Thick loess deposits in the central U.S.A. often contain incipient soil zones that haveslightly darker color, more clay, and in most cases, stronger soil structure than surroundingunweathered loess. These incipient so...Thick loess deposits in the central U.S.A. often contain incipient soil zones that haveslightly darker color, more clay, and in most cases, stronger soil structure than surroundingunweathered loess. These incipient soil zones can be interpreted as the direct result of warmer orwetter climatic episodes, or as the sedimentary result of changes in local loess deposition rate.High-resolution particle size analyses by laser diffraction support a sedimentary explanation forincipient soil zones in Illinois and Nebraska, U.S.A. The soil zones contain more fine silt and claythan loess above and below. This could have resulted from a temporary reduction in the localloess deposition rate, leading to a greater relative contribution of far-traveled dust that containedmore fine silt and clay.展开更多
文摘Thick loess deposits in the central U.S.A. often contain incipient soil zones that haveslightly darker color, more clay, and in most cases, stronger soil structure than surroundingunweathered loess. These incipient soil zones can be interpreted as the direct result of warmer orwetter climatic episodes, or as the sedimentary result of changes in local loess deposition rate.High-resolution particle size analyses by laser diffraction support a sedimentary explanation forincipient soil zones in Illinois and Nebraska, U.S.A. The soil zones contain more fine silt and claythan loess above and below. This could have resulted from a temporary reduction in the localloess deposition rate, leading to a greater relative contribution of far-traveled dust that containedmore fine silt and clay.
