Previous   |    Next

doi:10.2204/iodp.proc.325.102.2011

Specialist sampling of massive corals

Identification of massive corals

Massive corals suitable for paleoclimatic studies were visually identified in core sections through the transparent liners and from descriptions contained in the offshore visual core descriptions prior to core splitting. Those core sections containing massive corals longer than the core diameter (or shorter but apparently in good condition) were labeled prior to core splitting to prevent them from being split using the regular core-splitting procedure. The major goal was to recover pristine, long, continuous intervals of coral skeletons from individual colonies along the major axis of growth. The regular core-splitting procedure does not take into account the major growth direction of coral colonies. The core axis, or holes within a colony as a result of bioerosion, can be different from the major growth direction and can interrupt an otherwise continuous interval of the coral skeleton. Therefore, having obtained permission from the Curatorial Advisory Board, the liner was split for core sections containing massive corals using a handheld electric saw. One half of the liner was removed, and photographs of the colonies in situ within the core were taken for reference. With the core open, a coral paleoclimate specialist examined the section of coral and identified the optimum axis and plane for cutting. This axis was marked on the coral with a red wax pencil, and the core was then rephotographed with the coral thus marked.

Splitting of massive corals

After photographs were taken, massive corals were removed from the core liner and split along the plane of the corals’ major growth direction using a rock saw with a 1 mm thick blade and tap water. This often resulted in two unequal parts, so the procedure outlined in Figure F17 was followed to preserve 50% of the core volume for the archive half. One part was declared to be the archive half of the coral colony and the other the working half. The parts of the core not containing any coral colonies were then cut in half using the regular core-splitting method, and the archive and working halves were placed in their respective D-tubes. Once the working half of the core reached the sampling table, a 0.8–1 cm thick slab was cut from the coral colony for paleoclimate studies. A second slab was cut from the working half for other purposes, including dating or geochemical studies. In cases where the second slab appeared to provide the better sample, it was selected for paleoclimate studies and the central slab was used for other purposes. The orientation of all samples was recorded on the outside of the coral slabs using a red wax pencil (arrow pointing toward the top of the core). Note that this arrow records orientation in the core and does not necessarily reflect the original growth direction (which was annotated on the visual core descriptions).

Washing and drying of massive coral slabs for aleoclimatology

After slicing, coral slabs for paleoclimate studies were jet-washed with tap water (tap pressure focused using a nozzle) and dried at 40°C in an oven for ~12–24 h.

Top of page   |    Previous   |    Next