Morphologische Untersuchungen im nordöstlichen Matmata-Vorland (nördliche Djeffara, Südtunesien)

Abstract. Geomorphological investigations into the sequence of formation phases in the area of the two river-systems Oued Termamane — Oued Zigzaou and Oued en Negueb — Oued El Hallouf — Oued Oum Es Zessar in N. Djeffara in S. Tunisia permit us to distinguish above the recent river-bed, apart from youngest, anthropogenically caused deposits, a "younger accumulation" composed of fine sediments, a "main accumulation" consisting for the most part of coarse pebbles and remainders of at least 2 older, higher-lying levels which cannot be reliably correlated. The "main accumulation" is found in the entire area of the aforementioned Oueds, the „younger accumulation" on the other hand only in their middle and lower courses. The latter is missing in the main distribution area of the Matmata silts (primarily wind-deposited, later fluviatile remodelled sediments), in the mountains and on their edges. On the strength of the 14C-dating of 2 charcoal specimens (Hv 5566 and Hv 5400) the deposits of the „younger accumulation" may be placed in the period between 9000 — 7000 B.P. The dating of a calccrust from the top of the "main accumulation" showed a 14C-age of 21385 ± 235 B.P. (Hv 5402). Even taking into account the considerable possibilities of error in this dating, a Würm age may be assumed for the "main accumulation". The silts of Matmata overlie the "main accumulation" and come into consideration as supplier of material for the sediments of the "younger accumulation", accordingly the age of the silts may be assumed to be Würm to Early Holocene. Climatic conditions more humid than those today are indicated by a fossilized "Kalkbraunerde" in the Matmata silts, the occurence of calccrusts and a transport of pebbles at the time of the "main accumulation" reaching considerably further into the Matmata foreland than the pebble-transport of the recent river-beds.