The nature and early history of airborne dust from North Africa; in particular the Lake Chad basin

Evans, Robert D.; Jefferson, Ian; Kumar, R.; O’Hara-Dhand, Ken; Smalley, Ian

doi:10.1016/j.jafrearsci.2004.06.001

Cited by 29 publications

(22 citation statements)

References 15 publications

(16 reference statements)

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“…The largest extant areas of diatomite are those that were deposited in the deepest basins of Palaeolake MegaChad, which, some 6000 years ago, was the largest lake on earth, bigger than the present Caspian Sea (Drake and Bristow, 2006). It is diatomite, not highly weathered material (Evans et al, 2004), that is the source of by far the greatest proportion of the dust from the Bodélé.…”

Section: Introductionmentioning

confidence: 99%

Dust-raising in the dustiest place on earth

et al. 2007

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Section: Introductionmentioning

confidence: 99%

Dust-raising in the dustiest place on earth

et al. 2007

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“…The Lake Chad basin is a good source of clay-mineral based small dust[CMA particles] (Evans et al 2004, Smalley et al 2005, Stuut et al 2009 and Monte Carlo controls on dust size have been discussed (Smalley et al 2005). Mega-lake Chad, the old enormous Lake Chad was a great sink for sedimentary material and now provides an effective source for aeolian sedimentary material.…”

Section: The Lake Chad Basin As a Source Of Particulate Materialsmentioning

confidence: 99%

Loess and Bee-Eaters II: The ‘loess’ of North Africa and the nesting behaviour of the Northern Carmine Bee-Eater (Merops nubicus Gmelin 1788)

McLaren

Svirčev

O’Hara-Dhand

et al. 2014

Quaternary International

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The Northern Carmine Bee-eater lives and breeds in a well demarcated region stretching across Africa close to the 15N line of latitude. The Bee-eater zone appears to be associated with a band of loess, defined by Scheidig on his 1934 map as second-prder loess. Beeeaters are known to favour loess for nesting tunnels and it appears that the 15N material is sufficiently loess-like. Obvious sources of particulate material for the 15N band are the Fonta Djalon highlands which supply sedimentary material to the River Niger; the Bodele depression, the deepest part of old Lake Megachad, source of the dust for the World; the Ethiopian highlands at the eastern end of 15N which supply silt to the Nile system and particulates to the 15N region. In soil moisture terms the region is ustic, which is possibly a necessary condition for bee-eater nests. The clastic material requires an ustic environment. The River Niger can be seen as a loess river, in some senses a mirror image of a major loess river like the Danube, but where a restricted range of particle inputs leads to a restricted range of loess deposit outputs. Nevertheless loess river considerations can be applied. The Niger delivers second-order loess and important loessic admixtures to the landscape. Enough loess for selective nesters like the Carmine Beeeaters to build their nest tunnels in it. It seems likely that climate change will cause a change in bee-eater distribution; it seems unlikely that they will abandon their nesting regions, the living and breeding zones may shift. Quaternary InternationalWe the undersigned declare that this manuscript is original, has not been published before and is not currently being considered for publication elsewhere.We confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed. We further confirm that the order of authors listed in the manuscript has been approved by all of us.We understand that the Corresponding Author is the sole contact for the Editorial process. He/she is responsible for communicating with the other authors about progress, submissions of revisions and final approval of proofs.Signed by all authors as follows: C.H.Fry AbstractThe Northern Carmine Bee-Eater (Merops nubicus) lives and breeds in a well demarcated region stretching across Africa close to the 15°N line of latitude. The Bee-Eater zone appears to be associated with a band of loess, defined by Scheidig on his 1934 map as second-order loess. Bee-eaters are known to favour loess for nesting tunnels and it appears that the 15°N material is sufficiently loess-like. Obvious sources for particulate materials for the 15°N band are the Fonta-Djalon highlands which supply sedimentary material to the River Niger; the Bodele Depression, the deepest part of Lake Megachad, source of dust for the World; the Ethiopian highlands at the eastern end of 15°N which supply silt to the Nile system and particulates to the 15°N region. In soil moisture ...

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“…This novel mechanism probably accounts for most of the quartz dust. It can be complemented by already known mechanisms [3,9]; observations from satellites suggests strongly that these are the two main sources.…”

Section: Commentarymentioning

confidence: 99%

“…The formation of small CMA mineral dust in North Africa has been considered by Evans et al [9] and they have shown, by a simple Monte Carlo simulation, how the bottom structure of fine particle lake sediments develops and how this has a critical influence on the size of the eventual small dust particle. This may account for much of the desert dust but there will be a proportion which can be formed by sand grain impact, yielding a small-size fracture product, and it is this impact production of small particles which is considered in this paper.…”

Section: Introductionmentioning

confidence: 99%

Loess and dust on Earth and Mars: particle generation by impact mechanisms

O’Hara-Dhand

Taylor²,

Smalley

et al. 2010

Open Geosciences

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Impact between windblown quartz grains as a source of desert dust is consistent with laboratory abrasion experiments and has received some field confirmation in the Negev. The suggestion is that an important process on Mars now gains support from laboratory studies; even though their geochemical interpretation is controversial, they show that dust generation by impact is tenable even for quartz. A simple mechanism for small dust production from sand seas is proposed; internal stresses can be mobilized by impact energy. A speculative mechanism (the andesite scenario) is proposed for fine particle production by particle impact on Mars. The internal stress range in terrestrial sand grains may vary, depending on the nature of the source rock, and this may influence particle production by impact processes.

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The nature and early history of airborne dust from North Africa; in particular the Lake Chad basin

Cited by 29 publications

References 15 publications

Dust-raising in the dustiest place on earth

Dust-raising in the dustiest place on earth

Loess and Bee-Eaters II: The ‘loess’ of North Africa and the nesting behaviour of the Northern Carmine Bee-Eater (Merops nubicus Gmelin 1788)

Loess and dust on Earth and Mars: particle generation by impact mechanisms

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