Lithologic and Structural Mapping of Northeast Lake Ziway Area, Ethiopian Rift Using Landsat Digital Data
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Date
1992-09
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Addis Ababa University
Abstract
studies of interactively enhanced Landsat thematic
mapper (TM) imagery integrated with field survey and aerialphoto
interpretations were carried out to map the lithology
and structures of the study area located in the axial zone of
the Main Ethiopian Rift. The Ethiopian Rift has been studied
for decades using a variety of geological and geophysical
techniques, but synoptic mapping of the lithology and
structures and analysis of regional structural relationships
have not been previously studied applying high resolution
satellite digital data. By combining Landsat TM data with
results from conventional method of geological mapping four
major serieses of volcanic rocks have been identified,
namely: 1. A lower series of pyroclastic deposits dominated
by greyish green ignimbrite (Wedecha series), 2. A basalt
series of transitional to subalkaline basalts character
(Anole Series), 3. pyroclastic deposits of the Rift floor
dominated by pumice and ash falls (Bora Series) and 4. Recent
lava flows extruded through Wonji Fault Belt openings (Jano
Series). In addition, four sets of structures were mapped: 1.
Main marginal NE-SW striking normal faults, 2. E-W to NW-SE
striking strike slip faults that have dextrally displaced the
marginal faults, 3. NNW-SSE striking cross-rift lineaments
and 4. the youngest and active NNE-SSW to N-S striking faults
(Wonji Fault Belt). Using different techniques of enhancement
most lithologic contacts and lineaments that had not been
indicated in any existing geological and structural maps for
the region were carefully mapped with better accuracy,
minimum expense and shorter sorter field season. It has been
observed that tectonism preceeds volcanism in time and the
type of volcanic rocks assemblage and composition reflects
the degree of rifting and intensity of tectonism that had
initiated the volcanism.
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Biology