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A magnetic property study was conducted for a high-sedimentation rate core YZ-1, which was drilled from the Yangtze Delta. Magnetic property analysis on this core was made for generating high-resolution information of the paleoenvironment during the late Pleistocene. This work may help us to advance our understanding for the short-period change of climate.
High and low frequency susceptibility (χ), Natural Remanent Magnetization (NRM), Anhysteretic Remanent Magnetization (ARM), Isothermal Remanent Magnetization (IRM), Saturate Isothermal Remanent Magnetization (SIRM) and Isothermal Remanent Magnetization caused by reversing 300mT magnetization were measured. These magnetic parameters can be used for calculating other useful indices such as frequency dependent susceptibility, relative intensity of paleomagnetization and S-ratio. These magnetic parameters provide us more information about the composition, grain size and quantity of magnetic minerals in the core sample.
Based on the result of the analysis for the record, we found that the magnetic susceptibility is relatively high during the late Pleistocene. We suggest four possible processes to cause the high susceptibility: (1)the layers of stiff muds deposits in the Yangtze Delta; (2)more eolian sediment deposit during the cold period; (3)the compaction of sediment by pedogenesis; (4)the concentration of magnetic minerals by increased bacterial activity during the soil-forming processes.
The change of magnetic properties during Holocene seems to be associated with the climate change. Three high susceptibility intervals can be correlated with cold periods of climate. Major regressions which indicated by the foraminifer fossil assemblages are also synchronous with the low S-ratio. These relationships suggest that the magnetic properties of the core are controlled by the climate change, and also related to the sea level change in the Yangtze Delta region.
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