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Victoria University Antarctic Research Expedition Science and Logistics Reports 1984-85: VUWAE 29

Programme

Programme

The CIROS programme for 1984 called for the movement of 25 CIROS personnel (Table 1) to Antarctica on WINFLY in late August, opening of the Butter Point camp and setting up of the Longyear 44 rig at CIROS 1 by late September. If CIROS 1 were completed by early November CIROS 2 would be drilled. However, the sea ice in 1984 was thinner and more active than usual (Fig. 3), and active cracks on the supply route were a major problem (Fig. 4). Uncertainty as to the stability of the sea ice, along with the delays already experienced, led to the decision to forego drilling CIROS 1 in 1984 and move to the thicker and more secure ice at CIROS 2 (unpublished
page 4
Figure 2. A. Map of McMurdo Sound area, showing the main physiographic features, the location of MSSTS-1, and deep DVDP drill holes (numbers). X-Y locates the section shown in figure 2B. B. Geologic section across McMurdo Sound (line X-Y in figure 2A). Offshore structure extrapolated from Iles and Dibble (1981) and Wilson et al. (1981). Faulting has been inferred from topography (Webb and Wrenn 1982) but has in places been confirmed by field observations (P.G.Fitzgerald, pers comm).

Figure 2. A. Map of McMurdo Sound area, showing the main physiographic features, the location of MSSTS-1, and deep DVDP drill holes (numbers). X-Y locates the section shown in figure 2B.
B. Geologic section across McMurdo Sound (line X-Y in figure 2A). Offshore structure extrapolated from Iles and Dibble (1981) and Wilson et al. (1981). Faulting has been inferred from topography (Webb and Wrenn 1982) but has in places been confirmed by field observations (P.G.Fitzgerald, pers comm).

Table 1. Drill site personnel for CIROS 1984

Table 1. Drill site personnel for CIROS 1984

page 5 report by P.J. Barrett to the Ross Dependency Research Committee, December 1984). The rig was set up at CIROS 2 by October 10 (Fig. 5) and coring began on October 14. However, 5 of the 14 floats supporting the sea casing collapsed from water pressure causing the casing and drill strings to sag and break at the sea floor. The second coring attempt also ended with a broken drill string, but success was achieved on the third attempt (Fig. 6). Hours after basement was reached 100 knot winds severely damaged most of the drill site buildings and prevented electric logging of the hole. Fortunately the core was undamaged, and arrived at the New Zealand Geological survey's core store in good condition.
Figure 3. Growth is sea ice thickness at CIROS 1 compared with that at nearby DVDP 15 in 1975, a normal year.

Figure 3. Growth is sea ice thickness at CIROS 1 compared with that at nearby DVDP 15 in 1975, a normal year.

The Butter Point camp operated successfully throughout the operation (mid-September to mid-November, 1984). The camp and its operation are described in some detail in the Manager's report (Stephenson, 1985).

NOTE: Regular surveys of the CIROS 1 site from late September to mid-November show that it did indeed freeze 'solid' after the 6 m of movement in early October and remained in place through several major storms (Fig. 7). This shows that the site can be safely occupied at least until mid-November even in a 'thin ice' year. Had this data been available early in the season we would have probably elected to proceed with the drilling of CIROS 1, though the unexpected failure of the floats would have almost certainly led to termination of the hole before target depth.