Gullies of the Awka-Orlu escarpment within Anambra State, Nigeria, were studied using hydrochemical and geological properties for understanding the geo-environmental problems which underlies the gully-prone areas. This was achieved by conducting fieldwork which includes mapping, hydrogeological surveys and samples collection, followed by laboratory analyses of soil and water samples. The soil samples were subjected to particle size analysis, compaction. Water samples were analyzed using atomic absorption spectrophotometer and titrimetric methods. The results of surface water and groundwater revealed pH average values of 5.99 and 6.3, indicating slightly acidic. Such slightly-acidic water facilitates decomposition of the cementing material in the soil. The chemical composition of surface water revealed average concentrations of magnesium (1.57 mg/l), calcium (3.40 mg/l), sodium (2.27 mg/l), chloride (22.28 mg/l), iron (0.38 mg/l), bicarbonates (37.85 mg/l), nitrate (4.73 mg/l), sulphate (3.81 mg/l), for groundwater magnesium (2.57 mg/l), calcium (3.50 mg/l), sodium (2.26 mg/l), chloride (15.09 mg/l), iron (0.23 mg/l), bicarbonates (25.46 mg/l), nitrate (11.61mg/l), sulphate (8.49mg/l) and total dissolved solid (TDS) average values of 63.16mg/ and 50.90mg/l. Using the cations and anions values to plot the piper trilinear diagram sodium bicarbonate (Na-HCO-3). This is attributed to geochemical reactions of ion-exchange and oxidation-reduction in the soil. These reactions contribute to soil disaggregation, erosion and destruction of engineering structures build to control gully erosion. water type was identified. The soil is permeable with good infiltration capacity. The investigations showed the vulnerability of the soil to gullying. These findings are important for any planned, well-designed and executed gully erosion control programmes.

The water sources in parts of the River Mamu sub-Basin, southeastern Nigeria were evaluated for domestic and agricultural purposes using hydrogeology and water quality. Thirty water samples from both surface water and groundwater were collected and analysed for hydrochemical and biological parameters. The average depth to aquifers and their thicknesses are 109.9 and 11.8m respectively. The concentration of the major ions, TDS and EC are within the WHO permissible guidelines for drinking water. Heavy metals concentration range in mg/L for Cd 2+ (0 -0.06), Cr 3+ (0 -0.19), Hg 2+ (0 -1.0), As 3+ (0 -0.14) and total Fe (0 -2.4) which in some of the samples exceed the permissible guideline values. The fecal coliform range in 100ml/L of samples (0 -36) exceeds the guideline values in some of the samples. The water is Ca-Mg -Cl-SO 4 type with the dominant ions as Ca 2+ and SO 4 2for both groundwater and surface water. The dominant geochemical processes are rockwater interaction in groundwater, which is a major contributor of dissolved ions and precipitation in the surface water. The WQI (17.84-301.99) connotes some samples are of very poor quality for domestic purposes. Irrigation indices depict most of the water as good to excellent for agriculture.

Regolith derived from Nanka Formation; Southeast Nigeria was evaluated for their geotechnical characteristics. The methods of investigations include Fieldwork experiment and laboratory analysis of water and soil samples. The result of hydraulic parameters of the soil at 1meter, 2 meters depth and drilled cuttings from boreholes revealed permeability average values of 1.29E-05(cm/s) and 9.15E-6(cm/s), hydraulic conductivity average value of 1.27E-04(cm/s) and 8.93E-05(cm/s). Drilled cuttings from three boreholes revealed permeability average value of 8.15E-06(m/s), 2.68E-06(m/s) and 6.20E-06, hydraulic conductivity average values of 8.90E-03(m/s), 2.92E-03(m/s) and 6.75E-3(m/s).These values indicate permeable soil with high hydraulic conductivity typical of silty-clay and sand. The permeability/hydraulic conductivity accounts for the high infiltration/percolation of water into the soil. Infiltration of water through the soil initiates geochemical reactions and dissolution mineral which leaves the soil loose and unconsolidated. Geotechnical characteristics show low to medium plasticity and a liquid limit average of 42.36 and 35.45, indicating the capacity of the soil to absorb moisture and expand, bulk density average value of 1.90 mg/m3and compaction test of maximum dry density average value of 1.80 g/cm3 at an optimum water content average of 12.89% indicate low density. Shear strength components of cohesion values range from 0 to 55KN/m2 with average value of 25 KN/m2 and friction angle values range from 7° to 25° suggesting low cohesion and angle of internal friction. This is attributed to the low clay content and the cohesive force is not enough to sustain the soil. Field experiments of cone penetration test of in-situ results indicate a weak and incompetent soil material that is unstable and vulnerable to erosion. The finding would be relevant in soil mechanics problems.

Regolith derived from Nanka Formation; Southeast Nigeria was evaluated for their geotechnical characteristics. The methods of investigations include Fieldwork experiment and laboratory analysis of water and soil samples. The result of hydraulic parameters of the soil at 1meter, 2 meters depth and drilled cuttings from boreholes revealed permeability average values of 1.29E-05(cm/s) and 9.15E-6(cm/s), hydraulic conductivity average value of 1.27E-04(cm/s) and 8.93E-05(cm/s). Drilled cuttings from three boreholes revealed permeability average value of 8.15E-06(m/s), 2.68E-06(m/s) and 6.20E-06, hydraulic conductivity average values of 8.90E-03(m/s), 2.92E-03(m/s) and 6.75E-3(m/s).These values indicate permeable soil with high hydraulic conductivity typical of silty-clay and sand. The permeability/hydraulic conductivity accounts for the high infiltration/percolation of water into the soil. Infiltration of water through the soil initiates geochemical reactions and dissolution mineral which leaves the soil loose and unconsolidated. Geotechnical characteristics show low to medium plasticity and a liquid limit average of 42.36 and 35.45, indicating the capacity of the soil to absorb moisture and expand, bulk density average value of 1.90 mg/m3and compaction test of maximum dry density average value of 1.80 g/cm3 at an optimum water content average of 12.89% indicate low density. Shear strength components of cohesion values range from 0 to 55KN/m2 with average value of 25 KN/m2 and friction angle values range from 7° to 25° suggesting low cohesion and angle of internal friction. This is attributed to the low clay content and the cohesive force is not enough to sustain the soil. Field experiments of cone penetration test of in-situ results indicate a weak and incompetent soil material that is unstable and vulnerable to erosion. The finding would be relevant in soil mechanics problems.

The phosphorites of the Ameki Formation occur as nodules, pellets as well as primary phosphatic shales and siltstones. Geochemical analysis of the phosphate samples was carried out to determine its chemical composition as well as its depositional environment. The methodology applied include XRF, INAA, XRD and thin section petrography using Polarizing Microscope. The XRF result identified CaO- P2O5- F as the major mineral group, SiO2, Al2O3, Fe2O3, MgO and TiO2, which show minor occurrences and Cr, U, Pb, V, Cu, Zn, Se and Cd that occur in trace amounts. The nodules and pellets are of medium to high grade (25- 34wt% P2O5) whereas the primary phosphatic shales and siltstones are of low to medium grade (4.5– 22wt% P2O5). The phosphorites comprise mostly of francolites. The mean index of refraction estimated by Becke-line method using Standard Polarizing Microscope gave 1.634 and1.636.XRD analysis yielded an average values of 9.243 (± 0.002) A° and 6.715 (± 0.002) A° for a and c crystallographic axes respectively with an axial ratio (c/a) of 0.726for unit cell parameter, suggestive of low degree of carbonate substitution. An increase in P2O5 content is found to be accompanied by increase in CaO, CO2 and F contents, but by a decrease in H2O, organic carbon, SiO2 and Fe contents indicative of amorphous solid phase of calcium phosphate. The phosphorite is interpreted to form under high biologic productive, shelf setting. High nutrient availability in the ancient sea is linked to upwelling along the West African Coastline during the Eocene. Keywords: Phosphorites; Geochemistry; Paleoenvironment; Ameki; Francolites; Nodules