SMS On-Ice Report #6 - Nov. 26, 2007

November 26, 2007

The drilling team drilled down across the 1,000 meter depth mark on 21 November and completed coring with the HQ size drilling string (the middle-size drill pipe; diameter 6.12 cm) to a depth of 1011.08 meters. Core recovery continues to be very high, up to 98% of the cored interval! There is a lot of core to describe, sample and curate, and it just keeps coming up.

Emperors at drill site
Emperor penguins pay a visit to the drill site (photo: C. Millan)

 

Scientists at the drillsite (above) and in the Crary Lab of McMurdo Station are studying the cored sedimentary rocks very closely. However, at this depth we decided to shift gears and begin another stage of the planned ANDRILL research program, the process of downhole logging, and studying the geophysical properties of the rocks still inside the drillhole. This is accomplished by lowering many different tools and remote probes to the bottom of the borehole. These are then slowly raised to the surface while they record different physical properties such as density, magnetic susceptibility, gamma ray, sonic velocity, etc. These measurements are important to relate the sedimentary core. A camera is also lowered through the hole, to take a continuous, detailed and oriented picture of the borehole from the inside. The downhole logging program continued for several days and finished on 26th November.

Drill rig and science labs from helo
Drilling rig and drillsite science labs (photo: T. Cully)

 

Coring is now ready to start again, but with the smaller NQ-size drill string (diameter 4.5 cm), which fits inside the HQ pipe. We will continue drilling until time runs out. At the start of the project the scientists guessed what the total depth would be when we had to stop drilling. We plan to drill for another week and then start another phase of downhole measurements before we have to pack up the drill-rig, drill-camp and drillsite science laboratories (above) and bring them back to Scott Base and McMurdo Station where they will be stored for future ANDRILL projects.

Pumice height=
Layers of pumice recovered in the ANDRILL
core will help determine the age of the enclosing
sediments (photo: ANDRILL digital archives)

We recently encountered several large pieces of pumice (see figure), a type of glassy volcanic rock that has a lot of air trapped inside. These volcanic rocks will help the geologists determine the age of the sediments, so that we can interpret the timing of climate change events we are seeing in the core. Samples of these and other volcanic-rich layers will be sent to ANDRILL scientists in Italy, who will determine their ages and send results back to us in Antarctica. The age of the rocks can also be determined by studying the fossil remains of microscopic diatoms, one-celled algae that produce a glassy cell wall, which is preserved in the sediments. In addition to the studies done in Antarctica, ANDRILL scientists are also working in New Zealand, in Italy and in the United States on samples sent to them to measure the magnetic properties in the sediments that can also help assign geological ages to the cores. From these approaches we know that we have hit our geological target of the warm middle Miocene, between 14.5 to 18 million years ago.

Core techs at work
Core Technicians David Witkowski and Laura Haffert preparing new core for study in the drillsite science laboratory (photo: T. Falconer)

 

During the early morning of 26 November, drilling activities started again and we continue to recover core down to 1,017 meters below the sea floor. Science team members continue to study the core, but have also started to write reports on their findings. We will produce an ‘On-Ice Report’ before we leave Antarctica, which will grow and mature into an ‘Initial Report’ which we will publish later in 2008. This is the start of a long process to report our success and discoveries to other scientists around the world. The research we do now is for initial characterization of the core, detailed scientific study will continue for the next two years (!) and into the future.

David Harwood and Fabio Florindo
Co-Chief Scientists for SMS Project