Deposits: Evaluation of the Simultaneousness of Response of Alluvial Fans to Late Pleistocene and Holocene Climatic Changes in Marand and Parsian Plain

Relative dated deposit layers of Quaternary alluvial fans and their sequences in two regions in northwest of Iran, provide timelines for the assessment of the synchrony of the response of alluvial fans to late Pleistocene and Holocene climatic changes. In these regions three alluvial fan systems have been mapped: Two alluvial fans by the names of Koshksarsy and Sheykh-chay on the northern slopes of Mishow-dagh mountain range and Parsian fan on the northern slopes of Keyamaki-dagh mount. The conformity of deposition sequences in study area suggests a synchrony in climatic change phases, and a similarity in the response of alluvial fans to these changes. In the cold and wetter periods, high water and sediment supply from the catchments hillslopes is followed by debris-flow activity in Mishow-dagh alluvial fans that intensifies debris-flow in Parsian fan system. In the warm periods, depositional processes change from debris-flows to fluvial processes that provide the way for soil development on hillslopes and alluvial fan surfaces. In recent periods, other mechanisms such as calcium carbonate precipitation and tufa deposition were active on the Parsian fan surface.