THE LATE HOLOCENE STANDARD PROFILE OF NORTHERN TUNISIA

On the basis of 20 analyzed sediment-profiles within the Medjerda floodplain (Mediterranean Tunisia) a chronostratigraphical synthesis in the manner of a centennial scale standard profile is made possible.

Around 4.8 ka cal BP poorly sorted floodplain sediments cover an ubiquitous mid-Holocene soil. This indicates an enhancement of morphodynamic processes due to increasing aridity. Until Punic times (3.0 ka cal BP) sediments are fining up. After 3.0 ka cal BP for a short period increased morphodynamic processes are observable (dating of two fire places in one exposure). This aggradation of sandy deposits ends around 3.0 ka cal BP with a fining-up sequence. About 2.0 ka cal BP morphodynamic stability and soil formation can be observed, although the beginning of soil formation is still unknown. Heavy metal analyses prove Punic to Roman land use and mining activity leading to distinct heavy metal peaks in the correlated sediments. At 1.7 ka cal BP an accentuated restart of fluvial dynamics took place. At this time the morphodynamically stable Punic-Roman period ends and most of the soils were buried under coarse gravel layers. Certain sediment strata having ages between 1.2 and 0.8 ka cal BP show a humic enrichment, which must be due to a young Holocene soil formation period. Subsequently some minor floods yielding only fine sediments. The top of this sediment-sequence shows also a slight humification. At 0.4 ka cal BP (dating of a fire place) utterly devastating floods (YL-event) occur in the entire Medjerda basin, leaving thick laminated sediments bodies, referred to as Youngest Layer.

Acknowledgement

We would like to thank the Deutsche Forschungsgemeinschaft (DFG) for the financing of this project (FA 239/2-2).

References

Faust, D. and Zielhofer, C. (2002): Reconstruction of the Holocene water level amplitude of the Oued Medjerda as an indicator for changes of the environmental conditions in North Tunisia. Zeitschrift für Geomorphologie N.F. Suppl. 128, 161-175.

Faust, D., Zielhofer, C. and Baena Escudero, R. (in preparation): The centennial scale late Holocene standard profile of the mid-Medjerda valley (Northern Tunisia). The Holocene

Moldenhauer, K.-M., Faust, D. & Zielhofer, C. (accepted): Differenzierung fluvialer Sedimentserien aus dem Holozän Tunesiens anhand des Schwermetallgehalts. Geo Austria