Amba Aradam Formation

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Coordinates: 13°19′41″N 39°26′17″E / 13.328°N 39.438°E / 13.328; 39.438
Source: Wikipedia, the free encyclopedia.
Amba Aradam Formation
Ma
↓
Approximate paleocoordinates
15°12′S 28°30′E / 15.2°S 28.5°E / -15.2; 28.5
RegionTigray
Country Ethiopia
Extentnorthern Ethiopian Highlands
Type section
Named forImba Aradom mountain, near Hintalo
Named byWilliam Thomas Blanford
Year defined1868
Amba Aradam Formation is located in Ethiopia
Amba Aradam Formation

The Amba Aradam Formation is a

Harrar in southeast Ethiopia, both of Late Cretaceous age (100–66 million years ago).[2][3][4] The lithology of the Amba Aradam Formation makes it less suitable for rock church excavation; caves have however been blasted in this formation to serve as headquarters for the TPLF during the Ethiopian Civil War of the 1980s.[1]

Name and definition

The name “Amba Aradam Sandstone” was coined by geologist

British invading army in 1868. The formation is named after the Amba Aradam mountain, where the formation widely outcrops.[5] So far the nomenclature was not proposed for recognition to the International Commission on Stratigraphy
.

Stratigraphic context

The Amba Aradam Formation overlies the

Dogu’a Tembien; further to the west, it rests on the Antalo Limestone and then on the Adigrat Sandstone.[1] After the deposition of the sands that were to become the Amba Aradam Formation, planation has occurred.[7] This was then followed by the deposition of the Tertiary Trap Volcanics.[8]

Lithology

The Amba Aradam Formation comprises white or red

laterisation) makes the upper part of the formation harder, heavier and almost impervious for water.[1][9] Locally, conglomerates occur.[10]

Gumuara, here, at its westernmost occurrence, it directly overlies the Adigrat Sandstone

Rock sample gallery

  • Rock sample with cross-bedding, collected in Miheno
    Rock sample with cross-bedding, collected in
    Miheno
  • Rock sample, conglomeratic facies, collected on Imba Aradom
    Rock sample, conglomeratic facies, collected on Imba Aradom
  • Rock sample with slickenside collected along a fault on Imba Aradom
    Rock sample with slickenside collected along a fault on Imba Aradom

Geographical extent

Besides at

Tigray region of Ethiopia
.

Current geomorphology of the Amba Aradam Formation

The

claystone or siltstone. The formation does not have high vertical cliffs like the Adigrat Sandstone. The iron-cemented upper part of the formation forms however steep cliffs, which can be more than 10 metres (33 ft) high. These layers are also impermeable, what results in a spring line at the edge of the Amba Aradam sandstone cliff.[1][11]

Addi Geza'iti
; the previous TPLF headquarters were hewn in this cliff, at right

Caves used as headquarters during the Ethiopian Civil War

In the 1980s, during the

Ethiopian People’s Democratic Movement (EPDM) installed its HQ in a nearby cave at Melfa. Major military operations were coordinated from these caves almost until their victory against the Derg government in 1991. Both caves can be visited on appointment (contact at the Dogu'a Tembien district office, Hagere Selam, Tigray).[1]

References

  1. ^
    doi:10.1007/978-3-030-04955-3_8
    .
  2. ISBN 978-3-030-04954-6
    .
  3. ^ Bosellini, A.; Russo, A.; Fantozzi, P.; Assefa, G.; Tadesse, S. (1997). "The Mesozoic succession of the Mekelle Outlier (Tigrai Province, Ethiopia)". Mem. Sci. Geol. 49: 95–116.
  4. ^ Bussert, R.; Dawit Enkurie (2009). "Unexpected diversity: New results on the stratigraphy and sedimentology of Palaeozoic and Mesozoic siliciclastic sediments in Northern Ethiopia". Zentralbl Geol Paläontol. 3/4: 181–198.
  5. ^ Blanford, W.T. (1870). Observations on the geology and zoology of Abyssinia, made during the progress of the British expedition to that country in 1867-68. London: Macmillan and Co.
  6. S2CID 129046585
    .
  7. doi:10.1016/j.geomorph.2006.12.007
    .
  8. ^ Justin-Visentin, E. (1974). "Petrografia, chimismo e petrogenesi dei corpi subvulcanici di Macallè (Tigrai Etiopia)". Memorie dell'Istituto di Geologia e Mineralogia, Universita di Padova. 31: 1–33.
  9. ^ Beyth, M. (1972). To the Geology of Central-Western Tigre. Bonn: Dissertation Rheinische Friedrichs-Wilhelms-Universität Bonn. p. 159.
  10. ^ Shumburo, M. (1968). The Amba Aradam formation (formerly the Upper Sandstone). Mobil Petroleum Ethiopia Inc.
  11. S2CID 129417175
    .
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