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| dc.contributor.author | Lema, Awel | |
| dc.date.accessioned | 2026-09-16T07:22:25Z | |
| dc.date.available | 2026-09-16T07:22:25Z | |
| dc.date.issued | 2026-06 | |
| dc.identifier.uri | http://ir.bdu.edu.et/handle/123456789/17357 | |
| dc.description.abstract | The study area is a part of the NW Ethiopian Plateau, is presented in this thesis. The study area is located in the North Shewa district, specifically around Gishe Rabel, in central Ethiopia. The main objective of the study is to provide a complete lithostratigraphy of the research area based on a thorough field investigation (mapping and description), stratigraphic sampling, and petrographic (thin section) description of representative samples. Various techniques were used to achieve the research objectives, including field observation, remote sensing, and petrographic description. Furthermore, the study attempts to integrate these data to relate them to regional studies on geochemical, geochronological, and magma emplacement behavior data about the volcanic provinces of Ethiopia and fill the scarce in a detail volcanic history of the study area. Three volcanic lithostratigraphic units, Lower Basalt, Rhyolitic Lava Flow, and Upper Basalt, are identified in this study as part of the Cenozoic continental flood basalt sequence. The basaltic lava flows (fissural flows) are the dominant products, with interlayered ash and tuff; the felsic products dominate the middle part. These stratigraphic units are separated by a considerable time gap marked by an alteration/erosional surface, paleosol, or sediments, which are related to a decrease in magma flux in the system. The petrographic characteristics of basaltic units in the study area display a range of textures, including aphyric, mildly phyric, and porphyritic varieties. In the lower basaltic rocks, the principal phenocrysts are pyroxene and olivine, accompanied by opaque. In contrast, the rhyolitic ignimbrite samples are dominated by alkali feldspar (sanidine), quartz, and lithic fragments set within a glassy groundmass. The predominance of alkali feldspar phenocrysts in the felsic units suggests a relatively low magma flux during their formation. The upper basaltic rock is dominated by plagioclase phenocrysts. The occurrence of plagioclase in the upper basaltic rocks indicates that crystal fractionation took place within the shallow upper crust. Meanwhile, the presence of olivine and clinopyroxene (Olv + Cpx) mineral assemblages in some basaltic lavas suggests that fractionation also occurred at deeper crustal levels or near the crust–mantle boundary. | en_US |
| dc.language.iso | en | en_US |
| dc.subject | Petrology | en_US |
| dc.title | Petrography, and Stratigraphy of Volcanic Rock of Gishe Rabel Area, North Shewa, Central Ethiopia | en_US |
| dc.type | Thesis | en_US |
