Volume 18, Issue 47 (4-2007)
Abstract
A controversy in theories of loess formation is the origin of silt-size quartz grains which forms a large part of loess deposits. Glacial and eolian abrasion, physical and chemical weathering, volcanism and alluvial processes all can produce a large quantity of silt-size quartz grain. Also many controversies still exit about the origin of loess sediments of the world. By investigation of quartz grains surface texture, the contribution of different environments in giving silt for these deposits can be evaluated which can help in finding the source of these sediments. Therefore, in this research, surface texture of quartz grains in 105-350 and 75-105 sizes of serve loess outcrops in Golestan Province were studied by binocular and Scanning Electron Microscope (SEM) and major and minor environments in producing silts were evaluated. Surface texture types on quartz grains are as follows: conchoidal, parallel, sub-parallel and stepwise fractures and sharp and angular relief. In the other hand, in some regions, surface textures are of irregular solution cavities and rounded grains are found. It is concluded that glacial processes are the main silt-producing mechanism for Golestan Loess Deposits and fluvial and chemical weathering are less important mechanisms.
