Geomorphology and Paleoclimatology of Lake Lisan Terraces, Dead Sea, Jordan

冰川湖/近东(63-15ka B.P.)等封闭湖泊的水平(Kaufman等人，1992)是蒸发和降水变化的结果。但是，在一个活跃的下沉盆地，如死海(今天在425米处)，构造活动可能会导致湖平面下降。里桑湖的撤退留下了一系列的沉积物和海岸梯田。确定海岸线高度并确定其年代的能力为评估最后一次冰川期间的水文变化、古气候条件和构造活动提供了很好的可能性。因此，本研究的主要目的是：1)调查死海东侧六三湖侵蚀阶地的几何形态特征，如海拔、坡度、宽度、长度等，并对这些阶地进行年代测定。这项调查应该会给出更多的六三湖水位数据和水位退避率。此外，它还有助于建立湖泊水位回归模型，以便将湖泊水位与古气候变化联系起来；2)研究里三组上覆的达米亚组的分布和厚度。研究结果将缩小晚更新世湖面高水位的时间范围，并提供高水位的高度和后续时期的古环境信息；3)调查六三组的地层、岩性和矿物学，记录同沉积和沉积后滑动层的垂直分布，如滑塌和地震岩。这将给出该湖过去的水化学和古环境条件的指标。此外，它还将提供沿东西向断层的垂直位移信息，并指示六三湖的撤退是否受到构造沉降的影响。这些问题将在2005年8月至9月的实地考察活动中进行调查，届时将利用全球定位系统对梯田进行测量，并收集用于年代测定和比较沉积学分析的样品。

The levels of closed lakes such as the glacial Lake Lisan/Near East (63-15 ka B.P.) (Kaufman et al.,1992) are a result of changes in evaporation and precipitation.However, in an actively subsiding basin such as the Dead Sea (today at ¿425m) tectonic activity may contribute to the lake level recession. The retreat of Lake Lisan left behind a sequence of deposits and shore terraces. The ability to determine shore line elevations and to date them offers good possibilities to evaluate hydrologic changes, paleoclimatic conditions and tectonic activity during the Last Glacial. Therefore, the main goals of this study are: 1) investigating geometrical and morphological characteristics of Lake Lisan erosional terraces, in the eastern side of the Dead Sea, such as elevation, gradient, width, length etc. and dating these terraces. This investigation should give additional water level data and rates of level retreat for Lake Lisan. Moreover, it helps to construct a model of lake-level regression, which allows to correlate the levels of the lake with paleoclimatic changes; 2) examining the distribution and thickness of the Damya Formation which overlies the Lisan Formation. The results should narrow down the timing of the late Pleistocene period of the lake level high stand and give information on the altitude of the high stand and the paleoenvironment of the subsequent period; 3)Investigating the stratigraphy, lithology and mineralogy of the Lisan Formation, and recording the vertical distribution of syn- and postdepositional sediment sliding horizons, such as slumps and seismites. This shall give indicators of the past water chemistry and of the paleoenvironment conditions of the lake. Moreover, it will provide information on the vertical displacement along E-W faults and indicate whether the retreat of Lake Lisan was affected by tectonic subsidence or not. These questions will be investigated during a field campaign in August-September 2005, when the terraces will be surveyed by GPS and samples for dating and comparative sedimentological analysis will be collected.