Eruwa Oyo state, SW Nigeria field report (Group 4 presentation 2019)

1. OLABISI ONABANJO UNIVERSITY
PMB 2002, AGO-IWOYE, OGUN STATE.
GEOLOGICAL FIELD MAPPING REPORT WRITING
GEY 316
PRESENTED
BY
GROUP 4
SUBMITTED TO
EARTH SCIENCE DEPARTMENT,
FACULTY OF SCIENCE,
OLABISI ONABANJO UNIVERSITY.
25TH OF OCTOBER 2018

2. S/N NAMES MATRIC NO
1. BENEDICT DEBORAH M. SCI/16/17/0407
2. AMBALI AKEEM A. SCI/16/17/0303
3. OLUWOLE DAVID SCI/16/17/0871
4. OLASOJI IYANUOLUWA A. SCI/17/18/0849
5. AFOLABI BEULAH I. SCI/16/17/0190
6. OGUNYEMI TOLANI J. SCI/16/17/0749
7. OBIEKE MERCY N. SCI/16/17/0666
8. AKANBI FATIMAT O. SCI/16/17/0238
9. OKWENDO GODSPOWER SCI/15/16/1280
10. KAMORU NURUDEEN O. SCI/16/17/0577

3.  INTRODUCTION
 AIMS AND OBJECTIVES
 LOCATION AND ACCESSIBILITY
 GENERAL PHYSIOGRAPHY CHARACTER OF THE STUDY AREA
 PREVIOUS WORK
 GEOLOGY OF NIGERIA
 PRESENT WORK
 GEOLOGY HISTORY OF THE STUDY AREA
 TOOLS AND EQUIPMENT USED IN GEOLOGICAL FIELD
MAPPING
 STRUCTURAL GEOLOGY
 ECONOMY GEOLOGY OF THE STUDY AREA
 CONCLUSION AND RECOMMENDATION
 REFERENCES

4. Geologic map is a map that shows the aerial distribution of
various rock types of different ages. It usually consist
topographical map (a map giving information about the earth
surface) which is shaded or colored to show where different
rock unit occur at or just below ground or earth surface.
Geological field mapping is a process of selecting an area of
concern and identifying all the geological aspect of that area
with the purpose of preparing a geological report and a map to
summarize the report. Geological field mapping have been
found more useful in many geological aspect .

5. OBJECTIVES
 Identification and description of the rock types in the
study area
 Identification of the structures present in the rocks
studied
 Identification of minerals present in the rock in the
study area
 To obtain rock samples for petrographic studies
 To deduce the usefulness of rocks in the area for
economical and other purposes
 To train students in the technique employed in the
geological field mapping.
 To investigate the geologic and tectonic history of the
study area

6. The study area is located in Ibarapa east region of Oyo state,
Nigeria. Lying between latitude 7⁰ 33’ 00’’ - 7⁰ 35’ 00’’N and
longitude 3⁰ 24’ 00’’ - 3⁰ 26’ 00’’E. The study area is accessible
by a major road that connects it with other part of the state and so
many minor road and foot path. Places within the study location
include; AGASA,ABA-IJESHA,ALARIWO,AND OHU. The
study area falls within the Basement Complex of Nigeria.

9. RELIEF
The area mapped is an area of high relief towards the eastern region of the map
and low terrain at western region. The area has highlands with the highest
elevation of 209.8m above sea level.
CLIMATE
The climate of the study area is moderately hot ,humid tropic climatic zone of
southwestern of Nigeria. There are two types of climates namely the rainy and
dry season. The rainy season which takes the period from March/April to
October/November and the dry season with the period from
October/November to March/April. These influence two air masses. The dry
dusty continental air mass (CT) or the North-East trade wind emanating from
the northern part of Africa and the west tropical maritime air mass (MT) or the
south west Monsoon from the Atlantic ocean in the south (Oguntoyinbo 1978,
Adebayo 1986, Akanni 1992).

10. VEGETATION
 The vegetation of the study area is more of tropical rain forest and
is characterized by shrubs, thick dry grasses. The area studied has
a dense vegetation cover.
 The vegetation of the area is denser than it was as at the time of
the production of the Topographic map
 Crop such as cassava, maize, and fruits such as cashew, mango
etc. are the major agricultural produce
 Soils in the area are varied according to the geological history and
soil formation in different localities.
HUMAN ACTIVITIES
The major activities of the mapped area include farming majorly
cassava and cocoa plantation, nomadic farming, hunting, and some of
the rocks has undergone human activities as a result of physical
weathering such as using of sledge hammer and mechanized tools for
breaking of the rocks.

11. A previous work for papers have been shown that many
studies have been carried out on the geological mapping and
structural analysis of rocks in southwestern Nigeria, and even
Nigeria at large e.g Folorunso et al; 2013 etc.
Folorunso et al; 2013 carried out Geological Mapping,
Petrological study and structural analysis of pre Cambrian
basement complex rocks in part of OYO STATE southwestern
Nigeria. The work involved intensive geological mapping. The
type of rocks found are granite, porphyritic granite, gneiss,
granite gneiss, migmatites and many more, the study concluded
that the mineralogical assemblages of those rocks are Quartz,
micas, hornblende, feldspars and others.
However, this study is aimed at identifying and describing both
the geological classification and mechanical components of it
outcrops and to deduce the usefulness of the rocks for
economical embracement.

12. Nigeria lies approximately between latitudes 8O and 140N and
Longitudes 4Oand 14OE, within the Pan African mobile belt in
between the West African and Congo Cratons. It covers a
surface area of approximately 923,768sq.km and bounded to
the south by the southern Atlantic Ocean, North by chad
republic, east by Cameroun republic and on the west by Benin
republic.
The geology of Nigeria is made up of three major litho-
petrological components, namely:
 The Basement Complex
 Younger Granites
 Sedimentary Basins

14. The area mapped include some villages and forest that is
on the area given to be mapped, It takes a period of about
7days which started on TUESDAY 15TH OCTOBER to
WEDNESDAY 23RD OCTOBER 2019 .The
Geological Field Mapping was carried out systematically
and we were able to achieve the following which include;
Identifying the rock types present in the area, Identifying
structures present in the rock units, Identifying the
minerals present in the rock units observed, Constructing
the geologic and Tectonic history of the area and
Collection of rock samples for petrographic studies.

15. There are basically two types of rocks in the area of study of
latititude 7⁰ 33’ 00’’ - 7⁰ 35’ 00’’N and longitude 3⁰ 24’ 00’’ -
3⁰ 26’ 00’’E which are granite and gneiss. Granite being the
oldest was formed about 6million years ago during Pan
African Orogeny which later metamorphosed by regional
metamorphism then lead to the formation of Gneiss and
banded gneiss after several years. The entire outcrop visited in
the study area exhibit either light or dark colour (Leucocratic
or mesocratic).The entire outcrops in the study area experience
physical, chemical and biological weathering, tentative names
were given to the outcrops according to their
texture,colour,grain size and the visible mineral present.

16. Fig 4. Geological map of the study area
Cross-section X to Y

17. Fig 5. Picture showing solution cavities as a result of chemical weathering on
one of the outcrop in the study area.

18. The equipment used during the course of the geological field
mapping includes the following:-
 Topographical Maps
 Compass Clinometer
 GPS (Global Positioning System)
 Geological hammer
 Sample bags
 Measuring tape
 Field notebook
 Paper Tape
 Camera
 Chisel

19. Structural geology is concerned with deformation structures and
processes occurring in rocks due to tectonic forces. It include
studies of the forces that produces rock deformation. These
structures include
Folds
Fracture
Joints
Veins
Intrusions
Solution cavity

20. Folds are wave like structure that are produced by deformation of bedding,
foliation or other planar surfaces in the rocks and behave in a ductile manner.
Fig 6. Picture of an outcrop showing Folds

21. Fractures are points of discontinuity with limited displacement,
two main types of fracture are Joint and Fault.
Fig 7. Picture showing a type of fracture (Fault)

22. Joint is fracture in rock along which there has been no
displacement.
Fig 8. Picture showing joint on the rock of
the study area

24. Faults are fracture in rock along
which there is a discernable
displacement.
.Fig 10. Picture showing a
type of fault on the rock in
the study area

25. Vein is a distinct sheetlike
body of crystallized minerals
within a rock.
Fig 11. Picture showing a
cross cutting vein on the rock
in the study area.

27. Intrusion is any formation of
intrusive igneous rock which
forms when magma cools and
solidifies before it reaches the
surface.
Fig. 13. Picture showing Quartz
intrusion on the rock in the
study area.

29. They are rock fragment
enveloped in a body of rock.
Fig 15. Picture showing
Xenolith on the rock of the
study area.

30. Foliation refers to repititive layering in metarmorphic rocks and it
have a sheet-like structure.
Fig 16. Picture showing foliation
on the rock in the study area.

31. Economic geology is concerned with earth materials
that can be used for economic and/or industrial
purposes. The prominent minerals found in the study
area include Quartz(SiO2),Feldspar(KAlSi3O8-
NaAlSi3O8-CaAlSi2O8),Muscovite(KAl2
(AlSi3O10)(OH)2),Biotite (K (Mg,Fe)3(AlSiO10)(OH)2).
The granite and gneiss in the study area can be used in
the construction of roads, bridges, buildings, as a gem
stone, for decoration etc. and this will serve as a
means of revenue generation

32. The study area is a basement complex area composed of
the following rock types from youngest to the oldest,
Gneiss, porphyritic to Granite. It is hoped that further
research work on outcrops of part of Eruwa (Agasa)
Southwestern Nigeria; including, geochemical,
geotechnical, isotopic and geothermobarometric studies
will throw more light on the evolutionary history, tectonic
setting and economic significant mineral of the rock units
of the study area.

33. .
 Omosanya et al, Introduction to Geological Field Mapping (Field Guide and Notes);
 Oyawoye, M.O.(1972): The basement complex of Nigeria in African Geology, Ibadan 1970.
 Folorunso et al; (2013) carried out Geological Mapping