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Reliefumkehr Durch Rumpfflächenbildung in Tanganyika

1967; Taylor & Francis; Volume: 49; Issue: 2-4 Linguagem: Inglês

10.1080/04353676.1967.11879755

1468-0459

Herbert Louis,

Historical Geography and Geographical Thought

Click to increase image sizeClick to decrease image sizeAbstractThe large peneplain-region to the north, south and west of Masasi in southern Tanganyika is formed on crystalline rocks of the folded African Basement complex. At a distance of 150 km this peneplain slopes from west to east from 600 m above sea-level to between 350 and 100 m. Then it ends on the base of a zone of westward facing plateau-scarps. These have a socle of the Basement complex and are covered by horizontal sandstones, mainly Cretaceous. They form the plateaus of Rondo, Maconde and Mawia with hights of 700 to 800 m and separate the peneplain-region from the Indian Ocean. But major rivers as the Ruvuma and Lukuledi cross through the plateau-zone in deep (to 600 m) but large valleys.The west-facing scarps of the plateau-zone are not simple cuestas. This was already shown by v. Staff 1914. Here the African Basement complex plunges slowly eastwards to the Indian Ocean. The peneplain-region, though orographically of minor height, is placed on higher elevated geological fundament than the orographically high sandstone-plateaus. The west scarps of the sandstone-plateaus are filed up along a flexure-line, and have been developed to inversional relief. To attain this result the surface-erosion working in the peneplain-region must have been by far more effective here than the valley- erosion in the zone of the sandstone-plateaus. The reason of this fact may be found in the petrographic and climatic differences of the two regions.All erosional waste of the peneplain-region has surely been carried off by crossing the zone of the sandstone-plateaus in the valleys of the rivers Ruvuma and Lukuledi. So peneplanation has taken place in large distance from the coast, separated from it by a mountainous zone of considerable height, and it was done in rather high position above sea-level. Except the inselbergs there exist no distinct remnants of older reliefs in the peneplairegion. Peneplanation may have gone on here since very long time, but, as surface-erosion continues, all actual surfaces of this peneplain are recent. For hinting at this fact we can perhaps call the age of these surfaces persistently-recent or per-recent.