ABSTRACT
ABSTRACT: An integrated geochemical and sedimentological study of the Campano- Maastrichtian sediment of Ajali and Owelli Formation exposed within the southern portion of the Anambra basin was undertaken to determine the sandstone provenance, tectonic setting, and paleo-weathering conditions. All sandstone samples are enriched in quartz (Q) but poor in feldspar (F) andlithic-fragments (L). The major-element concentrations of these sandstones reveal the relative homogeneity of their source. Geochemically, the sandstones are classified as quartzarenite, sub-litharenite, and subarkose. Tectonic setting discrimination diagrams suggest a passive continental margin. The sediments are enriched in SiO2 and depleted in Na2O, CaO and TiO2.Chemical index of weathering (CIW) of the sample suggests intense recycling and high degree of weathering in a humid climatic condition. Results of the elemental ratios critical of provenance compared to those of felsic and basic derived sediment of UCC and PAAS values suggests a felsic source rock. Cu/Zn, U/Th, Ni/Co and (Cu+Mo)/Zn paleo-oxygenation ratios used as redox parameters depicts an oxic environment. Finally, presence of minerals, like Anatase, Rutile and Microcline depicts an igneous and metamorphic source terrain
Subject(s)
Geologic Sediments , Minerals , Nigeria , Trace ElementsABSTRACT
Lagos lagoon is a highly polluted water body; which receives enormous amount of domestic and industrial wastes from rivers and streams. In this study; two main Lagos urban rivers Odo-Iyaalaro and Shasha rivers that receive industrial effluents and empty into the Lagos Lagoon were examined. The sediments at the bottom of waters play a role in the study of pollution in the rivers. Upstream of Odo-Iyaalaro River (Point 1) receives the largest volume of effluents and showed the highest level of heavy metals in sediments with concentrations of 108.3mg/l for Pb; 805mg/l for Zn; 94.5mg/l for Cu; 31mg/l for Cr and 42.1 mg/l for Cd. Down the river; the levels decreased to 25mg/l for Pb; 64.5 mg/l for Zn; 22mg/l for Cu; 15.9 mg/l for Cr and 1.9 mg/l for Cd. A good correlation was found to exist between the level of Zn in water and sediment; and also between the CEC andsilt-clay of sediments. Shasha River receives relatively fewer amounts of industrial effluents; but is relatively the main receptacle for municipal and land-based waste. The levels of heavy metals in Shasha River were lower compared with that of Odo-Iyaalaro River; with the upstream points showing concentrations of 20.5mg/l for Pb; 25.3mg/l for Zn; 7.9mg/l for Cu; 30.8 mg/l for Cr and 1.5mg/l for Cd. A good correlation exists between the CEC and all the metals determined; and between theorganic carbon and all the metals determined. Compared with literature data; the results of heavy metals gave an indication of pollution