Climate Influences
Beginning late in the Cretaceous period and continuing throughout much of the Pleistocene, climate worked with the geology and tectonics by providing "both the energy and material that the fluvial systems needed to do their work." (Salameh, 1997; cf. also Ward, 1995; Strahler and Strahler, 1994; and Leuven, 1982). As variations in climate triggered changes in pluvial activity, the level of the Dead Sea and it predecessors (Lake Samra – fresh water, in the Lower Pleistocene; and Lake Lisan – 50-12,000 BD) changed many times. During these periods of base-level adjustment, the highly susceptible plateau limestone and underlying sandstone experienced significant erosion along channel walls and mouths. Today, we see the remains of these climatic oscillations in the more than 30 shore terraces that have been preserved and identified along the Dead Sea escarpment.
Associated with some of the climatic oscillations was a significant increase in the intensity and frequency of storm events. All along the eastern shoreline of the Dead Sea numerous remnants of these storm episodes can be seen in the relic deltas that are now exposed at the mouths of many wadis. Salameh (1997) argues that these were originally subaqueous deltas, deposited when Lake Lisan (fueled by Pleistocene storm events) was receiving huge accumulations of sediment coming from the erosion of channel walls and valleys (Odeh and Salameh, 1988). As the climate became more arid and the base-level of the lake lowered, the deltas and canyons we see today became fully exposed (approximately 18-23,000 BP). The surface of Lake Lisan is estimated to have been 200 meters above the present level of the Dead Sea.
As erosion and weathering (both mechanical and fluvial) was widening and deepening the stream channels, compression along the boundary between the adjoining plates was displacing and lifting (between 1,500 and 2,000 meters) the plateau block (Salameh, 1997). The net result was the uplifted and dissected plateau we see today. A detailed discussion on the differential of the uplift along the plate boundary can be found in Wdowinski and Zilbermann (1996).
Preservation of Relic Features in the Modern Landscape
How have these canyons been preserved? Why didn’t new drainage channels develop in response to the change in gradient of the uplifted plateau? It appears that the most important factor in the preservation of the relic channels is that which influenced channel location in the beginning ... faults and fractures. Given the magnitude of faulting and fracturing in the area it is unlikely that even a catastrophic event or events would or could completely alter the already established drainage network. Oberlander (1965) observed similar anomalies in his work on the Zagros Streams. Working in tectonically similar conditions to those found on the plateau, Miller and Dunne (1996) observed that in areas of compressional tectonics, mass wasting along surface-parallel or shallowly dipping fractures tended to preserve valley form over time. Though conducted in a humid environment, Potter (1978) observed similar results. He found that an already established drainage system would not significantly change when unlifted by tectonic reshaping (cf. also Cox, 1989). Burbank, et. al. (1996) suggested another factor may have contributed to the preservation of the original pre-uplift channels. Their work found that in most cases, drainage gradients were unchanged following uplift due to the failure of bedrock-uplift to keep pace with the rate at which channel valleys were continuing to incise their underlying bedrock.