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    Wyświetlanie 1-2 z 2
    Tytuł:
    Light minerals of beach sediments from Southern Tamilnadu, South East coast of India
    Autorzy:
    Cherian, A.
    Chandrasekar, N.
    Rajamanickam, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/47531.pdf
    Data publikacji:
    2004
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    sphericity
    Tamilnadu
    beach
    provenance
    India
    light mineral
    quartz
    sediment
    coast
    roundness
    Opis:
    A brief investigation of light minerals along the beaches between Valinokkam and Tuticorin has been carried out for the first time along the Southern Tamilnadu coast in order to discover the provenance of the sediments. The study spotlights a wide variation in light mineralogy along the three zones of the investigated area (Valinokkam, Vaippar and Tuticorin). A higher percentage of quartz is reported from the Valinokkam (48.34 to 68.63%) and Tuticorin zones (55.66 to 73.05%) than from the Vaippar zone (40.24 to 60.77%). The trend with regard to the maturity index is similar, with appreciably higher values in Valinokkam (1.15 to 1.89) and Tuticorin (1.61 to 1.94) than Vaippar (0.79 to 1.39). Morphological analysis of quartz grains shows a higher order of sphericity and roundness values in Valinokkam and Tuticorin as compared to Vaippar. Moreover, the surface texture of quartz grains observed with the aid of scanning electron microscope (SEM) photographs reveals the presence of different depositional environments and the multiple origin of beach sediments in the study area. From the present study of the light mineralogy of beach sediments, it is inferred that the source of the sediments is a mixed type: igneous and metamorphic crystalline rocks, together with palaeosediments.
    Źródło:
    Oceanologia; 2004, 46, 2
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Element enrichment and provenance of the detrital component in Holocene sediments from the Western Black Sea
    Autorzy:
    Dekov, V.M.
    Darakchieva, V.Y.
    Billstrom, K.
    Garbe-Schonberg, C.D.
    Kamenov, G.D.
    Gallinari, M.
    Dimitrov, L.
    Ragueneau, O.
    Kooijman, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/2079273.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    trace element concentration
    isotope analysis
    enrichment factor
    Holocene sediment
    catchment area
    geochemical analysis
    Black Sea
    Opis:
    Concentrations of a large set of major and trace elements, and Sr, Nd and Pb isotope ratios were measured in Holocene sediments cored in the western deep Black Sea in order to unravel: (1) the controls of element enrichment, and (2) sources of the detrital component. The transition of the basin from oxic to euxinic resulted in enrichment or depletion in a number of elements in the deep-sea sediments. Authigenic Fe enrichment appears to depend on the amount of Fe mobilized from the sediment through the benthic redox shuttle mechanism and free H2S in the water column (degree of “euxinization”). Manganese enrichment is controlled by diagenetic reactions within the sediment: the dissolution of Mn minerals, Mn2+ diffusion upward and reprecipitation. Barium enrichment is also controlled by diagenetic reactions, sulfate reduction and methanogenesis, that take place above and below the sulfate-methane transition, respectively. The major part of V, Co, Ni, Cu, Zn, Cr, Mo, Cd and Sb is inferred to have co-precipitated with Fe in the euxinic deep waters and to have been incorporated into authigenic Fe-sulfides. Basin reservoir effect additionally influences the Mo enrichment. The U enrichment is interpreted to have a different origin in the two organic-rich stratigraphic units (II and I). It is inferred to be: (i) at the expense of the U inventory of the deepwater pool and a result of inorganic reduction of U at euxinic conditions in the lower Unit II; and (ii) at the expense of the U inventory of the surface water pool and a result of biogenic uptake and transfer to the sediment by the plankton in the upper Unit I. The high field strength elements are closely linked to the detrital component and their depletion in the organic-rich sediments reflects a dilution of the detrital component by the biogenic one. The enrichments of REE, Sn and Th are likely controlled by adsorption on clay minerals. Sr-Nd-Pb isotope compositions of the alumino-silicate component of the studied sediments are relatively uniform. They are most likely controlled by riverine suspended matter supplied mainly in the NW Black Sea (Danube Delta) and transported southward by marine currents, and to a lesser degree by suspended matter from the small rivers draining SE Bulgaria and NW Turkey. Wind-blown dust from the Sahara Desert appears to have a minor contribution to the alumino-silicate component of the sediments. The slight shift in the Pb isotopes in Unit I upper layers is possibly caused by the addition of anthropogenic Pb.
    Źródło:
    Oceanologia; 2020, 62, 2; 139-163
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-2 z 2

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