Charophyte remains from Wadi Howar as evidence for deep mid-Holocene freshwater lakes in the eastern Sahara of Northwest Sudan

Field research in the eastern Sahara (Northwest Sudan) revealed extensive early- to mid-Holocene lake marl deposits bearing gyrogonites of Charophytes (green algae, stoneworts) along the lower course of the Wadi Howar, an extinct tributary to the Nile. The Charophyte flora of a paleolake southwest of Jebel Rahib (17°31′N/26°52′E) dated prior to 4720 ± 110 yr B.P. is mainly composed of the ecologically sensitive species Nitellopsis obtusa which indicates permanent, relatively deep (4–12 m) and cool oligotrophic freshwater. The study of Nitellopsis sites provides a new and promising approach to the reconstruction of Quaternary paleoenvironments of deserts.