CONTRIBUTIONS OF ENVIRONMENTAL MAGNETISM TO THE CONSTRUCTION OF PALEOCLIMATE RECORDS FROM OCEAN SEDIMENT CORES

Magnetic susceptibility (κ) and its applications to soil sequences and lacustrine sediment launched the discipline of environmental magnetism. Environmental magnetism uses a suite of magnetic analyses to characterize the abundance, magnetic particle sizes, and mineralogy of iron oxide and sulfide minerals in order to investigate environmental and climate processes. κ was a latecomer to the array of paleomagnetic and physical properties tools available on ocean research vessels, and was not routinely measured on the Glomar Challenger during the Deep Sea Drilling Program. Once continuous κ logging systems were installed on the JOIDES Resolution, κ became the ultimate rapid reconnaissance parameter for marine sediment cores due to the low cost technology, ease of use, non-destructive nature of the analysis, and ability to rapidly process whole cores or split cores at high resolution. κ profiles from ocean sediment cores were initially used for core correlation, identification of metal contamination of sediment cores by the drill string, and visualization of compositional variations to guide sub-sampling. It is now used for the generation of high resolution time series data, and is particularly important in polar regions where continuous accumulation of biogenic calcite is rare. The ease of measurement of κ belies its complex signal. κ represents the combined response of the entire sediment assemblage, including ferromagnetic, paramagnetic and diamagnetic minerals, necessitating the use of induced remanences, and field- and temperature-dependent parameters that target magnetic mineralogy and domain state in order to correctly interpret the κ signal. This evolving suite of parameters have since been used to identify climate-driven orbital and sub-orbital processes related to glacial-interglacial cycles, deglaciation and ice-rafting events, monsoon intensity, ocean circulation, sediment transport processes, solar cycles, behavior of wind systems, supply of dust to the ocean, paleoproductivity, and diagenetic alteration of sediment assemblages. Here we review seminal environmental magnetism contributions from the last 50 years of ocean drilling, and discuss future applications of environmental magnetism to the study of ocean-atmosphere-cryosphere-lithosphere dynamics.