan, which has a complicated structure, and the mouth bars. In most cases, the structure of the mouth fan presents several successive layers. There are the following 1) abovewater and submarine sand layers; 2) layer of silty sediments of the sea slope of the mouth fan; 3) gently sloping layers of clay, component the foot of the mouth fan; 4) layer of shelf sand, not related to the formation of mouth fan. Each of these layers is characterized by a specific size and composition of sediments. Under intensification of abrasion of the mouth accumulative forms (accordance with the stage of this abrasion), the sediments significantly differed by composition, can be penetrate in the lithodynamic coastal system. A rather complex topography of the underwater slope rugged canyons is typical for the Russian coast of the Black Sea. Through these canyons, sediments, entering the river mouth area and playing an important role in the dynamics of coastal accumulative forms, can be delivered to the depths. These depths exclude of their return.

Phytoplankton Response to Freshwater Runoff: The Diversion of the Eastmain River, James Bay

1985 ◽  
Vol 42 (6) ◽  
pp. 1216-1221 ◽  
Author(s):  
R. Grant Ingram ◽  
Louis Legendre ◽  
Yvan Simard ◽  
Serge Lepage
Keyword(s):  
Phytoplankton Bloom ◽  
River Mouth ◽  
Mean Flow ◽  
Tidal Amplitude ◽  
James Bay ◽  
Hydroelectric Development ◽  
Water Column Stability ◽  
Freshwater Runoff ◽  
Before And After

Phytoplankton, nutrients, and hydrodynamic conditions were regularly sampled in the estuary of the Eastmain River (Québec) and offshore in James Bay, before and after the diversion of the river for hydroelectric development on 19 July 1980. In the estuary, mean flow decreased by over 90% and the semidiurnal tidal amplitude increased significantly over a 5-d period. The most dramatic event was a major phytoplankton bloom in the river mouth, during a 10-d period of higher water column stability in late August; the cells then remained and bloomed in the thin photic layer. This stresses the role of hydrodynamics (as determined here by the freshwater runoff) in the timing of phytoplankton blooms.

scholarly journals The role of Lithodoras dorsalis (Siluriformes: Doradidae) as seed disperser in Eastern Amazon

2017 ◽  
Vol 15 (2) ◽  
Author(s):  
Thiago A. P. Barbosa ◽  
Luciano F. A. Montag
Keyword(s):  
River Mouth ◽  
Stomach Contents ◽  
Euterpe Oleracea ◽  
Important Process ◽  
Seed Predator ◽  
Important Species ◽  
Seed Disperser ◽  
Flooded Forests ◽  
High Diversity

ABSTRACT Ichthyochory is an important process responsible for the high diversity of plant species in tropical flooded forests. Thus, this study aimed to investigate the role of a catfish species, Lithodoras dorsalis, as seed disperser in the flooded forests at the Amazon River mouth, Brazil. Analyzing the stomach contents of 371 individuals of Lithodoras dorsalis, the Germination Potential (GP%) and Germination Speed Index (GSI) of seeds that were removed intact were investigated. This allowed us to evaluate the germination performance of two important species of plants in Amazonia, Euterpe oleracea (Açaí) and Montrichardia linifera (Aninga), after passage through the digestive tract of this catfish species. Given that digestion by L. dorsalis reduced the germination viability of M. linifera and that seeds were often destroyed during consumption, we suggest that L. dorsalis may have a limited role as seed disperser of M. linifera and instead mostly act as seed predator. However, for the species E. oleracea, L. dorsalis was a potential disperser, since the performance of germination of these seeds was improved after digestion. In addition, the number of seeds consumed was directly proportional to the catfish’s body size, reinforcing the role of doradids as potential seed dispersers in tropical forests.

scholarly journals The Role of Bedload Transport in the Development of a Proglacial River Alluvial Fan (Case Study: Scott River, Southwest Svalbard)

Hydrology ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 173
Author(s):  
Waldemar Kociuba
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
River Mouth ◽  
Active Role ◽  
Bedload Transport ◽  
Alluvial Fan ◽  
Surface Erosion ◽  
The Individual ◽  
Active Channel

This study, which was conducted between 2010 and 2013, presents the results of direct, continuous measurements of the bedload transport rate at the mouth section of the Scott River catchment (NW part of Wedel-Jarlsberg Land, Svalbard). In four consecutive melt seasons, the bedload flux was analyzed at two cross-sections located in the lower reaches of the gravel-bed proglacial river. The transported bedload was measured using two sets of River Bedload Traps (RBTs). Over the course of 130 simultaneous measurement days, a total of 930 bedload samples were collected. During this period, the river discharged about 1.32 t of bedload through cross-section I (XS I), located at the foot of the alluvial fan, and 0.99 t through cross-section II (XS II), located at the river mouth running into the fjord. A comparison of the bedload flux showed a distinctive disproportion between cross-sections. Specifically, the average daily bedload flux QB was 130 kg day−1 (XS I) and 81 kg day−1 (XS II) at the individual cross-profiles. The lower bedload fluxes that were recorded at specified periods in XS II, which closed the catchment at the river mouth from the alluvial cone, indicated an active role of aggradation processes. Approximately 40% of all transported bedload was stored at the alluvial fan, mostly in the active channel zone. However, comparative Geomorphic Change Detection (GCD) analyses of the alluvial fan, which were performed over the period between August 2010 and August 2013, indicated a general lowering of the surface (erosion). It can be assumed that the melt season’s average flows in the active channel zone led to a greater deposition of bedload particles than what was discharged with high intensity during floods (especially the bankfull stage, effectively reshaping the whole surface of the alluvial fan). This study documents that the intensity of bedload flux was determined by the frequency of floods. Notably, the highest daily rates recorded in successive seasons accounted for 12–30% of the total bedload flux. Lastly, the multi-seasonal analysis showed a high spatio-temporal variability of the bedload transport rates, which resulted in changes not only in the channel but also on the entire surface of the alluvial fan morphology during floods.

scholarly journals Sediment transfer in the Rhône River Basin, Switzerland: the role of localized severe Alpine storm events on triggering turbidity currents in Lake Geneva

2021 ◽  
Author(s):  
François Mettra ◽  
Koen Blanckaert ◽  
Ulrich Lemmin ◽  
David Andrew Barry
Keyword(s):  
Large Scale ◽  
River Mouth ◽  
Sediment Concentration ◽  
Turbidity Currents ◽  
Storm Events ◽  
Lake Geneva ◽  
High Concentration ◽  
Low Velocity ◽  
Sediment Transfer

<p>In Lake Geneva, a deep peri-Alpine lake in Switzerland, the sublacustrine Rhône River delta presents a deep canyon, the Rhône Canyon. Previous studies and recent observations show that low-velocity underflows and high-velocity turbidity currents pass frequently in the Rhône Canyon. The former carry little sediment, are long-lasting, slow moving and typically occur in winter when the lake is destratified, whereas the latter are sediment-rich, short-lived and occasionally generate high velocities. In the present study, we revisit three different event types that can trigger turbidity currents in the Rhône Canyon: large-scale floods of the Rhône River, sublacustrine slides on the Rhône delta and short high concentration sediment transport events induced by localized severe storms in the Rhône watershed (~5500 km<sup>2</sup>). Simultaneous observations of hyperconcentrated sediment-laden floods or debris flows in small sub-catchments (as small as 4 km<sup>2</sup>), suspended sediment concentration at the Rhône river mouth, and velocity profiles in the Rhône canyon demonstrate how localized storm events trigger turbidity currents in the canyon. Evidence that these turbidity currents can continue into the deep hypolimnion of Lake Geneva is provided. Preliminary estimations of the frequency of turbidity currents relative to their type of triggering and their contribution to the total sediment load discharged into Lake Geneva are discussed.</p>

Bryozoa from the reefs off the Amazon River mouth: checklist, thirteen new species, and notes on their ecology and distribution

Zootaxa ◽  
2021 ◽  
Vol 4950 (1) ◽  
pp. 1-45
Author(s):  
LAÍS V. RAMALHO ◽  
FERNANDO C. MORAES ◽  
LEONARDO T. SALGADO ◽  
ALEX C. BASTOS ◽  
RODRIGO L. MOURA
Keyword(s):  
New Species ◽  
New Records ◽  
River Mouth ◽  
Amazon River ◽  
Northern Brazil ◽  
The Caribbean ◽  
Hard Structures ◽  
Turbid Zone ◽  
Upper Slope

The reef system off the Amazon River mouth extends from Amapá state to Maranhão state along the Brazilian Equatorial Margin, encompassing more than 10,000 km2 of rhodolith beds and high-relief hard structures on the outer shelf and upper slope. This unique hard bottom mosaic is remarkable for being influenced by the turbid and hyposaline plume from the world’s largest river, and also for representing a connectivity corridor between the Caribbean and Brazil. Bryozoans were recently recognized as major reef builders in the Southwestern Atlantic, but their diversity off the Amazon River mouth remained unknown. Here, we report on recent collections obtained from 23 to 120 m depth in Northern Brazil. Sixty-five bryozoan taxa were characterized using scanning electron microscopy, including 57, five and three taxa of Cheilostomatida, Cyclostomatida and Ctenostomatida, respectively. Cribrilaria smitti and three genera (Cranosina, Glabrilaria and Thornelya) are new records for Brazil, and 13 new species are herein described: Antropora cruzeiro n. sp., Cranosina gilbertoi n. sp., Cribrilaria lateralis n. sp., Crisia brasiliensis n. sp., Glabrilaria antoniettae n. sp., Micropora amapaensis n. sp., Parasmittina amazonensis n. sp., Plesiocleidochasma arcuatum n. sp., Poricella bifurcata n. sp., Pourtalesella duoavicularia n. sp., Stephanollona domuspusilla n. sp., Therenia dianae n. sp., and Thornelya atlanticoensis n. sp. Our results highlight the biodiversity significance of the Amazon reefs and the need for more comprehensive sampling to clarify the role of bryozoans in modern turbid-zone reefs and rhodolith beds. 

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