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| Loess (sediment) | |
|---|---|
| Name | Loess |
| Type | Unconsolidated, windblown sediment |
| Primary lithology | Silt, quartz, feldspar, carbonate |
| Other lithology | Clay, sand, organic matter |
| Region | Global |
Loess (sediment) Loess is a predominantly silt-sized, wind-deposited sediment commonly forming extensive, loosely cemented blankets across continents. It occurs as homogenous, pale yellow to brown deposits that produce highly productive soils and distinct landforms, and its study intersects research by institutions such as Smithsonian Institution, United States Geological Survey, Chinese Academy of Sciences, and Max Planck Society.
Loess is defined as a nonfossiliferous, eolian sediment dominated by silt-sized particles with moderate porosity and weak stratification; it was described in classic studies by investigators from Geological Society of America, Royal Society, and researchers associated with University of Cambridge, Harvard University, and Peking University. Characteristic features include open fabric, vertical jointing, and high carbonate content derived from provenance regions such as Loess Plateau (China), Central Asia, and Midwestern United States. Typical mineral constituents—quartz, feldspar, mica—were characterized in lab programs led by teams at Massachusetts Institute of Technology, University of Oxford, and ETH Zurich.
Loess formation is linked to sediment production in glacial, periglacial, and arid source areas and subsequent aeolian transport and deposition documented by researchers affiliated with University of Bern, Stanford University, and University of Bonn. Processes include glacial grinding at ice sheets like the Laurentide Ice Sheet and Weichselian glaciation producing silt, wind entrainment across outwash plains such as those studied near Mississippi River and Yellow River, and long-distance transport associated with atmospheric circulation patterns studied by groups at National Oceanic and Atmospheric Administration and European Centre for Medium-Range Weather Forecasts. Deposition commonly occurs downwind of dust sources in topographic traps documented in studies at Loess Plateau (China), Pamir Mountains, and Himalaya foothills.
Major loess provinces include the Loess Plateau (China), the Midwestern United States loess belt adjacent to the Mississippi River, the Eurasian Steppe loess across Ukraine and Russia, the Danube Basin covers in Austria and Hungary, and the Pamir Plateau and Tibetan Plateau margins. Other significant deposits occur near the Loess Hills (Iowa), the Rhine Valley in Germany, the Taurida region of Crimea, and the Andean Altiplano studied by teams from University of Buenos Aires and National University of La Plata. Regional syntheses have been advanced by collaborations involving International Union for Quaternary Research and national geological surveys like Geological Survey of Canada.
Sedimentological analyses reveal grain-size distributions, microstructures, and mineral assemblages examined by laboratories at Max Planck Institute for Biogeochemistry, Woods Hole Oceanographic Institution, and Scripps Institution of Oceanography. Loess typically has a bimodal grain-size signature with dominant silt and subordinate clay and sand fractions, with mineralogy dominated by Quartz, Feldspar, Calcite, and accessory Mica species; provenance studies have invoked techniques developed at Lamont–Doherty Earth Observatory and Australian National University. Geochemical fingerprints using isotopes and trace elements were pioneered in programs at Oak Ridge National Laboratory, Centre National de la Recherche Scientifique, and University of Tokyo.
Loess sequences preserve high-resolution records of Quaternary environmental change analyzed by teams at Columbia University, Peking University, University of Copenhagen, and University of Heidelberg. Loess-paleosol cycles correlate with glacial-interglacial oscillations tied to orbital forcing described in studies of Milankovitch cycles and amplified by regional dynamics such as monsoon variations investigated by groups at International Geosphere–Biosphere Programme and World Meteorological Organization. Paleoclimatic proxies from loess—including magnetic susceptibility, grain-size variation, and stable isotopes—have been calibrated against records from Greenland ice cores, Vostok Station, and marine sediment cores recovered by expeditions of the Integrated Ocean Drilling Program.
Loess-derived soils, including fertile chernozems and loessial soils, underpin agriculture in regions such as the North China Plain, Midwestern United States, Pannonian Basin, and parts of Argentina. Soil geomorphology and pedogenesis on loess have been the focus of research at FAO, International Maize and Wheat Improvement Center, and national agronomy institutes like Chinese Academy of Agricultural Sciences. Management of loess soils intersects practices promoted by United Nations Environment Programme and regional extension services in Iowa State University and Nanjing Agricultural University to mitigate erosion and sustain crop yields.
Engineering studies highlight loess susceptibility to collapse, subsidence, and piping when wetted, with case studies from Shaanxi Province, Henan Province, Missouri, and Xian informing practice. Geotechnical investigations by firms and agencies including American Society of Civil Engineers, European Geotechnical Society, and national ministries of transport have developed guidelines for foundation design, slope stabilization, and landslide mitigation in loess terrain. Hazards such as gully erosion, dust storms linked to Dust Bowl conditions, and infrastructure failure have driven mitigation programs involving World Bank and national disaster agencies.
Category:Sedimentology