Seasonal Changes in Magnetic Properties of Surficial Tidal Flat Sediment and Their Response to Sedimentation Dynamics: a case study from the coast of the Hangzhou Bay

Key words: 
• sediment /
• magnetic properties /
• sedimentation dynamics /
• tidal flat /
• Hangzhou Bay

Abstract: This study discussed the monthly variations of magnetic properties of surface intertidal sediments along the northern bank of the Hangzhou Bay and their response to sedimentation dynamics. Fortynine surface sediment samples were collected at a fixed sampling site in the middle tidal flat from September 2004 to August 2005. The results indicate that magnetic properties of surface sediments vary significantly with month. From late December of 2004 to early May of 2005, the values of SIRM, χARM, χfd%, χARM/χ and χARM/SIRM in surface sediments are relatively higher, suggesting higher concentration of ferrimagnetic minerals with finer grain size. Samples with such magnetic properties occur in the period of tidal flat accretion with a finer sediment particle size composition. For samples from the remaining months, the above magnetic parameters have lower values, corresponding to a period of tidal flat erosion with a coarse particle size composition. Therefore, magnetic properties of surface sediments can reflect the changes in sedimentation dynamics during the process of tidal flat accretionerosion cycle.