Abstract: Stone ash and clamshell are a material that comes from the nature and is very rarely used as a mixture of artificial reefs made from concrete. This study uses stone ash and clamshell because, high silica content in stone ash can strengthen the artificial reef concrete, while the use of clamshell is expected to reduce the abundant waste in coastal areas. In order to know the potential of both media types of artificial reefs stone ash and clamshell as a place to live or attached to marine biota needs to be evaluated, evaluation seen from result of biota number, type composition, density and rate of attachment of biota which has been obtained after 3 months of media placed in waters. The results of data processing and statistical analysis of mann-whitney u test performed showed significant value of 0.755 or P > 0.05, which means no significant difference, indicating that both types of artificial reef media using stone ash and clamshell have a role to resemble the characteristics of natural reef as a place to live, a place to eat, a shelter and a place to spawn for marine biota which then repair or replace the ecosystem that has been damaged.

Abstract: Rare earth and trace element compositions of stream sediments samples from Ijero Ekiti, Southwest, Nigeria were analyzed using Inductively Coupled Plasma Mass Spectrometer (ICP-MS). Data obtained were utilized to investigate the source rocks, depositional environment and paleo-redox conditions of the study area. Results showed that the average concentrations of the elements Nb (172.04), Zr (432.20), Hf (13.00), Ta (50.62), Th (14.69) and U (8.85) were higher relative to upper continental crust (UCC), post Archean average Australian shale (PAAS) and North American shale composite (NASC) respectively and therefore enriched in felsic rocks rather than the mafic counterparts. The average ratios of geochemical parameters such as Th/Sc (1.53), La/Th (3.31), and Th/Co (1.54) are higher than the PAAS suggesting a felsic nature of the source rocks, while Cr/Th ratio (36.60) found in one location fell into mafic source. The relative enrichments of incompatible elements, light rare earth elements (LREE; 186.51) and Th (14.69) relative to PAAS (167.16) and Th (14.6) respectively over compatible elements Sc ( 10.57) and Co (12.77) relative to PAAS confirm the felsic average provenance. The chondrite- normalized rare earth elements diagram showed an inclined LREEs whereas the heavy rare earth elements (HREEs) reflected a nearly flat pattern with a negative Eu anomaly. The high LREE/HREE ratio with a negative Eu anomaly confirm the source of sediments to be from igneous most probably granitic gneisses and pegmatite inclusive. Geochemical parameters such as U/Th, Ni/Co, V/Cr and Cu/Zn indicate that the sediments were deposited under oxic environmental condition. V/Ni and V/( V+Ni) ratios showed the sediments were deposited under anoxic conditions. However, the plots of V/( V+Ni) versus Ni/Co indicated that the sediments were deposited under oxic to dysoxic conditions. The use of Co/Ni ratio confirmed that the sediments were deposited under a strongly oxygen -rich marine environment.