scholarly journals THE IMPACT OF SEASONAL CHANGES ON HEAVY MINERALS CONCENTRATION FROM A PART OF EAST COAST OF INDIA

2020 ◽  
Vol 5 (1) ◽  
pp. 12-21
Author(s):  
Ali Mohammad ◽  
E.N. Dhanamjayarao
Keyword(s):  
Seasonal Changes ◽  
East Coast ◽  
Heavy Mineral ◽  
Heavy Minerals ◽  
Sediment Characteristics ◽  
Seasonal Fluctuations ◽  
Post Monsoon ◽  
Seasonal Circulation ◽  
Mineral Concentrations ◽  
The Impact

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.

Seasonal changes of motile polychaetes in the fouling assemblage developed on test panels submerged on a tropical coast

2013 ◽  
Vol 93 (6) ◽  
pp. 1525-1531 ◽  
Author(s):  
S. Satheesh ◽  
S.G. Wesley
Keyword(s):  
Coastal Waters ◽  
Seasonal Changes ◽  
Dominant Species ◽  
East Coast ◽  
Monsoon Season ◽  
Polychaete Species ◽  
Post Monsoon ◽  
Platynereis Dumerilii ◽  
Post Monsoon Season ◽  
Tropical Coast

The diversity and distribution of polychaete species under the families Nereididae, Syllidae and Eunicidae in sub-tidal fouling assemblage was studied by submerging wood as test substratum. Wooden panels were fitted onto a raft and submerged in Kudankulam coastal waters (south east coast of India) in pre-monsoon, monsoon and post-monsoon seasons from May 2003 to July 2005. Panels (in replicate) were retrieved from the raft at 15-day intervals. A total of 24 polychaete species belonging to the three families were identified from the test panels.Perinereis cultrifera,Platynereis dumerilii,Syllis variegata,Syllis truncata, andEunice australiswere the dominant species observed on the test panels. The abundance of major polychaete group was varied considerably between the panel series submerged in May 2003 (post-monsoon), November 2003 (monsoon) and July 2004 (pre-monsoon). The major difference in the polychaete community structure was the low abundance of both nereidids on pre-monsoon season panels and the eunicids on monsoon and post-monsoon season panels.

Quaternary sedimentation and marine placers along the North Shore, Gulf of St. Lawrence

1993 ◽  
Vol 30 (3) ◽  
pp. 553-574 ◽  
Author(s):  
Frances J. Hein ◽  
James P. M. Syvitski ◽  
Lynda A. Dredge ◽  
Bernard F. Long
Keyword(s):  
Current System ◽  
Heavy Mineral ◽  
Heavy Minerals ◽  
Coarse Grained ◽  
Mineral Concentration ◽  
Lawrence Estuary ◽  
North Shore ◽  
The North ◽  
Late Wisconsinan ◽  
Mineral Concentrations

Offshore areas, along the North Shore of the St. Lawrence Estuary, have major lithostratigraphic and seismostratigraphic units that relate to the advance or retreat of the Late Wisconsinan Ice Sheet, subsequent marine transgression or regression, and reworking of postglacial deposits. Glacial diamicton and glaciomarine units (acoustic units 1 and 2) were emplaced between >18 and 14.5 ka, by basal meltout or ice-marginal sedimentation; they reflect ice-proximal sedimentation associated with ice-terminal stillstands. Deep-water muds (acoustic unit 3) represent ice-distal accumulation of glaciomarine sediment from glaciofluvial plumes between 13.5 and 11 ka. After this time exceptionally thick nearshore coarse-grained deltaic and estuarine successions (acoustic unit 4) were deposited. The uppermost postglacial sediment (acoustic unit 5) forms the seabed and reflects a reworking phase concomitant with a lowering sea level and ablating Late Wisconsinan ice sheets.Glacioisostatic rebound, which occurred about 23 ka to the present, uplifted glacial and marine deposits and resulted in extensive reworking and production of modern placers. Heavy-mineral concentrations vary as follows: terrestrial tills, 9–20%; modem storm-berm and delta top deposits, 43–60%; delta slope deposits, 25–55%; and deep (170+ m) offshore sediments, 0–2%. Three stages occurred in marine placer formation: (1) 6700 BP, fluvial discharge was high, and fluvial-dominated deltas were built; marine limit was 30 m asl, with progradation of deltas and delivery of sediments with at most 2% heavy minerals; (2) 5200 BP, fluvial discharge was reduced; marine limit was 15 m asl, deltaic sediments were reworked, increasing heavy mineral concentration to 2–8%; (3) 2800 BP, fluvial input was greatly reduced, waves and tides were more influential, a strong littoral current system developed, causing significant reworking of nearshore sediments, heavy mineral concentrations increased, with values exceeding 20% locally. Mass budget calculations show that the second-cycle reworked sediment (acoustic unit 5) is a potential economic target (1 km3, or 1700 Mt). If 7% (using atomic weights) of this target sediment is ilmenite (FeTiO3). then 27 Mt of titanium may be available.

scholarly journals Characteristics of Sediment at Littoral Zone of Anoi Itam Beach (Eastern Weh Island, Indonesia) Based on Seasonal Changes

2020 ◽  
Vol 9 (3) ◽  
pp. 111-119
Author(s):  
Syahrul Purnawan ◽  
Sofyatuddin Karina ◽  
Rizka V Ayudia ◽  
Yopi Ilhamsyah ◽  
Ichsan Setiawan
Keyword(s):  
Seasonal Changes ◽  
High Variability ◽  
Seasonal Difference ◽  
Sediment Characteristics ◽  
South West ◽  
Littoral Zones ◽  
Sediment Data ◽  
The Impact ◽  
Sw Monsoon ◽  
Skewness And Kurtosis

Anoi Itam Beach (AIB), located in the eastern part of Weh Island, has the sediment characteristic of dark-sand color. Climatologically, the beach is influenced by two seasons, i.e., south-west (SW) monsoon and northeast (NE) monsoon. Sediment data are collected in the upper and lower littoral zones that are divided into six stations alongshore. Data were collected on October 2016 and April 2017, representing post-SW monsoon and post-NE monsoon events. To examine the effect of seasonal, sediments statistics, e.g., mean, sorting, skewness, and kurtosis, have been calculated. AIB was characterized as well sorted to poorly sorted sediment. Sediments were identified as mesokurtic in October, varied to leptokurtic and platikurtic in upper littoral and lower littoral, respectively, in April. Grain size in both upper and lower littoral had increased from October to April. The impact on sediment sortation was minor due to the seasonal difference. Sediments in the upper littoral vary slightly skewed than lower littoral, which response to a more positively skewed during seasonal change from SW-monsoon to NE monsoon. The results suggested that lower littoral provide high variability of sediment characteristics depend on the season. 

scholarly journals Anomalous radioactivity level and high concentrations of heavy minerals in Lemme area, South-West Estonia

Baltica ◽  
2014 ◽  
Vol 27 (2) ◽  
pp. 93-104 ◽  
Author(s):  
Anto Raukas ◽  
Rein Koch ◽  
Krista Jüriado ◽  
Johanna-Iisebel Järvelill
Keyword(s):  
Heavy Mineral ◽  
Heavy Minerals ◽  
Radiocarbon Dates ◽  
Radioactivity Level ◽  
Near Shore ◽  
Buried Soil ◽  
High Concentrations ◽  
The 1960S ◽  
The Baltic ◽  
Mineral Concentrations

Abstract As early as in the 1960s, extensive heavy-mineral concentrations containing zircon, monazite, and xenotime were discovered in the Lemme region of south-western Estonia. These concentrations contribute to the elevated radioactivity levels of the enclosing sediments. The near shore sands of the Litorina Sea contain up to 10-cm-thick interlayers with a heavy mineral content of up to 80%. These anomalous layers were formed during the transgressive phase and result from a complicated cross- and alongshore migration of sedimentary material, derived mainly from local Devonian bedrock. Radioactivity level in the study area is higher relative to the majority of the Devonian plateau. The Lemmeoja buried soil has 13 radiocarbon dates in an area of renewed interest for the investigation of the Baltic Sea history.

Qualitative Petrographic Interpretation of Potsdam Sandstone (Cambrian), Southwestern Quebec

1971 ◽  
Vol 8 (8) ◽  
pp. 853-882 ◽  
Author(s):  
D. W. Lewis
Keyword(s):  
Heavy Mineral ◽  
Heavy Minerals ◽  
Coarse Grains ◽  
Mineral Concentrations ◽  
Petrographic Study

The Cambrian Potsdam Group in southwestern Quebec comprises the quartzo-feldspathic Covey Hill Formation (up to 2000 ft (610 m) thick), and the unconformably overlying and overlapping Chateauguay Formation, which is subdivided into the lower Cairnside Member (up to 500 ft (152 m) thick) of pure quartz sandstone and the Upper Theresa Member of interlayered quartz sandstone and dolostone. Petrographic study concentrated on Covey Hill and Cairnside lithologies from three deep cores near Montreal. Traditional interpretation of Potsdam Sandstone as a pure quartz blanket deposited by transgressing seas applies only to the Cairnside Member.The Covey Hill Formation comprises subround-round sands, sparse rounded gravels, scattered penecontemporaneous clay clasts, and rare thin mud layers. Juxtaposition of well and poorly sorted laminations of different sand sizes, mica-clay, and heavy mineral concentrations, attests fluctuating depositional energies. Presence of silt-free clayey matrix and scattered coarse grains set amongst much finer sands attests marked predepositional eolian activity. Composition of quartz, fresh and partly weathered K-feldspar, micas, and stable heavy minerals is inferred to reflect a prolonged predepositional history during which unstable minerals were destroyed. Hematitization of biotite flakes, and other diagenetic modifications, are inferred to result from pedogenesis in an alluvial environment of deposition.

Ten Demi-Culverins for Aldeburgh: Whitehall, the Dunkirkers, and a Suffolk Fishing Community, 1625–1630

2019 ◽  
Vol 58 (2) ◽  
pp. 315-337 ◽  
Author(s):  
Thomas Cogswell
Keyword(s):  
North Sea ◽  
East Coast ◽  
Central Government ◽  
Fishing Community ◽  
Close Attention ◽  
The North ◽  
The North Sea ◽  
The Impact

AbstractHistorians have not paid close attention to the activities of freebooters operating out of Dunkirk in the late 1620s. This essay corrects that omission by first studying the threat from Dunkirk to England's east coast and then addressing how the central government, counties, and coastal towns responded. A surprisingly rich vein of manuscript material from Great Yarmouth and particularly from the Suffolk fishing community of Aldeburgh informs this case study of the impact of this conflict around the North Sea.

scholarly journals Observations of Winter Ablation on Glaciers in the Mount Everest Region in 2020–2021

2021 ◽  
Vol 13 (14) ◽  
pp. 2692
Author(s):  
Mauri Pelto ◽  
Prajjwal Panday ◽  
Tom Matthews ◽  
Jon Maurer ◽  
L. Baker Perry
Keyword(s):  
Remote Sensing Data ◽  
Time Data ◽  
Mount Everest ◽  
Monsoon Period ◽  
National Geographic ◽  
Freezing Level ◽  
Post Monsoon ◽  
Base Camp ◽  
Dry Conditions ◽  
The Impact

Recent observations of rising snow lines and reduced snow-covered areas on glaciers during the October 2020–January 2021 period in the Nepal–China region of Mount Everest in Landsat and Sentinel imagery highlight observations that significant ablation has occurred in recent years on many Himalayan glaciers in the post-monsoon and early winter periods. For the first time, we now have weather stations providing real-time data in the Mount Everest region that may sufficiently transect the post-monsoon snow line elevation region. These sensors have been placed by the Rolex National Geographic Perpetual Planet expedition. Combining in situ weather records and remote sensing data provides a unique opportunity to examine the impact of the warm and dry conditions during the 2020 post-monsoon period through to the 2020/2021 winter on glaciers in the Mount Everest region. The ablation season extended through January 2021. Winter (DJF) ERA5 reanalysis temperature reconstructions for Everest Base Camp (5315 m) for the 1950–February 2021 period indicate that six days in the January 10–15 period in 2021 fell in the top 1% of all winter days since 1950, with January 13, January 14, and January 12, being the first, second, and third warmest winter days in the 72-year period. This has also led to the highest freezing levels in winter for the 1950–2021 period, with the January 12–14 period being the only period in winter with a freezing level above 6000 m.

scholarly journals Seasonal feeding plasticity can facilitate coexistence of dominant omnivores in Neotropical streams

2021 ◽  
Author(s):  
Mayara P. Neves ◽  
Pavel Kratina ◽  
Rosilene L. Delariva ◽  
J. Iwan Jones ◽  
Clarice B. Fialho
Keyword(s):  
Seasonal Variation ◽  
Fish Species ◽  
Resource Availability ◽  
Seasonal Changes ◽  
Dry Season ◽  
Diet Overlap ◽  
Isotopic Niche ◽  
Neotropical Streams ◽  
Feeding Plasticity ◽  
The Impact

AbstractCoexistence of ecomorphologically similar species in diverse Neotropical ecosystems has been a focus of long-term debate among ecologists and evolutionary biologists. Such coexistence can be promoted by trophic plasticity and seasonal changes in omnivorous feeding. We combined stomach content and stable isotope analyses to determine how seasonal variation in resource availability influences the consumption and assimilation of resources by two syntopic fish species, Psalidodon aff. gymnodontus and P. bifasciatus, in the Lower Iguaçu basin. We also tested the impact of seasonality on trophic niche breadth and diet overlap of these two dominant omnivores. Seasonal changes in resource availability strongly influenced the consumption and assimilation of resources by the two fish species. Both species exhibited high levels of omnivory, characterized by high diversity of allochthonous resources in the wet season. Terrestrial invertebrates were the main component of diet during this season. However, in the dry season, both species reduced their isotopic niches, indicating diet specialization. High diet overlap was observed in both seasons, but the isotopic niche overlap was smaller in the dry season. Substantial reduction in the isotopic niche of P. bifascistus and a shift toward aquatic invertebrates can facilitate coexistence during this season of resource shortage. Feeding plasticity allows omnivorous fish to adjust their trophic niches according to seasonality, promoting the exploitation of different resources during periods of greater resource diversity. This seasonal variation could be an important mechanism that contributes to the resource partitioning and coexistence of dominant omnivores in Neotropical streams.

scholarly journals Seasonal changes in water quality and macrophytes and the impact of cattle on tropical floodplain waterholes

2012 ◽  
Vol 63 (9) ◽  
pp. 788 ◽  
Author(s):  
N. E. Pettit ◽  
T. D. Jardine ◽  
S. K. Hamilton ◽  
V. Sinnamon ◽  
D. Valdez ◽  
...  
Keyword(s):  
Water Quality ◽  
Seasonal Changes ◽  
Aquatic Macrophyte ◽  
Plant Cover ◽  
Critical Role ◽  
Dry Season ◽  
Nutrient Concentrations ◽  
Wet Season ◽  
Dry Tropics ◽  
The Impact

The present study indicates the critical role of hydrologic connectivity in floodplain waterholes in the wet–dry tropics of northern Australia. These waterbodies provide dry-season refugia for plants and animals, are a hotspot of productivity, and are a critical part in the subsistence economy of many remote Aboriginal communities. We examined seasonal changes in water quality and aquatic plant cover of floodplain waterholes, and related changes to variation of waterhole depth and visitation by livestock. The waterholes showed declining water quality through the dry season, which was exacerbated by more frequent cattle usage as conditions became progressively drier, which also increased turbidity and nutrient concentrations. Aquatic macrophyte biomass was highest in the early dry season, and declined as the dry season progressed. Remaining macrophytes were flushed out by the first wet-season flows, although they quickly re-establish later during the wet season. Waterholes of greater depth were more resistant to the effects of cattle disturbance, and seasonal flushing of the waterholes with wet-season flooding homogenised the water quality and increased plant cover of previously disparate waterholes. Therefore, maintaining high levels of connectivity between the river and its floodplain is vital for the persistence of these waterholes.

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