Southern McMurdo Sound Project Underway

SMS LogoDuring the austral summer of 2007 the ANDRILL Program is drilling from a sea-ice platform in Southern McMurdo Sound to obtain new information about the Neogene Antarctic cryosphere and evolution of Antarctic rift basins. A team of more than 56 on-ice scientists, engineers, technicians, students and educators are engaged in the recovery and study of sediment and rock cores recovered by drilling below the seafloor from a sea-ice platform supporting the drill rig and field camp. Additional work to characterize these cores is conducted by the ANDRILL team in the Crary Laboratory of McMurdo Station, and by groups of collaborators off-ice, working in their home institutions.

Target strata for the SMS Project are middle Miocene to Quaternary in age (~17 Ma to present) and span several key steps in the evolution of Antarctic climate. The key aim of the SMS Project is to establish a robust history of the Neogene Antarctic ice sheet variation and climate evolution that can be integrated into continental and global records toward a better understanding of Antarctica’s role in the past, present and future global system. To achieve this aim, one drillhole (>1000 m) will sample a sequence of strata identified on seismic lines and inferred to represent a lower Miocene and younger sequence of seismic units that expand basin-ward.

The recovery of lower to middle Miocene Antarctic stratigraphic sequences is required to evaluate the history derived from global proxy records that invoke a change from a warm climate optimum (~16 Ma) to the onset of major cooling (~14 Ma) and the formation of a quasi-permanent ice sheet on East Antarctica. Secondary target strata of the Pliocene and Pleistocene age from a distal marine setting will complement and build on coastal and fjord sediment records from Dry Valley Drilling Project (DVDP) Sites 10 and 11, and CIROS-2 drillcores that are interpreted to reflect repeated Late Neogene alternation between ‘interglacial’ and ‘glacial’ conditions.

The paleoclimatic, paleoceanographic, and tectonic objectives of the SMS project are to:

  • Document the initial onset and subsequent history of sea-ice presence/absence
  • Document the evolution and demise of Neogene terrestrial vegetation
  • Establish a local Late Neogene sea-level record
  • Test whether stable cold-polar climate conditions persisted for the last 15 m.y.
  • Document melt-water discharge events from the adjacent Dry Valley/Transantarctic Mountain (TAM) system
  • Construct a composite event history of glacial and interglacial events across a coastal to deep basin transect
  • Provide chronostratigraphic control for the regional seismic framework in the western Ross Sea
  • Develop provenance and exhumation proxies within Neogene sediment from the Transantarctic Mountains
  • Document and describe the regional stress regime

Several distinct seismic packages have been identified from previous studies in the Victoria Land Basin. These units are separated by distinct seismic reflection surfaces, three of which appear to be regional erosional surfaces. The SMS site can be correlated to the grid of seismic lines in the Victoria Land Basin; therefore, the recovered sections will provide excellent chronostratigraphic control for regional seismic surfaces and units important for interpreting regional stratal architecture and for dating Neogene and younger subsidence and rift fault history.

The Southern McMurdo Sound Project (SMS) drillcore will also record a tectonic history of the Antarctic Rift system (Victoria Land Basin), the Transantarctic Mountains and the Erebus Volcanic Province. Fault- and flexure-related subsidence associated with rifting and volcanic loading has provided accommodation space adjacent to the rising Transantarctic Mountains. This basin preserves a sediment history of this important region, which is also influenced by three significant components of the Antarctic cryospheric system: the East Antarctic Ice Sheet (EAIS), Ross Ice Shelf (RIS)/ West Antarctic Ice Sheet (WAIS), and the Ross Embayment sea-ice.