A major hydrobiological change in Dasht-e Arjan Wetland (SW Iran) during the late glacial-early Holocene transition revealed by subfossil chironomids

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Aubert, Cyril, Djamali, Morteza, Jones, Matthew, Lahijani, Hamid, Marriner, Nick, Naderi-Beni, Abdolmajid, Sharifi, Arash, Ponel, Philippe, Gandouin, Emmanuel
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: NRC Research Press 2019
• Subjects: General Earth and Planetary Sciences; NGRIP
• Online Access: https://doi.org/10.1139/cjes-2018-0256; https://nottingham-repository.worktribe.com/file/1486100/1/Aubert%20Et%20Al.%20%20Arjan%20Chironomid%20Record%20-%20FINAL; https://nottingham-repository.worktribe.com/output/1486100

The late glacial-early Holocene transition is a key period in the Earth’s history. However, although this transition is well studied in Europe, it is not well constrained in the Middle East and palaeohydrological records with robust chronologies remain scarce from this region. Here we present an interesting hydrobiological record showing a major environmental change occurring in the Dasht-e Arjan Wetland (SW Iran, near to Persepolis) during the late glacial-early Holocene transition (ca. 11,650 years cal BP). We use subfossil chironomids (Insecta: Diptera) as a proxy for hydrological changes and to reconstruct lake-level fluctuations. The Arjan wetland was a deep lake during the Younger Dryas (YD) marked by a dominance of Chironomus plumosus/anthracinus-type, taxa adapted to anoxic conditions of deep waters. At the beginning of the Holocene a drastic decrease (more than 80% to less than 10%) of Chironomus plumosus/anthracinus-type, combined with diversification of littoral taxa such as Polypedilum nubeculosum-type, Dicrotendipes nervosus-type and Glyptotendipes pallens-type suggest a lake-level decrease and a more vegetalized aquatic environment. We compare and contrast the chironomid record of Arjan with a similar record from northwestern Iran. The palaeoclimatic significance of the record, at a local and regional scale, is subsequently discussed. The increase in northern hemisphere temperatures, inferred by geochemical data from NGRIP, at the beginning of the Holocene best explains the change from the YD highstand to early Holocene lowstand conditions in the Dasht-e Arjan wetland. However, a contribution of the melt-water inflow from small local glaciers in the catchment basin is not excluded.