High-Resolution Rock Magnetic and Paleointensity Study of Sediments from IODP Site U1389 (West Iberian Margin of the North Atlantic Ocean)

Abstract

High resolution rock magnetic and paleomagnetic data from a section spanning 36 to 107 meters composite depth of the Integrated Ocean Drilling Program (IODP) Site U1389 are discussed. Site U1389 is located in the North Atlantic Ocean at 36° 25.515’N; 7° 16.683’W in 644 m water depth. The main overall objective is to study the Mediterranean Outflow Water (MOW) and its effects on the short term and long term climate and contourite system of the Iberian margin over the past six million years. The sedimentary section at Site U1389 consists of a thick and consistent succession of contouritic sediments with sedimentation rates of ~40 cm/kyr. The age model was obtained by tuning planktonic foraminifer oxygen isotope data to the NGRIP ice core record. Through alternating field (AF) demagnetization of the natural remanent magnetization (NRM), the characteristic remanent magnetization is isolated while the low stability component is removed. The average maximum angular deviation, calculated from the principal component analysis ~1.2°, illustrates the excellent quality of the preserved magnetic signal. Consistent behavior of the magnetic samples during AF demagnetization and acquisition curves of the isothermal remanent magnetization suggests magnetite as the main magnetic carrier mineral. By normalizing the NRM by the anhysteretic remanent magnetization, isothermal remanent magnetization, and magnetic susceptibility, the relative paleointensity (RPI) was calculated. RPI records from Site U1389 conforms to the desirable attributes of relative paleointensity criterial (e.g. Tauxe, 1993); hence, Site U1389 may be used for future global relative intensity correlation. Qualitative analysis of the RPI proxies and the RPI normalizers are presented with the aim of determining the driver of environmental change.