SIGHTS AND SOUNDS OF THE GEOLOGY OF NIGERIA FIELD EXERCISE 2014 ~ NMGS Lautech

The geological field trip exercise of the students of the department of earth sciences, Ladoke Akintola University of technology, Ogbomosho, Oyo state held from 5^th of December through 9^th of December 2014. Different geological materials and/or equipment such as geological hammer, compass clinometer, hand held lens, field camera, field notes, measuring tapes, sample bags and global positioning system (GPS) were used for surface identification of outcrops and to obtain fresh samples. The objectives of the exercise to students are as follows;

To orientate the students in the aspect of evaluation, identification and mapping of various outcrop and landforms within an area with respect to mineralogical composition in Nigeria.
Exposing students to obtaining a practical experience in the techniques and principles involved in geological field mapping such as Identification and measurement of the physical structures such as joints, strikes, dips on the rocks.

3. To train students to be able to recognize the various structural, textural and other geological features existing in rock and interpret the geological history of a rock formation, bearing in mind, the various geological principles.

To furnish the student with the geological overview of Nigeria, both the basement complex and the sedimentary basins formation and infer the geological history of an area and possibly the economic importance.

The areas covered include Akure, Igarra, Auchi, Fuga-Agenebode, Owo, Ifon to mention a few across four statesto mention a few seeing rare features from basement complex of south-western Nigeria to parts of the Bida and Anambra basins. The Basement complex rocks are rocks formed by processes about 2.5 billion – 600 million years at orogenic cycles during crustal evolution. The most recognized orogenic cycle attributed to Nigeria is the Pan-African orogeny about 600 million years ago which are part of the Nigeria Basement complex. Five major groups of rocks have been classified according Prof. M.A Rahaman in 1973.

· Migmatite-gneiss complex which comprises biotitic and biotitic hornblende gneisses, quartzites and quartz schist and small lenses of calc-silicate rocks.

· Slightly-migmatised paraschists and meta-igneous rocks which consist of politic schists, quartzite’s amphilibolites, talcose, rocks, meta-conglomerates, marbles and calc-silicate rocks.

· Charnockitic rocks.

· Older Granites which comprise rocks varying in composition from granodiorite to true granites and potassic syenite.

· Unmetamorphosed dolerite dykes believed to be the youngest.

These rock types depicts features such as mineralogical composition, prevailing temperature and pressure in the area at the time of emplacement and scale of occurrence. They rocks observed during the field trip include, Charnockites, Porphyritic Granites, Polymictic Metaconglomerates, Diorite, Quartzites, Hornblende-Hornfels, Calc-silicate, Syenite, Lamprophyre, Fault Breccia, Marble and Phyllite.

The sedimentary aspect of the fieldtrip was characterized by places where considerable thicknesses of sediments have accumulated (in places up to 20 km). Sedimentary basins are widespread both onshore and offshore. The sedimentary basins of Nigeria formed during the Cretaceous period belong generally to the post Hercynian basin of West Africa. These sedimentary basins are result of pre-existing tectonic forces in the past that affected the floor of the basins. Most sedimentary basins in Nigeria consist of different types of sedimentary deposits which occur in different environments. The sedimentary basins comprise different Formations as a result of distinctive sediments that make up the lithologies of each type area and the paleontologies that describe them. There are 6 sedimentary basins in Nigeria which are Benue trough, Bornu basin, Sokoto basin, Mid-Niger (Bida) basin, Dahomey basin, Niger Delta basin. The basins mapped during the fieldtrip are the Bida basin believed to be of Late Cretaceous times and the Anambra basin (failed arm of the Benue trough) believed to be of Campanian- Paleocene of age both formed from the Santonian tectonic inversion depositional cycle of fully marine Mamu shale formation to fluvio-deltaic Ajali sandstones. Also observed is a part of the Abeokuta formation at Ifon, Ondo state. Rock types include Sandstones, Shales and Metaconglomerates. The paleo-environmental reconstruction of the areas observed where also attempted with the aim of determine the origin, processes, mode of formation and time at which the rocks of that area occurred giving an insight to how the basin formed as a key to unlocking its potentials.

In Conclusion, the various rock types and sequences of the event that led to the evolution of similar rock types in other parts of the country to the south-western Basement complex and sedimentary basins of Nigeria, a direct correlation can be drawn between them broadly suggesting the origin of the rocks in Nigeria can be linked to;

· Magmatic Intrusion

· Metamorphism and Deformation

· Sedimentation

The field exercise has thereby increased the awareness of students to the benefits of studying geology in Nigeria as a pre-requisite to National development towards the urgent need for young, intelligent and adventurous geologists. The impact of geology is limitless has it is been linked to almost all sectors of the economy for example the manufacturing sector, energy sector, environmental and agricultural sectors and with recent studies, the health sector through medical geology. Finally, more geological and purposeful research has to be carried out in the areas of geochemistry, geochronology, and structural geology on the rocks of the south-western part of Nigeria to help in properly understanding their formation process, age relationship, and structural relationship which could lead to wealth generation in the Agricultural, Manufacturing, Oil and Gas Industries.

PICTURES SECTION