Core handling |
In the case of cores collected in metal tubes with plastic liners, the liner containing the sediment sample is usually removed from the bottom end after taking off the nose piece or cutter. Ideally this can be done without laying the tube down since the upper tube may contain a layer of water which -- when horizontal -- will mix with sediment and destroy some of the core's integrity. Inconveniently, a 20 ft. liner being removed from a 20 ft. tube briefly creates a 40 ft. tall item! With a short lift tower over shallow water that can be a problem. Unlined tubes are simpler to handle, especially if clear plastic tubes are used. First, the retrieved core tube is capped and taped securely at the bottom end while still vertical. In the clear tube, the sediment- water interface is visible, and a small hole can be drilled just above it to drain off the excess water. Then the tube is cut and capped at its upper end. At that stage the core can be laid down and transported without disturbing the contents greatly. Key information (station, date, time, length, etc.) can be written with a permanent marker on the top cap. The bottom end of the core still contains the catcher fastened inside it, and so is always recognizable. Sealed cores prior to processing should always be maintained at original or lower temperatures to prevent expansion and leakage from the capped ends. |
