摘要
Based on detailed rock magnetic measurements like magnetic susceptibility versus high/low temperature curves,thermal demagnetization curve,hysteresis loops and FORC diagrams,the authors have investigated the magnetic properties of Heqing core lacustrine sediments.Rock magnetic measurements revealed that magnetite was the dominant magnetic mineral in the upper section while SD greigite and PSD magnetite dominated the magnetic property in the lower section.Greigite which presented in lower section(before 1.8 Ma)had an octahedrite crystal and displayed SD magnetic behavior.The maximal diameter of this large grained autogenetic greigite could achieve about 2 μm.The strong post-depositional diagenesis indicated that the paleolake before 1.8 Ma in Heqing Basin would have deep water,and climate here would be suitable.