Spatial variation of sediment components in the marine deposits of Hong Kong

The continental shelf of Hong Kong is generally less than 25m deep and is characterized by an extensive blanket marine mud, interrupted locally by sandier deposits associated with tidal channels and areas exposed to high wave energy. The mud blanket is often considered to be uniform in its sedimentology. However, this study has shown that there are distinct, though often subtle, variations in composition and sedimentation rates. Organic matter ranges between 2 and 32%, with most samples containing between 5 and 15%. Carbonate generally comprises 2-25% of the mud, though local coquinas also occur. Biogenic silica is a minor component, with diatoms and sponge spicules dominating. Species diversity and abundance show clear spatial variation. Particle size trends are subtle but distinct. Sedimentation rates reported here range between 0.17 and 0.51cm/a. Attempts to date sediments failed in western Hong Kong, possibly because of bioturbation effects.