Analysis of major and trace elements by INAA to predict the thousands year old sediment deposition environment in the Meghna river delta

Major, trace and rare earth elements have been measured in sediments of different layers to determine the controls of constituent minerals on the distribution of elements and sediment deposition environment in the Meghna river delta. The geochemical composition of sediments was enriched in SiO2, Ca, Mg and Ba and depleted in Al, Fe, Ti, Mn, and Sr relative to PAAS (Post-Archaen Average Shale) value. The X-ray diffraction and elemental analyses demonstrate the dominant presence of quartz, micas, feldspar, chlorite, amphibole and clay minerals in sediments. The very low contents of trace elements suggest that the oxic condition was more prevalent during sediment deposition of Pleistocene-Holocene period and reflect the massive chemical weathering by biogeochemical reactions. The enrichment of light rare earth elements and La/Yb ratio reflect the intense silicate weathering of crustal materials and the high sediment depositional rate in the Meghna river delta. (author)