Holocene stratigraphy of the Dead Sea: Correlation of high‐resolution seismic reflection profiles to sediment cores

Abstract

Abstract. The northern basin of the Dead Sea is occupied by a -300-m-deep lake. A series of cores in the deep-water part of the lake provide information about the top 365 cm of the sediments. The cores were correlated with high-resolution 3.5-kHz seismic profiles from this area and provide lithologic and age constraints for the high-resolution seismic reflection data. Visual comparison of the two data sets shows that strong surface and shallow subsurface reflectors (A and B) correlate to the massive salt at the seafloor surface and the indurated salt at the base of the cores, respectively. Calculations of an average seismic velocity based on the interval between these reflectors and the corresponding sedimentary thickness yield an average 3500 m/s velocity. This agrees closely with velocities determined from direct measurements of compressional velocities for sediment samples. Ultrasonic wave velocity measurements of salt samples from the cores and dry rock salt cores from the southern basin of the Dead Sea indicate that wave velocities are independent of the burial depth at shallow depths; however, velocities show strong dependence on porosity. At low hydrostatic pressure a reduction in porosity as well as closure of microcracks in the crystals cause an increase in the velocities. This increase disappears at higher stress levels. Synthetic seismograms of the upper 3 ms and the entire 25 ms penetrated by the seismic profiles reinforce the lithologic and seismic stratigraphic correlation and confirm that prominent reflectors in the basin represent the top boundary of halite layers which are separated by laminated sequences of evaporites and clastics. The salt in the upper salt sequence is deposited at a very fast rate of more than 20 mm/yr. However, at shallow depths, considerable compaction takes place. Variations in appearance and velocities of the upper salt sequence and middle salt sequence indicate that the porous, granular, and fine-grained precipitates of the surface salts are diagenetically altered to a coarse and compact crystalline aggregate by re-solution and crystallization with burial. The sedimentary sequences recovered in the cores suggest that significant lake level fluctuations took place in the past in response to climatic changes. The detailed correlation of the cores and seismic profiles makes it possible to extrapolate climatic data from earlier periods beneath the maximum core penetration by analyzing the seismic stratigraphic sequences of the seismic reflection data. IntroductionThe Dead Sea basin is one of the deepest active strike-slip basins on Earth. It is located along the Dead Sea transform, a plate boundary which separates the Arabian plate from the African and Sinai plates. The Dead Sea is a topographic depression over 110 km long and more than 400 m below sea

Alluvial deposition and lake-level fluctuations forced by Late Quaternary climate change: the Dead Sea case example

“…Based on 14 C dating of the upper and lower layers, Yechieli et al (1993) have indeed proposed that the halite layer formed between 11315 F 80 and 8440 F 95 years B.P. This layer probably is the same as the one identified by Ben-Avraham et al (1999) from seismic reflection profiles in the Dead Sea basin, and dated about 8 to 7 kyears B.P. It is probably during this regression that lake Lisan formed the numerous wave-cut shorelines carved into the talus apron and terraces on top of the Late Pleistocene fan delta at the base of the cliff flanking the Dead Sea.…”

Pollen analysis of core DS7-1SC (Dead Sea) showing intertwined effects of climatic change and human activities in the Late Holocene

“…Core DS7-1SC (in short DS7), 365 cm long, 12 cm in diameter, taken at 203 m bsl (level of 1993) was recovered from a rise adjacent to the western border fault of the Dead Sea graben. It is located northeast of Ein Gedi by 31 29.363 0 N and 35 26.101 0 E (Heim et al, 1997;Ben-Avraham et al, 1999). The lithology consists of an alternation of two units ( Fig.…”

Collapse and subsidence associated with salt karstification along the Dead Sea

“…Yechieli 1993;Migowski et al 1998;Neev and Emery 1995;Ben Avraham et al 1999). Some examples are given in Figure 2.…”

“…This salt lies under the regionalwater table in most places, and is permeable compared with older salt units (Yechieli 1995). Younger, thin salt layers were deposited in the Dead Sea basin during the late Holocene (Neev 1964;Heim et al 1997;Ben-Avraham et al 1999). …”