Geomagnetic and mineral magnetic characterization of the Anthropocene
Ian Snowball, Mark W. Hounslow, Andreas Nilsson, 2014. "Geomagnetic and mineral magnetic characterization of the Anthropocene", A Stratigraphical Basis for the Anthropocene, C. N. Waters, J. A. Zalasiewicz, M. Williams, M. Ellis, A. M. Snelling
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Geomagnetic and mineral magnetic data provide geological indices that are both independent of human impact (i.e. geomagnetic) and respond to human-induced environmental impact (i.e. mineral magnetic). We provide the first discussion of such magnetic events for help in defining the Anthropocene. Within the Holocene, a potential geomagnetic marker for the Anthropocene is the low dipole latitude at c. 2700 cal a BP, which is associated with distinct palaeosecular variation features in northerly mid- to high-latitude sites. Mineral magnetic records from lake and marine sediments identify major deforestation and soil delivery events from catchment systems in many parts of the world during the last 4000 years. In Europe, clusters of these events occur around both 2600 cal a BP and AD 1100, the former coinciding with a low in geomagnetic field dipole latitude and peak intensity. Mineral magnetic records in peats and lake sediments can reflect particulate pollution from fossil fuel burning. The expansion of major coal burning began c. AD 1800 in western Europe and eastern North America, but around AD 1900 this expanded due to more widely distributed coal use, and this event is the most clear mineral magnetic marker for the base of the Anthropocene.
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A Stratigraphical Basis for the Anthropocene
Humankind has pervasively influenced the Earth’s atmosphere, biosphere, geosphere, hydrosphere and cryosphere, arguably to the point of fashioning a new geological epoch, the Anthropocene. To constrain the Anthropocene as a potential formal unit within the Geological Time Scale, a spectrum of indicators of anthropogenically-induced environmental change is considered, and shown as stratigraphical signals that may be used to characterize an Anthropocene unit, and to recognize its base. This volume describes a range of evidence that may help to define this potential new time unit and details key signatures that could be used in its definition. These signatures include lithostratigraphical (novel deposits, minerals and mineral magnetism), biostratigraphical (macro- and micro-palaeontological successions and human-induced trace fossils) and chemostratigraphical (organic, inorganic and radiogenic signatures in deposits, speleothems and ice and volcanic eruptions). We include, finally, the suggestion that humans have created a further sphere, the technosphere, that drives global change.