Karstic spring wetlands of the Persepolis Basin, southwest Iran: unique sediment archives of Holocene environmental change and human impacts

Abstract

Palustrine carbonates are frequently found with active and dried karstic springs in the foothills of the mountains bordering the Persepolis Basin, southwest Iran. A combination of geological conditions favours their formation, including (i) the presence of karstic limestone aquifers in the limbs of anticlines cut through by fault systems; (ii) very gentle slopes from the spring resurgence point towards the centre of the alluvial plain, creating a flat waterlogged area; and (iii) a semiarid climate with marked precipitation seasonality or significant fluctuations in water discharge and wetland water table. We suggest the term “anastomosing wetlands” or “anastomosing palustrine environments” to denote the studied karstic spring–fed carbonate wetlands, because of similarities with anastomosing river systems in aerial view. The common presence of extended anastomosing wetland carbonates in the Persepolis Basin and adjacent basins in the central and southern Zagros suggests that they can play an important role in the geological records of collision-related basin-and-range settings dominated by karstic limestones. Karstic spring wetlands are a main source of fresh water hosting a rich biodiversity, which attracts human communities, whose impact is visible in the archaeological material imbedded in the wetland stratigraphy. Fresh water availability, through these spring wetlands, partly explains why the semiarid Persepolis region was selected by successive civilizations, from Elamites to Persians until early Islamic entities, to establish regional centres throughout the period from the third millennium B.C. to the first millennium A.D. Only a few of these ecosystems have survived the intensive human activities of recent decades.

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

“…2). A recent publication by Djamali et al (2018) has shown that similar age inversions (too young ages) have also been reported from a palustrine carbonate facies in the western Persepolis basin. We have retained the ages provided by the samples Poz-Arj503, Poz-Arj614, and Poz-Arj671 because they are composed of in situ organic matter (gyttja to very fine grained peat) formed within the aquatic environments through biological processes.…”

Springs, palm groves, and the record of early hominins in Africa

“…Despite the fact that groundwater-fed areas leave well-recognized evidence in the geological record, their importance in defining the type of habitat available to hominins and other elements of the fauna is rarely recognized (but see Barboni, 2014;Beverly et al, 2015;Cuthbert et al, 2017;Deocampo and Tactikos, 2010;Djamali et al, 2018;Reynolds et al, 2011). Yet, we have shown here that the occurrence of springs is not anecdotal in the African hominin and human record (Table 1).…”

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

“…The analogy with modern pond sediment suggests that the percentages of peat and plant debris decrease from the littoral macrophytic belt toward the central pond basin, where carbonate mud (lime) becomes the dominant sediment type. The carbonate mud is mostly chemically and biochemically precipitated from the spring waters saturated in bicarbonates (Ashjari & Raeisi, 2006; Djamali et al, 2018). Thus, the following facies succession appears to represent a gradient from the littoral macrophytic vegetation belt to the deep lake/pond deposits close to the spring resurgence point: Phragmites peat, fine‐grained peat/gyttja, carbonate bioclastic organic mud, organic carbonate mud, and carbonate mud.…”

“…Understanding such hydraulic work and its effects on natural hydrological evolution of this freshwater ecosystem is crucial for several reasons. First, springs and spring wetlands have played a significant role in the socioeconomic and cultural evolution of societies in the arid to semi‐arid lands of the Iranian plateau, not only as permanent freshwater sources but also as places of gathering for religious rituals (Boucharlat, 1979; Canepa, 2018; Djamali et al, 2018; Huff, 1972, 2014). Second, the pond is an inseparable architectural element in the Ardashir Palace complex and therefore an excellent case study to examine the extent and techniques of possible landscape modification by Sasanians.…”