干旱区生态环境知识资源中心

Teri sands from the southeast coast of Tamil Nadu were examined by magnetic methods, including magnetic susceptibility measurements, acquisition of isothermal remanent magnetization, and geochemistry. Four sections were excavated up to 5-7m with three inland deposits (KCV, SKM and TPV) and one near coastal (THOP). Magnetic parameters show the important contribution of hematite structures to the studied sands, namely in SKM and KCV samples. In TPV and THOP samples, magnetic parameters indicate the presence of multidomain magnetite or mixed mineral contents of magnetite and antiferromagnetic minerals. SKM samples present the highest quantity of hematite and smallest quantity of magnetite, as is shown by the highest values of HIRM% and smallest of S-300 and SIRM. The positive correlation between chi with clay in TPV, THOP and KCV sections indicates that the clay matrix carries magnetic susceptibility. In SKM, magnetic susceptibility is due to the silt fraction. Presence of magnetite in THOP and TPV sections is probably of oceanic origin carried by strong offshore winds. In SKM the wet environments due to cultivation (associated with a arid climate) may contribute to the prevalence of the necessary conditions for the dominant presence of hematite.