Relation Ship Sbetween Geology, Mor Phology and Soil Associations of Bichena Area ( S. E. GOJAM )
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Date
1981-10
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Addis Ababa Universty
Abstract
The study investigates the extent of influence of the geolog- ical history , essentially parent rock * topography and time , on
soil formation and distribution in Bichena , Southeastern Gojjam *
Lithostratigraphy of the Mesozoic sedimentary sequence and
Cenozoic volcanics is described * An attempt has been made to
reconstruct the morphologic evolution of the area * Four soil
mapping units in close relationship with the parent material
and geomorphology have been differentiated: Vertisol, Mollisol,
Alfisol and Entisol Orders 0 The soils are found to assume different
states when the above considered soil forming factors are changed *
The vertisol development from aphanitic basalts is determined
by the evolution of the structural plateau geomorphic surface
through lateral planation, which has allowed for two cycles of
pedogenesis* The Mollisols have developed from porphyritic plagio- clase-Olivine basalt* These indicate that soil parent materials
with similar mineralogy give way to soil varieties * A lateral variat- ion in some soil properties of the Mollisol order is found to be
strongly explained in terms of the slope gradient * The study shows
that the Plio-Pleistocene neotectonic uplift and subsequent develop- ment of a deep canyon including morphogenetic threshold slopes has
resulted in lack of sufficient time for pedogenic horizons to develop
in Alfisols and Entisols *
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Keywords
Bichena