Abstract

CIROS-1, sited 12 km off Butter Point in western McMurdo Sound (Lat 77° 34′55″; Long 164° 29′55″), was successfully drilled to a depth of 702 m below the sea floor in marine glacial strata dating back to the early Oligocene (based on a preliminary study of foraminifera). The continuous nature of the core makes it an excellent record of glacial advances and retreats and will make it easier to date using microfossils and paleomagnetic stratigraphy.

The core also records changes in sand and pebble composition that reflect the progressive erosion of the Transantarctic Mountains. The abundance of coaly fragments and the dolerite boulders near the bottom of the hole suggest proximity to local bedrock of Permian coal measures intruded by Jurassic dolerite.

An asphaltic residue was found in sand 632 m down the hole. It indicates that petroleum has been generated in the Victoria Land Basin, and at this site was trapped but later released naturally.