Magnetochronostratigraphic Data From Three Sediment Cores Recovered From the SE Pacific, Off Patagonia, Chile

Abstract

Three long sediment cores recovered from the SE Pacific were subjected to a comprehensive magnetostratigraphic investigation. According to the partly preliminary age models obtained, the cores reach 48, 140, and 482 ka back in time, respectively. At two sites (PC02 and PC03 at ∼46°S) sedimentation rates are highly variable, ranging from about 2 to 100 cmka⁻¹, whereas sedimentation rates are significantly lower at the southernmost site (PC04, ∼51°S), ranging from about 1 to 20 cmka⁻¹. All three cores provide evidence for the Laschamps geomagnetic excursion at 41 ka. However, the excursion was recorded during times of low sedimentation rates and thus, only little detail on geomagnetic field variability could be obtained. Nevertheless, the excursion is documented in inclination and declination, thus as a full reversal, and is associated with a deep low in relative paleointensity. At site PC04, the Iceland Basin excursion (∼195 ka) was also recorded as a short almost reversed phase, followed by an apparently long phase of non-dipolar directions, all associated with a deep low in paleointensity. This is interpreted as the result of variable sedimentation rates not resolved by the preliminary age model of the core. A directional anomaly coinciding with a deep low in paleointensity at around 220 ka is interpreted as the Pringle Falls excursion. Besides these findings, no evidence for further excursions could be found in the studied cores.