摘要
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.
Thick loess deposits in the central U.S.A. often contain incipient soil zones that have slightly darker color, more clay, and in most cases, stronger soil structure than surrounding unweathered loess. These incipient soil zones can be interpreted as the direct result of warmer or wetter 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 for incipient soil zones in Illinois and Nebraska, U.S.A. The soil zones contain more fine silt and clay than loess above and below. This could have resulted from a temporary reduction in the local loess deposition rate, leading to a greater relative contribution of far-traveled dust that contained more fine silt and clay.
