| Popis: |
At the left side of the OuedTamri mouth, a palaeo-sea-level (Unit 1) consists of marine and fluvio-marine deposits at ca. + 6 m a.s.l. The U/Th dating method applied to one marine shell of Patella sp. has yielded ages of 100,02 ± 1,662 ka and 101,188 ± 1,339 ka (MIS5.3) The overcoming dune (Sx) is dated at 84 ± 4 ka by OSL (MIS5.1). At TighrineImksaoun (200 m South of the mouth) the same MIS 5.3 palaeo-sea-leveliscovered by coastaldune sands and colluvial deposits on more than 20 m thickness. The latter show numerous interstratified red palaeosoils and calcretes which indicate run-off at intermediate moisture-periods, and enable to distinguish three main units (U2, U3, U4): (U2), lower Aeolian interdune accumulation Unit, mainly of colluvial and run-off detritic facies, numerous land-snails, and scarce lithic artefacts; (U3), middle aeolian accumulation Unit, with several series of dunes separated by palaeosoils and calcretes; the dune (S5) is dated at 92 ± 6 ka (MIS5.3 or MIS5.2) by OSL, and the palaeosoil (S6) countains a lithic industry with cleavers; (U4), upper, not well consolidated, aeolian accumulation Unit, lying on a calcreted basal palaeosurface (S6/S7) where Epipalaeolithic (?) artefacts are found; the uppermost serie (S8) was 14C dated at more than 30 ka on Ostrich eggs. The geomorphologic, sedimentologic and petrographic analyses helped us to build a sedimentary model of accumulation at the foot of a dead-cliff,model that is expected to resolve the apparent inconsistence between the position of the lithic industries and the dating results. |
