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Victoria University Antarctic Research Expedition Science and Logistics Reports 2001-02: VUWAE 46

McMurdo Ice Shelf, Hut Point Peninsula to White Island & Black Island to Brown Peninsula

McMurdo Ice Shelf, Hut Point Peninsula to White Island & Black Island to Brown Peninsula

After 4 days at Scott base re-supplying the drilling team began setting up and test drilling on the ice shelf. The 19km long seismic line was surveyed and shot holes and pegs flagged in stages. Operational drilling was completed between the 2nd and 12th of November. The seismic survey was completed between the 6th and 13th of November. Shot tests were carried out to establish charge size. Although 10 PPP primers were used per shot it was decided that an optimal charge size of 8 primers would be used in future surveys. The coupling of source and receiver was excellent due to extension spikes on geophones and shot placement at 18-20m depth. Source was high-frequency and a high-resolution producing high-frequency record with 5m resolution to 1.5 seconds (see Bannister and Naish, 2002 for details). After a helicopter reconnaissance to locate any crevasses in the study area and establish a safe operating environment, the magnetics and gravity team deployed out to the McMurdo Ice Shelf camp. A local gravity base station was established at the camp and six days of surveying saw a 20km by 20km grid (Fig. 3) of magnetic and gravity measurements. Again, surveying was undertaken during the afternoon to early page 12 morning hours local time. Gravity measurements were much more straightforward as the Ice Shelf provided a very stable surveying platform. The K114 camp was returned to Scott Base by tractor train, and an additional gravity and magnetics survey undertaken over Hut Point peninsula from Scott Base. K114W redeployed to NZ in early December.

On December 30th K114W deployed a second time to undertake a reconnaissance survey of the southern McMurdo Ice Shelf between Black Island and Brown Peninsula, Mount Discovery and Minna Bluff (Fig. 1). A camp and GPS and gravity base station was established on the SW corner of Black Island. Over an 8-day period ice movement was monitored by GPS and a preliminary gravity survey was undertaken by snowmobile. The weather was fine and unseasonably warm and large melt ponds and lakes developed over much of the McMurdo Ice Shelf preventing a complete survey and making travel extremely slow and difficult. Because of this, a few critical additional gravity measurements were made later in January from helicopter. From January 12th, K114D began the aeromagnetic survey as outlined above. Survey flights were undertaken in the evening and early morning hours, the window of stable ambient magnetic field behaviour was between 4pm and 2 am local time. Flying began as soon as the helicopter had completed its daytime flying often this was quite late (7-9pm) which sometimes only allowed a single flight each night. The survey flights departed and returned to the McMurdo helicopter pad and required hand launching and catching of the magnetometer "bird" beneath the helicopter. In late January, unusual weather including low cloud cover and ice shelf fog prevented flying on many occasions. The survey was delayed and not completed until January 30th. Navigational GPS data was hand entered by the pilot for each day which was time consuming. A more streamlined system needs to be employed for and future helicopter-borne aeromagnetic surveys.