The Magnetic Susceptibility Characteristics Of Aeolian Deposit In South China And Its Environmental Significance

(1) The content of magnetic minerals is very different among three types of eolian sediments. Weathering crust red earth contain the most ferromagnetic minerals, sedimentary red earth take the second place, aeolian sand contain the least ferromagnetic minerals. The average content of antiferromagnetic mineral is: sedimentary red earth> weathering crust red earth> aeolian sand. The ferromagnetic minerals changes with maximum range in different layer of sedimentary red earth, weathering crust red earth take the second place, the changes of ferromagnetic minerals among the layer of aeolian sand are slightly.(2) The grain size of magnetic minerals changes with the sediment types. The grain size of magnetic minerals in sedimentary red earth is coarser than the grain size of magnetic minerals in aeolian sand and weathering crust red earth. Grain size of magnetic minerals in Xiashu Loess is between the grain size of sedimentary red earth and aeolian sand. The main grain size of sedimentary red earth, aeolian sand and weathering crust red earth, Xiashu Loess are MD-PSD, SD-SP and SSD. Grain size of magnetic minerals in aeolian sand of different locations shows little difference, grain size of magnetic minerals in sedimentary red earth and red earth developed of different locations have significant difference, grain size of magnetic minerals in Xiashu Loess is similar with the grain size of magnetic minerals in sedimentary red earth.(3) Magnetic minerals are similar in different types of eolian sediments. The main magnetic mineral in sedimentary red earth, aeolian sand and weathering crust red earth is ferromagnetic minerals, secondly for antiferromagnetic minerals. In aeolian red earth, homogeneous red earth and yellow-brown earth mainly containing ferromagnetic minerals, vermicular red soil usually contain more antiferromagnetic minerals. Ferromagnetic minerals are dominant in both Xiashu Loess and yellow-brown earth.(4) Magnetic minerals in sedimentary red earth are mostly distributed in coarse clay and silt (2μm-32μm); in weathering crust red earth magnetic minerals are well distributed; magnetic minerals in eolian sediments enriched in medium grained sand and coarse grained sand (250μm-1000μm). The distribution of magnetic minerals positively correlated with the grain size of sediments.(5) The magnetic characteristics of sediments show obviously zonal distribution. With the decreasing of latitude, magnetic minerals, SP and grain size of magnetic minerals increased. It indicate that in southern China the water and heat condition in south is better than the water and heat condition in north, and the pedogenesis in south is stronger than north, sedimentary environment in south is much more complicated.