High-Resolution Magnetostratigraphy, Relative Geomagnetic Paleointensity and Paleoenvironmental Change from Eocene to Pleistocene Sediments, IODP Expedition 369, Site U1514 (Mentelle Basin, Australia)

Abstract

International Ocean Discovery Program (IODP) Site U1514 is the northernmost and deepest (3850 m water depth) site cored during Expedition 369. The greater paleodepth of the site relative to other sites cored in the Mentelle Basin provides the opportunity to characterize the evolution of deep-water circulation in this region. The upper part of the sediments (12.6 – 68.1 m) recovered from Hole U1514A forms the basis of this project, the aim of which is to improve the magnetostratigraphy, determine the Neogene relative geomagnetic paleointensity (RPI), and determine the paleoenvironmental change within the Mentelle Basin using data acquired from Hole U1514A. The lithology consists of nannofossil ooze that gradationally transitions into nannofossil-rich clay. Paleomagnetic measurements were made on U-channel sediment samples. Alternating field (AF) demagnetization of the natural remanent magnetization (NRM) resulted in the isolation of the primary magnetization and removal of the secondary magnetization. The average maximum angular deviation of 2º demonstrates that the sediment samples in Hole U1514A are excellent recorders of the paleomagnetic field. A high-resolution magnetostratigraphy was constructed based on the interpretation of the preliminary shipboard magnetostratigraphy. The relative paleomagnetic intensity (RPI) estimate for Hole U1514A was calculated from the normalization of the NRM by the anhysteretic remanent magnetization (ARM) and magnetic susceptibility (k) which is consistent with the desirable criteria RPI reliability (Tauxe, 1993). RPI records as far back as 34 – 2 Ma which is the time interval of deposition of the sediment samples are very sparse if not non-existent; hence the calculated RPI record can be used as a baseline for which other records within this time interval can be compared. The likelihood of environmental influence on the RPI signal was investigated, the result of which shows no influence on the signal.