SMS On-Ice Report #5 - Nov. 19, 2007

November 19, 2007

This week started with the drill bit at a depth of 669.74 meters below sea-floor (mbsf). Core recovery continues to be excellent, usually above 98%. The core displays alternating diamictite with intervening muddy sandstone with variable clasts and interlaminated facies. Macrofossils are sparse (mollusk shells and serpulid worm fragments) and diatoms continue to be present through this depth, their preservation is perhaps aided by silica from encompassing volcanic-rich sediments. Two horizons of c. 2-3 cm-thick pumice lapilli erupted from local volcanoes may be excellent sources of radiogenic ages to help date the SMS core. We anticipate that drilling will continue with the HQ size drill-string until approximately 21 November when the geophysical logging team will then begin their downhole data collection activities. At the end of nightshift, November 19, the HQ drill bit is at 931.16 mbsf.

Dry Valley area
Dry Valley area and Transantarctic Mountains in relation to the SMS drillsite. (Image by Robert Simmon, based on data provided by the NASA GSFC Oceans and Ice Branch and the Landsat 7 Science Team)

 

On November 13 and 14, geological field trips provided many SMS scientists with an opportunity to become familiar with local geology of the Dry Valley Region of the Transantarctic Mountians (see figure), where most of the sediments recovered in the SMS core were sourced. Co-chief Harwood and seven SMS science team members visited Taylor Valley (discovered by the explorer Robert Falcon Scott in 1903); Scott Ishman and seven SMS science team members visited Wright Valley. Direct knowledge of Dry Valley geology will help ANDRILL scientists understand paleoenvironmental changes, especially those associated with late Miocene and Pliocene marine sediments deposited when Wright and Taylor valleys were ice-free marine fjords, and help recognize coeval evidence in the ANDRILL MIS and SMS Project cores.

On Sunday November 18, the SMS team organised a very successful ANDRILL Open House in the Crary Lab of McMurdo Station. This was a nice opportunity for the McMurdo and Scott Base communities to learn what we do and what we are discovering in the sediment cores. During the two-hour tours, attendees handled drilling equipment and bits, visited the core splitting and imaging facilities, then admired some of the actual cores. Sedimentologists and paleontologists told tales of geological events and times long since past, and told a paleoclimate and paleoenvironmental history of the SMS Project site, as ‘read from the rocks’. The final stop provided an opportunity to move about different stations, work as scientists using microscopes and other equipment to learn about the scientific analyses done on-ice.

Hard at work
Cleaning a new core just received in the drillsite science labs (photo: L. Reichelt).

 

During the week between November 12 to 18, several media events visited the teams working at the drillsite and Crary Lab in McMurdo Station to learn about ANDRILL activities. These included: (1) the Nebraska Educational Telecommunications NET and WGBH Boston - NOVA film crew, led by Gary Hochman, who will produce a documentary, Antarctica’s Icy Secrets, to provide ANDRILL’s geological perspective on how Antarctica played, and will play, a major role in affecting global climate, ocean currents and sea-level; (2) Moira Rankin of Soundprint Media Center, who will collaborate with four international polar research partners to produce IPY: Pole to Pole, a multi-part radio series with documentaries, short radio features, oral histories (other collaborating partners include Australian Broadcasting Co.; BBC World Service, Radio Deustche-Welle, and Radio New Zealand); (3) Simon Lamb and David Sington, who will produce a documentary on climate change, The Tipping Point, to document climate change issues through the eyes and words of a diverse group of scientists, engineers, politicians, community leaders, and activists; (4) Italian photojournalist Lucia Simion, who plans to produce articles and photojournalistic essays regarding the ANDRILL Program and SMS Project research; (5) New Zealand photojournalist Mike Scott, who reported on the ANDRILL Program in the Taranaki Daily News; Doug Fox, a freelance science reporter; and (6) Megan Berg of Megan Berg Designs, who is contacted by the ANDRILL Science Management Office to produce original education and outreach materials, including six videos and supporting educational materials, and to maintain ANDRILL’s Project Iceberg website.

We are pleased to welcome Professor Peter-N. Webb of The Ohio State University back to Antarctica and into the fold of the SMS Science Team. Peter was a member of the first geological field party in the Dry Valleys fifty years ago, as part of the International Geophysical Year in 1957-58, and was a key leader in advancing prior scientific drilling activities in the McMurdo sound region. He provides a valuable perspective from where we have come, and prompts good questions we should be developing regarding the recovered core.

In celebration of drilling to a depth of 500 mbsf, one-half of the drilling target depth for the SMS Project, members of the science team held a festive march and parade - - the UNDRILL 500 - - over a distance of 500 meters (below). The spirit in the team remains high!

UNDRILL 500
Celebratory parade of the UNDRILL 500 (photo: S. Nielsen).

 

A Pebble's Story

Granite Boulder
Image of sediment core that drilled through
a boulder of granite that was larger than the
drillbit (photo from the SMS digital data files).

When the ANDRILL drilling bit cores deeply through the sedimentary section in central McMurdo Sound, it cuts through many types of rocks. Most of these rocks are derived from the Transantarctic Mountains and local volcanoes. To date, more than 40,000 pebbles, stones and “clasts” (pieces of pre-existing rocks) ranging in size from granule to boulders are dispersed throughout the sedimentary succession recovered by the SMS cores. These have been identified and their position recorded. These clasts of volcanic, sedimentary, igneous rocks, etc., have been described by the science team. Each individual clast can tell us a fascinating story, from origin, through erosion, transporation, modification, alteration, to eventual recovery by the ANDRILL drilling system. The story of any given pebble may go in time several hundred million years. Among these, granite pebbles (see figure) tell their histoy; originally part of a magma that slowly cooled (crystallization) in a very deep seated magmatic chamber, within the upper continental crust (usually greater than 2 km and up to 20 km depth). The cooling of this granite body was sufficiently slow to allow crystals in the granite the time to grow up to a centimeter and larger scale. Emplacement of these granitoid rocks was then followed, many millions of years later by a regional uplift and denudation. Portions of these rocks, exposed extensively along the coastal strip of the Transantarctic Mountains sector inland from SMS drillsite, were successively eroded by ancestral glaciers, transported offshore in icebergs or beneath the ice sheet, rounded and reduced in size, and deposited at the SMS Project site, perhaps falling from an iceberg through the ocean. The last stage of this pebble’s story involves being cut into a narrow cylinder by a rotating pipe, the end of which was studded with industrial diamonds (the drill bit), and brought from great depth to the drilling rig floor on the surface of floating sea-ice. ANDRILL scientists are eager to examine this pebble’s physical shape, orientation, surface features, density, geochemical composition, mineralogy, and any other physical and chemical properties, so that its unique story can be told.

That’s the low down on ANDRILL’s drilling success, and various elements of our research and outreach activities.
Keep watching this space, and please visit http://andrill.org/iceberg.

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