CIROS Project: Obtaining Cenozoic history of the Ross Sea by coring sedimentary strata offshore

The CIROS (Cenozoic Investigation in the Western Ross Sea) drilling project was conducted to obtain a record of the early history of the Antarctic Ice Sheet and the rise of the Transantarctic Mountains. The strata beneath the floor of McMurdo Sound was cored to record the major glacial advances and retreats and to find out when they began. The core was expected to show evidence of the uplift history of the Transantarctic Mountains also. Two cores were obtained, CIROS-1 and CIROS-2. The CIROS-2 core was obtained in the 1984-85 season and was drilled first due to the sea ice conditions at the time. The drill site was situated 3km from the north wall of Ferrar Valley, 1.2km east of the Ferrar Glacier Tongue snout. One hole was drilled near the middle of Ferrar Fjord, western McMurdo Sound in 211m of water through 165.5m of sediment into basement gneiss, with a 67% core recovery. The CIROS-1 drill site was situated 12km off Butter Point in western McMurdo Sound. The core was drilled in the 1986-87 season to 702 m below the sea floor in marine glacial strata dating back to the early Oligoscene. The core was continuously cored from 27 m below sea floor to 702 m, with over 98% recovery. Once coring ended, the hole was logged with several probes recording various properties such as density, natural radioactivity and temperature. The core was analysed by several contributing scientists for paleomagnetic stratigraphy, diatom assemblages, radiometric dating of basaltic material, etc.