The geochronology of some Precambrian rocks of southern West Africa

1968 ◽  
Vol 5 (3) ◽  
pp. 639-642 ◽  
Author(s):  
A. I. Tougarinov ◽  
K. G. Knorre ◽  
L. L. Shanin ◽  
L. N. Prokofieva
Keyword(s):  
West Africa ◽  
Sierra Leone ◽  
Sedimentary Rocks ◽  
Structural Complexity ◽  
Metamorphic Rocks ◽  
The North ◽  
Upper Proterozoic ◽  
Lower Proterozoic ◽  
Metamorphic Complexes ◽  
Archean Basement

Age determinations completed during the last two years indicate a structural complexity previously undetected in the southern part of West Africa. Holmes and Cahen identified very ancient metamorphic rocks in Sierra Leone, in the western part of the Nigerian Shield. Their date of 2900 m.y. for monazite by the U–Pb method is comparable to a date of 2540 m.y. for biotite, recently determined by the K–Ar method.A Lower Proterozoic geosyncline, developed on the Archean basement, was deformed and metamorphosed 1800 to 2000 m.y. ago. The metamorphic complexes of the Ivory Coast and Ghana belong mainly to this period. The dominant trend of foliation is north to northeast.On the north slope of the Guinean crystalline complex younger granites are dated at 980 m.y. Associated extrusive rhyolites give an age of 1000 m.y.In eastern Ghana and Togo a thick sequency of conglomerates, sandstones, and pelitic sedimentary rocks contain glauconites dated at 620 m.y. These sedimentary rocks are the miogeosynclinal portion of an Upper Proterozoic geosyncline. The eugeosynclinal portion of this geosyncline was metamorphosed about 600 m.y. ago to form the Nigerian gneissic complex. The younger granites in Nigeria were intruded 170 m.y. ago.

Guinea

2020 ◽  
Author(s):  
Marius Schneider ◽  
Vanessa Ferguson
Keyword(s):  
West Africa ◽  
Sierra Leone ◽  
Ivory Coast ◽  
Official Language ◽  
The South ◽  
Guinea Bissau ◽  
The North

Guinea, also sometimes referred as Guinea-Conakry, is found in West Africa. It is bordered by Guinea-Bissau, Senegal, and Mali in the north and Sierra Leone, Liberia, and Ivory Coast in the south. In 2016, Guinea had a population of 12.6 million over a territory of 245 860 square kilometres (km). Its capital and largest city is Conakry. The official language of Guinea is French, and the currency used is the Guinean franc (GNF).

English Traders on the Guinea Coast, 1657–1668: An Analysis of the East India Company Archive

1989 ◽  
Vol 16 ◽  
pp. 237-284 ◽  
Author(s):  
Margaret Makepeace
Keyword(s):  
West Africa ◽  
Sierra Leone ◽  
East India Company ◽  
Guinea Coast ◽  
Charles I ◽  
Cape Of Good Hope ◽  
The North ◽  
Manufactured Goods ◽  
Council Of State ◽  
The Way

English trade with Guinea in west Africa was regulated during the late sixteenth and early seventeenth centuries by royal letters patent. In 1631 Charles I issued a patent which entitled the Guinea Company, headed by Sir Nicholas Crispe, to the monopoly of trade from Cape Blanco to the Cape of Good Hope for a period of thirty-one years. The Guinea Company continued to operate during the Interregnum in spite of increased competition both from freelance merchants, known as interlopers, and from rival European powers. The Council of State in 1651 decided to allow the monopoly to run for a further fourteen years, but restricted the Company to an area lying between two points set twenty leagues to the north of Cormantine, its headquarters in Guinea, and twenty leagues south of the fort at Sierra Leone, leaving the remainder of the coast open to all English traders.The East India Company was eager to gain a part in the Guinea trade because ships calling there on the way to India could exchange a cargo of European manufactured goods for a consignment of gold and ivory which was used to sustain operations at the factories in India. In this way the Company had less need to export large quantities of bullion from England to India, a practice which was both heavily criticized and formally restricted before 1660. In 1649 the East India Company reached an agreement with the Assada adventurers that the Guinea and East India trades should be united, but decided that this scheme could not be effected immediately.

Liberia

2020 ◽  
Author(s):  
Marius Schneider ◽  
Vanessa Ferguson
Keyword(s):  
West Africa ◽  
Atlantic Ocean ◽  
Sierra Leone ◽  
North Atlantic ◽  
Ivory Coast ◽  
North Atlantic Ocean ◽  
Capital City ◽  
The North ◽  
The North Atlantic

Liberia is situated in the southern part of West Africa on the North Atlantic Ocean, bordered by Sierra Leone, Guinea, and Ivory Coast, covering an area of 111,369 square kilometres (km) with a population of 4,958,454. The majority of the population live in the Montserrado county and home to the capital city of Monrovia, with approximately 25 per cent of the Liberian population living in greater Monrovia. Monrovia is the capital and most populous city in Liberia and has the largest artificial port in West Africa. Typically, business hours are Monday to Friday from 0800 to 1700 with banks closing at 1500. The official currency of Liberia is the Liberian dollar (LRD).

Around the Bend: Nanga Parbat, Namche Barwa

2013 ◽  
Author(s):  
Mike Searle
Keyword(s):  
Sedimentary Rocks ◽  
Lower Boundary ◽  
Indian Plate ◽  
Metamorphic Rocks ◽  
The West ◽  
Northern Margin ◽  
The North ◽  
Nanga Parbat ◽  
Namche Barwa ◽  
The Himalaya

From the geological mapping, structural, and metamorphic investigations along the main Himalayan Range from Zanskar in the west through the Himachal Pradesh and Kumaon regions of India and along the whole of Nepal to Sikkim, a similar story was emerging. The overall structure and distribution of metamorphic rocks and granites was remarkably similar from one geological profile to the next. The Lesser Himalaya, above the Main Boundary Thrust was composed of generally older sedimentary and igneous rocks, unaffected by the young Tertiary metamorphism. Travelling north towards the high peaks, the inverted metamorphism along the Main Central Thrust marked the lower boundary of the Tertiary metamorphic rocks formed as a result of the India–Asia collision. The large Himalayan granites, many forming the highest peaks, lay towards the upper boundary of the ‘Greater Himalayan sequence’. North of this, the sedimentary rocks of the Tethyan Himalaya crop out above the low-angle normal fault, the South Tibetan Detachment. The northern ranges of the Himalaya comprise the sedimentary rocks of the northern margin of India. The two corner regions of the Himalaya, however, appeared to be somewhat different. The Indian plate has two major syntaxes, where the structural grain of the mountains swings around through ninety degrees: the western syntaxis, centred on the mountain of Nanga Parbat in Pakistan, and the eastern syntaxis, centred on the mountain of Namche Barwa in south-east Tibet. Nanga Parbat (8,125 m) is a huge mountain massif at the north-western end of the great Himalayan chain. It is most prominent seen from the Indus Valley and the hills of Kohistan to the west, where it seems to stand in glorious isolation, ringed by the deep gorges carved by the Indus and Astor Rivers, before the great wall of snowy peaks forming the Karakoram to the north.

Données nouvelles sur le protérozoïque inférieur du domaine nord-armoricain (France): age et signification

1980 ◽  
Vol 17 (4) ◽  
pp. 532-538 ◽  
Author(s):  
Bernard Auvray ◽  
René Charlot ◽  
Philippe Vidal
Keyword(s):  
West African ◽  
The Other ◽  
The West ◽  
West African Craton ◽  
Northern Margin ◽  
The North ◽  
Upper Proterozoic ◽  
Lower Proterozoic ◽  
Proterozoic Basement ◽  
Armorican Massif

Orthogneisses from the Tregor area of the North Armorican Massif have been dated using the U/Pb method on zircons. Ages of between 1.8 and 2.0 Ga have been obtained, thus significantly extending the known size of the Lower Proterozoic basement in this area. It is argued that the presence of such a substantial area of basement is a further argument for an Upper Proterozoic (Brioverian) south-dipping subduction zone which was located to the north of the Armorican Massif. On the other hand, the similarities between the North Armorican block and the northern margin of the West African craton during the Proterozoic are emphasized.

Cover gneisses of the Monashee Terrane: a record of synsedimentary rifting in the North American Cordillera

1990 ◽  
Vol 27 (5) ◽  
pp. 712-726 ◽  
Author(s):  
Robert J. Scammell ◽  
Richard L. Brown
Keyword(s):  
North American ◽  
Alkaline Magmatism ◽  
Pyroclastic Deposits ◽  
North American Cordillera ◽  
Metasedimentary Rocks ◽  
The North ◽  
Upper Proterozoic ◽  
Lower Proterozoic ◽  
Proterozoic Basement ◽  
Siliciclastic Sediments

The Monashee Terrane of southeastern British Columbia is composed of Lower Proterozoic basement gneisses unconformably overlain by cover gneisses. The latter constitute a thick (> 2000 m) and laterally extensive (> 150 km) upper-amphibolite-grade succession of metasedimentary rocks, locally intercalated with minor intrusive and extrusive units. This succession is interpreted as reflecting initial broad, amagmatic subsidence and sedimentation on a cratonic platform (basement gneisses), most likely of North American affinity. Throughout most of the terrane, syndepositional magmatism is first marked by a laterally extensive (> 100 km) stratiform pyroclastic carbonatite, which is part of intermittent (long-lived?) alkaline magmatism. One alkaline body was intruded at ca. 740 ± 36 Ma (U–Pb zircon), suggesting that it may be part of initial Windermere rifting. Post-pyroclastic-carbonatite syndepositional extensional tectonism is further evidenced at the north end of the terrane by interlayered mature and immature siliciclastic sediments, with rapid facies changes, intercalated with ultramafic and mafic sills and flows, plus minor felsic pyroclastic deposits. All of these later deposits lie above stratigraphy correlated with strata hosting a stratiform Pb–Zn deposit with an Early Cambrian galena Pb-isotope age and, therefore, may be correlative with a rift–drift transition recorded in Hamill Group strata to the east. Rift tectonism recorded in cover gneisses may reflect one or more documented rift and rift–drift events recorded in Upper Proterozoic to Lower Cambrian strata of the western North American continental terrace prism.

Studies on the Breeding Places and Control of Anopheles gambiae and A. gambiae var. melas in Coastal Districts of Sierra Leone

1946 ◽  
Vol 36 (2) ◽  
pp. 185-252 ◽  
Author(s):  
R. C. Muirhead Thomson
Keyword(s):  
West Africa ◽  
Anopheles Gambiae ◽  
Sierra Leone ◽  
Infection Rate ◽  
Distinct Species ◽  
Mangrove Swamp ◽  
Sporozoite Rate ◽  
North Shore ◽  
The North ◽  
And Control

The eggs of A. gambiae var. melas are distinctly different from those of typical gambiae, and it is now regarded as a distinct species, A. melas. Other workers have found that the larvae also differ, physiologically and structurally. All adults with an extra dark band on the palps—4-banded forms— are known to be melas, but those adults with normal 3-banded palps can so far only be distinguished from typical gambiae by egg characters.A. melas is now known to be an important vector of malaria in coastal districts in West Africa. In some estuarine and mangrove swamp areas it may be even more important than typical gambiae. In melas caught in Freetown estuary (mostly from Wellington village), 42 out of 1,000 glands dissected were positive, giving a sporozoite rate of 4·2 per cent. for all months of the year. The oocyst rate was 4·7 per cent., and the total infection rate was 7·8 per cent.In Freetown estuary melas is rare in Freetown itself, and in the adjoining village of Kissy, but in all other parts of the estuary is at least as important as typical gambiae. In many places it is the dominant vector. In Wellington to the east of Kissy, and on the Bullom shore which forms the north shore of the estuary, melas forms about 90 per cent. of Anophelines caught in houses.

The Influence of Wharfs on School Children: A Case Study of Portee Wharf in Freetown, Sierra Leone

2019 ◽  
Vol 2 (3) ◽  
pp. 128-140
Author(s):  
Alhaji Bakar Kamara
Keyword(s):  
West Africa ◽  
Sierra Leone ◽  
School Children ◽  
Research Area ◽  
Background Information ◽  
Control Problems

The focus of this research is to investigate the influence of wharfs on school children. Therefore it will report the findings of the result on the influences of wharfs on school children with specific case on Portee Wharf in Freetown, Sierra Leone in West Africa. In this regard, the introduction describes the research area, stating the statement of the problem, the overall goal and specific objectives that will be attained in this study, justification for selecting the topic, problems to be encountered during the course of carrying out this research and major influences. Besides, an indication of the methods used to investigate the topic will also be highlighted. Moreover, the studies will analyze the actual responses of the respondents of the activities of the wharf on school-going children. It will address the questionnaire in accordance with the following: Background information of respondents, this investigated areas such as sex, age, religion, occupation and tribe; It enquires about the activities of the wharfs, reasons and consequences of children engaged in wharfs and strategies to control problems that may emanate from the wharf. The paper will show the findings, gives the summary, conclusion and recommendations of problems identified while carrying out the research.

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