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Osl dating of sediments from deserts in northern china

Loess is homogeneous, porous, friable, pale yellow or buff, slightly coherent, typically non-stratified and often calcareous.

Loess grains are angular with little polishing or rounding and composed of crystals of quartz, feldspar, mica and other minerals. Loess deposits may become very thick, more than a hundred meters in areas of China and tens of meters in parts of the Midwestern United States.

The source region for this loess is thought by some scientists to be areas of fluvio-glacial depostis the Andean foothills formed by the Patagonian Ice Sheet.

Other researchers stress the importance of volcanic material in the neotropical loess.

At times it suffered erosion rates of over 10 kilograms per square meter per year.

Today this loess deposit is worked as low till or no till in all areas and is aggressively terraced.

It generally occurs as a blanket deposit that covers areas of hundreds of square kilometers and tens of meters thick.

Loess often stands in either steep or vertical faces.

osl dating of sediments from deserts in northern china-15osl dating of sediments from deserts in northern china-22

(1994) Since the 1980s, thermoluminescence (TL), optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) dating are available providing the possibility for dating the time of loess (dust) deposition, i.e.Because the grains are angular, loess will often stand in banks for many years without slumping.This soil has a characteristic called vertical cleavage which makes it easily excavated to form cave dwellings, a popular method of making human habitations in some parts of China. In several areas of the world, loess ridges have formed that are aligned with the prevailing winds during the last glacial maximum.The largest deposit of loess in the United States, the Loess Hills along the border of Iowa and Nebraska, has survived intensive farming and poor farming practices.For almost 150 years, this loess deposit was farmed with mouldboard ploughs and fall tilled, both intensely erosive.The fine grains weather rapidly due to their large surface area, making soils derived from loess rich.One theory states that the fertility of loess soils is due largely to cation exchange capacity (the ability of plants to absorb nutrients from the soil) and porosity (the air-filled space in the soil).The neotropical loess is made of silt or silty clay.Relative to the pampean loess the neotropical loess is poor in quartz and calcium carbonate.The fertility of loess is not due to organic matter content, which tends to be rather low, unlike tropical soils which derive their fertility almost wholly from organic matter.Even well managed loess farmland can experience dramatic erosion of well over 2.5 kg /m per year.

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