HUMAN INFLUENCED SEDIMENTS IN KARST SYSTEMS

Sediments in karst voids serve as repositories for environmental information over time frames going back more than 4 million years. These records, both chemical (speleothem) and clastic, have been exploited for numerous studies of terrestrial conditions and paleoclimate. Their utility as recorders of human activities related to settlement, agricultural activity, and industrialization, however, has been much less explored, and represents a novel and potentially significant resource for understanding human-driven environmental change. Clastic sediments in caves are of tripartite origin: autogenic (breakdown), allogenic (primarily alluvium), and anthropogenic (for example archeological materials). Allogenic deposits make up the bulk of materials in most epigene cave systems, and reflect the environmental conditions within the hydrologic catchment for the cave. Land use changes, such as conversion from primary forest, lead to changes in ongoing sedimentation, and may even be considered a special case of “legacy” sediments. In some cases, direct emplacement of human materials through trash disposal, mortuary practices, or other activities is present. In other instances, materials may be removed (i.e. mining of guano or saltpeter). In practice, cave deposits can be mixtures of all 3 genetic modes, and it is frequently challenging to decipher the history of a given deposit. By applying standard stratigraphic methods, as well as dating techniques (paleomagnetism, radioisotopes, etc.), it is possible to decipher the records. Major challenges include discontinuous deposition, “sieving” at input points, uncertain correlations, and the overall difficulty of working in the subterranean environment. It is highly likely that most effects of human activities on cave sediments have gone completely unrecognized.