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

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

Early Sasanian landscape modification: New geoarchaeological evidence from the Ardashir Pond in southwest Iran (Palace of Ardashir, third century CE)

The Sasanian period (224–651 CE) marked an era of large‐scale urban projects insouthwest Asia, including Iran's semi‐arid highlands, with particular efforts to ma-nipulate water bodies. This study presents a recent interdisciplinary investigation ofa spring‐fed pond at the entrance of the Palace of Ardashir (Firuzabad plain,southwest Iran), part of a recently registered World Heritage site. Historical ac-counts suggest that the entire water system of the plain, including the pond, un-derwent a hydraulic re‐organization at the beginning of the Sasanian period, a factthat has never been investigated geoarchaeologically. A series of sediment coreswere retrieved from the pond to probe its evolution and examine the extent of itslandscape modification. The cores were sedimentologically described andradiocarbon‐dated with age–depth models established based on 57 AMS (accel-erator mass spectrometry)14C dates to understand the basin's depositional history.The results indicate that (i) Ardashir Pond has existed as part of a larger wetlandcomplex since at least 4500 years ago, (ii) it was substantially enlarged at the be-ginning of the Sasanian era, and (iii) it was abandoned at the end of the Sasanianperiod. The Ardashir Pond is one of the first geoarchaeologically investigated casestudies to demonstrate the Sasanian landscape in the framework of the“Iranshahr”sociopolitical concept