NEW AGE CONSTRAINTS FOR PLEISTOCENE ENVIRONMENTAL CONDITIONS IN SOUTHERN JORDAN: THE JAFR BASIN AND WADIS BURMA AND GHARANDAL
Studied sediments at the western margin of the present Jafr playa are either homogenous unconsolidated or recrystallized and cemented carbonates with root voids, or silty to sandy sediments with horizontal bedding. Gastropod and ostracod shells and charophyte gyrogonites preserved in the topmost section of the carbonates indicate a shallow, probably permanent and oligohaline water body. Radiocarbon dating of biogenic materials revealed an age of 35 cal ka BP. In contrast, nearby exposed detrital sediments represent alluvial and wetland conditions. Ostracod shells from these wetland deposits yielded an age of 43 cal ka BP.
Exposed sediments in Wadi Burma are mostly homogenous consolidated silty sands, occasionally containing few gastropod and ostracod shells. Nine new OSL samples from a section at Jurf ed Darawish yielded minimum ages of >100 ka in the lower part and ages between 40-25 ka in the upper part. A depositional setting with less episodic and erosional but more frequent and aggradational runoff events is inferred. Available moisture was apparently sufficient to support wetlands and springs in the valley floor.
The evidence from Wadi Burma is supported by four radiocarbon age data from alluvial and wetland deposits in Wadi Gharandal. Intercalations of organic-matter rich wetland sediments within a sequence of alluvial sands yielded ages between 40 and 25 cal ka BP.
New age data for the Jafr Basin and the Wadis Burma and Gharandal all indicate that slightly wetter conditions existed in southern Jordan in Marine Isotope Stage 3. Instead of sporadic and erosive flash flood events in the present-day Wadis Burma and Gharandal, probably more regular runoff supported sediment accumulation within the valleys and the formation of wetlands from time to time. A shallow permanent water body probably existed in the Jafr Basin sometime during this slightly wetter period between 40 and 25 ka.