Phonolite series in North Ethiopia

Phonolite Series
Stratigraphic range: Middle Miocene
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S
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P
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Pg
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Phonolite Series; Stratigraphic range: Middle Miocene PreЄ Є O S D C P T J K Pg N ↓
	Plug at Addi Amyuq in Dogu’a Tembien
Type	Geological formation
Overlies	Tertiary Basalts
Lithology
Primary	Phonolite
Location
Coordinates	14°09′29″N38°56′42″E / 14.158°N 38.945°E Coordinates: 14°09′29″N38°56′42″E / 14.158°N 38.945°E
Approximate paleocoordinates	0°N0°E / 0°N 0°E
Region	Tigray
Country	Ethiopia
Extent	Aksum-Adwa-Dogu’a Tembien
	Phonolite series in North Ethiopia (Ethiopia)

Last updated January 26, 2020

The phonolite or clinkstone of northern Ethiopia is a shallow-seated igneous rock. The phonolites intruded and punctured the Mesozoic sedimentary rocks and the Tertiary flood basalts some 19 to 11 million years ago.^[1]^[2]

Stratigraphic context

The formation occurs as plugs that have punctured the Tertiary flood basalts of the Ethiopian plateau, and form the highest peaks in their surrounding.^[1]

Lithology

These phonolites are composed of alkali pyroxenes and nephelines; there are also elongated plagioclase crystals. Pyroxenes have a skeletal texture, whereas nepheline crystals are hexagonal to rectangular.^[1]^[3] The phonolites of pink to light grey colour. The outcrops hold massive (up to 25 metres long), moderately weathered blocks, generally of elongated shape; in some locations it also forms spherical outcrops.^[1]

Geographical extent

These silica-poor rocks belong to the Adwa-Aksum trachy-phonolite volcanic field.^[4] They are also exposed in Addi Amyuq, some 3 kilometres north of Hagere Selam, on the northern slope of the ridge. The morphology of the Addi Amyuq phonolite outcrop is similar to that of Gobo Dura where the Aksum obelisks were quarried.^[1]

Obelisks and church bells

The phonolites are among the best exploited rocks of northern Ethiopia. Notably, they were used to carve the monolithic obelisks and other monumental stones during the Aksumite kingdom. In Tembien they are used as church bells (in line with the name clinkstone) and dimension stones.^[1]

Related Research Articles

The Obelisk of Axum is a 4th-century CE, 24-metre-tall (79-feet) phonolite stele/obelisk, weighing 160 tonnes, in the city of Axum in Ethiopia. It is ornamented with two false doors at the base and features decorations resembling windows on all sides. The obelisk ends in a semi-circular top part, which used to be enclosed by metal frames.

The Lioness of Gobedra is a rock sculpture located in Gobo Dura (Gobedra), Ethiopia. It is a representation of a crouching lioness around three metres long, which was carved into a relief on a large phonolite rock outcropping situated two kilometers west of Axum. It was first described by German archeologists in 1913.

Hagere Selam is a town in northern Ethiopia. Located on the Mekelle-Abiy Addi regional road, it is located at an elevation of 2650 metres above sea level. The town is the administrative center of the Dogu'a Tembien woreda. The weekly market is on Saturdays.

The Alaji (upper) Basalts are the youngest series of the Ethiopian flood basalts. The most recent flows are only 15 million years old.

The Ashangi Basalts are the earliest Tertiary volcanic rocks in north Ethiopia, hence they are in the lowest position. These dark porphyritic basalts are separated from the Mesozoic formations below it by basal conglomerates. The basalts hold phenocrysts that developed before the magma reached the earth surface. These basalts are weathered, partially eroded and have a sub-horizontal stratification, particularly at the lower part. This series was created during the first period of the flood basalt eruptions in north Ethiopia, in the Oligocene.

Between 29 and 27 million years ago, the extrusion of Ethiopia’s flood basalts was interrupted and deposition of continental sediments occurred. Inter-trappean beds outcrop in many places of the Ethiopian highlands. They consist of fluvio-lacustrine deposits, that are generally a few tens of metres thick. Often, these interbedded fluvio-lacustrine deposits are very visible because their bright colours strongly contrast with the basalt environment.

Mika’el Abiy is a tabia or municipality in the Dogu’a Tembien district of the Tigray Region of Ethiopia. The tabia centre is in Megesta village, located approx. 7 km to the southeast of the woreda town Hagere Selam.

Melfa is a tabia or municipality in the Dogu'a Tembien district of the Tigray Region of Ethiopia and ancient capital of Tembien. The tabia centre is Melfa village itself, located approximately 3 km to the west of the woreda town Hagere Selam.

Debre Nazret is a tabia or municipality in the Dogu'a Tembien district of the Tigray Region of Ethiopia. The tabia centre is in Togogwa village, located approximately 19 km to the east-southeast of the woreda town Hagere Selam.

Arebay is a tabia or municipality in the Dogu'a Tembien district of the Tigray Region of Ethiopia organised around the Arebay mountain peaks. The tabia centre is in Arebay village, located approximately 13 km to the east-northeast of the woreda town Hagere Selam.

Haddinnet, also transliterated as Hadnet, is a tabia or municipality in the Dogu'a Tembien district of the Tigray Region of Ethiopia. The tabia centre is in Addi Idaga village, located approximately 6.5 km to the northeast of the woreda town Hagere Selam.

Mahbere Sillasie Municipality in Ethiopia

Mahbere Sillasie is a tabia or municipality in the Dogu'a Tembien district of the Tigray Region of Ethiopia. The tabia centre is in Guderbo village, located approximately 2.5 km to the west-northwest of the woreda town Hagere Selam.

Aregen is a tabia or municipality in the Dogu'a Tembien district of the Tigray Region of Ethiopia. The tabia centre is in Addi Gotet village, located approximately 11 km (6.8 mi) to the west-southwest of the woreda town Hagere Selam.

Menachek is a tabia or municipality in the Dogu'a Tembien district of the Tigray Region of Ethiopia. The tabia centre is in Addi Bayro village, located approximately 12 km to the southwest of the woreda town Hagere Selam.

Mizan is a tabia or municipality in the Dogu'a Tembien district of the Tigray Region of Ethiopia. This tabia includes the rock church of Debre Sema'it, as well as Arefa, reputedly birthplace of the Queen of Sheba. The tabia centre is in Kerene village, located approximately 16 km to the southwest of the woreda town Hagere Selam.

Mizane Birhan is a tabia or municipality in the Dogu'a Tembien district of the Tigray Region of Ethiopia. The tabia centre is in Ma’idi village, located approximately 13 km to the southeast of the woreda town Hagere Selam.

Selam is a tabia or municipality in the Dogu'a Tembien district of the Tigray Region of Ethiopia. The tabia centre is in Addi Werho village, located approximately 3 km to the northeast of the woreda town Hagere Selam.

Seret is a tabia or municipality in the Dogu'a Tembien district of the Tigray Region of Ethiopia. The tabia centre is in Inda Maryam Qorar village, located approximately 11 km to the southwest of the woreda town Hagere Selam.

Lim’at is a tabia or municipality in the Dogu'a Tembien district of the Tigray Region of Ethiopia. The tabia centre is in Maygwa village, located approximately 8 km to the southwest of the woreda town Hagere Selam.

Ayninbirkekin is a tabia or municipality in the Dogu'a Tembien district of the Tigray Region of Ethiopia. The tabia centre is in Halah village, located approximately 8 km to the east of the woreda town Hagere Selam.

References

1 2 3 4 5 6 Miruts Hagos and colleagues (2019). The volcanic rock cover of the Dogu'a Tembien massif. In: Geo-Trekking in Ethiopia's Tropical Mountains, the Dogu'a Tembien District. SpringerNature. ISBN 978-3-030-04954-6.
↑ Le Bas, M.J.; Mohr, P.A. (1968). "Feldspathoidal rocks from the Cainozoic volcanic province of Ethiopia" (PDF). Geologische Rundschau. 58 (1): 273–280. doi:10.1007/BF01820608.
↑ Miruts Hagos; Koeberl, C.; Jourdan, F. (2017). "Geochemistry and Geochronology of Phonolitic and Trachytic Source Rocks of the Axum Obelisks and Other Stone Artifacts, Axum, Ethiopia". Geoheritage. 9 (4): 479–494. doi:10.1007/s12371-016-0199-7.
↑ Machado, M.J. (2015). Geomorphology of the Adwa District. In Landscapes and Landforms of Ethiopia. Dordrecht: Springer. pp. 163–178. doi:10.1007/978-94-017-8026-1_8.

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[miruts2019-1] 1 2 3 4 5 6 Miruts Hagos and colleagues (2019). The volcanic rock cover of the Dogu'a Tembien massif. In: Geo-Trekking in Ethiopia's Tropical Mountains, the Dogu'a Tembien District. SpringerNature. ISBN 978-3-030-04954-6.

[2] Le Bas, M.J.; Mohr, P.A. (1968). "Feldspathoidal rocks from the Cainozoic volcanic province of Ethiopia" (PDF). Geologische Rundschau. 58 (1): 273–280. doi:10.1007/BF01820608.

[3] Miruts Hagos; Koeberl, C.; Jourdan, F. (2017). "Geochemistry and Geochronology of Phonolitic and Trachytic Source Rocks of the Axum Obelisks and Other Stone Artifacts, Axum, Ethiopia". Geoheritage. 9 (4): 479–494. doi:10.1007/s12371-016-0199-7.

[4] Machado, M.J. (2015). Geomorphology of the Adwa District. In Landscapes and Landforms of Ethiopia. Dordrecht: Springer. pp. 163–178. doi:10.1007/978-94-017-8026-1_8.