GEOLOGY OF MMAKU AND ITS ENVIRONS AWGU LOCAL GOVERNMENT AREA, ENUGU STATE, NIGERIA
This project work covers Mmaku town and its environs in Awgu Local Government area of Enugu state. It is bounded by Latitudes N6061011 and 6091011N and longitudes E70251011 and 70281011 which cover an area extent of about 32km2. Three distinct geological formations desigJnated as unit1, unit 2, and unit 3; Owelli sandstone, Mamu formation and Ajalli sandstone respectively. The ages of these formations are coniacian, campanion and maastrichtian respectively. The Awgu shale consists of bluish-grey shale with intercalation of four grained sandstone with thin beds of limestone. The Owelli sandstone lies unconformably on the Awgu shale is characterised by hard ferruginised sandstone. The sandstone is mostly coarse grained. The manufacture comprises of shale with well bedded fine medium grained sandstone. The area such as bedding, cross bedding, unconformity, and joints. The hydrology of the area course result shows that streams of the study area are slightly acidic with pH value ranging from 6.0 to 6.4. The major geologic materials of economic substance include laterite materials of economic importance include laterite, sand clay, shale deposit, ferruginised sandstone, and water resources. The samples collected in the study area were used to conduct the laboratory analysis (sieve analysis). Atterbergs limit results shows that the clay limit of Awgu shale has high liquid limit and plastic limit relative to the clay of Mamu formation.
1.1 Location and Accessibility - - - - - - 1
1.3 Physiography and Geomorphology - - - - 1
1.3.1 Vegetation - - - - - - - - 1
1.3.2 Climate - - - - - - - - 2
1.3.3 Topography - - - - - - - - 4
1.3.4 Drainage - - - - - - - - 5
1.3.5 The Soil - - - - - - - - 7
1.4 Methodology - - - - - - - - 8
1.5 Literature Review - - - - - - - 9
REGIONAL GEOLOGIC SETTING OF BENUE TROUGH
2.1 Review of the Geology of South-eastern Nigeria - - 11
2.2 Sedimentation Episode of Benue Trough - - - 15
2.3 Local Geology - - - - - - - 18
LOCAL GEOLOGY OF MMAKU
3.1 Lithologic Description - - - - - - 23
3.2 Report of sieve analysis - - - - - - 26
4.1 Surface Water Hydrology - - - - - - 33
4.1.1. Subsurface Water Hydrology - - - - - 38
4.1.2 Hydrogeochemistry - - - - - - 40
4.1.3 Water Quality Assessment - - - - - 41
4.1.4 Results and Interpretation - - - - - - 44
ENGINEERING AND ECONOMIC GEOLOGY
5.1 Atterberg Limit Test - - - - - - - 47
5.2 Liquid Limit Test - - - - - - - 47
5.3 Plastic Limit test - - - - - - - 53
5.4 Interpretation of Result - - - - - - 55
6.1 Gullies - - - - - - - - - 61
6.1.1 Major causes - - - - - - - 58
6.1.2 Prevention and Control Measures - - - - 59
6.1.3 Pollution - - - - - - - - 60
6.1.4 Major Causes - - - - - - - 61
6.1.5 Prevention and Control Measures. - - - - 63
6.2 Summary and Conclusion - - - - - - 64
References - - - - - - - - 67
1.1 Location and Accessibilty
The study area Mmaku and its environs lies within latitude6o6’0’’ and 6o9ꞌ0’’N and on longitude 7o251011 and 7o281011E. Mmaku and its environ is located in Enugu state. It is accessible through tarred and untarred roads.
The study areas are well accessible with vehicle, motorcycle and other means of transport. Many places in the study area are well accessible, but the thick forest areas, gullies and mountainous areas are not accessible. But some of the forest areas become accessible during the harmattan because of drying up of some of the vegetation.
1.3 Physiography and Geomorphology
The study area and its environs are located in south-western Nigeria which consists of main rain forest vegetation and few savannah vegetation. The rain forest vegetation in the study area consists of mainly of trees with some shrubs, grasses and climber. The vegetation in Mmaku and its environs are thick during the rainy season and sparse during the dry season or harmattan.
In Mmaku and its environs rainforest vegetation are assisted with the low land and deep gullies =, this is because of softness of the soil which support the growth of luxuriant trees such is found mainly along Mmaku-Oweli road and in the foot plains in Mmaku.
Savannah vegetation also occur in Mmaku and its environs. By definition savannah vegetation is the type of vegetation which consists mainly of grasses and few shrubs and trees. In Mmaku-Owelli-Amolli area, savannah vegetation occurs in the hills in the area. This is because those hills consists of hard rocks which did not support the growth of luxuriant trees but it support the growth of shallow rooted plants mainly grasses.
Generally, Mmaku and its environ consist of few main types of vegetation which are rainforest vegetation and savannah vegetation. The rain forest vegetation is associated with low land in Mmaku and its environs while the savannah vegetation are associated with the hills in the area.
The vegetation in Mmaku and its environ are thick during the rainy season and sparse during the dry season except at the river bank and stream beds or banks in the area.
The study area is part of equator which is located at in the Greenwich Meridian. The equator location of the study area made it to have equatorial climate. The temperature in the study area are high throughout the year except during the harmattan.
The rainfall in the study area are high. It occur mainly in form of orographic rainfall, frontal rainfall, and relief rainfall. The rainfall in the study area are associated with strong wind and thunderstorm. The rainfall in the study area starts mainly from the months of April to September or October and sometimes November. The rainfall in the study area decreases towards august which is known as August break. The humidity in the study area are high during the rainy season. The harmattan in the study area starts from the month of November or sometimes December till the January or February of the coming year.
The atmospheric pressure in the study area are high mainly at the mountaneous region in the area which are mainly in Mmaku plateau and many elevated area around Nkwe-Ugbookpara area. The atmospheric pressure in the mountaneous regions of Mmaku and its environ are about 880 to 960 mmhg (Iloege, 1992). The atmospheric pressure in the low land, in Mmaku and its environ are about 760mmhg to 780mmhg.
Rainfall distribution in Mmaku and its environ are highly affected by the atmospheric pressure and by vegetations in the area.
Mmaku and its environs consist of rough elevated topography. The rough topography in Mmaku and its environ indicated different in the homogeneity of rock hardness.
Mmaku-Owelli-Obeagu and Ugbookpara area consist of highly elevated area with deep gullies. The elevated area consist of highly elevated area deep gullies. The elevated area in the study area had been termed geanticline or anticlinorum by early works such as( Obi et al1991) and( Uma et al1993).
The elevated area in Mmaku-Nkwe-Obeagu and ugbokpara are consists of hard rocks which are highly lithfied and compacted. The highly lithified and compacted rocks resists weathering which makes them to form elevated area while the low land area in Mmaku and its environ consist of soft rock in Mmaku-Nkwe-Amolli-Owelli-obiagu and Ugbokpara had been termed syncline or syclinorium by early workers among them area (Benkhill 1986; Obi et al, 1991 & Uma et al, 1993).
The study area Mmaku and its environ are sedimentary environment. It consist of tendritic pattern of drainage system which flow in southeast ward with other distributaries joining it. The drainage system in the study area are conspicous during the rainy season and sparse during the dry season because of the dying up of some of the streams.
The streams in Mmaku which is at the border between Mmaku and Owelli flows south-eastward were they joined Enugu River which flow southward.
Fig 1.1 Drainage map of the study area
1.3.5 The Soil
Soil type in Mmaku and its environs consist mainly of sandy soil, clay soil and with small amount of sandy-clay, silt soil and humus soil. The sandy soil covers many places in Mmaku and its environs. The sandy soil in Mmaku and its environs display mainly facies from highly compacted sandy shale to poorly compacted sandy soil and from well sorted sandy soil and from highly ferroginised sandy soil to medium ferroginised then to unferroginised sandy soil. The poorly compacted sandy soil in Mmaku area is found along Mmaku-Owelli road while the highly compacted soil in Mmaku is found along Mmaku-Nkwe-Obeagu-Ugbokpara road.
The clay soil in Mmaku are abundantly occur in Amolli-Mmaku road. The clay soil in Mmaku and its environ are dark and bulky while some are earthly brown. Most of the clay soil in Mmaku and its environs are covered by hard lateritic layers which formed by the ferroginisation and lithification of the surface of the clay.
Silt soil occurs abundantly along Amolli-Nkwe-Mmaku gulley erosional site. The siltstones or soil in the area are light to brown coloured while some are dark coloured. The silt stone along Mmaku-Owelli area display concretion.
Sandy clay soil also occur in Mmaku in Obeagu and Ugbopkara are, the sandy clay in Mmaku occur in places where there are contact between shale and sandstone.
Humus soil in Mmaku and its environs capped many soil in the area. Humus soil occur in forested areas in Mmaku where they formed by decaying of plants materials on the surface of the soil. Humus soil in the study area are dark coloured.
The field mapping out exercise was carried out for two weeks. The aim of the field mapping exercise is to study the detailed geology of Mmaku and its environs and to analyse water sample, soil sample and rock samples.
Many geological instrument was used during the field mapping. Among them are; Burton compass which was used to measure the dip, strike and dip amount of the bed, measuring tape was used to measure the width and length of the bed, geologic map was used to locate the stations in the field. Hand lens was used to study the mlansfossils in the field, ground positioning system (GPS) was used to take the coordinate in the field. Geologic hammer was used to hit out the rock samples from the outcrops,geologic tape was used to measure the width and length of the bed, geologic bag was used to keep the samples collected in the field. Photographic camera was used to take the photograph of the outcrops and geologic structures in the field. Cotton wool was used to store the delicate fossils covered in the field. Aqueous solution of hydrochloric acid was used to test for calcium carbonate content of the rock samples while small empty plastic containers was used for the collection of water samples in the field.
1.5 Literature Review
The detailed geology of Mmaku and its environs had been studied by many workers among them are Reyment 1965, Murat 1972, onwuemesi 1986, Ofoegbu 1980, Egboka nd Uma 1984 and many other.
They all come to the conclusion that Mmaku consist of cretaceous sediments which formed the geologic formations in the area that the geologic formation in Mmaku and its environs rested uncomfortably in the Precambrian basement complex (Ekwueme, 1995).
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