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Oil shale deposits of the mid-Eocene Wadi Shallala Formation in northern Jordan consist of organic-rich limestones and chalks. These organic-rich deposits are exposed at the surface near Wadi Ash Shajara, in a 12-m-thick outcrop. For this study, a total of 21 oil shale samples were analysed for bulk elemental geochemistry, inorganic geochemistry, organic geochemistry and microfacies analysis. Three microfacies types were recognised: pelagic mudstone/wackestone, foraminiferal packstone and bioclastic packstone/wackestone. The observed cyclicity of these microfacies in the study area indicates fluctuations in depositional conditions in Neo-Tethys during the mid-Eocene. A shallow-water, calm, restricted marine environment with limited water circulation and low energy currents evolved into a deeper-water environment with open circulation at or just below the wave base. Wadi Shallala Formation in Wadi Ash Shajara composes mainly of chalk (CaCO3 = ~92 wt%) with a TOC of up to 5 wt % and comprises abundant calcareous nannofossils, foraminifera and ostracods as well as non-clastic components like calcitic fragments. The sulphur content of the analysed samples is significant (1.24 wt %) and is associated with the organic matter. Redox-sensitive elements (Fe, Ni, Zn, S and Zr) are enriched in the oil shale samples, indicating an anoxic depositional environment fluctuating between euxinic and sub-euxinic. These fluctuations in depositional conditions of the basin are a result of many factors such as climate, and tectonisms affected deposition of oil shales during Middle Eocene time.

The objectives of the current study were to determine the chemical partitioning of Pb, Ni, Zn, Co, Cr, Mn, Fe and Cd using sequential extraction procedure and to assess the environmental risk associated with these metals in the farming soils along Zerqa River. Metal concentrations were measured by atomic absorption spectrophotometer. The study area demonstrated a wide range for pH, organic matter, carbonate contents, and cation exchange capacity, and is polluted with Pb, Cd, Mn, and Cu. The extensive use of fertilizers and pesticides in the agricultural activities, and discharge of treated and untreated wastewater are the major sources of pollution in the study area. Principal component analysis coupled with Pearson’s correlation analysis between the heavy metals revealed strong and positive correlation between these metals in the study area. According to the Risk Assessment Code (RAC), major portions of Cd and Mn are contained in exchangeable and carbonates fractions and therefore can easily enter the food chain. These metals pose a high to very high risk to the environment. Cu, Ni, Pb, and Zn pose medium risk, while Cr poses a low environment risk.