Bücker, CJ et al. (2001): Geophysical logging on sediment core and hole CRP-3 from the Ross Sea, Antarctica. doi:10.1594/PANGAEA.510759, Supplement to:Bücker, Christian J; Jarrard, Richard D; Wonik, Thomas (2001): Downhole temperature, radiogenic heat production, and heat flow from the CRP-3 drillhole, Victoria Land Basin, Antarctica. Terra Antartica, 8(3), 151-160, hdl:10013/epic.28281.d001
Cape Roberts drillhole CRP-3 in the northern part of McMurdo Sound (Ross Sea, Antarctica) targeted the western margin of the Victoria Land basin to investigate Neogene to Palaeogene climatic and tectonic history by obtaining continuous core and downhole logs (Cape Roberts Science Team, 2000). The CRP-3 drillhole extended to 939.42 mbsf (meters below seafloor) at a water depth of 297 m. The first downhole measurements after drilling were the temperature and salinity logs. Both were measured at the beginning and at the end of each of the three logging phases. Although an equilibrium temperature state may not have been fully reached after drilling, the temperature and salinity profiles seem to be scarcely disturbed. The average overall temperature gradient calculated from all temperature measurements is 28.5 K/km; remarkably lower than the temperature gradients found in other boreholes in the western Ross See and the Transantarctic Mountains.
Anomalies in the salinity profiles at the beginning of each logging phase were no longer present at the end of the corresponding logging phase. This pattern indicates that drilling mud invaded the formation during drilling operations and flowed back into the borehole after drilling ceased. Thus, zones of temperature and salinity anomalies identify permeable zones in the formation and may be pathways for fluid flow. Radiogenic heat production, calculated from the radionuclide contents, is relatively low, with average values between 0.5 and 1.0 pW/m3. The highest values (up to 2 µW/m3) were obtained for the lower part of the Beacon Sandstone below 855 mbsf. The heat flow component due to radiogenic heat production integrated over the entire borehole is 0.7 mW/m2. Thermal conductivities range from 1.3 to 3 W/mK with an average value of 2.1 W/mK over the Tertiary section. Together with the average temperature gradient of 28.5 K/km this yields an average heat flow value of 60 mW/m2.
CRP-3 * Latitude: -77.006000 * Longitude: 163.719000 * Date/Time Start: 1999-10-09T00:00:00 * Date/Time End: 1999-11-19T00:00:00 * Elevation: -295.0 m * Recovery: 936.00 m * Penetration: 939.00 m * Location: Ross Sea * Campaign: CRP-3 * Basis: Sampling/drilling from ice * Device: Core wireline system (CWS) * Comment: 11.76 km at 76° true from Cape Roberts, 2.04 km at 225° true from CRP-2. Fast ice thickness: 2.0 to 2.2 m. Sea rise embedded to 9.55 mbsf. Lateral ice movement from spudding 5.0 m to 82° true. HQ core to 345.85 mbsf. NQ core to 939.42 mbsf. Core recovery 97%. Phase 1 logging to 345 mbsf, Phase 2 logging to 773 mbsf, Phase 3 logging to 918 mbsf. Deepest Cenozoic lithology and depth: sandstone breccia from 822.87 to 823.11 mbsf. Age of oldest Cenozoic strata: earliest Oligocene or latest Eocene. Deepest core lithology and depth: light red-brown quartz-cemented quartz sandstone to 939.42 mbsf. Age of bedrock: (mid?) Devonian.