Magnetostratigraphy and environmental magnetism of old cores from Ross Sea Sector (Antarctica)
Kenneth L. Verosub1, Luigi Jovane1-2, and Gary Acton1
1 Department of Geology, University of California, Davis, CA, 95616, USA
2 Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143, Roma, Italy
We undertake new paleomagnetic and rock magnetic studies on old cores from the Ross Sea sector of Antarctica. Our goals are to 1) to gain new insights into the timing and nature of paleoclimate events in the Ross Sea sector, especially as they relate to the availability of sediment and its transport into the basin; 2) to stimulate new research on a large collection of cores from the Ross Sea sector that were collected at great expense and that have been subjected to little or no scientific study; and 3) to provide a broader context for interpreting results from cores from the Ross Sea sector that will be obtained from the ANDRILL project.
The first systematic piston coring of the Southern Ocean was conducted during the 1960s by the USNS Eltanin as part of Operation Deep Freeze. Of particular interest are Cruise 27 in 1968 and Cruise 32 in 1969, which collected several dozen cores from the Ross Sea sector. Subsequent piston coring in the Ross Sea sector was done by the USCGC Glacier (1970s), R/V Polar Duke (1980s), and the R/V Nathaniel B. Palmer (1990s to present).
We have acquired preliminary data from 8 sites that demonstrate that even after thirty years there is valuable magnetic information that can be gathered from these cores. Following the removal of a low-coercivity overprint, which probably originates from drilling, handling, or storage, most cores have a strong, stable remanent magnetization between about 25-50 mT. We have been able to construct magnetostratigraphies and, in some cases, relative paleointensity records from the stable characteristic remanent component, which provide new age constraints. Given the occurrence of normal polarity only for many cores and the relative shallow depths of coring in most holes, the sediment can often only be limited to be of Brunhes age. In addition, environmental magnetic data are being obtained to gain new insights about geologic processes, such as weathering, erosion, transport, deposition and post-depositional alteration. When tied with the chronostratigraphic observations, our results provide new constraints on the timing and nature of paleoclimate events in the Ross Sea sector, especially those that affect the availability of sediment and its transport into the basin.
