Abstract: Drilling in Antartica

Samuel B. Treves

The Dry Valley Drilling Project (DVDP) is an international program sponsored by Japan (Natl. Inst. of Polar Research and Japanese Antarctic Research Assoc.), New Zealand (Dept. Scientific and Industrial Research-Antarctic Div.), and the United States (Natl. Sci. Foundation, Office of Polar Programs). Its purpose is to drill critical sequences in the McMurdo Sound area to investigate the Cenozoic geologic history of Antarctica. The McMurdo Sound region was chosen for the drilling because several continental and marine environments impinge on each other in the area. Thus it was expected that the cores would record the expansion and contraction of the Antarctic ice cap and, perhaps, even signal the initiation of Antarctic glaciation. Toward this end, 15 holes were drilled ov r four austral summers, from 1972 to 1976. The entire operation was conducted under severe environmental restraints which were enforced by on-site environmental monitors. Postdrilling monitoring will continue for several years.

The first three holes were drilled on Ross Island. The cores consist, primarily, of intermediate, alkaline lava flows, in contrast to the surface units, which are mainly basalt (basanite) and trachyte (phonolite). These flows lie on a thick, hyaloclastite pile. Detailed studies by many investigators indicate that the rocks are mantle derived and that the hyaloclastite pile may record a Cenozoic advance of an ice sheet.

The next 11 holes were drilled in the Dry Valleys, about 70 air-mi (113 km) from McMurdo Station. Supplies, materials, and drilling equipment were moved to the drill sites using tractor trains and helicopters. Drill sites were supported and serviced by helicopters.

Analyses of the cores and data collected during the drilling and subsequent study indicate:

1. Lake Vanda, a deep, chemically and thermally stratified lake, is floored by lacustrine, glacial, and marine sedimentary rocks; the thermal stratification probably is related to solar radiation.

2. Don Juan Pond, which consists of calcium chloride-saturated water, is recharged with fresh ground water that may stem from a sub-ice cap freshwater lake that is near the edge of the polar plateau.

3. The cores from Taylor Valley record a change from a deep fjord environment in middle Miocene time to the present and the record is punctuated by periods of erosion that are related to the expansion and grounding of an ice sheet. The Tertiary rocks of these cores are, in part, correlatable with the DSDP core from site 273A.

The last hole was drilled offshore in water depths of 400 ft (122 m) to sample the thick sediment pile of McMurdo Sound. The drill and camp sites were on the annual ice about 15 mi (24 km) from shore. Drilling was terminated for safety reasons in late November after penetrating about 200 ft (61 m) of basaltic sand.

AAPG Search and Discovery Article #90973©1976-1977 AAPG Distinguished Lectures