Nature and age of Late Quaternary basin fill deposits in the Basin of Persepolis/Southern Iran

Late Quaternary basin fill deposits exposed in the north-western part of the plain of Marvdasht were investigated in order to elucidate the nature of near-surface basin fill deposits as well as the timing of sediment aggradation, soil formation and incision of Kor River. Besides sedimentological and paleopedological analysis, a chronological frame was set up by infrared stimulated luminescence (IRSL) and radiocarbon dating. The near-surface basin fill consists of silty to clayey fluvial and aeolian deposits documenting gradual horizontal and vertical changes of low velocity fluvial and limnic sedimentation on the one hand and subaerial deposition on the other hand. The accumulation of the sediments decreased during a phase of soil formation possibly between 27 and 22 ka. This phase is represented by a strongly developed brown paleosol which developed under a climate similar to today, while contemporaneously formed grey paleosols indicate topographically wet conditions in backswamp paleo-environments. Between about 21 and 7 ka, high rates of sediment deposition occurred and the upper sediments of the plain accumulated, probably under drier and cooler climatic conditions than today. From about 16 to 10 ka, a gradually dessicating lake covered parts of the plain. At the same time, several weakly developed brown and grey paleosols were formed indicating comparatively stable paleo-environments with strongly reduced sediment accumulation and/or topographically moist paleo-environments in the alluvial plain. The formation of the strongly developed modern soils started after a change to moister climatic conditions during the early to mid Holocene, most likely between 7 and 4 ka. Increased river incision has started at about 10ka and was likely retarded at about 4ka owing to mid Holocene tectonic uplift in the lower parts of the basin. (C) 2008 Elsevier Ltd and INQUA. All rights reserved.