Abstract
This paper reports the results of fieldwork conducted in the 2010 and 2011 DMP field seasons and of analysis of samples collected during these and previous years. Research has involved 1) studying palaeolake sediment outcrops, 2) using ground penetrating radar (GPR) to determine their extent under the Daha¯n Uba¯rı¯, and 3) coring palaeolakes in order to determine their palaeoenvironmental records. Research on these samples is continuing but some initial findings are discussed in this paper. The most extensive palaeolake sediments are found within the al-Mahruqah Formation and were deposited by a giant lake system that developed in the Fazza¯n Basin during past humid periods. Stratigraphic analysis of Lake Megafazza¯n sediments suggests two different sedimentary successions, a lake margin succession distinctive for its lacustrine and palaeosol carbonates, and a clasticdominated, intensely rootleted, basin-centre succession which has terrestrial intervals (aeolian and palaeosols) as well as in the upper parts lacustrine limestones. Both basin margin and basin centre successions are underlain by fluvial deposits. Magnetostratigraphy suggests that the formation may be as old as the mid-Pliocene. After the Lake Megafazza¯n phase, smaller palaeolakes developed within the basin during subsequent humid periods. One of the largest is found in the Wa¯dı¯ al-Haya¯t in the area between Jarma and Uba¯rı¯. Similar deposits further west along the Wa¯dı¯ at progressively higher altitudes are interpreted as small lakes and marshes fed by springs issuing from aquifers at the base of the escarpment, last replenished during the Holocene humid phase. Dating of sediments suggests that this was between c. 11 and c. 8 ka. The Wa¯dı¯ ash-Sha¯t¸ı¯ palaeolake core also provides a Holocene palaeoclimate record that paints a slightly different picture, indicating lake conditions until around 7 ka, whereupon it started oscillating until around 5.5 ka when sedimentation terminates. The reasons for the differences in these records are discussed.