Do magnetic fabrics of marine deposits preserve orbital forcing? A test case in the Southern Ocean, Antarctic Peninsula

Abstract

The anisotropy of magnetic susceptibility (AMS), or magnetic fabric, of marine sediments is related to depositional current strength; higher AMS values indicate stronger currents. We have collected a 3.1 m.y. record of AMS data from the abyssal silts of Drift 4 (Ocean Drilling Program Site 1101) on the Pacific margin of the Antarctic Peninsula. Spectral analyses of these data show strong, uniform, 100 k.y. and 400 k.y. power in-phase with minima in Earth's eccentricity throughout the long record. However, significant variability related to the 40 k.y. period of obliquity is absent. The unchanging strong 100 k.y. power and the apparent absence of 40 k.y. variability in the AMS record are in contrast to the behavior of most other paleoclimatic proxies for late Pliocene and Pleistocene time.