Loesses

Basalt, granite, manganese nodules, shale, flint clay, iron formation materials, phosphate rock, fertilizers Calcareous loam soil, loess, polluted farmland soil, sand soil... 

Data extracted from Certificate for CRM RTH 912, Loess Soil from Switzerland, produced by Pro-mochem GmbH, Germany, with permission). All units mg/kg... 

Comparable evidence for environmental change is available from resolution ocean cores, loess sequences, ice cores and other archives. 

Rowe PJ, Maher BA (2000) Cold stage formation of calcrete nodnles in the Chinese Loess Plateau evidence from U-series dating and stable isotope analysis. Palaeogeogr Palaeochmatol Palaeoecol 157 109-125... 

FIGURE 52 Preceramics. Cracked loess crusts after firing in an open fire, found in a ravine (a) and (c) inside unfired (b) and (d) outside unfired. 

Dunes and sand plains form where strong winds carry sand grains in saltation over short distances. Particles finer than sand are transported in suspension and over greater distances until they settle as loess , predominantly in the steppe regions adjacent to the desert zone. 

Chinese records make mention of extensive loess deposition between 400 and 600 AD, between 1000 and 1200 AD and between 1500 and 1900 AD (during the Little Ice Age ). However, the most extensive... 

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. 

Loess is a well-sorted, usually calcareous, non-stratified, yellowish-grey, aeolian clastic sediment. It consists predominantly of silt-sized particles (2-50 mm), and contains normally less than 20 percent clay and less than 15 percent sand. It covers the land surface as a blanket, which is less than 8 meters thick in the Netherlands (exceptionally 17 meters) but can reach up to 40 meters in Eastern Europe and 330 meters in China. 

Loess settles when dust-laden winds slow down to speeds between 7 (on dry surfaces) to 14 meters per second (on moist surfaces). The pore distribution of loess lets it quickly be retained by capillary forces if it lands on a moist surface. The presence of a vegetation cover may also enhance the rate of loess deposition, and many authors maintain that the northern limit of loess deposition coincides with the northernmost extent of grass steppes during arid periods in the Pleistocene. 

Vast undulating till plains occur in North America, between the Canadian shield area and the loess belt. This area is either covered with thick tills or with deglaciation sediments, lacustrine sediments in particular. The lake areas are level as such but the till landscape has a typical hummocky relief. The main characteristic of hummocky tills (40% of the total area) is the predominance of very local drainage patterns (mainly in depressions). Tills and loess have in common that they are internally uniform and that they all date back to deglaciation periods. 

The vast loess and till plains are now colonized by grasses and/or forest. They are the home of some of the best soils of the world the black earths . Deep, black Chernozems occupy the central parts of the Eurasian and North American steppe zones. Brown Kastanozems are typical of the drier parts of the steppe zone and border on arid and semi-arid lands. Dusky red Phaeozems occur in slightly more humid areas such as the American prairies and pampas. 

Though the process of wind action and transport of material is clearly recognized, it is difficult to measure its impact in the accumulation zones. Such measurements are most successful in the immediate neighborhood of the deflation zones where the thickness and volume of sand or loess deposits can easily be calculated. In the northern periphery of the Negev, aeolian deposits range from a few cm to several meters, which corresponds to an average accumulation of 10 to 100 mm/millennium since the Lower Pleistocene. 

Data from Liu, 1996. The data cover North China Plain, Loess Plateau, and Xinjiang Province. 

Total Mo in soils of China varies from 0.1-6 mg/kg with an average of 1.7 mg/kg. Arid and semi-arid soils have 0.2-4.2 mg/kg total Mo. Average Mo contents in arid and semi-arid regions are 1.58 mg/kg. In general, lower Mo contents are found in soils of arid and semi-arid regions than the humid and tropic/subtropic soils. In soils derived on loess, total Mo is from 0.21-1.45 mg/kg with an average of 0.62 mg/kg. Soils in the North... 

Soils in Uzbekistan have an average Co of 17 mg/kg. Total Cu in humic soils is in the range of 18-22 mg/kg, and total Zn is 83 mg/kg. In subdesert soils formed on loessial clayey loams and saline alkali soils, total Mo is 2.6-4.5 mg/kg, and Mo in some soils is as high as 8 mg/kg. Total Zn in subdesert soils varies from 60-112 mg/kg. Sodium acetate-extractable Zn in these subdesert soils is 2.1-3.2 mg/kg, accounting for 2.3-5.1% of total Zn. In saline alkali soils formed on loess and marine clays, total B content is 160 mg/kg. The exchangeable Mn in arid and semi-arid soils is 7-50 mg/kg, accounting for 0.7-7.8% of total Mn. Saline soils in the Ustyurt region contain 42-80 mg/kg of Pb. 

In chernozems derived on loess of Cluj and Dobrudja regions of Romania, total Cu is in the range of 25-45 mg/kg. Chernozems formed on loess contain 73 mg/kg of total Zn and 17-30 mg/kg of total Ni. 

Figure 7.6. Decreases in bioavailability (as NH4N03-extractable) of Cu, Ni and Zn in an Israeli loess soil receiving metal salts and incubated under field capacity regime for one year (data from Han and Banin, 1999)...

Soils in the North China Plain and Loess Plateau regions contained 0.04-3.01 mg/kg DTPA-extractable Zn with an average of 0.44 mg/kg. The concentrations of DTPA-extractable Zn in northern China are presented in Table 7.7. In the loessial soils of the Loess Plateau, 64% of the soil samples had less than 0.5 mg/kg of bioavailable Zn. The bioavailable Zn in the arid soils of North China varied from 0.08-11.84 mg/kg with an average of 1 mg/kg, with 41% of the soil samples having < 0.5 mg/kg of bioavailable Zn. The average amount of bioavailable Zn in calcareous soils was 0.35 mg/kg (trace - 1.12 mg/kg). The North China Plain and Loess Plateau are major Zn-deficient regions in China. Calcareous paddy soils frequently displayed Zn deficiency in rice. Zinc fertilizers have been applied to rice, maize, sorghum, wheat, cotton and fruit trees where bioavailable Zn was less than 0.5 mg/kg. 

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