133 Quaternary Geology/Geomorphology (Posters) I

LAKE-LEVELS AND SEQUENCE STRATIGRAPHY OF THE LATE PLEISTOCENE LAKE LISAN, DEAD SEA BASIN

Paper number: 133-23
Program: Technical Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

Sediments of the late Pleistocene Lake Lisan (70-15 ka) were deposited in two main depositional environments: beach and fan-delta complexes and offshore environment that produced mainly aragonite alternated with silty laminae. The beach deposits are used as lake-level indicators and the deeper water deposits provide U-series and C14 ages. Sequence stratigraphy methods applied to these lacustrine settings produced independent information on the major base-level changes over the same time span. Since sequence architecture is influenced by both sedimentary input and lake-levels (tectonic subsidence is negligible) we selected the fan-delta setting for the reconstruction of the basin fill history. The lake level indicates short-term fluctuations around 280-290 m below msl during the period of 55-30 kyr., punctuated by a drop event to at least 340 m below msl between 48-43 kyr. At ~27 kyr the lake began to rise sharply and arrived to its maximum elevation of about 164 m below msl between 26 23 kyr.; then it dropped to 300 m below msl at ~15 kyr. During the Holocene the Dead Sea stabilized at ca. 400 m below msl with minor fluctuations.

The sequence stratigraphy analysis indicates a sequence boundary with truncation and channel rejuvenation and low-stand system tract forming at 48-43 ka. A flooding surface and a transgressive system tract onlaping the basin margin followed this time interval. The high-stand system tract is short (26-23 kyr.) and its sediments can also be found inside the tributary valleys around the basin with a retrogradational stacking pattern. The upper sequence boundary is related to the rapid Holocene lake-level drop with many recessional shorelines.

The consistency between the two independent techniques for lake-level reconstruction shows the validity for the sequence stratigraphy framework in small lakes and its reliability for detecting high order base-level changes throughout the Pleistocene.