Geology Reference
In-Depth Information
from Kiejo is reckoned to have taken place about
AD
1800
(Harkin,
1960).
References
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(1974). The Inland Wa tes of Trop ical
Afica .
London: Longman.
BUCKLE, C.
(1978). Landoms in Afica.
London:
Longman.
BURKE, K. & DEWEY, J. F.
(1974).
Two plates
n
Africa during the Cretaceous.
Na ture 249, 313-16.
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(1966). The
Geochronoloy of Equatorial Africa.
Amsterdam:
North Holland Publishing Co.
CAHEN, L., SNELLING, N. J., DEL HAL, J. & VAIL,
J. R.
(1984). The Geochronoloy of Africa .
Oxford:
Oxford University Press.
CLIFFORD, T. N.
(1970).
The sructural framework
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African Magmatism and Te tonis,
ed.
T. N. Clifford and I. G. Gass, pp.
1-26.
London:
Oliver
&
Boyd.
CROSSLEY, R.
(1979).
The Cenozoic stratigraphy
and structure of the westen part of he Rift Valley
in southern Kenya.
Jounal of the Geological Sociey
136, 393-406.
DIETZ, R. S. & HOLDEN, J. C.
(1970).
Reconsrucion of Pangaea: breakup and dispersion
of continents, Permian to Present.
Jounal of
Geophysical Research 75, 4939-56.
DIXEY, F.
(1956). Th e East African Rift Sys tem.
Overseas Geological Mineral Resources Bulletin
Supplement No.
l.
London: HMSO.
DOWNIE,
c.
& WILKINSON, P.
(1972). The Geoloy
of Kilimanjaro.
Sheffield: Geological Suvey of
Tanzania and Deparment of Geology, Sheffield
Universiy.
DU TOIT, A. L.
(1937). Our Wa ning ontinents.
Edinburgh: Oliver and Boyd.
EMBLETON, 8. J. J. & MCELHINNY, M. W.
(1975).
The palaeoposition of Madagascar: palaeomagneic
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Earth and Planetay
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27,
329-41.
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Marine magneic anomalies, paleomagnetism and
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FLORES, G.
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Suggested origin of the
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Transations of the Geologial
Soiety of South Afria
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FLORES, G.
(1984).
The S. E. Africa riple junction
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Geoloy
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GUEST, N. J. & LEEDAL, G. P.
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Volcanic
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3,
40-6.
Conlusion
The geological history of the easten part of East
Africa is long and interesing. Palaeomagneic
evidence from different African cratons (rigid
crust no longer afected by deformaion) indicates
that the bulk of Africa has behaved as an integral
unit during the period
2300400
mr
BP
(Piper,
1976).
During the Mesozoic era, Karroo auling
profoundly affected the face of eastern Africa,
down-throwing grabens in which vast thicknesses
of sediments and evaporites accumulated, and up-
lifing the forerunners of the present-day block
mountains. The fragmentaion of Gondwanaland
commenced in the Jurassic with the widening and
flooding of some of these coastal grabens, creaing
marine condiions along the present-day coast-
line. Madagascar split rom easten Africa at an
early stage in the ragmentaion and from India
much later.
The normal processes of weathering and ero-
sion operated at the surface throughout the
period. Mountains and hills were levelled to
plains in the course of the erosional cycle while
tectonic aciviy disrupted and dislocated these
areas of low relief, rejuvenaing the rivers and
renewing the cycle, creaing younger plains at
lower levels. The younger (Neogene) surfaces are
sill covered by weathered material at various
stages of soil formaion
During the Neogene the East African Rift Val-
ley developed, possibly in another attempt at con-
inental breakup, but more likely in response to
upper mantle and lower crustal meling. Ten-
sional auling affected many parts of the region,
reacivaing old zones of weakness, some of which
were iniiated in the Karroo, others in the Pre-
cambrian. Volcanic acivity accompanied this rift-
ing in some areas, and together these gave rise to
mountainous landscapes conrasing srongly with
the plainlands. It is the varying relief of easten
Africa rather than its underlying rock types and
soils that accords it much of its uniqueness.
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