Magnetostratigraphy and Rock Magnetism of Expedition 318 Sediments

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Intellectual MeritThe overall objectives of IODP Expedition 318, January ? March 2010 (Wellington ? Hobart) were: 1) to determine the timing of the arrival of ice at the Wilkes Land margin, 2) to determine the nature and age of possible transitions from a wet-based to a cold based glacial regime, 3) to obtain a high-resolution record of Antarctic climate variability during the late Neogene and Quaternary, and 4) to obtain an ultra high resolution record of the Holocene from drilling in the Ad´elie Basin. IODP Expedition 318 drilled seven sites and recovered ∼2500 m of Lower Eocene to Holocene sediments. A critical aspect of the stated goals of Expedition 318 is documenting the age of the sediments and sedimentary hiatuses. Preliminary magnetostratigraphic data provide crucial constraints as well as calibration for the biostratigraphies in the Southern Ocean, where direct calibration is notably scarce. For example, cores from the conjugate margin of Tasmania drilled during ODP Leg 189 recovered sediments of similar age, but the magnetic stratigraphy for the Paleogene portion so far is inadequate for the purposes of calibrating the geological time scale. Magnetic fabrics, mineralogy and grain size information from Expedition 318 sediments provide intriguing clues to environmental changes recorded in this unique sedimentary sequence. Another prime objectives of IODP Expedition 318 was to obtain an ultra high resolution record of the Holocene from drilling in the Ad´elie Basin, a 190 m thick sequence of diatomaceous ooze overlying a glacial diamict with an age of ∼11 ka. Site U1357 revealsh the first annually resolved time series of oceanographic and climatic variability derived from the Southern ocean. Data obtained from shipboard measurements of the archive half of U1357A documented an unrivaled record of secular variation (SV) of the geomagnetic field, which promises not only an unprecedented SV record but also will provide critical constraints for hole to hole correlation. This proposal requests funds for the paleomagnetic and rock magnetic analyses of material obtained from Expedition 318 drilling. It also seeks modest funding for sampling and analysis of cores drilled during ODP Leg 189 and housed in the Kochi Repository in Japan.Broader ImpactsThe history of Cenozoic glaciation as revealed by compilations of oxygen isotopic values and its relationship to inferred atmospheric CO2 is of major scientific interest. The Antarctic cryosphere plays a key role in the global climate system and its history therefore plays a role in the current climate change debate. The proposed work is essential for placing the Wilkes Land sediments into a high resolution chronostratigraphic framework. Global paleosecular variation models are extremely useful for exploring the behavior of the geomagnetic field, as a dating tool for archeomagnetism and as a means for assessing the control of the geomagnetic field on radiocarbon production. Despite broad utility, the models are only as good as the data from which they are derived and as of now there are very few records from the southern hemisphere. Moreover, no record obtained to date has the resolution of that achievable at Site U1357. Therefore, the proposed work has the potential to substantially improve the paleosecular variation models. This proposal will also contribute to the education of a post-doctoral scholar, Dr. Saiko Sugisaki. She sailed as a shipboard paleomagnetist on Expedition 318, although her training was in optically stimulated luminescence. Having spent several months intensively engaged in paleomagnetic research, and also having taking the online paleomagnetism class offered through Scripps (http://magician.ucsd.edu/∼ltauxe/sio247), she has decided to continue her education as a post-doctoral scholar in the paleomagnetic laboratory at Scripps. The PI is well known for outreach efforts to the broader community by conducting short courses, by making the textbook Essentials of Paleomagnetism available for free access, by conducting online, free access, courses and by making the PmagPy paleomagnetic software package open source. This proposal will provide partial support for these education/outreach activities