@article{SchulzJosephBaumhaueretal.1990,
  author    = {Schulz, Erhard and Joseph, Alain and Baumhauer, Roland and Schultze, Ekkerhard and Sponholz, Barbara},
  title     = {Upper Pleistocene and Holocene history of the Bilma region (Kawar, NE-Niger)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-86828},
  year      = {1990},
  abstract  = {A 42 m drilling was pertormed in the depresalon of Bilma, Xawar, NE-Niger. The sediment and pollen records show that after an initial deposition of dune sands there were repeated lake phases which terminated by desiccation and consolidation of spring mounds. The pollen record indicates a continuous presence of savanna vegetation. The record probably covers the period between the Upper Pleistocene and the Late Holocene. The climate was characterised by a monssonal summer rain regime giving effective rain fall of about 450-500 mm per year. Groundwater recharge was possible but estimates of the amount of water resources are difficult because of the karstic system of the escarpment and the nearly unknown hydrogeological situation.},
  subject      = {Pleistoz{\"a}n},
  language  = {en}
}
@article{Sponholz1994,
  author    = {Sponholz, Barbara},
  title     = {Ph{\´e}nom{\´e}nes karstiques dans les roches siliceuses au Niger oriental},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-86833},
  year      = {1994},
  abstract  = {Dans le Niger oriental, des ph{\´e}nomenes karstiques sont fr{\´e}quents dans les roches siliceuses: gres, silcretes, cro{\^u}tes ferrugineuses, roches cristallines. A partir des {\´e}tudes g{\´e}omorphologiques et micromorphologiques, on peut conclure a une kartsification, au sense de production de formes par dissolution. Les r{\´e}sultats permettent de dater du Tertiaire inf{\´e}rieur la principale p{\´e}riode de karstification. La r{\´e}partition r{\´e}gionale des formes induites par cette karstification indique une d{\´e}pendance probable des conditions pal{\´e}oclimatiques. Actuellement le karst influe encore sur le d{\´e}veloppement des autres formes de relief.},
  language  = {fr}
}