ALBERT

Description: The radiocarbon timescale has been calibrated by dendrochronology back to 11.8 ka cal BP, and extended to 14.8 ka cal BP using laminated marine sediments from the Cariaco Basin. Extension to nearly 23.5 ka cal BP is based on comparison between 14C and U-Th ages of corals. Recently, attempts to further extend the calibration curve to 〉40 kyr are based on laminated sediments from Lake Suigetsu, Japan, foraminifera in North Atlantic sediments, South African cave deposits, tufa from Spain, and stalagmites from the Bahamas. Here we compare these records with a new comparison curve obtained by 234U-230Th ages of aragonite deposited at Lake Lisan (the last Glacial Dead Sea). This comparison reveals broad agreement for the time interval of 20–32 ka cal BP, but the data diverge over other intervals. All records agree that Δ14C values range between ∼250–450‰ at 20–32 ka cal BP. For ages 〉32 ka cal BP, the Lake Suigetsu data indicate low Δ14C values of less than 200‰ and small shifts. The other records broadly agree that Δ14C values range between ∼250 and 600‰ at 32–39 ka cal BP. At ∼42 ka cal BP, the North Atlantic calibration shows low Δ14C values, while the corals, Lisan aragonites, and the Spanish tufa indicate a large deviations of 700–900‰. This age is slightly younger than recent estimates of the timing of the Laschamp Geomagnetic Event, and are consistent with increased 14C production during this event.

Description: This article presents the role of climate fluctuations in shaping southern Levantine human history from 3600 to 600 BCE (the Bronze and Iron Ages) as evidenced in palynological studies. This time interval is critical in the history of the region; it includes two phases of rise and decline of urban life, organization of the first territorial kingdoms, and domination of the area by great Ancient Near Eastern empires. The study is based on a comparison of several fossil pollen records that span a north-south transect of 220 km along the southern Levant: Birkat Ram in the northern Golan Heights, Sea of Galilee, and Ein Feshkha and Ze'elim Gully both on the western shore of the Dead Sea. The vegetation history and its climatic implications are as follows: during the Early Bronze Age I (∼3600–3000 BCE) climate conditions were wet; a minor reduction in humidity was documented during the Early Bronze Age II–III (∼3000–2500 BCE). The Intermediate Bronze Age (∼2500–1950 BCE) was characterized by moderate climate conditions, however, since ∼2000 BCE and during the Middle Bronze Age I (∼1950–1750 BCE) drier climate conditions were prevalent, while the Middle Bronze Age II–III (∼1750–1550 BCE) was comparably wet. Humid conditions continued in the early phases of the Late Bronze Age, while towards the end of the period and down to ∼1100 BCE the area features the driest climate conditions in the timespan reported here; this observation is based on the dramatic decrease in arboreal vegetation. During the period of ∼1100–750 BCE, which covers most of the Iron Age I (∼1150–950 BCE) and the Iron Age IIA (∼950–780 BCE), an increase in Mediterranean trees was documented, representing wetter climate conditions, which followed the severe dry phase of the end of the Late Bronze Age. The decrease in arboreal percentages, which characterize the Iron Age IIB (∼780–680 BCE) and Iron Age IIC (∼680–586 BCE), could have been caused by anthropogenic activity and/or might have derived from slightly drier climate conditions. Variations in the distribution of cultivated olive trees along the different periods resulted from human preference and/or changes in the available moisture.

Description: The Holocene Dead Sea and the late Pleistocene Lake Lisan were characterized by varying radiocarbon reservoir ages ranging between 6 and 2 ka in the Dead Sea and between 2 ka and zero in Lake Lisan. These changes reflect the hydrological conditions in the drainage system as well as residence time of 14C in the mixed surface layer of the lake and its lower brine. Long-term isolation of the lower brine led to 14C decay and an increase in the reservoir age. Yet, enhanced runoff input with atmospheric 14C brings the reservoir age down. The highest reservoir age of 6 ka was recorded after the sharp fall of the Dead Sea at ~8.1 ka cal BP. The lower reservoir age of zero was recorded between 36 and 32 ka cal BP, when the Lake Lisan mixed layer was frequently replenished by runoff.

Description: The precise determination of the age of historical and geological events by radiocarbon dating is often hampered by the long intersection ranges of the measured data with the calibration curve. In this study we examine the possibility of narrowing the calibrated range of the 14C ages of earthquake-disturbed sediments (seismites) from the Late Holocene lacustrine section in the Dead Sea Basin. The calibrated ranges of samples collected from seismites were refined by applying stratigraphic constraints and tuning the calibrated ranges to known historical earthquakes. Most of the earthquakes fall well within the 1σ error envelope of the 14C age. This refinement demonstrates that the lag period due to transport and deposition of vegetation debris is very short in this arid environment, probably not more than a few decades. This assessment of seismite 14C ages attests to the validity of 14C ages in Holocene sediments of the arid area of the Dead Sea. Furthermore, it demonstrates our ability to achieve highly precise (correct to within several decades) 14C ages.

Description: A continuous and high-resolution record of the radiocarbon reservoir age (RA) has been recovered from the primary aragonites that were deposited from the last glacial Lake Lisan. The RA is calculated as the difference between the measured 14C “apparent” age in the aragonite and the atmospheric age at any particular time. The RA shows temporal decreases during the time interval of ≃28 to ≃18 ka cal BP. This behavior is attributed to a continuous addition of low RA-high bicarbonate freshwater into the high RA-Ca-chloride (low bicarbonate) brine solution filling the lake. The mixing of the brine with freshwater drives the precipitation of CaCO3 in the form of aragonite from the lake epilimnion (surface layer). The runoff-brine mixture in Lake Lisan is also reflected by the Sr/Ca ratios that are positively correlated with the RA. Nevertheless, the 14C content in the epilimnion did not drop at the same rate as the atmospheric value but rather remained nearly constant. We suggest that turbulent mixing with the much saltier hypolimnion (lower layer) across the hypolimnion/epilimnion interface at a depth of about 390 m below sea level, buffered the 14C content as well as the Sr and Ca concentrations in the aragonite precipitating solution. The RA-Sr/Ca related limnological model developed here opens the way to determine the reservoir-age-corrected atmospheric ages of Lisan Formation aragonites beyond 28 ka cal BP.

Description: The drilled Inter-Continental Drilling Project core at the deeps of the Dead Sea reveals thick sequences of halite deposits from the last interglacial period, reflecting prevailing arid conditions in the lake’s watershed. Here, we examine sequences of intercalating evaporates (halite or gypsum) and fine-detritus laminae and apply petrographic, micro-X-ray fluorescence, and statistical tools to establish in high-temporal resolution the hydroclimatic controls on the sedimentation in the last interglacial Dead Sea. The time series of the thickness of the best-recovered core sections of the layered halite, detritus, and gypsum reveals periodicities of ~11, 7–8, and 4–5 yr, pointing to a North Atlantic control and possibly solar influence on the hydrology of the Dead Sea watershed during the regionally arid period of the last interglacial period. Similar periodicities were detected in the last glacial and modern sedimentary sequences of the Dead Sea and other archives of the central Levant, indicating a persistent impact of the solar cycles on regional hydrology, possibly through the effects of the North Atlantic Oscillation.

Description: A comprehensive record of lake level changes in the Dead Sea has been reconstructed using multiple, well dated sediment cores recovered from the Dead Sea shore. Interpreting the lake level changes as monitors of precipitation in the Dead Sea drainage area and the regional eastern Mediterranean palaeoclimate, we document the presence of two major wet phases (∼ 10–8.6 and ∼ 5.6–3.5 cal kyr BP) and multiple abrupt arid events during the Holocene. The arid events in the Holocene Dead Sea appear to coincide with major breaks in the Near East cultural evolution (at ∼ 8.6, 8.2, 4.2, 3.5 cal kyr BP). Wetter periods are marked by the enlargement of smaller settlements and growth of farming communities in desert regions, suggesting a parallelism between climate and Near East cultural development.

Description: Lake Lisan, the late Pleistocene precursor of the Dead Sea, existed from ∼70,000 to 15,000 yr B.P. It evolved through frequent water-level fluctuations, which reflected the regional hydrological and climatic conditions. We determined the water level of the lake for the time interval ∼55,000–15,000 cal yr B.P. by mapping offshore, nearshore, and fan-delta sediments; by application of sequence stratigraphy methods; and by dating with radiocarbon and U-series methods. During the studied time interval the lake-level fluctuated between ∼340 and 160 m below mean sea level (msl). Between 55,000 and 30,000 cal yr B.P. the lake evolved through short-term fluctuations around 280–290 m below msl, punctuated (at 48,000–43,000 cal yr B.P.) by a drop event to at least 340 m below msl. At ∼27,000 cal yr B.P. the lake began to rise sharply, reaching its maximum elevation of about 164 m below msl between 26,000 and 23,000 cal yr B.P., then it began dropping and reached 300 m below msl at ∼15,000 cal yr B.P. During the Holocene the lake, corresponding to the present Dead Sea, stabilized at ca. 400 m below msl with minor fluctuations. The hypsometric curve of the basin indicates that large changes in lake area are expected at above 403 and 385 m below msl. At these elevations the lake level is buffered. Lake Lisan was always higher than 380 m below msl, indicating a significantly large water contribution to the basin. The long and repetitious periods of stabilization at 280–290 m below msl during Lake Lisan time indicate hydrological control combined with the existence of a physical sill at this elevation. Crossing this sill could not have been achieved without a dramatic increase in the total water input to the lake, as occurred during the fast and intense lake rise from ∼280 to 160 m below msl at ∼27,000 cal yr B.P.

Description: This study presents an assessment of the potential application of Mn content in rock varnish laminae as a paleoclimate indicator. To investigate the environmental controls on varnish formation, we determined Mn composition in rock varnish formed on flint artifacts produced during the earliest Holocene from eight coeval prehistoric sites in the Negev desert, Israel. These sites lie along a north–south annual rainfall transect ranging between 120 and 30 mm yr− 1. The varnish is ~ 100 times enriched in Mn relative to the content in the desert dust source material. Chemical profiles across the varnish display 4–6 distinct Mn peaks in all sampled sites, pointing to systematic fluctuations within the varnish along a wide range of environmental settings. The mean Mn contents in the various sites range between 10.7 and 15.6 at.%, yet within this range, the Mn content in the Negev varnish does not show a correlation with mean annual rainfall. As moisture is needed for Mn mobility, wetting cycles by dew or light rain, which are not adequately represented by the mean annual rainfall amounts but control the number of wetting–drying cycles may explain the variance within the results from the arid and hyperarid Negev varnish.

Description: The Dead Sea is a terminal lake of one of the largest hydrological systems in the Levant and may thus be viewed as a large rain gauge for the region. Variations of its level are indicative of the climate variations in the region. Here, we present the decadal- to centennial-resolution Holocene lake-level curve of the Dead Sea. Then we determine the regional hydroclimatology that affected level variations. To achieve this goal we compare modern natural lake-level variations and instrumental rainfall records and quantify the hydrology relative to lake-level rise, fall, or stability. To quantify that relationship under natural conditions, rainfall data pre-dating the artificial Dead Sea level drop since the 1960s are used. In this respect, Jerusalem station offers the longest uninterrupted pre-1960s rainfall record and Jerusalem rains serve as an adequate proxy for the Dead Sea headwaters rainfall. Principal component analysis indicates that temporal variations of annual precipitation in all stations in Israel north of the current 200 mm yr−1 average isohyet during 1940–1990 are largely synchronous and in phase (∼70% of the total variance explained by PC1). This station also represents well northern Jordan and the area all the way to Beirut, Lebanon, especially during extreme drought and wet spells. We (a) determine the modern, and propose the past regional hydrology and Eastern Mediterranean (EM) climatology that affected the severity and length of droughts/wet spells associated with multiyear episodes of Dead Sea level falls/rises and (b) determine that EM cyclone tracks were different in average number and latitude in wet and dry years in Jerusalem. The mean composite sea level pressure and 500-mb height anomalies indicate that the potential causes for wet and dry episodes span the entire EM and are rooted in the larger-scale northern hemisphere atmospheric circulation. We also identified remarkably close association (within radiocarbon resolution) between climatic changes in the Levant, reflected by level changes, and culture shifts in this region.