The Geological Collection from the South Centeal Sahara

Abstract

As the Central Sahara is geographically one of the least-known areas in Africa, knowledge of its geology is naturally scanty, and all additional information is welcome, especially from its bearing on the relations of the North African and Equatorial seas and on the problem whether the Cretaceous sea of the Sahara and Northern Sudan is a branch of the Tethys, or crossed Africa from the Gulf of Aden to the Niger. The collection made by Mr. F. R. Rodd, during his journey in 1927, has been sent to us for examination. He has described the geography of the area in the Geographical Journal and also in his book ‘The People of the Veil’. The Massif of Aïr was reported by H. Barth to consist of gneiss, slate, marble, and granite, with flows of basalt and trachyte, and to be flanked by sandstones. Knowledge of the geology of the Aïr Massif and its neighbourhood is due mainly to the work of R. Chudeau, who collected fossils there, and described its geology in his ‘Sahara Soudanais’ and in a series of papers. He discovered Cretaceous limestones with ammonites (1909, 2) and lamellihranchs, which he identified as Turonian; and, on the basis of his work, an extensive area in the Central Sahara has been since regarded as marine Upper Cretaceous and as connected either with the Mediterranean or with the Indian Ocean. E. Haug, J. W. Gregory, and E. Hennig have represented the Cretaceous of the plains south of Aïr as part of