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The Cameroon Line: A Review 275 9 The Cameroon Line: A Review 14 , '., B. Deruelle, C. Moreau, C. Nkoumbou, R. Kambou, J. Lissom, E. Njonfang, i l\ .. GZ R. T. Ghogomu and A. Nono ~ Mh Mb.. ..:;-..~.~:av .S.Nyp 1 Introduction 'or 8 Nn G<;>. ..M Since the work of VonBaumann (1887)the Cameroon Line (Fig. 1)is known as a ma- .:::::::::::: . G~F..rM ~. jor geological feature in Central Africa. The Cameroon Line is an alignment of o '. ~D : :... N oceanic and continental volcanic massifs and of anorogenic plutonic complexestrend- ~ S ing N 30° from Pagahi Island to Lake Chad (Geze 1941). It is now considered ..Da~~l"" '!fii1tJ (Moreau et al. 1987b) as a Pan-African lineament more or less permanently re- ::::::::::::-:.. 'MD Adarnawa 6'; juvenated from the Late Precambrian to the Present. The oceanic segment of the D Cameroon Line is composed of the four volcanic islands of the Gulf of Guinea (Pagahi, formerly Annob6n, SiloTome,Principe and Bioko, formerly Fernando P6o). RH .~:]I\;~;~:.' Its continental segment is represented by the volcanic massifs of Mount Cameroon, ~€3":'::::~~ Rumpi, Manengouba, Bambouto, Oku and the volcanic outpourings of the Benue J Valley(Westof Garoua) and of the Kapsiki Plateau and by more than 60 anorogenic 4 "N~B ..- -....... plutonic complexesfrom Mount Koupe to Waza. Extensions of the Line to Ascension E"k.. ~/ \ CHAD (Gouhier et al. 1974) or to Saint-Helena (lYrrell 1934; Furon 1953, 1968; Vincent '0\ .':'::::'::'.tt: / I 1970b) for the oceanic segment, or to Tibesti (Furon 1953, 1968;Vincent 1970b) or G u I f ....... \ lJ I~ ' Southeastern Libya (Tempier and Lasserre 1980) for the continental one have been ./ ," \ " ) suggested. The Cameroon Line has also been described as a Y-shaped zone (Fitton I -, 1980, 1983) with the trunk represented by a line from Pagahi to Mt Oku and the "\ ' o f /' I" branches by the Adamawa and the Biu plateaux. /" I/- / I / A. I From a geomorphological point of view,the Cameroon Line is composed of a suc- / Y , cession of horsts and grabens. The horsts are represented by the four islands of the I I C.A.R. I 0 \ Gulf of Guinea and the continental areas of high relief (the massifs of Mount G u o CAMEROON \ Dv \ E.G. \ \I / 0 \1 --_(- - - - I o 0 ~~:-I I-,'--_J . S.T.p.~ J Fig. 1. Sketch map of the Cameroon Line (see upper inset for location in Africa: W.A. C. West <:J " / African Craton; C. C. Congo Craton; K. C. Kalahari Craton, and lower inset for location in Central ~ GABON'~ C. Africa, C. Congo; C.A. R. Central African Republic; E. O. Equatorial Guinea; N Niger; S. T. P. Silo .100km, ,V I Tome and Principe). Cainozoic volcanic rocks (dotted areas) are indicated conjointly with anorogenic ---I ring-complexes. From South to North, anorogenic ring complexes (Roman type) large letters for the 8 massifs studied in the present work (Chap. 4, 1 to 8): B Bana; NA Nda Ali; N Ntumbaw; MD Mayo Darle; 0 Guenfalabo. and small letters for the other massifs; K Koupe; Nl Nlonako; No Namboe; S Sabri; B Bonhari; 00 Gounguel; F Fourou; Nn Nan; M Mana; T Tchegui; P PoIi; Ny Nyore; Ko Kokoumi; Mn Mouhour; Gr Grea; WWaza; volcanoes (italic type) large letters for the volcanoes studied in the present work (Chap. 5, 1 to 16): E Etinde; RH Rumpi Hills; BP Bamoun Plateau; BV Benue Valley; K Kapsiki Plateau, and small letters for the other massifs: TM Tchabal Mbabo; D Djinga; N Nganha; Biu Biu Plateau. Legends of Figs. 1 and 2 are complementary r 276 Ring Complexes and Related Structures The Cameroon Line: A Review 277 Cameroon, Rumpi, Manengouba, Bambouto, Mbam and Oku) which alternate with Gongols I grabens (Kumba, Tombel, Mbo, Ndop, Tikar Plain). The topographical expression of ___")" I_I " Yola t"'~' / the northern part of the Cameroon Line (northwards of the Oku massif and the Tikar ' " Plain) is less pronounced. The Cameroon Line intersects the Adamawa direction ,J I _ Garoua', / ___ I ~ "~o ~ north of Oku Massif. ".' ,;. t,., " ,.' ' '", The Adamawa plateau represents a large horst limited to the north by the great 8 e ,r ./ , Adamawa (also named Ngaoundere) fault zone and to the south by the Djerem-Mbere (\ basin. e " ,. ," I A remote sensing analysis of the continental part of the Cameroon Line and the II- ~ ...1'" \ Adamawa plateau accompanied by a study of geological maps has been used to show \ _" ,_J " ",J , " O&t1'&"'&N ;.;-;; , ,~ gaoundere that the Cameroon Line is a major structural feature and not a mere alignment of / ' /" -Banyo subvolcanic and volcanic massifs, ",., Ok ~ \ , ~J~ ~.,l tA,,8 ""fl!!.~ Ndo''''- "Mbam" ".,PIa;. oj."" ~ / S '.f'.. dJ .,. ,r . ~~.amb"'-"uto /\ - } ->-.. , ~ \ 2 Various Interpretations of the Cameroon Line ~ . }j.">M' ' \ .. ~T' anengouba " .~~ fu~~ " \ " Numerous interpretations have been given to the Cameroon Line: 4 ~~ c ameroon I A) It has been considered as a volcanic alignment made of a succession of horsts and grabens (Geze 1943, and references therein). Epeirogenic uplift along the Line (Black and Girod 1970) has induced normal and reverse faulting (Fig, 2) G u I f (Deruelle 1982; Deruelle et al. 1983a). This alignment has been considered as J-- """"''''''" a unit independent of the Adamawa structure (Fail et al. 1970; Gouhier et al. 1974). B) The southern part of the Cameroon Line (from Pagalu to the Oku massif) and 0~princiPe the Adamawa Plateau have been considered by some authors as a whole and a f named "Cameroon Line itself" (Fig. 3) (Burke et al. 1970;Cornacchia and Dars 1983); the northern part of the Line (from Oku to Lake Chad) being excluded A N from this definition. o ~sao Tome C) Another point of view is that the Cameroon Line is the southernmost geosuture of a Pelusium megashear system which is supposed to extend from the Amazon G u Basin to Anatolia (TInkey)via the Atlantic equatorial fracture zone and across ,100km, Africa from the Gulf of Guinea to the Nile Delta (Neev et al. 1982). 1 Similarly, the Cameroon Line and the Adamawa fracture zone have been sup- Pagalu 8 12 posed to be the more or less well-fitted prolongation of the Santonian transform fault (north of Ascension transform fault) at the beginning of the opening of the Fig. 2. The Cameroon Line, succession of horsts (Roman type) and grabens and rifts (italic type) South Atlantic Ocean (Fig. 4) (Sibuet and Mascle 1978; Sykes 1978). They have (after Deruelle et al. 1983b). The Adamawa horst, the Djerem Mbere graben and the Yola-Garoua, also been supposed to be the prolongation of the Ascension transform fault at Gongola and Benue rifts are also indicated Present time (Cornacchia and Dars 1983). Nevertheless, all these interpretations are doubtful and uncertain for correlations beyond the Santonian (Figs. 14, 15 and 11 in Sibuet and Mascle 1978). Mascle 1976)or the Patos (BenkhelilI986) faults (NE Brazil) before the opening The transform faults of the Atlantic Ocean appear to extend into the African con- of the Atlantic Ocean and is thus considered as a major Pan-African lineament tinent, not along the Cameroon Line, but rather through the Adamawa fracture (Fig. 5) as has been recognized in Nigeria (Ajakaiye et al. 1986). zone (Vincent 1968, 1970b; Le Marechal and Vincent 1970;Mascle 1976). This D) The Cameroon Line has also been interpreted as a volcanic and subvolcanic align- last waspropagated by the Pernambuco (De Almeida and Black 1967;Louis 1970; ment resulting from hot-spot activity (Tchoua 1974a; Duncan 1981;Morgan 1982; 278 Ring Complexes and Related Structures The Cameroon Line: A Review 279 Fig. 3. Hypothetical propagation of the Cameroon Line with the Adamawa-Yade shear zone (after Cornacchia and Dars 1983). Sedimentary cover, 1 Cainozoic s.l; 2 Mesozoic; Basement; 3 Upper and Late Precambrian; 4 Lower and Medium Precambrian; Eruptive rocks; 5 Cainozoic [l]]]DImiJ.. volcanism; 6 Granitic batholiths; 7 Upper 3 4 5 6 7 Precambrian dolerites D m....:.: ;,:.;;: m 's:'.'':;;;i ODD 0 1 2 3 4 5 6 7 Fig. 5. Reconstitution of the African - South American block at the beginning of the opening of the South Atlantic Ocean (after Louis 1970). Sanaga fault, after Benkhe1il1986. The propagation of the Pernambuco fault (NE Brazil) by the Ngaoundere (Adamawa) fault is noteworthy (De Almeida and Black 1967). 1 Cainozoic-Mesozoic; 2 Paleozoic; 3 Upper Precambrian; 4 Pan-African; 5 Old cratons (1, 2 and 3, respectively West-African, Sao Francisco and Congo cratons); 6 rifts; 7 thrusts Van Houten 1983).Moreover, various hypothetical motions of the African plate over a Cameroon hot-spot have been formulated (Fig. 6). E) Following the hypothesis that "the Cameroon-Adamawa zone is a new ridge/rift Africa feature where separation has not yet taken place and where a rift valley form has not yet developed" (Burke et al. 1970), an inventive model has been proposed which considers the Cameroon Line as a unique exampleof a rift systemproduced actively by a thermal anomaly in the asthenosphere. This model is essentially based upon the approximate shape and size of the Benue trough and the Cameroon Line (continental segment) - Adamawa horst - Biu Plateau. In this model, "the 'Y~shaped hot zone in the asthenosphere which would have lain beneath the Benue trough in the Cretaceous became displaced (relative to the lithosphere) so that it now lies beneath Cameroon and the Gulf of Guinea" (Fit- Fig. 4. Location of the Cameroon Line and the Adamawa fault zone on a reconstruction of the South ton 1980, 1983) (Fig. 7). In the view arguing for the rift model, numerous lavas American and African continents at the end of Santonian (Anomaly 34, 79 Ma) (after Sibuet and of the Cameroon Line have been erroneously qualified as transitional (Fitton Mascle 1978) 1980, 1983) despite of their alkaline character.
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    Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021 African Rift tectonics and sedimentation, an introduction H.G. Reading Rifts are one of the most spectacular features of Gulf of Elat rift lies along a lineament that global morphology. Within oceans they separate separates two lithospheric plates and, as Arabia plates as new oceanic crust is created. Within moves northwards relative to the Palestinian continents they may form deep valleys such as the (Mediterranean) block and faults curve or side- Rhine graben, within which runs one of the step each other, extensional pull-apart basins are world's busiest waterways. They are often floored formed, such as the Dead Sea whose surface lies by deep lakes, such as Lake Baikal, the deepest further below sea level than any other place in the lake in the world today whose floor lies 1700 m world. A feature of these strike-slip rift valleys is below the surface of the lake. Ancient rifts are the that the extensional valleys pass, along the rift, sites of petroleum accumulations beneath the into mountainous zones of compression and margins of the Atlantic, in the North Sea and in uplift. Rapid erosion from these mountains leads China, of coals and oil shales and of minerals, to substantial sediment supply for the basins from including phosphates, barite, Cu-Pb-Zn sul- within the fault system itself. Ancient strike-slip phides and uranium (Robbins 1983). Of all the rift basins are therefore characterized by very world's rifts none can match in scale and diversity thick, rapidly accumulated basin fills with areas the Great Rift System, which runs for over of contemporaneous compressional tectonics and 7000 km and includes the East African Rift unconformities not far away.
  • Community Forest Management: a Strategy for Rehabilitation, Conservation and Livelihood Sustainability: the Case of Mount Oku, Cameroon

    Community Forest Management: a Strategy for Rehabilitation, Conservation and Livelihood Sustainability: the Case of Mount Oku, Cameroon

    Journal of Geoscience and Environment Protection, 2020, 8, 1-14 https://www.scirp.org/journal/gep ISSN Online: 2327-4344 ISSN Print: 2327-4336 Community Forest Management: A Strategy for Rehabilitation, Conservation and Livelihood Sustainability: The Case of Mount Oku, Cameroon Jicenta N. Foncha*, Dora Mojoko Ewule Department of Development Studies, Pan African Institute for Development-West Africa (PAID-WA) Buea, Buea, Cameroon How to cite this paper: Foncha, J. N., & Abstract Ewule, D. M. (2020). Community Forest Man- agement: A Strategy for Rehabilitation, Con- Well-managed forests are major sources of livelihoods for the fringed com- servation and Livelihood Sustainability: The munities. However, the remoteness, inaccessibility of most forested areas Case of Mount Oku, Cameroon. Journal of coupled with conflicts from adjacent forest communities, who often depend Geoscience and Environment Protection, 8, 1-14. on it for livelihood is a daunting task in implementing conservation, viz-a-viz https://doi.org/10.4236/gep.2020.82001 the Sustainable Development Goals. The Mt Oku forest is a unique, remote but represents novelty in forest management in remote areas in Cameroon, with Received: August 2, 2019 Accepted: January 19, 2020 devolution of management rights. The forest is well noted for its high level of Published: January 22, 2020 endemism. This study is focused on the legal, institutional, socio-economic and regulatory framework put in place, for appropriate conservation and live- Copyright © 2020 by author(s) and lihood sustenance as forest management rights were devolved to the local com- Scientific Research Publishing Inc. This work is licensed under the Creative munity. A multidimensional framework guiding the development of testable Commons Attribution International hypothesis that assesses the relationship between the forest users’ activities License (CC BY 4.0).