Palaeo-environmental implications derived from lake and sabkha deposits of the southern Rub' al-Khali, Saudi Arabia and Oman

Shallow lakes and sabkha deposits are evidence of past periods of higher groundwater table than today, and hence reflect increased humidity in the Rub' al-Khali, the large desert in the southern part of the Arabian Peninsula. Reported here are the observations made during four expeditions into this remote area in combination with luminescence dating constraining the age of the deposits. The results presented extend the spatial coverage of evidence and show that most of the deposits correlate to MIS 5 (ca. 130–70 ka) and the Early/Mid Holocene (ca. 11–5.5 ka). A single sample points towards potentially more humid conditions during the transition MIS 4/3 (ca. 65–55 ka). The presence of the mussel Unio in some of the deposits attributed to MIS 5 is indirect evidence for the presence of fish in the lakes, which must have supported a rich and diverse fauna (and probably also flora). Together with other evidence, this demonstrates that a number of small persistent lakes were spread across the Rub' al-Khali for at least some of the time. These lakes would not only have been a potential source of freshwater but could also have provided an additional and easy accessible food source via the fish for humans migrating through the area. The presented palaeoenvironmental data underlines that parts of MIS 5 represent a time window of opportunity for a potential expansion of modern humans across Arabia.