Dead Sea Sediments Research Articles

Radiocarbon dating of primary aragonite by sequential extraction of CO2

This paper describes the potential of correcting the 14C age shift resulting from the contamination of primary aragonites by detrital carbonates using online sequential extraction of CO2. The experiments were carried out on laminated lacustrine aragonites collected from Holocene Dead Sea sediment sections. X-ray diffraction analysis revealed the presence of detrital calcite interpreted to originate from the watershed and transported to the lake with runoff. The contamination could not be separated physically from the sample, potentially contributing decayed 14C (‘dead carbon’) and increasing the age of the aragonite. Sequential extraction of successive fractions of CO2 unveiled the effect of detrital material on the 14C ages, and showed that the first CO2 extract represents the least contaminated 14C fraction that provides the best approximation for the true 14C age (which includes the lake’s reservoir age). We calculated the age offset contributed by the contamination range encountered in this study (1-21%) to be about 900 years per 10% contamination. The sequential extraction procedure is recommended for 14C dating of Holocene age lacustrine carbonates suspected to be contaminated with extraneous carbon-bearing materials.

The role of volcanic eruptions in blocking the drainage leading to the Dead Sea formation

The shrinkage of the Lisan Lake (LL) to form the recent Dead Sea (DS) was mainly a result of the reduction of the catchment area from around 157,000 km2 during Late Pleistocene to 43,000 km2 presently. The reduction in the catchment area resulted from the eruption and spread of the basalt flows of Jabal Arab-Druz (JAD), which together with the resulting deposition of thick rock debris and gravels occupied the drainage system. The filling of the pre-basalt drainage system, which used to feed the Dead Sea, with basalts and alluvial sediments blocked the inflows from reaching the Dead Sea. Local base levels along the basalt flow boarders such as Azraq Oasis, Sirhan Basin and Damascus Oasis, and numerous pools and mud flats were created.

Soft sediment deformation by Kelvin Helmholtz Instability: A case from Dead Sea earthquakes

The standard explanation for soft sediment deformation is associated with overturn of inverted density gradients. However, in many cases, observations do not support this interpretation. Here we suggest an alternative in which stably stratified layers undergo a shear instability during relative sliding via the Kelvin–Helmholtz Instability (KHI) mechanism, triggered by earthquake shaking. Dead Sea sediments have long stood out as a classical and photogenic example for recumbent folding of soft sediment. These billow-like folds are strikingly similar to KHI structures and have been convincingly tied to earthquakes. Our analysis suggests a threshold for ground acceleration increasing with the thickness of the folded layers. The maximum thickness of folded layers (order of decimeters) corresponds to ground accelerations of up to 1 g. Such an acceleration occurs during large earthquakes, recurring in the Dead Sea.

Sources and distribution of trace and minor elements in the western Dead Sea surface sediments

Twenty Dead Sea surface sediment samples were analyzed for their major, minor and trace element compositions. The samples represent muddy sediments along the western parts of the lake, from water depths of 8–250 m. These sediments were deposited after 1983, under oxic conditions, following the overturn of the water column in 1979, which ended about 300 years of meromictic stratification with an anoxic lower water mass. The changes in their metal concentrations are discussed in view of the different brine oxidation state. The sediments consist of detrital minerals—carbonates, quartz and clays and authigenic minerals—aragonite, halite and traces of gypsum. Calculations indicate that all mud samples contain more than 3.6% authigenic aragonite, which was found to precipitate preferentially in near shore sediments. An increase in Ca and a decrease in Al concentrations with decreasing water depths and in a transect from N to S were observed. These are attributed to differential settling of detritus and authigenic carbonates close to the shore and fine Al-silicates in the deep waters, and to the southward decrease in the contribution of clay minerals, mostly derived from the Jordan river. Fe, Ce, Be and Eu were found to exhibit conservative behavior with respect to Al during the transition from stream sediments in the drainage basin to lake sediments. When compared to normal marine sediments, the Dead Sea sediments have similar Cu, Ni, Zn, Be, Ce and Eu concentrations, whereas Cd is enriched by nearly 1 order of magnitude. A good correlation exists between Cd and P, suggesting that the Cd enrichment arises from outcrops of Cd-rich phosphate rocks that are found in the Dead Sea basin. The somewhat depleted Pb concentrations in the lake muddy sediments might be explained by the somewhat high Pb concentrations (normalized to salinity) in the Dead Sea water column, as compared to seawater and by its removal, mainly through halite precipitation. The unusual distribution of Mn concentrations in the surface sediments and its association with authigenic aragonite imply, as has already been suggested, that Mn co-precipitates with aragonite.

Nutrients in pore waters from Dead Sea sediments

Nutrients in pore waters from Dead Sea sediments

A procedure for the selective enrichment ofHalobacteroides halobiusand related bacteria from anaerobic hypersaline sediments

Abstract In enrichment cultures for halophilic anaerobic chemo-organotrophic bacteria from hypersaline sediments a variety of bacterial types developed. However, when the sediment samples were first heated to 80–100°C for 10–20 min, bacteria resembling Halobacteroides halobius were selectively enriched. Terminal endospores were observed in some of the cultures of this type of bacterium, previously unknown to produce endospores. Halobacteroides -type cells were found not to be restricted to Dead Sea sediments, but were isolated also from seawater evaporation ponds. The finding of endospore formation in Halobacteroides supports its proposed phylogenetic relationship with other endospore-forming anaerobic halophilic bacteria.

Comparative isotope study of two short sediment cores from the dead sea

Two short sediment cores from the Dead Sea have been analyzed for the following isotopes: 18 O, 13 C, 137 Cs, 210 Pb, U, Th and 40 K. In the northerly core, taken from the Jordan River discharge area, the δ 13 C and δ 18 O of the carbonates is quite homogeneous and very similar to that found in the suspended material of the inflow. In the southerly core, taken nearshore in the central part of the lake, the stable-isotope composition of the carbonates is depth-variable and generally more enriched in both isotopes. The carbonates of this core are derived from two main sources: allogenic carbonates with an isotopic composition similar to that of the northerly core and endogenic aragonite from the Dead Sea, which is relatively more enriched in both isotopes. 137 Cs and 210 Pb are used to show that near the Jordan River inflow sedimentation rates are higher by an order of magnitude over the nearshore central region. The first systematic measurements of U and Th in Dead Sea sediments are presented; the values are found to be within the range encountered in sedimentary environments.

Comparative isotope study of two short sediment cores from the Dead Sea

Two short sediment cores from the Dead Sea have been analyzed for the following isotopes: 18O, 13C, 137Cs, 210Pb, U, Th and 40K. In the northerly core, taken from the Jordan River discharge area, the δ 13C and δ 18O of the carbonates is quite homogeneous and very similar to that found in the suspended material of the inflow. In the southerly core, taken nearshore in the central part of the lake, the stable-isotope composition of the carbonates is depth-variable and generally more enriched in both isotopes. The carbonates of this core are derived from two main sources: allogenic carbonates with an isotopic composition similar to that of the northerly core and endogenic aragonite from the Dead Sea, which is relatively more enriched in both isotopes. 137Cs and 210Pb are used to show that near the Jordan River inflow sedimentation rates are higher by an order of magnitude over the nearshore central region. The first systematic measurements of U and Th in Dead Sea sediments are presented; the values are found to be within the range encountered in sedimentary environments.

Iron in the Dead Sea

The distributions of dissolved and of particulate iron in the Dead Sea during the period which preceeded its overturn and thereafter (1977–1980) are reported. During 1977–1978, the vertical profiles of the iron phases revealed facets of the mixing pattern: the progressive deepening of the pycnocline, restricted mixing within the upper water mass and penetration of surface waters into the deepest layer. The inventories of particulate iron suggest resuspension of bottom sediments in November 1978 and after the overturn the gradual disappearance from the water column of iron sulfides and iron oxy-hydroxides. Fluxes of iron from and to the lake in the undisturbed meromictic Dead Sea have been estimated: it appears that diffusion of divalent iron from bottom sediments was the major source for the standing crop of iron in the lower water mass. Low settling velocities of solid particles in the dense and viscous Dead Sea is one of the causes for the relatively large concentrations of particulate iron. The rate constant for oxidation of divalent iron in Dead Sea sediment interstitial waters is larger by two orders of magnitude than in other natural waters.

Halobacteroides halobius gen. nov., sp. nov., a Moderately Halophic Anaerobic Bacterium from the Bottom Sediments of the Dead Sea

Summary An anaerobic, long rod-shaped, motile, Gram-negative, non-sporulating bacterium wasisolated from Dead Sea sediment. It required NaCl concentrations between 1.4 and 2.8 mol/l, and optimal growth with doubling times of about 1 hour was found in 1.5-2.5 mol NaCl/l and 37-42 °C. Fermentation products on glucose were ethanol, acetate, hydrogen and carbon dioxide. Fermentable substrates included several mono- and oligosaccharides, starch and pyruvate. The Guanine plus Cytosine content of its DNA was 30.7 mol . Analysis of the oligonucleotides in a digest of its 16S rRNA showed that the isolate was an eubacterium, but was not a member of any of the major eubacterial subgroups defined to date. We propose to name it Halobacteroides halobius gen. nov., sp. nov., belonging to a new family, the Haloanaerobiaceae. The type strain is strain MD-1 (ATCC 35273).

Clostridium lortetii sp. nov., a halophilic obligatory anaerobic bacterium producing endospores with attached gas vacuoles

A strain of Clostridium was isolated from Dead Sea sediment, differing from the previously described Clostridium types in its halophilic character. It required NaCl concentrations between 1 and 2 M, and optimal growth was found in 1.4–1.5 M NaCl at 30° C and in 1.7 M NaCl at 45° C. In sporulating cells gas vacuoles developed, generally near the developing terminal endospore only, and these vacuoles remained attached to the mature endospore after degeneration of the vegetative cell. Fermentation products included acetate, butyrate and hydrogen. Glucose and a few other carbohydrates stimulated growth, though they were poorly utilized. A new species name has been proposed for the organism: Clostridium lortetii.

Recent climatic changes recorded by the salinity of pore waters in the Dead Sea sediments

The salinity of lakes is subject to variations imposed by climatic changes. These variations are recorded in the salinity profile of pore waters. Meromictic lakes, such as the Dead Sea, are a special case where waters which underlie the mixolimnion reflect salinity variations. In a sediment core from Dead Sea shallow waters, the salinity profile exhibited a minimum at about 1.9 m depth. It is shown by a diffusion model that this minimum can be attributed to lower salinities which prevailed at the sediment water interface for several decades around the turn of this century. No such minimum was observed in a sediment core from the deepest part of the lake where, during the last two centuries, the overlying brines had a constant salinity.

The stereoisomeric composition of phytanyl chains in lipids of Dead Sea sediments

Lipid extracts from five recent Dead Sea sediments were analyzed for isoprenoid compounds and the following were isolated: free and phospholipid-bound di- O-phytanylglycerol, free phytanol and free and esterifled phytanic acid. The phytanyl groups of the diether and the free phytanol were oxidized to the corresponding phytanic acid; the stereoisomeric composition of the derived phytanic acids as well as of the ester-bound phytanic acid was determined by open-tubular gas-liquid chromatography of the corresponding methyl esters on butanediolsuccinate polyester. Only the 3 R,7 R,11 R-isomer of phytanic acid was detected in each of the phytanate samples, indicating that these phytanyl chains in the Dead Sea sediments are most likely derived from extremely halophilic bacteria rather than from phytol of chlorophyll origin. These findings also provide further evidence that the mixtures of RRR and SRR-phytanic acids previously isolated from organic-rich shales were most likely derived from the phytyl chain in chlorophyll.

Minor and trace elements in Dead Sea water

The average concentration of several metals in six water profiles taken from the Dead Sea are: Sr = 308−330 mg/l; Li = 17−21 mg/l; Mn = 3.1−8.0 mg/l; Cu = 300−500 μg/l; Zn = 500 μg/l; Fe = 10−15 μg/l; Ni = 20−25 μg/l; Co = 8 μg/l, Cd = 8−10 μg/l, Pb = 120−300 μg/l; I = 80−120 μg/l and U = 1.5−2.5 μg/l. The mechanisms which govern the behavior of metals in the Dead Sea are: (a) incorporation into authigenic carbonates and sulfides in the sediment (Sr, Zn, Cd, Fe); (b) formation of soluble salts or soluble chloridic complexes (Li, Mn, Pb); and (c) removal due to reduction and formation of sparingly soluble compounds (U). High concentrations of Mn (up to 135 mg/l) were found in interstitial water separated from the sediments. Several sets of experiments on interstitial water from the Dead Sea and marine sediments indicate that the high concentration of Mn is not due to the formation of high-molecular-weight organic complex but rather to the formation of inorganic complexes similar to that of the alkali and alkaline-earth metals. In the Dead Sea the evidence strongly points towards chloridic complexes.

The microbiology and biogeochemistry of the Dead Sea

The Dead Sea is a hypersaline water body. Its total dissolved salts content is on the average 322.6 gm/liter. The dominant cation is Mg (40.7 gm/liter), followed by Na (39.2 gm/liter), Ca (17 gm/liter) and K (7 gm/liter). The major anion is Cl (212 gm/liter), followed by Br (5 gm/liter); SO4 and HCO3, are very minor. The lake contains a limited variety of microorganisms and no higher organisms. The number of recorded species is very low, but the total biomass is reasonably high (about 10(5) bacteria/ml and 10(4) algal cells/ml). The indigenous flora is comprised mainly of obligate halophylic bacteria, such as the pink, pleomorphicHalobacterium sp., aSarcina-like coccus, and the facultative halophilic green alga,Dunaliella. Sulfate reducers can be isolated from bottom sediments. Recently a unique obligate magnesiophile bacteria was isolated from Dead Sea sediment. Several of the Dead Sea organisms possess unusual properties. TheHalobacterium sp. has extremely high intercellular K(+) concentration (up to 4.8M) and extraordinary specificity for K(+) over Na. TheDunaliella has very high intracellular concentration of glycerol (up to 2.1M). The microorganisms exert marked influence on some biogeochemical processes occurring in the lake, such as the control of the sulfur cycle and the formation and diagenesis of organic matter in the sediments. The Dead Sea is an excellent example of the development of two different mechanisms for adjusting to a hostile environment. The algae adjust to the high salinity by developing a mechanism for the exclusion of salts from the intracellular fluid and using glycerol for osmotic regulation. On the other hand, the bacteria adapt to the environment by adjusting their internal inorganic ionic strength, but not composition, to that of the medium. The problem of population dynamics and limiting factors for algal and bacterial productivity are discussed in view of the total absence of zooplankton and other consumers other than bacteria.

Relationship between Ratio of Pristane to Phytane, Crude Oil Composition and Geological Environment in Australia

ACYCLIC isoprenoid hydrocarbons have been identified in sediments1–4, coal5 and petroleum6–11. Although isoprenoid hydrocarbons up to C25 have been recognized11, pristane (C19) and phytane (C20) are usually the most important in terms of concentration. Both are considered to be products of the diagenesis of the phytyl side chain of chlorophyll5, although other sources are possible12–14. In coals5, pristane is formed by decarboxylation of phytanic acid and phytane by dehydration and hydrogenation of phytol. Differences in the ratio of pristane to phytane may reflect variations in the degree of oxidation during the early stages of chlorophyll degradation5. Thus the formation of phytanic acid, the precursor of pristane, should occur to a greater extent on land during the initial, aerobic stages of plant decay than in an aquatic environment where totally anaerobic decomposition is more likely. High ratios of pristane to phytane, which are found in bituminous coals5 and certain Australian oils5, may reflect source material of terrestrial origin. The ratios of phytanic acid to phytol (plus dihydrophytol) in Dead Sea sediments were 4.7 and 5.5 in two oxidizing environments and 1.1 and 3.4 in two reducing environments14. Clearly the formation of phytanic acid is favoured in an oxidizing environment. But the precise mode of formation of phytanic acid in the natural environment is not fully understood because reduotion of the double bond as well as oxidation of the alcohol part of the molecule is necessary to form phytanic acid from phytol.

Biological Productivity in the Dead Sea Part II. Evidence for Phosphatidyl Glycerophosphate Lipid in Sediment

AbstractReducing surface sediment from a depth of 300 m in the Dead Sea was found to contain phytanic acid (520 μg/Kg), dihydrogen phytol (800 μg/Kg) and phytane (17 μg/Kg). An investigation revealed that glycerol phytanyldiether could be isolated from the sediment by hydrolysis of a lipid soluble fraction. The phytanyldiether is probably derived from the phosphatidyl glycerophosphate lipid, which has been demonstrated by Kates and co‐workers to be the dominant lipid present in red halophilic bacteria. Comparison of results by analysis of Halobacterium cutirubrum, using the same analytical procedure as was used for the sediment investigation, confirmed the authenticity of the lipid characterization. In view of this finding, it is suggested that phytane in the Dead Sea sediment has been derived from this lipid and that long‐chain isoprenoid hydrocarbons in some ancient environments may have had a similar origin.