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

O’Hara-Dhand, Ken; Taylor, Richard L.; Smalley, Ian; Krinsley, David H.; Vita‐Finzi, Claudio

doi:10.2478/v10085-010-0001-z

Cited by 12 publications

(9 citation statements)

References 23 publications

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“…Both the Puerto Rico (PR) and Anza Borrego (AB) bedrock comprise predominantly igneous crystalline material (PR-granodiorite and minor metadiorite; AB-tonalite); such isotropic plutonic rocks are generally considered more durable than foliated (schistose and gneissic) metamorphic rocks, owing to the fabric heterogeneities that impart additional unstable surfaces in the latter (Palomares and Arribas, 1993), as well as the more highly stressed quartz in metamorphic rocks (O'hara-Dhand et al, 2010). Accordingly, one might expect mechanical disintegration to proceed at the fastest rate for the foliated rock types, but our results refute this assumption.…”

Section: Influence Of Starting Lithology On Sand Durability and Potenmentioning

confidence: 99%

Silt production as a function of climate and lithology under simulated comminution

Soreghan

Joo

Madden

et al. 2016

Quaternary International

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Production of the silt-sized particles composing loess represents a critical step in its ultimate formation, but the volume and rate of production in different settings remain underdetermined. This study addresses the influence of climate and source lithology on silt formation by subjecting natural alluvial/fluvial sand from systems characterized by varying climatic setting to simulated comminution. Bulk samples from comparable transport distances were collected from a hot-arid (California desert) alluvial system, hot-humid (Puerto Rico) fluvial system, and cold-humid (Norway) proglacial fluvial system, and sieved to isolate the coarse-very coarse sand fraction for experimental milling. Source rocks in all three systems consist of granitoids, with some contributions from foliated coarse-grained metamorphic rocks (gneissic and schistose) in Norway. Results indicate that contributions from coarse-grained foliated lithologies impart a negligible effect on rate of silt production from the sand starting material. Climatic setting imparts no significant difference on sand durability, but influences clay production at later stages of comminution for the Puerto Rico sample, presumably owing to the effects of deep chemical weathering prior to physical transport. Comminution and silt production in all experiments exhibit exponential decay wherein rapid initial rates diminish with time. This is interpreted to reflect the effects of the dynamic milling conditions (particle size and distribution, and slurry viscosity), as well as particle strength, with the latter including both relative strengths of different minerals in general, and the influences of lattice defects and microfractures in quartz in particular. Empirical observations reveal that silt fractions of the natural alluvial/fluvial samples, collected at comparable transport distances (5-7 km) in the respective systems, exhibit significant

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Section: Influence Of Starting Lithology On Sand Durability and Potenmentioning

confidence: 99%

Silt production as a function of climate and lithology under simulated comminution

Soreghan

Joo

Madden

et al. 2016

Quaternary International

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“…The Danube is a loess river (Smalley et al 2010). It collects loess material from the Carpathian mountains, from the Alps, from the Dinaric Alps, from highlands ringing the basin.…”

Section: Rivers and Loess: The River Niger Situationmentioning

confidence: 99%

“…It can be lifted from desert regions and transported vast distances at great heights. Various particle production mechanisms are involved (Smalley et al 2005, O'Hara-Dhand et al 2010, Crouvi et al 2008). …”

Section: Desert Loessmentioning

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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“…The essential question appears to be: are there rock systems on Mars wherein the formation mechanism has introduced stresses which can be exploited when the weathering process occurs? A combination of stresses may be essential for efficient particle production, as occurs in the recently appreciated mechanism [7] for the production of small quartz dust from sand sea deposits.…”

mentioning

confidence: 99%

“…All of the above presents a strictly terrestrial scenario. Producing silt on Mars requires different processes [7]. Mars lacks quartz; in fact Martian lithology may lack a well-placed eutectic reaction to establish some size control on finer particle sizes.…”

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confidence: 99%

A size control for quartz silt (making particulates at planetary surfaces)

Smalley

Vita‐Finzi

2011

Open Geosciences

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Quartz silt is widespread in terrestrial sediments [1]. Its ubiquity has led to its neglect as a geomaterial, and studies of silt as such are relatively rare, but it presents an interesting and continuing petrological problem. Is silt a specific geological material, is it defined by a formation process, and a set of size parameters? In the world of clastic quartz sedimentology there are obvious mode sizes; there is a sand mode at around 300-500 µm and a silt mode, an order of magnitude smaller, at 30-50 µm. Are these both defined by specific geological processes?Keywords: quartz silt • formation mechanism • Mars sedimentsIt has been known for almost 50 years that the formation mechanism for quartz sand produces a specific size range, determined by the eutectic-type reaction in the parent quartz-bearing rock [2]. We propose a specific mechanism, related to sand formation, that provides a defined range of silt particles. Two important mechanisms are involved in sand formation [1] a eutectic-type reaction in the parent granitic rock determines the universal size of quartz sand and [2] the cooling quartz goes through a displacive transformation from high quartz to low quartz which produces tensile stresses in the system. These aid in the particle breakout process as the weathering front proceeds through the parent rock. This

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

Cited by 12 publications

References 23 publications

Silt production as a function of climate and lithology under simulated comminution

Silt production as a function of climate and lithology under simulated comminution

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

A size control for quartz silt (making particulates at planetary surfaces)

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