@inproceedings{Sponholz1993,
  author    = {Sponholz, Barbara},
  title     = {Holocene fulgurite formation in the southern Central Sahara (Niger)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-56584},
  year      = {1993},
  abstract  = {Fulgurites (= natural glasses formed by lightning strikes to the ground) are indicators of thunderstorms (e.g. Julien 1901). The distribution pattern of fulgurites in the study area (Grand Erg de Bilma and Erg de Tenere between 11.5°E and 16.5° and 18.5°N) shows decreasing fulgurite concentration from south to north. The fulgurite sites are concentrated in the area of fossil dune complexes, where they occur topographically above palaeolimnic deposits in mid-slope position of interdune depressions.},
  subject      = {Geographie},
  language  = {en}
}
@article{Sponholz1994,
  author    = {Sponholz, Barbara},
  title     = {Silicate karst associated with lateritic formations (examples from eastern Niger)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-53852},
  year      = {1994},
  abstract  = {Silicate and iron crust karst pits and sinkholes in eastern Niger are filled with reworked lateritic sediments or with unconsolidated palaeosoils and aeolian deposits. The fillings facies depend on the environmental conditions during deposition. Geomorphological and sedimentological studies on the karst fillings and the interpretation of various karst/filling associations allow an approach to the chronology of landscape development in eastern Niger plateaus.},
  subject      = {Geographie},
  language  = {en}
}