Middle Paleocene to Early Miocene Palynostratigraphy of Sediments in Bende – Umuahia Area, Niger Delta Basin, Southeastern Nigeria.

ABSTRACT Cenozoic sediments outcrop in the Niger Delta Basin. Deposits in the Basin thicken southward (down-dip) but thin northward (up-dip) around Bende – Umuahia area where approximately 260 m thick exposure was logged from base to top. Sieve analysis and petrography were carried out to establish the depositional settings of sediments while palynological analysis was undertaken in order to identify palynomorphs and establish their biozonations, determine and correlate age of sediments, ascertain their palaeoenvironments of deposition, and evaluate kerogen quantity and maturation. Five lithological units were encountered. They include carbornaceous shale, fossiliferous limestone, sandstone, mudstone and coal. A total of 65 sporomorphs and 51 dinoflagellate species were identified and described. Six informal palynological assemblage zones labeled (A - F) were established across the study area, which comprise: Zone A Scabratriporites simpliformis-Bombacidites annae zone, Middle Paleocene; Zone B Foveotricolporites crassiexinus-Mauritidiites crassiexinus zone, Late Paleocene; Zone C Striatopollis catatumbusMomipites africanus zone, Early Eocene; Zone D Margocolporites umuahiaensisGemmastephanocolporites brevicolpites zone, Middle Eocene; Zone E Cicatricosisporites dorogensis-Perfotricolpites nigerianus zone, Late Eocene; and Zone F Verrucatosporites usmensis-Magnastriatites howardii zone, Oligocene-Early Miocene. Three main palynofacies (A, B, and C) were recognized based on the significant changes in the particulate organic matter constituents of the kerogen samples. Age determination and correlations were achieved based on selected index palynomorph assemblages. Imo Formation was dated Middle Paleocene – Early Eocene age based on the following assemblage: Proxapertites operculatus, Scabratriporites simpliformis, Bombacidites annae, Foveotricolporites crassiexinus and Striatopollis catatumbus. Ameki Formation was assigned Early to Late Eocene age with the following species, Monoporites annulatus, Momipites africanus, Proxapertites cursus, Retistephanocolpites williamsi, Margocolporites umuahiaensis, Spinizonocolpites echinatus, and Retibrevitricolpite triangulatus. Ogwashi Formation was dated Oligocene-Early Miocene age based on Verrucatosporites usmensis, Magnastriatites howardii, Retibrevitricolporites protrudens, R. obodoensis, R. ibadanensis, and Chenopodipollis dispersus. Palynomorphs of environmental value indicated that Imo Formation was deposited in a marginal marine setting ranging from estuary at the base, upper to lower shoreface towards the middle, and tide-dominated estuary at the top. Ameki Formation ranged from open marine at the base to beach/ fluvial towards the middle and estuarinelagoon/marine at the top, while Ogwashi Formation was deposited between freshwater upper to brackish water lower deltaic plain within the tropical rainforest.

TABLE OF CONTENTS

Title page…………………………………………………………………………………….…i

Certification …………………………………………………………………………………...ii

Dedication……………………………………………………………………………….…….iii

Acknowledgements……………………………………………………………………….…...iv

Table of Contents …………………………………………………………………………......vi

List of Figures ………………………………………………………………………………....ix

Abstract ……………………………………………………………………………………….xvii

CHAPTER ONE: INTRODUCTION………………………………………………..............1

1.1 Location and Accessibility ………………………………………………………….....1

1.2 Geography: ………………………………………………………………………….....1

1.2.1 Relief and Drainage……………………………………………………………………..1

1.2.2 Climate and Vegetation………………………………………………………………....3

1.3 Objectives of the present Work……………………………………………………….7

1.4 Scope of Work/Statement of Problem…………………………………………...........7

CHAPTER TWO: REVIEW OF LITERATURE..………………………………………....8

CHAPTER THREE: GEOLOGY…………………………………………………………...16

3.1 Niger Delta Sedimentary Basin …………….……………………………………………16

3.2 Stratigraphy of Niger Delta Basin………………………………………………………..16

CHAPTER FOUR: MATERIALS AND METHODS OF STUDY………………………21

4.1 Outcrop Logging and Sampling………………………………………………………21

4.1.1 Sample collection………………………………………………………………………21

4.1.2 Laboratory analyses…………………………………………………………………….21

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4.1.2.1 Grain size analysis…...………………………………………………………………........21

4.1.2.2 Petrography of limestone…………………………………………………………………22

4.1.2.3 Palynological sample preparation…………………………………………………….......23

CHAPTER FIVE: LITHOLOGICAL DESCRIPTIONS OF STUDY AREA……………..30

5.1. Outcrop descriptions………………………………………………………………………..30

5.1.1 Imo Formation …...………………………...…………………………………................30

5.1.1.1a Carbonaceous Shales …..…………………………...…………………………………...30

5.1.1.1b Fossiliferous nodular limestone………………………………………………………….33

5.1.1.2 Sandstones …..……………………………………………………………………………33

5.1.1.3 Mudstone …..………………………...…………………………………………………..45

5.1.2 Ameki Formation …...………………………...…………………………………..........47.

5.1.2.1a Carbonaceous Shale …..…………………………...…………………………………....47

5.1.2.1b Septarian limestone nodule……………………………………………………………...47

5.1.2.2 Sandstones………………………………………………………………………………..47

5.1.2.3 Mudstones …..…………………………………………………………………………...52

5.1.3 Ogwashi Formation …...………………………...………………………………….......52

5.1.3.1 Mudstone …..…………………………...…………………………………......................52

5.1.3.2 Coal……………………………………………………………………………………….61

5.1.3.3 Carbonaceous Shale…..………………………………………………………………….61

5.1.3.4 Sandstones………………………………………………………………………………...61

CHAPTER SIX: LABORATORY RESULTS………………………………………………..66

6.1 Grain size result ………………………………………………………………………….....66

6.2 Petrography……………………………………………………………………………….....76