Aeolian dunes

The sand grains that make up aeolian dunes can include detrital biogenic carbonate grains (e.g. Ward, 1973, 1975), ooids (e.g. Budd, 1988) and... 

Hunter, R.E. (1977) Basic types of stratification in small aeolian dunes. Sedimentol-ogy 24, 361-387. 

EC Cross-stratified aeolian dune bodies Trough cross-bedded sand (Ste) planar laminated sand (Spe) low angle cross-bedded sand (Sle) horizontally laminated sand (She) ripple cross-laminated sand (Sre) massive sand (Sme) Tabular, lenticular and wedge-shaped 1-3 m thick > 1 km lateral extent Fine to lower coarse, moderately to well sorted sand/sandstone Scattered ovoid to elongate concretions and small type 1 and type 3 phreatic tabular units... 

Kocurek, G. (1981) Significance of interdune deposits and bounding surface in aeolian dune sands. Sedimentology, 28, 753-780. 

Aeolian sands are deposited by wind action, either in dunes or in extensive sheets ( cover sand areas ) Wind action is particularly effective in hot and dry regions such as deserts but sand dunes are also common in (sub)humid regions with sparse vegetation, notably in overgrazed areas and along beaches and fluvial braid plains . The (weathering) history of the parent materials in the source area determines whether the sands are rich in quartz and/or carbonates. 

The area of actual erg and dune formation is delimited by the 150 mm/yr isohyet. This precipitation boundary appears to have shifted strongly in the recent past. Between 20,000 and 13,000 yr BP, the southern limit of active dune formation in the Sahara desert was 800 km south of its present position and most of the now sparely vegetated Sahelian zone was an area of active dune formation at that time. These dunes, mostly of the longitudinal type, are now fixed by vegetation, but their aeolian parentage is still obvious from their well-sorted material. A similar story can be told for the Kalahari sands. Overgrazing in recent times has reactivated aeolian transport in many regions with sands. 

Clearly, aeolian processes were much more important at that time than at present. Large parts of the present temperate zone, from the cover sands of the Netherlands to the sand dunes in north-east Siberia are Ice Age (aeolian) sands. South and east of this cover sand belt lies a belt of loess deposits, extending from France, across Belgium, the southern Netherlands, Germany and large parts of Eastern Europe into the vast steppes of Russia, and further east to Siberia and China. A similar east-west loess belt exists in the USA and less extensive areas occur on the Southern Hemisphere, e.g. in the Argentinean pampas. 

Wind-blown sand dunes are accumulations of sediment laid down by aeolian processes and fashioned into bedforms by deflation and deposition (Livingstone and Warren, 1996). A supply of sand grains, either marine carbonate material or terrigenous lithoclasts that can be entrained by the... 

The Norphlet sands were derived primarily from erosion of the southern Appalachian Mountains located to the north (Mancini et al. 1985,1990). In the Mobile Bay area, the Norphlet is interpreted as an aeolian deposit composed of large dune complexes and associated interdune deposits (Mancini et al. 1985 Marzano et al. 1988 Dixon et al. 1989). The Jurassic-age Pine Hill Anhydrite and the Louann Salt lie directly beneath the Norphlet and the Oxfordian marine carbonates of the Smackover Formation occur directly above (Fig. 2). 

Excluding the highly cemented tight-zone, reservoir quality can generally be related to aeolian facies and stratification type (Marzano et al. 1988 Dixon et al. 1989 Thomson Stancliffe 1990). All examples of the interdune facies have extremely low porosity and permeability and do not contribute to hydrocarbon production (Fig. 8). Sands exhibiting dune avalanche cross-stratification have, as a population, higher porosity and permeability than... 

Aeolian soils are those formed by aeolian action, that is, materials transported, eroded and deposited by winds. These soils appear as sand dunes or calcitic silt. Pavement construction on sand dunes, which are not protected by topsoil, appears to be problematic. A cut on calcitic silt may have very high gradient (slope) owing to the cohesive properties of calcium. The usage, however, of disturbed calcitic silt on embankment is problematic because cohesion has been lost. 

Oiling involves the covering of aeolian material with a suitable oil product (e.g. high-gravity oil) that stabilizes the treated surface and may destroy dune forms. It is, in many deserts, a quick, cheap and effective method... 

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