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Victoria University Antarctic Research Expedition Science and Logistics Reports 1979-80: VUWAE 24

Onsite handling and description of core (ARP)

Onsite handling and description of core (ARP)

The procedure for extracting core from the core tube varied depending on the core size being drilled. HQ core (dia. ≈ 63 mm) was recovered in a split tube ("splits") within the core tube. The 10 foot long splits containing core were hydraulically extracted from the tube and transferred intact and unfrozen onto the specially constructed bench in the Science Hut. The smaller sized NQ & BQ core tubes did not have splits. Core therefore was directly removed from the tube onto an HQ 'split' by gently tapping the tube and extruding the core with a steel rod. Often the tube had to be heated in a "Herman Nelson" hot air hose to unfreeze water surrounding the core before extraction could proceed. NQ & BQ cores therefore suffered some sub-horizontal fracturing resulting from core extraction. These fractures, however, were fresh and easily distinguished from natural fracturing within the core. Boxing, initial examination and description was done on the unfrozen core in the Science Hut.

The primary purpose of the onsite description was to record as accurately as possible the depth from which core was recovered and any features which might be changed by freezing and transportation to the core lab.

Information from the driller often enabled a more accurate determination of from where core was recovered during the coring run. This was particularly important when recovery was less than 100%. The position of core recovery was shown at the graphic log, a double line being used to indicate the bottom depth of the run when the run was not the full 10 feet. When doubt existed about the exact depth of "the core, it was assumed to have come from the top of the run.

Fracturing was noted on the graphic log and where possible determined as natural or induced from drilling and core extraction. Some mudstone lithologies initially recored and intact cylindrical blocks suffered extensive conchoidal fractures on subsequent freezing.

The colour of the core was compared with the "Revised Standard Soil Colour Charts" (Japan). Bioturbation and bedding was often most easily seen when the core was fresh and wet.