Papers by Balemwal Atnafu
Zenodo (CERN European Organization for Nuclear Research), Nov 23, 2022
Bulletin of volcanology, Mar 11, 2024
This paper presents new stratigraphic correlation and naming for younger basalt lavas (<24 Ma)... more This paper presents new stratigraphic correlation and naming for younger basalt lavas (<24 Ma) and enclosed rhyolites near the intersection of the southern Red Sea rift and the Ethiopian rift valley, based upon three volcano-stratigraphic sections located over about 30 kilometres, and they bracket the timing of eruption of the upper sequence with existing geochronology. The correlations are based on the petrography (thin sections) of ca. 32 samples taken from these three sections, combined with outcrop description. The stratigraphy is proposed as 5 new formations, partially placed into an existing stratigraphic framework, based on the dominant unit-basalt or rhyolite in the package of sequences. These new stratigraphic columns also include non-volcanic units (interlayered sedimentary strata, paleosols and weathering surfaces), which are not usually described in the volcanic pile, showing that there was more complexity in this succession than previously known. This new stratigraph...
Materials and Geoenvironment
in English The Mekelle Basin comprises carbonate and siliciclastic rocks which could have potenti... more in English The Mekelle Basin comprises carbonate and siliciclastic rocks which could have potential for petroleum as previous studies reported without enough evidence. This research is intended to assess source rock characteristics of selected samples from the Adigrat Sandstone, Antalo Limestone and Agula Shale. Four outcrop sections were investigated and fifteen limestone and shale samples were collected. TOC was deduced by Leco SC-632 carbon analyzer, and Rock-Eval pyrolysis was determined using Rock-Eval 6. The TOC values range from 0.11 wt.% to 0.42 wt % for 80% of the samples which is less than the minimum requirements for source rocks. However, a few samples have TOC between 0.5 wt % and 1.0 wt %, indicating fair organic matter richness. The kerogen is mainly Type IV and inert. The S1 (0–0.02 mgHC/g) and S2 (0–0.07 mgHC/g) values are very low, with very high Tmax (475–527 °C), indicating very poor potential with over-mature dry gas. Therefore, the analyzed samples have low org...
We present data from the Lake Afdera (13.26N; 40.90E) and its surrounding. Equipped with a small ... more We present data from the Lake Afdera (13.26N; 40.90E) and its surrounding. Equipped with a small inflatable boat and an echosounder (Humminbird, 899ci hd si system), we surveyed the lake to obtain its first complete bathymetric map. We further investigated the fault pattern around the lake to interpret the lineaments observed in the bathymetry.
This study focused on the identification, detailed systematic descriptions and stratigraphical di... more This study focused on the identification, detailed systematic descriptions and stratigraphical distributions of different foraminifera and other species to make the first systematic paleontological analysis, interpret paleoenvironment and determine the age of Antalo Limestone of the Mekelle Basin. Fieldwork and section logging, with sample collection at seven outcrop locations, followed by petrography and standard micropaleontological analysis were carried out. Abundant foraminifera fossils of 17 species were identified from 42 thin sections and 5 washed samples of marl and shale. The faunal assemblage also comprised dasyclad green algae, calpionellid, brachiopods and stromatoporoids (Cladocoropsis mirabilis). The benthic foraminiferal assemblage is represented by 3 species of the order Lituolida (Freixialina planispiralis, Nautiloculina circularis and N. oolithica), 11 species of the order Loftusiida (Alveosepta jaccardi, Choffatella tingitana, Conicokurnubia orbitoliniformis, Ever...
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2003
Geology, Ecology, and Landscapes
Journal of Sedimentary Environments
Antalo Limestone in the Mekele Basin, northern Ethiopia was studied to interpret depositional env... more Antalo Limestone in the Mekele Basin, northern Ethiopia was studied to interpret depositional environment through facies analyses and provide insights on its Jurassic sedimentological evolution and paleogeographic implications. The full thickness of the unit was investigated through outcrop description, section logging and sample collection at eight outcrop locations. Two of the sections represent the lower to middle parts of the unit with about 200 m and 270 m thickness. Five of the sections represent the middle to upper parts of the unit with thicknesses ranging from 175 to 285 m and one section represents about 72 m-thick uppermost part of the unit. The field descriptions of the unit, in terms of lithology, texture, composition, bedding and sedimentary structures, show eighteen lithofacies types made up of limestone, sandstone, shale and marl. The petrographic analyses of the samples also identify seventeen limestone microfacies ranging from mudstone to grainstones including boundstone, one dolomitic limestone and two sandstone facies (quartzwacke and quartzarenite). The facies analysis indicates that the studied unit was deposited within shallow-to deep-marine environments. There are six facies associations that were correlated with the standard microfacies types and facies zones, indicating a typical homoclinal carbonate ramp with tidal flat, lagoon, sand shoal, mid-ramp, outer-ramp and deep basin depositional systems from the shore to open sea environments, respectively. The lack of reef facies, in the studied sections, has also been considered as evidence to deduce a homoclinal carbonate ramp for the unit. These sub-environments were juxtaposed and, the lateral shifting of their position through time caused the development of vertical facies successions of different environments. It is also deduced that marine water from the Tethys Sea covered the Mekele area since the early Callovian and persisted until the Tithonian, creating favorable conditions for carbonate production and sedimentation. Therefore, the Jurassic sedimentation history of Antalo Limestone was synchronous with that of equivalent carbonate platform sequences of the Horn of Africa and other peri-Tethyan regions, confirming a related paleogeographical setting.
&amp;amp;lt;p&amp;amp;gt;The Afar Depression forms a triple junction between three rift s... more &amp;amp;lt;p&amp;amp;gt;The Afar Depression forms a triple junction between three rift systems: the Red Sea Rift, the Gulf of Aden Rift and the Main Ethiopian Rift. Rifting began in the Oligocene after the eruption of the Ethiopian Flood Basalts. It represents a unique modern example of hotspot-influenced continental breakup. Its emerged position allows detailed field and remote sensing investigations. Important mapping efforts in the area during the 60s and 70s provided very valuable input for the understanding of the local geology but also for the development of global tectonic, volcanological and sedimentary concepts in continental rift settings.&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;This study presents the compilation of a new geological map which covers the complete Afar depression and includes its Phanerozoic sedimentary and magmatic cover. The map is based on extensive literature research, remote sensing and fieldwork. The geological history of the Afar Depression has also been reviewed. The map evidences the complexity of the rift system with the interaction of distinct tectonic plates, blocks, rift segments, sedimentary basins and volcanic areas that evolve through time and space. This integrative geological map and review is used to reassess and discuss aspects of the style, evolution, kinematics and dynamics of this rift system. Studying this unique modern example of active rifting will help in the better comprehension of rift processes and passive margin development worldwide.&amp;amp;lt;/p&amp;amp;gt;
Sinet, Ethiopian Journal of Science, 2014
The area between Gohatsion town and the Abay River in Central Ethiopia is witnessing severe probl... more The area between Gohatsion town and the Abay River in Central Ethiopia is witnessing severe problems of landslides during rainy seasons. These landslides in the area affect the safe functioning of the road, which is an essential link between Addis Ababa and the northwestern part of the country. In the present study, an attempt is made to delineate the area into landslide hazard zones (lhz). The landslide hazard zonation was carried out by “Landslide Hazard Evaluation Factor” (lhef) rating scheme. The lhef is an expert evaluation technique that is based on the observational past experience gained over causative factors and their contribution for instability of slopes in the area. The causative factors responsible for landslide activity, which were considered during the present study, are: relative relief, slope morphometry, geology, groundwater and land use/ land cover. The information pertaining to these causative factors was collected from the field and analyzed as per the lhef sch...
Erlangen, Nürnberg, University, Diss., 2003.
A Thesis Presented to the School of Graduate Studies of Addis Ababa University in Partial Fulfill... more A Thesis Presented to the School of Graduate Studies of Addis Ababa University in Partial Fulfillment of the Requirements for the Degree Master of Science in Geology.
Journal of African Earth Sciences, 2018
Abstract We investigated the evolution of the Mekele Sedimentary Basin (MSB) in northern Ethiopia... more Abstract We investigated the evolution of the Mekele Sedimentary Basin (MSB) in northern Ethiopia using geologic field and gravity data. The depth to Moho and lithospheric structure beneath the basin was imaged using two-dimensional (2D) radially-averaged power spectral analysis, Lithoflex three-dimensional (3D) forward and inverse modeling, and 2D forward modeling of the Bouguer gravity anomalies. Previous studies proposed that the basin was formed as part of a multi-branched rift system related to the breakup of Gondwana. Our results show that the MSB: (1) is circular to elliptical in map view and saucer shaped in cross sectional view, (2) is filled with terrestrial and shallow marine sedimentary rocks, (3) does not significantly structurally control the sedimentation and the major faults are post-depositional, (4) is characterized by a concentric gravity minima, (5) is underlain by an unstretched crust (∼40 km thick) and thicker lithosphere (∼120 km thick). These features compare positively with a group of basins known as IntraCONtinental Sags (ICONS), especially those ICONS formed over accretionary orogenic terranes. Since the MSB is located above the Neoproterozoic accretionary orogenic terranes of the Arabian-Nubian Shield (ANS), we propose that the formation of the MSB to be related to cooling and thickening of a juvenile sub-continental lithospheric mantle beneath the ANS, which most probably provided negative buoyancy, and hence subsidence in the MSB, leading to its formation as an ICONS. The MSB could be used as an outcrop analog for information about the internal facies architecture of ICONS because it is completely exhumed due to tectonic uplift on the western flank of the Afar Depression.
Palaeogeography, Palaeoclimatology, Palaeoecology, 1999
In the central sector of the Main Ethiopian Rift, the Ziway-Shala lake basin system includes four... more In the central sector of the Main Ethiopian Rift, the Ziway-Shala lake basin system includes four present-day residual lakes, from north to south, lakes Ziway, Langano, Abijata, and Shala. This region of East Africa is under the influence of the Intertropical Convergence Zone seasonal migration. Thus it has been designated as a potential core site by the ERICA Project ('Environmental Research for Intertropical Climate in Africa'). The four lakes have been subjected to strong changes in water level and water salinity at least during the Late Pleistocene. The purpose of this study is to produce a model of basin formation and sediment accumulation for this system of lakes, in order to separate the effects of climatic change from environmental variations induced by local or regional factors such as volcano-tectonic forcings. In addition to an exhaustive synthesis of available data, various investigations have been used to develop this model: 3D remote sensing, high-resolution seismics, coring, and structural, sedimentological, and hydrological field studies. New AMS radiocarbon dating helped to refine the pre-existing stratigraphic framework for this region, and basin age estimations were calculated using mean sediment accumulation rates. The history of the Ziway-Shala lake basin system has been reconstructed from
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Papers by Balemwal Atnafu