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The Up per Cre ta ceous Ajali Sand stone is an ex ten sive strati graphic unit of the Anambra Ba sin in south ern Ni ge ria. It consists of fri a ble, white cross-bed ded sand stones ex hib it ing a fin ing up ward se quence. Struc tures such as bioturbation, pla nar and her ring bone cross beds in di cate vari abil ity in depositional en vi ron ment rang ing from fluviatile to deltaic. Petrographic and geo chem i cal com po si tions (ma jor and trace el e ments) of these sand stones have been in ves ti gated to de ter mine their prov e nance, tec tonic set ting and weath er ing con di tions. Fif teen sand stone sam ples ex am ined are rich in quartz but poor in feld spar and lithic frag ments. Tex tur ally, the frame work grains of the sand stones are fine-to me dium-grained, sub-an gu lar to sub-rounded, mod er ately sorted to poorly sorted, pos i tively skewed and leptokurtic. The sand stones are tex tur ally im ma ture as de picted by their sub-an gu lar edges of grains, but min er al og i cally ma ture in terms of high per cent age of quartz. The high chem i cal in dex of al ter ation (CIA) val ues (71.0-99.2%) for these sand stones sug gests that they were de rived from highly weath ered rocks in the source area. The com po si tion of the ma jor ox ides in the sand stones re vealed that SiO 2 (49.1-99.7%), Al 2 O 3 (0.2-30.3%), Fe 2 O 3 (0.4-1.8%) and TiO 2 (0.06-3.2%) were the most abun dant el e ments in all sand stone sam ples in dicat ing a high de tri tal quartz and clay min eral con tent. The Al 2 O 3 /TiO 2 ra tios (1.47 to 12.48), Ti/Zr (6.48-18.63) and Zr/Cr (2.24-22.36) sug gest that the sand stones were de rived from vari able base ment com plex rocks, in clud ing some con tri bu tion from mafic or ultra mafic com po nents. In fer ences from the plots of K 2 O/Na 2 O ver sus SiO 2 in di cated a pas sive mar gin tec tonic set ting for the sand stones. The high load ing of CaO and Na 2 O in more than 50% of the sam ples is in dic a tive of terrigenous input, mainly in the form of car bon ates and sil i cates. These re sults are gen er ally con sis tent with a der i va tion of the sand stones from ad ja cent ig ne ous and meta mor phic base ment com plexes (Cam er oon-Adamawa high lands and Oban Mas sif) while the ex ten sive and blan ket-like ge om e try of the Ajali Sand stone is in dic a tive of an ex cel lent res er voir for ground wa ter in the Anambra Ba sin.

Exploitation of petroleum began recently in Umutu area, a part of the prolific Niger Delta Oil province, Nigeria. Soil profiles at six locations in this area were investigated to determine the current status of Cr, Cu, Cd, Co, Ni, Zn, Pb, Mn and Fe, and their bioavailability, in order to have reference data for future monitoring of their bioaccumulation. The procedure used sequential extraction technique. Except for the high contents of Cu, Cd, Co, Zn, and Pb in Site B (an automobile mechanic waste dumpsite), mean metal levels in mgkg-1 for Umutu soils are Cd (0.65-1.83), Cu (2.20-6.30), Pb (4.06-5.90), Cr (7.10-15.60), Ni (1.10-2.00), Zn (33.00-45.00), Co (0.01-0.06), Fe (1126.22-2955.87) and Mn (1.83-18.81). Sequential extraction shows that the bioavailability of Cr except for Site E (all horizons) and Site D (0-15cm) are high. That of Fe is also high at depths of 0-15cm. Monitoring programme is herein suggested.

Geochemical analysis of fluvial sediments on the banks of River Ero using inductively coupled plasma mass spectrometry illustrates their maturity, provenance and tectonic setting. The analysed sediment samples show low SiO 2 /Al 2 O 3 ratios of 2.92-2.99 (units FL_A, FL_B and FL_E) and high SiO 2 /Al 2 O 3 ratios of 4. FL_D, FL_F and FL_G). Sediments were geochemically classified as shales (units FL_A, FL_B and FL_E) and greywackes (units FL_C, FL_D, FL_F and FL_G). Ključne besede: rečni sedimenti, Eu anomalija, SW Nigerija, izvor, tektonska uvrstitev

Analyses of lead, copper, chromium, cadmium, nickel, zinc and manganese contents in Otofure and Teboga waste dumps in Benin City, Nigeria were carried out to determine trace metal enrichment and distribution in the soils around the dump sites and environs. Results of analyses show that trace metal concentrations in the waste dumps were greater than those from the reference background sites by magnitude concentration differences of Pb (18. ) and Mn (161.349 mgkg -1 ) in Teboga area. The calculated contamination/pollution (C/P) index values show that the dump sites were slightly polluted while the reference sites showed insignificant contamination. Analysis of enrichment factor shows that the dump sites are enriched in lead and zinc, and these decreased with distance away from the waste dump sites. The geochemical association of Cr-Cu-Zn in the soil among others shows their inclination towards anthropogenic sources. This study shows slight metal enrichment in lead and zinc content over other metals studied, but generally the average concentrations of trace metals were below international guideline values for environmental quality criteria.

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