Rock-magnetic carriers of century-scale susceptibility cycles in glacial–marine sediments from the Palmer Deep, Antarctic Peninsula

Abstract

A 4200 year long magnetic susceptibility profile from the Palmer Deep records century- and millennial-scale variability in paleoenvironmental conditions along the western Antarctic Peninsula. The susceptibility profile shows regularly spaced highs and lows over the last 3360 years B.P. then drops to uniformly low values. These features are formed by the variable dilution of terrigenous material with biogenic sediments and shifts in magnetic mineralogy. High-susceptibility intervals are characterized by multi-domain (MD) pure magnetite. Low-susceptibility intervals are characterized by pseudo-single-domain (PSD) magnetite and titanomagnetite. Prior to 3360 years B.P., the magnetic mineral assemblage is dominated by fine PSD titanium-rich titanomagnetite and superparamagnetic particles, suggesting a change in sediment provenance and/or sediment transport processes. The absence of MD magnetite suggests a cessation in locally derived ice-rated debris. This horizon represents the transition from the mid-Holocene climatic optimum to the Neoglacial period, marked by an increase in glacial sedimentation.