Environmental magnetism: Past, present, and future

Environmental magnetism involves the application of rock and mineral magnetic techniques to situations in which the transport, deposition, or transformation of magnetic grains is influenced by environmental processes in the atmosphere, hydrosphere, and lithosphere. The first explicit description of environmental magnetism as a distinct field was in 1980. Since that time environmental magnetism has become a broad field that is finding application in an ever‐increasing array of scientific disciplines. In this review of the present state of environmental magnetic studies, we divide the field into three broad, but arbitrary, categories. The first involves the use of mineral magnetic assemblages in the geological record to study physical processes in depositional environments. This category includes the correlation of sediment cores using magnetic susceptibility measurements, studies of geomagnetic field behavior, the analysis of depositional and postdepositional mechanical processes that affect sediments, and the examination of magnetic parameters that might represent proxies for paleoclimatic variation. The second category encompasses studies of the processes responsible for variations in the magnetic minerals brought into a sedimentary environment. These provenance investigations include studies of changes in catchment‐derived sediment in lakes, fluctuations in contributions from terrigenous, aeolian and glaciogenic components in deep‐sea sediments, and the origin of atmospheric particulates. The final category addresses in situ changes and transformations of magnetic minerals in sedimentary environments, including pedogenesis, authigenetic/diagenetic formation of ferrimagnetic phases, dissolution of magnetic minerals due to reductive diagenesis, and contributions of biomagnetism to sedimentary magnetism. Because environmental magnetism can address problems in so many disciplines and because many of these problems may be inaccessible to other techniques, it is likely that the scope of environmental magnetism will continue to expand rapidly. Environmental magnetism is capable of providing important data for studies of global environmental change, climatic processes, and the impact of humans on the environment, all of which are major research initiatives in the international scientific community. These factors suggest that environmental magnetism has a bright and diverse future.