The nature of anthropogenic deposits and landscape modification
The deliberate anthropogenic movement of reworked natural and novel manufactured materials represents a novel sedimentary environment associated with mining, waste disposal, construction and urbanization. Anthropogenic deposits display distinctive engineering and environmental properties, and can be of archaeological importance. This paper shows that temporal changes in the scale and lithological character of anthropogenic deposits may be indicative of the Anthropocene. However, the stratigraphy of such deposits is not readily described by existing classification schemes, which do not differentiate separate phases or lithologically distinct deposits beyond a local scale. Lithostratigraphy is a scalable, hierarchical classification used to distinguish successive and lithologically distinct natural deposits. Many natural and anthropogenic deposits exhibit common characteristics; they typically conform to the Law (or Principle) of Superposition and exhibit lithological distinction. The lithostratigraphical classification of surficial anthropogenic deposits may be effective, although defined units may be significantly thinner and far less continuous than those defined for natural deposits. Further challenges include the designation of stratotypes, accommodating the highly diachronous nature of anthropogenic deposits and the common presence of disconformities. International lithostratigraphical guidelines would require significant modification before being effective for the classification of anthropogenic deposits. A practical alternative may be to establish an ‘anthrostratigraphical’ approach, or ‘anthrostratigraphy’.
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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.