FOUR-THOUSAND-YEAR SEISMIC RECORD WITHIN OUTCROPPING HOLOCENE LAMINATED SEDIMENT ON THE LISAN PENINSULA, SOUTHEASTERN DEAD SEA, JORDAN

Catastrophic spillway erosion has produced an extraordinary 2.1-km-wide exposure of Holocene finely laminated Dead Sea mud on the Lisan Peninsula in the country of Jordan. On March 22, 2000, at the Lisan Peninsula of the Dead Sea, a large salt evaporation pond of the Arab Potash Company became structurally unstable, and its northern dyke was breached. Within one hour, 55 million cubic meters of brine was released northwestward producing the 2.1-km-wide spillway. Brine descended 17 m from the pond’s floor (elevation -396 m msl) to the lake’s surface level (elevation -413 m msl). A labyrinth of channels was incised within the spillway in places over 6 m deep. These fine-grain Holocene laminites of the Lisan Peninsula are distal to clastic sediment sources and resemble the deep-basinal mud facies within the lake. Well-studied Holocene Dead Sea laminites at En Gedi, Wadi Ze’elim and En Feshkha are proximal to clastic sediment sources. These proximal laminites on the western shore of the Dead Sea are coarser grained, have thicker laminae, and possess significantly more clastics. Lisan seismites are typically symmetrical or recumbent folds, differing from the common intraclast breccias on the western shore. The M=7.2 Jericho earthquake of 31 BC, largest Dead Sea earthquake in the last 2,500 years, is displayed in Lisan laminates as symmetrical and recumbent folds, not intraclast breccia as on the western shore. Because of finer texture and lower silt content, Lisan laminites display higher cohesive strength during earthquakes. The effective viscosity of these Lisan laminites is higher, depressing the sediment's Reynolds Number, inhibiting turbulent mixing at the sediment-water interface, and suppressing formation of intraclast breccia seismites. Laminated mud on the Lisan Peninsula was calibrated by depth beneath the 1960 AD lake floor. The 6.5-m-deep sequence of Lisan laminites in one gully displays varves spanning the last 4,600 years of the lake’s history. Seismites of 33 AD, 31 BC, ~750 BC, ~1000 BC, ~1400 BC and ~2050 BC appear to be especially well displayed within the uppermost 6.5 m of the Lisan deposit. Varves average 1.4 mm thick through 6.5 m depth. Extraordinary exposure of the laminites within the spillway invites wide area correlation, varve counting and mechanical analysis of seismite deformation.