POTENTIAL OF SURVEYING WORK OF SUBMARINE PIPELINES AND CABLES FOR STUDYING THE LATE QUATERNARY EVOLUTION OF CONTINENTAL SHELVES:

For sustaining the continuous economic growth in the world, the installation of submarine pipelines and cables are needed. In this paper, the potential of using surveying work of submarine pipelines and cables for studying the Late Quaternary evolution of the northern South China Sea continental shelf is highlighted. The surveying work of submarine pipelines and cables commonly involves: (1) Geophysical surveys including side-scan sonar, multi-beam swath mapping and seismic profiling. (2) In-situ cone penetration testing of the strength of seafloor materials. (3) Coring of the seabed using a vibrocorer or gravity corer at ca. 2-km intervals for pipeline surveys and at ca. 10-km intervals for cable surveys. If the seabed is indurated, a grab sampler or a dredge is often used to provide confirmatory information. In the northern South China Sea continental shelf off Hong Kong, the surveying work of a submarine pipeline including vibrocores along a 93-km transect and the surveying work of a submarine cable with gravity cores or grab samples along a 440-km transect were studied. Seismic profiling information was interpreted to provide information on the Holocene-Pleistocene boundary and seafloor areas affected by acoustic turbidity was mapped. The core samples obtained were logged, measured for magnetic susceptibility and sub-samples were taken for radiocarbon dating in order to permit the reconstruction of sea-level position during the post-glacial transgression. A call is made to researchers in different countries to lobby their respective governments to ensure that similar opportunities in other continental shelves are used for undertaking research work. Such work is seen to be needed to throw light on the contribution of sub-aerially exposed continental shelves to the global carbon cycle.