RAPID: Collaborative Research: Paleomagnetic and Rock Magnetic Investigation of IODP Expedition 318 Site U1357 Sediments

University Of California-San Diego Scripps Inst Of Oceanography, La Jolla CA

Investigators

Abstract

One of the prime objectives of IODP Expedition 318, January to March 2010 (Wellington to Hobart) was to obtain an ultra high resolution record of the Holocene from drilling in the Adelie Basin. The Adelie Basin contains a 190 m thick sequence of diatomaceous ooze overlying a glacial diamict with an age of about 11 ka. Sediments obtained at Site U1357 reveal an ultra-high resolution record with the first annually resolved time series of oceanographic and climatic variability derived from the Southern ocean. Site U1357 was triple cored. Hole U1357A was split and processed during the expedition while Holes U1357B and C were sealed in nitrogen flushed bags and only split during the sampling party (June 27, 2010 - July 3, 2010). 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. During post-cruise sampling we bolstered our confidence in the reliability of this unique record, but also discovered that the magnetic mineralogy degrades extremely rapidly after exposure to air. While the discrete samples have been placed in nitrogen flushed bags for transport, immediate measurement is urgently required. Also, because the magnetic mineralogy is likely to be quite unusual (for example biogenic iron sulfides), it must also be characterized prior to as well as after oxidation. We therefore request funding via the RAPID funding mechanism. Support for the remaining Expedition 318 paleomagnetic efforts will be requested using the usual EOR mechanism.