TRACE ELEMENTS GEOCHEMISTRY OF FINE-GRAINED SEDIMENTS FROM THE MAMU FORMATION (ANAMBRA BASIN, NIGERIA): IMPLICATIONS FOR PALEOCLIMATE, SALINITY AND REDOX CONDITIONS
Keywords:
Mamu Formation, Paleodepositional conditions, Salinity, RedoxAbstract
Seven samples of silty muds and a coal sample were collected from two outcropping locations of the Mamu Formation of the Anambra Basin in order to reconstruct paleoclimate, paleosalinity and paleoredox depositional conditions of the sediments using discriminating geochemical indices. The samples were subjected to Energy Dispersed X-ray Fluorescence (EDXRF) analysis in order to reveal major trace elemental concentrations. With respect to Post Archean Australian Shales (PAAS), enriched trace elements in the fine grained sediments includes V, Cr, Cu, Ga, Zr and Zn, while depleted elements are Sr, Ba, Co, Ni and Rb. Sr/Cu ratios ranges from 0.393 – 3.75, with an average of 1.105, while Rb/Sr ratios ranges from 0.023 – 0.69 with a mean of 0.251.These values suggests a warm and humid climate with very minor influence of arid conditions. The Sr/Ba ratios ranged between 0.28 – 3.03, averaging 27.60, while Ba/Ga ratios ranges from 1.37 – 82.27 with a mean of 27.60, indicating a predominantly marine conditions interspersed with minor episodes of brackish and freshwater. The V/Cr ratios of the samples ranges between 0.17 – 3.39 with an average of 1.72, while ratios Ni/Co ranged from 0.252 -4.63, with a mean of 3.92, suggestin a more oxic depositional setting with minor dysoxic and anoxic events
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