Alfred Scheidig (1934) in his classic book 'Der Loess und seine geotechnischen Eigenschaften' stated that: In addition to the aforementioned loesses, which are mainly of glacial origin, there are continental loesses in the fringe regions around desert and steppe zones. Keilhack (1920) mentions this in Texas, Shaler (1899) in Montana, Henning (1911) in Colorado, New Mexico and Arizona. In the latter two areas, the loess is closely related to the formation known as 'adobe' (pronounced adobi) in fact, in most cases it is identical to adobe (translated by LL).
Adobe is widely used as a building material in Africa- in and around the 15N region; it is also used in the S.W.USA; these are probably the best known adobe regions. The sources of adobe material in Africa can perhaps be demarcated.
On the map <<< FJ is the Fonta-Djalon highlands; BD is the Bodele depression; EH is the Ethiopian highlands. Also indicated- the catchment of the River Niger. The highlands can be seen as particle-source regions- possibly for loess sized particles. The Bodele depression is the classic source region for small dust particles- derived from deposits in ancient Lake Chad. This can deliver clay-mineral material and silica diatoms. A lot of interesting particulate material is available in the 15N region. For the adobe reaction to function effectively there needs to be some carbonates in the system. The Ethiopian Highlands deliver large amounts of silt-sized material for the Nile Valley deposits and also makes material available for the eastern parts of the adobe region. There are actually few well defined loess deposits in Africa- but there must be a large amount of usable material in accessible regions.
Onn Crouvi and associates have provided a neat map of Africa showing loess deposits and the critical regions. The countries of Mauritania, Mali, Niger and Chad cover much of this region; classic adobe buildings are found in this zone.
Crouvi, O., Amit, R., Enzel, Y., Gillespie, A.Ar. 2010. Active sand seas and the formation of desert loess. Quaternary Science Reviews 29, 2087-2098.
On the map <<< FJ is the Fonta-Djalon highlands; BD is the Bodele depression; EH is the Ethiopian highlands. Also indicated- the catchment of the River Niger. The highlands can be seen as particle-source regions- possibly for loess sized particles. The Bodele depression is the classic source region for small dust particles- derived from deposits in ancient Lake Chad. This can deliver clay-mineral material and silica diatoms. A lot of interesting particulate material is available in the 15N region. For the adobe reaction to function effectively there needs to be some carbonates in the system. The Ethiopian Highlands deliver large amounts of silt-sized material for the Nile Valley deposits and also makes material available for the eastern parts of the adobe region. There are actually few well defined loess deposits in Africa- but there must be a large amount of usable material in accessible regions.
Onn Crouvi and associates have provided a neat map of Africa showing loess deposits and the critical regions. The countries of Mauritania, Mali, Niger and Chad cover much of this region; classic adobe buildings are found in this zone.
Crouvi, O., Amit, R., Enzel, Y., Gillespie, A.Ar. 2010. Active sand seas and the formation of desert loess. Quaternary Science Reviews 29, 2087-2098.
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