Phytoliths and Pollen from a Desert Wetland Through the Last Glacial–Interglacial Cycle in Azraq, Jordan

Phytoliths, pollen, and spores in a stratigraphic sequence from the Shishan Wetland (Azraq Basin, Jordan) and supported by modern pollen and phytolith data provide information on vegetation, climatic trends, and the influence of fire through MIS 2 and MIS 1. Additionally, a pilot study introduces an innovative approach that uses shape and morphometric parameters of Bulliform phytoliths to assess hydro-climatic changes. The phytolith terrestrial–aquatic ratio, grass–pollen size, and the Artemisia–Amaranthaceae ratio (A:C) indicate that during the Last Glacial Maximum (LGM), the study area was a wetland surrounded by steppe, and that during the deglaciation period (c. 20–11 ka), the wetland vegetation remained almost unchanged but the surrounding area tended to aridity. The phytoliths’ terrestrial ratio, the presence of C4 grass phytoliths, and the low A:C is characterized by a reduced wetland and the establishment of a hot desert, like the present. The record at Shishan Marsh shows effective moisture trends concurrent with other records in the western southern Levant, but climatic events (Heinrich Stadial 1 and Younger Dryas) are not recorded because of the low time-resolution of the studied sequence. This study shows that combining pollen and phytoliths strengthens vegetation reconstruction by discerning local from regional floristic components and that Bulliform phytoliths are a potential tool to reconstruct hydro-climatic conditions.