This is a good time to provide an update on the status of Dr. Marchant’s field work for this field season. In addition to the team’s ongoing research on late Cenozoic climate change, Dr Marchant wanted to reach two specific drilling goals this drilling season: (1) drill to 20 m in 3 locations; and (2) test the new ICDS (Ice Core Drilling Services) drill.
The drilling began at Site 1 in Mullins Valley where the team surpassed the goal depth of 20 m and drilled to 23 m.
Base map provided by J Walker RPSC 29 November 2006
The drilling was relatively easy because at this site the ice is clean. Dave explained that the glacier contains scattered debris further down glacier (sites 2 and 3). The debris is a mixture of rockfall and sand veins, the latter being the vertical extension of sand filled cracks associated with polygons on the ground surface.
This is an aerial view of polygons taken from the helicopter.
Sand veins truncate glacier ice beneath each of the these polygon troughs.
I joined the team at Site 2 in Beacon Valley. The team reached a depth of 4 m and hit ice cement - the drilling name for ice-cemented sand veins. After several unsuccessful attempts to penetrate through the ice cement, the decision was made to abandon the hole and move to Site 3 located approximately 30 m south of Site 2.
These ice cemented sand veins in glacier ice are the vertical extension of polygons on the ground surface.
The team had reached a depth of 8 m on Monday, November 24, 2008 at which time drilling stopped due to equipment failure. This required Tanner Kuhl, the driller, to go to McMurdo to have the equipment repaired. The weather took a turn for the worst in McMurdo, and Tanner did not return to Beacon Valley Camp until Monday December 1, 2008.
Notice that the ice is clear and does not contain rocks or debris. Image credit: David Marchant.
Photograph of Drilling Site 2 in Beacon Valley. Image credit: David Marchant.
Notice the sand debris mixed in with the ice. Image credit: David Marchant.
This ice is clear like the ice at Site 1. Notice the gas bubbles. Image Credit: David Marchant.
Dr. Marchant also excavated numerous soil pits down to the ice in preparation for additional drilling. In one pit he uncovered a volcanic ash layer directly on top of cobble-rich ice (the cobbles represent an ancient rock fall onto the glacier accumulation zone). Based on Dave's past research, the gray volcanic ash at the site is probably around 4 million years old, providing a minimum age for underlying ice. Dave and the team need to drill down though this rocky ice layer to get to pristine glacier ice. This will be the hardest test of the season.
Dave cleans the ice surface in the soil pit in preparation for drilling
Dave collects ash from the soil pit.
Dave and the team take very detailed field notes and review them at the end of each day.
Dave explains the complexity of the area to Jackie Hams. Image Credit: Sean Mackay.