Chapter I: Preface

The observations upon which these outlines of the Geology and Geography of Northern Nigeria are based, were made in the course of the operations of the Mineral Survey of the Protectorate of which I had the honour to be the principal officer. The Survey was instituted by the Colonial Office in 1904 upon the recommendation of Professor Wyndham R. Dunstan, under whose general direction the work of investigation was carried out both in Nigeria and in the laboratories of the Imperial Institute. From 1904 to 1909 five expeditions in all were made to Northern Nigeria, in the course of which every province of the Protectorate was visited in turn. On the first two expeditions I was accompanied by Mr. Douglas R. Home, F.R.G.S., and on the remaining three by Mr. Arthur Longbottom, B.A., F.G.S. On an average seven months of each year were devoted to the actual field work, but the great extent of territory to be investigated, coupled with the difficulties of transport, rendered it impossible to do more in the time available than make a series of cross traverses through the various provinces with the object of ascertaining in a general way their geological structure and mineral resources.

In the following pages I have attempted to correlate the various observations which were made in the course of our travels and to weave a more or less consecutive story out of the disconnected contents of our notebooks. I am myself, however, only too conscious that many of my deductions may have been drawn from insufficient data and that further knowledge may overturn many of my hypotheses. In a new land someone must do the pioneering, and I shall be amply satisfied if my work affords some foundation, however insecure, for the investigations of future workers.

It is with the deepest regret that I have to record the death of my friend and former colleague, Mr. Arthur Longbottom, since this work went to press. He died of dysentery, after much suffering, in November, 1910, at Naraguta, on the Bauchi plateau in Northern Nigeria, whither he had returned on a tour of inspection on behalf of a private syndicate. We had hoped that he would be able to continue the work which we had begun together and that he would return to England with a fresh store of observations which would increase our scanty knowledge of the geology and geography of the Protectorate. His extensive experience in various parts of Northern Nigeria would have rendered those observations of the greatest value, but his untimely death has put an end not only to a most promising career but to all hope of any further immediate advance in our knowledge of the structure of this outlying portion of the Empire.

Before he left England Mr. Longbottom contributed all the paragraphs and sections throughout the book marked with his initials (A. L.). He also supplied the photographs from which have been prepared Plates I, II, VI, VII, VIII, Fig. 1, and XVI. For Plate VIII, Fig. 2, I am indebted to the Public Works Department of Northern Nigeria. Mr. Woods has kindly contributed the Appendix on the Cretaceous Mollusca and the note upon the Eocene fossils on p. 165.

I gratefully acknowledge a Grant towards the cost of publication of this work from the Carnegie Trust for the Universities of Scotland. I am especially indebted to Sir Archibald Geikie for help and encouragement in the matter of publication. My acknowledgments are due also to various friends for assistance and advice, and more particularly to Professor James Geikie, Professor Wyndham R. Dunstan, Professor Knight, Dr. Horne, and Dr. Flett.

J. D. FALCONER.

JANUARY, 1911.

CONTENTS

CHAPTER I

PAGE

PHYSICAL GEOGRAPHY 1

Introduction 1

Hydrographical Systems 3

The Niger 4

The Benue 10

The Niger Provinces:—Kabba, Ilorin, Borgu, Kontagora, Nupe 16

The Benue Provinces:—Bassa, Nassarawa, Muri, Yola 25

The Central Provinces:—Zaria, Bauchi 35

The Northern Provinces:—Bornu, Kano, Sokoto 50

CHAPTER II

CRYSTALLINE ROCKS 63

Typical Traverses 64

Borgu and the Niger Valley between Jebba and Yelwa 69

Kabba and Ilorin 75

The Central Crystalline Area 86

Southern Muri and Yola 103

CHAPTER III

PETROGRAPHY OF THE GNEISSES AND SCHISTS AND ASSOCIATED IGNEOUS 108
INTRUSIONS

The Gneisses and Schists 108

The Intrusive Rocks 123

_a._ The Older Granites 123

_b._ The Younger Intrusions 129

1. Granites and Pegmatites 129

2. Syenites and Diorites 135

3. Porphyries, Porphyrites, Diabases and Basalts 137

CHAPTER IV

CRETACEOUS ROCKS 144

The Cretaceous Rocks of Muri Province 147

The Cretaceous Rocks of Yola Province 154

The Cretaceous Rocks of Bauchi and Bornu 157

CHAPTER V

EOCENE ROCKS 164

The Sokoto and Lokoja Series 165

The Duguri, Gombe, and Kerri-Kerri Sandstones 175

The Upper Benue Sandstones 184

CHAPTER VI

SUPERFICIAL ACCUMULATIONS 194

In Hausaland and Borgu 196

In Bornu and Katagum 215

In the Middle Gongola Valley 222

In the Benue Valley 223

CHAPTER VII

TERTIARY CRUSTAL MOVEMENTS AND DRAINAGE CHANGES 227

CHAPTER VIII

TERTIARY VOLCANIC ACTION 253

APPENDIX I—Mineral Resources 265