A Paleomagnetic and Environmental Magnetic Record from the Eastern South Pacific Sector of the Southern Ocean (0-1.7 Ma): IODP Site U1543

• Main Author: Monito, Lindsey
• Other Authors: Stoner, Joseph S., Walczak, Maureen H., Brook, Edward J., College of Earth, Ocean, and Atmospheric Sciences
• Format: Master Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: North Atlantic; Southern Ocean
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/z316q8991

This research presents a u-channel based study of the natural remanent magnetization (NRM), the laboratory magnetization, Anhysteretic Remanent Magnetization (ARM), and magnetic susceptibility (k), from the upper 100 m of International Ocean Discovery Program (IODP) Expedition 383 Site U1543 in the eastern South Pacific sector of the Southern Ocean. Alternating field (AF) demagnetization of u-channel samples defines a well resolved, high fidelity, low coercivity NRM with inclination values centered around ±70°, consistent with the geocentric axial dipole (GAD) prediction for both polarities. Well defined polarity reversals and a series of excursions from both polarities are observed, providing distinct stratigraphic markers and paleo-geomagnetic observations from an understudied part of the world. This record captures the Brunhes-Matuyama Boundary, Jaramillo, and Cobb Mountain subchrons, providing robust stratigraphic constraints. The physical properties of these sediments that are especially well illustrated by magnetic susceptibility seem to vary on glacial-interglacial cycles. An age model was developed first using the observed polarity boundaries and then combined with correlations of magnetic susceptibility to the global benthic oxygen isotope stack, LR04. This age model suggests the studied interval extends back 1.7 Ma with generally constant sedimentation rates (~6 cm/kyr). Support for these correlations are based on the consistent relationship between reversal and magnetic susceptibility correlations. Based on initial age estimates, other directional anomalies observed at U1543 may be associated with known excursional events, including the Laschamp, Big Lost, Santa Rosa, Punaruu, Gilsa, and possibly the Kamikatsura. This further supports the age model, while also raising the question of why these excursions are so well observed at this medium resolution site while not as well preserved at much higher resolution records from the North Atlantic. In addition to paleomagnetic observations, rock magnetic data ...