Contributions to the Petrology of British East Africa

1903 ◽  
Vol 13 (61) ◽  
pp. 228-263 ◽  
Author(s):  
G. T. Prior
Keyword(s):  
East Africa ◽  
Rift Valley ◽  
Volcanic Rocks ◽  
Central Africa ◽  
British Museum ◽  
Basaltic Rocks ◽  
Basement Rocks ◽  
Great Rift Valley ◽  
Rock Specimens

The following notes on the petrology of British East Africa are the result of an examination of rock-specimens collected by Professor J. W. Gregory on his well-known expedition from Mombasa to Mt. Kenya and Lake Baringo in 1892-3, and of rock-collections from the Uganda Protectorate which have been recently presented to the British Museum by Sir Harry Johnston.The collections include examples of the Archaean gneisses, schists, and granites which constitute the prevailing basement rocks of Central Africa; of ferruginotls schists, coarse sandstones, and quartzites belonging to the Palaeozoic Karagwe series ; and of an interesting series of Tertiary volcanic rocks comprising phonolites, phonolltic traehytes, riebeckite-rhyolites, kenytes, and basalts from the volcanoes of the Great Rift Valley, as well as of nephelinites and basaltic rocks containing melilite and perofskite from Mr. Elgon.

Petrology and the Western Rift of Central Africa

1932 ◽  
Vol 69 (11) ◽  
pp. 497-510 ◽  
Author(s):  
A. W. Groves
Keyword(s):  
Rift Valley ◽  
Volcanic Rocks ◽  
Central Africa ◽  
Volcanic Field ◽  
Thin Sections ◽  
Basement Rocks ◽  
Geochemical Study ◽  
Northern Half ◽  
Tectonic Significance ◽  
Near Future

IN the course of several journeys between Masindi and Butiaba, and one from Butiaba to Hoima (via Waki Camp), specimens of the various gneisses were collected from roadside exposures. Thin sections of these were subsequently studied by the writer in England with the result that they were found to yield evidence of tectonic significance. In addition, the writer has, during the last three years, examined petrographically a large number of other rocks from those parts of Uganda bordering the Lake Albert Depression. In particular he has made a special study of the Charnockite Series, which are widely spread over the northern half of the Protectorate, with the result that it has been possible to observe the effects of the rift valley movements on these rocks in the regions adjacent to Lake Albert. It is hoped to publish a petrological and geochemical study of the Charnockite Series of Uganda in the near future. In the following pages it is proposed in Part I to present petrological evidence from the basement rocks of various districts in the hinterland of the Lake Albert scarps and then in Part II to point out the tectonic significance of this evidence in the light of the various theories of rift valley formation. In Part III the relation between the petrological characters of the volcanic rocks and the rift valley tectonics will be briefly reviewed. In the case of the basement rocks the remarks will be confined to the Lake Albert Depression, but in the case of the volcanic rocks the discussion will extend also to Lakes George and Edward and the Birunga volcanic field.

Etat actuel des connaissances sur le volcan Niragongo (Republique democratique du Congo)

1966 ◽  
Vol S7-VIII (2) ◽  
pp. 176-200 ◽  
Author(s):  
Haroun Tazieff
Keyword(s):  
Chemical Composition ◽  
East Africa ◽  
Gaseous Phase ◽  
Rift Valley ◽  
Accessory Minerals ◽  
République Démocratique Du Congo ◽  
Great Rift Valley

Abstract The Niragongo volcano of the Congo region is located in the western Great Rift Valley in east Africa. The cone is formed of feldspathoidal lavas containing augite and accessory minerals, and the crater contains terraces representing ancient lava levels. Studies were conducted on the chemical composition and petrography of the rocks, on the chemistry of the gases and sublimates, and on the temperature of the lavas. The magnetic and gravimetric values for the volcano and the area were measured and energy discharge was estimated. The study confirmed the importance of the gaseous phase in volcanic phenomena.

The Age and Tectonic Relationships of East African Volcanic Rocks

1944 ◽  
Vol 81 (1) ◽  
pp. 15-27 ◽  
Author(s):  
P. E. Kent
Keyword(s):  
East Africa ◽  
Rift Valley ◽  
Volcanic Rocks ◽  
East African ◽  
Great Volume ◽  
Geological Features ◽  
Tertiary Period

The great volume of extrusive rocks which has accumulated during and since the Tertiary period is one of the most important geological features of East Africa, and one which various people have related to the formation of the Rift Valley System.

A New Ceratotrochus from the Upper Cretaceous of Portuguese East Africa

1930 ◽  
Vol 67 (10) ◽  
pp. 475-477 ◽  
Author(s):  
J. W. Gregory
Keyword(s):  
East Africa ◽  
Rift Valley ◽  
Upper Cretaceous ◽  
Great Rift Valley

Three small simple corals were collected by Mr. F. P. Mennell from the Upper Cretaceous of the Cheringoma district, Portuguese East Africa. The area is of special geological interest as it includes the southern end of the Great Rift Valley and furnishes useful evidence as to the date of the formation of that valley. A coral from almost the same horizon has been figured by Schlosser, and, as it is clearly a different species, the horizon may be expected to yield a good fauna of simple corals.

The Great Rift Valley in Northern German East Africa

1914 ◽  
Vol 44 (5) ◽  
pp. 494
Author(s):  
J. W. G. ◽  
Fritz Jaeger
Keyword(s):  
East Africa ◽  
Rift Valley ◽  
German East Africa ◽  
Great Rift Valley

Soils of the lowland forests of West and Central Africa

1996 ◽  
Vol 104 ◽  
pp. 15-29 ◽  
Author(s):  
A. S. R. Juo ◽  
L. P. Wilding
Keyword(s):  
East Africa ◽  
Central Africa ◽  
Congo Basin ◽  
The West ◽  
Forest Zone ◽  
Lower Elevation ◽  
Lowland Forests ◽  
West And Central Africa ◽  
Hydrological Cycles ◽  
Great Rift Valley

The forest zone of West and Central Africa comprises the coastal and adjacent inland regions bounded the semi-deciduous forests in the west and the equatorial forests in central Africa and the Congo basin. Sedimentary plains, developed mostly on weathered sandy materials, lie along the coastal stretches and cover vast areas of the Congo basin. Behind the coast the plain rises gradually to hills and plateaus of much lower elevation than those of the highlands of East Africa. Two great rivers, the Niger and the Congo, which discharge huge volumes of fresh water to the Atlantic Ocean, are major contributors to the hydrological cycles of the rain forests ecosystems of the Guinea–Congo Region. The Niger originates from the forested highlands of Guinea and discharges its waters into the Bight of Benin by way of a large delta in southern Nigeria. The Congo basin occupies an immense area of 750 000 km2, surrounded by Pre-Cambrian uplands. The alluvial floor of the saucer-shaped basin is flat, and marshes and swamps comprise a large proportion of the total area. The highlands and plateaus along the rim are low to the west and north and higher to the south. To the east, they merge with the mountains of the Great Rift Valley of East Africa (Gann & Duignan 1972; Hance 1975; Grove 1978; Hamilton 1989).

Vote on the alkali-lavas of Mount Nimrud, Armenia

1928 ◽  
Vol 21 (121) ◽  
pp. 485-488 ◽  
Author(s):  
G. T. Prior
Keyword(s):  
East Africa ◽  
Rift Valley ◽  
British Museum ◽  
Lake Van ◽  
Deep Lake ◽  
The West ◽  
West Side ◽  
Thin Slices

The object of this note is not to give elaborate descriptions of rocksections, but to call attention to tile fact that the old volcano of Nimrud, situated on the west side of lake Van in Armenia, was the centre of eruption of alkali-lavas presenting striking similarities to some of the alkali-rocks of the tlift Valley in East Africa.To Dr. Felix Oswald, in his book on the geology of Armenia, we owe a detailed description of this ancient volcano, of which the vast crater, now half occupied by a deep lake, is more than five miles across. An interesting series of the lavas from the volcano was collected by Dr. Oswald and was presented by him to the British Museum. On looking over thin slices of these rocks under the microscope, I was at once struck by the surprising resemblance of some of them, with their phenocrysts of anorthoclase and scattered tufts of aegirine and the soda-amphiboles, riebeckite and cossyrite, to rocks in Prof. J. W. Gregory's collection from the Rift Valley which I had described.

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