GEOLOGY AND GEOCHEMISTRY OF TWO CARBONATE ROCKS IN THE CALABAR FLANK

ABSTRACT
Two-limestone outcrops in the Calabar Flank was studies, and comparison of the chemical contents of these rocks was made and also total organic matter was also determined. Sample collected form an exposure around Itakpini village and New Netim Marl, where analysed for metal content using the Atomic Absorption Spectrophotometer (AAS) and total organic matter method. Chemical results of the two limestone rocks show an increase in metal contents (Al, Ca, Fe, Mg, Mn, Si, Ti was absent) of the Itankpini limestone and a decrease in total organic matter as compared to the New Netim marl of higher total organic matter and lesser metal contents. Deposition within the Calabar flank began with the formation of a basal conglomerate of Awi formation, these where as a result of marine transgression during the Cretaceos. Mfamosine and Itankpini limestone, of the Albian – Cenomanian age, overlay this formation, during the Turonian was another marine transgression and this resulted in the deposition of the dark Ekenkpon shale. In the Coniacian rapid evolution of organic matter resulted, an indication of oxygenated environment, hence a marine transgression resulted in deposition of the New Netim marl, dung the Campanian-maastrictian deposition of the Ekenkpon shale occurred and was later overlain by the Benin formation.

TABLE OF CONTENTS
Title page – – – – – – – – – i
Certification – – – – – – – – – ii
Dedication – – – – – – – – – iii
Acknowledgement – – – – – – – iv
Abstract – – – – – – – – – v
Table of content – – – – – – – – vi
CHAPTER ONE
1.1 Introduction – – – – – – – – 1
1.2 Justification of Study – – – – – – 2
1.3 Location – – – – – – – – 3
1.4 Literature Review – – – – – – – 4
1.5 Method and Scope of Work – – – – – 5
1.6 Climate – – – – – – – – – 5
1.7 Vegetation – – – – – – – – 7
1.8 Relief – – – – – – – – – 7
1.9 Drainage – – – – – – – – 8

CHAPTER TWO
2.1 Stratigraphy and geology history of the calabar flank – – 9
2.2 Awi Formation – – – – – – – 10
2.3 Odukpani Group – – – – – – – 10
2.4 Nkporo Shale – – – – – – – – 12
2.5 Sedimentary Structures – – – – – – 19
CHAPTER THREE: GEOCHEMISTRY OF THE CARBONATE ROCKS
3.1 Lime Stone – – – – – – – – 24
3.2 Composition and Origin – – – – – – 25
3.3 Diagenesis of Limestone – – – – – – 30
3.4 Marlstone – – – – – – – – 34
CHAPTER FOUR: DATA PRESENTATION, DATA REDUCTION AND DISCUSSION
4.1 Data Reduction – – – – – – – 39
4.2 Result of Chemical Analysis – – – – – 39
4.3 Discussion – – – – – – – – 41
CHAPTER FIVE: SUMMARY, CONCLUSION AND RECOMMENDATION
5.1 Summary – – – – – – – – 42
5.2 Conclusion – – – – – – – – 43
5.3 Recommendation – – – – – – – 44
REFERENCES – – – – – – – – 45

CHAPTER ONE

1.1 INTRODUCTION

The Calabar flank was first proposed by Murat (1972) as that southern Nigeria sedimentary basin, characterized by cruster blocks, fault trending in a NW-SE direction. However an attempt has been madeinrecent time to define the calabar flank and to establish it as a distinct geological province.
Several theories have been proposed for the origin of the Southern eastern Nigeria sedimentary basin (Calabar flank) Kennedy (1965) suggests of rift valley system. Stonley (1966) that the basin formation was as a results of slight adjustment in the shape of the Africa during its separation from the South America (Wright 1966, Burke et, al 1972, Murat 1972 Nwanchukwu, 1972) the origin of the calabar flank is associated with the development of the Benue rift system and both events are related to the existence of the RRR triple junction which was active in the early cretaceous time. The Calabar flank is bounded at the North by the Urban massif and the Calabar hinge line delineating the Niger delta basin in the south.
The sedimentary succession of the calabar flank is mostly of cretaceous age, comprising of an ancient River-borne sand stone Awi formation and the overlying marine Odukpani group of the Albian to late cretaceous age. The Odukpani group comprises of the Itankpini limestone, which is an extension of the Mfamosing limestone and the New Netim marl, and the Ekenkkpon shale. Based on the ammonites found on the shale Reyment (1968) conclude that the limestone is of Cenomanian and Fayose (1978) supported that the limestone could be of Cenomanian age. The calcareous marl deposition increase on an importance in the Coniacian.

1.2 Justification of Study
This research work is solemnly aimed at carrying out a detailed geological and geochemical investigation of some carbonate rocks in the calabar flank. However the various stratigraphy and geochemical enrichment of these rocks are peculiar to the geologic process and history, marine transgression and regression, environments as well as abundance of organic matter at one point in time such organic matters include ammonites, foraminifera and are used for relative dating, due to their carbon contents.
The understanding of the geology and geochemical contents of these carbonates rocks will no doubt provide a better economic empowerment and the deposit adequately being harnessed.

1.3 Location
The studies area is located between longitude 80 001E and 80 451E and latitude 50 and latitude 50 351 N and 50 001N found in the south eastern part of Nigerian. The studied area are characterized by sparely rugged peaks and intensive area about 27km south of Calabar is a boundary between the Urban massif and the overlying Awi formation, 25km south of calabar in the Mfamosine Limestone, 24km south calabar is the Ekenkpon shale, 23km south of calabar in the New Netim marl and 19km south calabar Nkporo shale. However major roads running from Abia – Ikot Ekpene-Odukpani – Calabar – Akwa Ibom were observed, although no motorable road to Itankpini, this made accessibility to the area difficult.

1.4 Literature Review
According to Reyment (1965) a sequence of sand, limestone, shale, and sandy shale unconformable overlies the basement complex, which is the oldest known sediment in the calabar flank. He gave the name as Odukpani formation to this units, and tentatively assigned a Cenomanian to lower limestone member based on Ammonite fauna. This age assigned to limestone was later supported by Desauvagie (1968) and Fayose (1978) based on foraminifera evidence Fayose however pointed out that the basal arenaceous member of the Odukpani formation is both petrographically as well as tectonically correlated with mamfe formation of probably Albian Age. Different views expressed on the age of the earliest sediments in the south eastern Nigeria by Murat (1970) and Kogbe (1976) are also shown in Figure 1.

1.5 Method and Scope of Work
A total number of four fresh sample was collected from an out crop in Odukpani area, two sample were collected from the Intanpini (Lime stone) and New Netim (Marl) with the aid of sledge hammer and compass was used to determine the direction and kilometers for dip and strike. However field identification carried out on these sample show a rapid effervescence on addition of Hydrochloric acid to the limestone compared to the impure limestone (marl). These sample where latter analysed in the laboratory using the Atomic Absorption Spectrophotometer, to determine the concentration of metal and the total organic analysis to determine the organic content.

1.6 Climate
The climate of the studied area is similar to that obtained in other part of the Niger Delta and its altitude and position. The altitude of the studied area bring about a reduction in the temperature that might be expected for it latitude comparism with other place located in the delta’s. The studied area falls within the rainforest and in experienced between the month of October – March intermittent but torrential rain observed. The wet season last from April to September. A monthly average temperature range between 26.70 – and do not fall below 12.80. The month of December, January and February are characterised by harmattan, haze where as the month of March and April have record of higher temperature. Torrential rain are usually accompanied by hail, storm in wet season.
Weathering
Climate is generally considered the most important factor influencing physical and chemical weathering processes.
Physical weathering: Is especially important during the early stages of soil development. Rock can be disintegrated by changes in temperature, which produces differential expansion and contraction. Changes in temperature can also cause water to freeze. The forces produced by water freezing can be as great as 10^5kpa which can split rocks apart, wedge rocks upward in the soil, and heave and churn soil material.
Chemical weathering: The principal agent is percolating rainwater charged with carbon dioxide form the atmosphere. Parent material becomes hydrolyzed by the acidic solution to produce minerals and to release cations.

1.7 Vegetation
The area mapped has vegetation similar to that obtained in other part of the Niger Delta, the vegetation is that of typical rain forest, the hills and Rivers, Valley are covered with thick vegetation. The thick forest has being inhabitant by wild animals and encourages hunting, timber falling was prominent. The vegetation of the mapped area is related to the soil type and climate of the area.

1.8 Relief
The area mapped is found within the urban massif and the Calabar Flank and reflect the characteristic of the Niger delta, the topography is slightly high especially around the massif and relative low around the flank. And weathering of granodiorite rck in some location and descend gently to the lateral enrichment.

1.9 Drainage
The area is situated within the southern eastern axis of Nigeria and is drained by heat water tributaries of the Cross River and kwa rivers.
Dendritic pattern of drainage is seen to occur due to the presence of slightly peak and rapid peculation in some location due to sandstone availability, these slightly peak radiate stream into gently sloping directions. The stream are controlled by the joint and fractures system of the slope the area has a season rain fall pattern of the delta and as a result of this most of the stream are seasonal with the highest floor in August also due to the slightly relief of the area it is due to increase porosity and fracture opening which allow water to enter the bedrock and store, this water gathered in some area and forming pool. The fieldwork was undertaken toward the middle part of the year June, and vegetation covers almost the entire surface, with little exposure. As a result of low coefficient of Runoff in some area and villages around such area are usually faced with shortage of water during the dry season.