Microfacies Analysis of Mesozoic Carbonate Units of Dire Dawa Area, South Eastern Ethiopia
| dc.contributor.advisor | Atnafu, Balemwal (PhD) | |
| dc.contributor.author | Fufa, Geramu | |
| dc.date.accessioned | 2020-11-10T12:28:10Z | |
| dc.date.accessioned | 2023-11-09T14:12:04Z | |
| dc.date.available | 2020-11-10T12:28:10Z | |
| dc.date.available | 2023-11-09T14:12:04Z | |
| dc.date.issued | 2014-05-05 | |
| dc.description.abstract | The lithostratigraphy and microfacies analysis of three selected stratigraphic sections were studied using field data and about thirty four thin sections analysis. These were used to understand the depositional environments, diagenetic settings and age of the carbonate succession (the Antalo Limestone Formation) of the Dire Dawa area, in South Eastern Ethiopia. The field observations, microfacies analysis, and biostratigraphic examinations on the carbonate successions of the area, which sandwiched between lower and Upper Sandstone units, reveal that: these carbonate units have about (~306 m) thickness , have been deposited during Bathonian-Kimmeridgian time; and can be sub-divided into three sub-units, according to their facies contents and stratigraphic positions. These, from older to younger are: (1) The lower sub-unit (Bathonian-Callovian) which is (~119m) thick and consists of mixed siliciclastic - carbonates units of tidalflat-lagoon deposits; and peloidal and ooilitic grainstone facies of carbonate shoal/barrier deposits of the shallow marine setting, (2)The middle sub-unit(Oxfordian-lower Kimmeridgian) is about (~84m ) thick , conformably overlies the lower sub-unit , consists of the foreshoal facies of thick, allochemical rich wackestone-grainstone limestones, mainly dominated by reworked intraclastic grains and rare amounts of patches of colonial organisms, and (3) The upper sub-unit (Kimmeridgian) is about (~103m) thick, overlies the middle sub-unit conformably and topped unconformably by the Upper Sandstone. It consist of low energy deposits of fine grained dark micritic limestones with some cherts and clastic shale interbedded at its lower; and some colonial and carbonate buildup organism bearing layers at its upper part. The overall microfacies and facies successions throughout the unit shows a carbonate ramp depositional setting , under which various submarine depositional environments ranging from shoreline carbonate deposits( including low energy tidalflat and lagoon) and high energy platform margin carbonate sand bodies) of inner ramp , foreshoal deposits of midramp to the offshore deposits(basin margins and open sea) of outer ramp, successively from bottom to top. The diagenetic sequence of these carbonate units, when ordered form early to late stage, comprises the following: micritization, dissolution, early marine cementation, meteoric calcite cementation, mechanical and chemical compaction, fractures; stylolitization, dolomitization, silicification and burial cementation. These processes have taken place with varying intensities and occurrence throughout the area. Lastly deposition and facies patterns throughout this unit are related to already established paleogeoraphic changes particularly involving the transgression of the sea on the horn of Africa. These deposits are also correlated with some of equivalent deposits in major Ethiopian sedimentary basins and with the Sana a basin of Yemen. | en_US |
| dc.identifier.uri | http://10.90.10.223:4000/handle/123456789/23151 | |
| dc.language.iso | en | en_US |
| dc.publisher | Addis Ababa University | en_US |
| dc.subject | Dire Dawa | en_US |
| dc.subject | Microfacies | en_US |
| dc.subject | Diagenesis | en_US |
| dc.subject | Depositional Environments | en_US |
| dc.subject | Ramp | en_US |
| dc.title | Microfacies Analysis of Mesozoic Carbonate Units of Dire Dawa Area, South Eastern Ethiopia | en_US |
| dc.type | Thesis | en_US |