Loess

A few links for the area around here ..enjoy

for-natchez.org/loess.html
www.exploresouthernhistory.com/natchezloess.html
www.natcheztracetravel.com/natchez-trace-mississippi/lorman-natchez-ms/192-loess-bluff.html

Mystery Solved.

www.sciencedirect.com/topics/earth-and-planetary-sciences/loess



Distribution

Loess covers approximately 10% of the earth's land surface (Figure 1) and is generally associated with semiarid to semihumid climate regimes. The thickest deposits are found in China, where approximately 500 000 km2 is blanketed by loess that is up to 300 m thick. The Great Plains has the largest area of loess in North America. Loess there can be more than 60 m thick. Other loess deposits include the Pampas of Argentina, parts of Europe, the Ukraine, large areas in central Asia, the Palouse and Snake River Plain of the US Pacific Northwest (PNW US), parts of Alaska, and parts of northern Africa. Thinner and less extensive deposits are found worldwide.



Loess in the Quaternary

Loess occupies large areas of China, Central Asia, Russia, Europe, Argentina, New Zealand, and North America. Most loess is concentrated in mid-latitude regions (Figure 5), and its texture and mineralogy make it one of the most favorable parent materials for agricultural soils. Indeed, loess-derived soils produce crops that support literally millions of people in Asia, South America, North America, and Europe. Loess is dominated by silt-sized particles (50–2 μm diameter), although most loess contains smaller amounts of sand and clay. This particle size distribution, along with slight carbonate cementation, produces interparticle binding that makes loess stand in vertical bluffs in exposures



The importance of loess in Quaternary studies is that it is one of the few terrestrial deposits that may contain nearly complete records of glacial–interglacial cycles. A classical model of loess is that it forms primarily during glacial periods, when continental ice sheets or valley glaciers produce silt-sized rock ‘flour’ by grinding. This silt is in turn transported and sorted by fluvial processes as outwash, deposited on floodplains, and ultimately entrained by the wind. It is now also known that nonglacial processes also produce silt-sized particles. Nevertheless, even in areas known to contain nonglacial loess, it appears that the most favorable times for loess entrainment, transportation, and deposition are during glacial periods. Mahowald et al. (1999) have pointed out several factors, including generally drier climates, decreased vegetation cover, stronger winds, and a decreased intensity of the hydrological cycle, that enhance loess and dust transport during glacial periods. The latter factor can account for loess or finer grained dust staying in suspension longer than is the case under nonglacial climates. Thus, Quaternary stratigraphic studies have shown that loess is characteristic of glacial periods in most regions



It is laid down over many years.