This study analyzes pollen, non-pollen-palynomorphs, and charcoal from the deep-drilled Dead Sea 5017-1A sediment cores. It reconstructs a high-resolution vegetation and environment history of the southern Levant at 147–89 ka, encompassing the late penultimate glacial (147.3–130.9 ka), the initial warming (130.9–124.2 ka), the last interglacial optimum (124.2–115.5 ka), and the early last glacial (115.5–89.1 ka).
The result shows that the late penultimate glacial and early last glacial were cool and were characterized by steppe and desert expansions. Sub-humid conditions were confined to the mountains where moderate amounts of deciduous oaks were distributed. The initial warming was marked by a prevalence of desert components and a virtual absence of trees and shrubs. A concomitant increase in frost-sensitive pistachio trees suggests that the extensive aridity was accompanied by a prominent warming. The last interglacial optimum was initiated by an abrupt grass expansion replacing desert components and was followed by a fast spread of woodlands in the mountains. A remarkable sclerophyllous increase points to enhanced Mediterranean rains superimposed by strong seasonal drought.
The predominance of herbaceous pollen during the whole investigated interval suggests that steppe and desert vegetation was persistently close to the Dead Sea in the low latitudes. Due to the prominent vegetation gradient in the southern Levant, the relatively low arboreal pollen contents probably underestimate the actual density of trees and shrubs in the northern mountains (e.g., the Galilee Mountains). The major headwater area of the Dead Sea is located in these places, where a strong arboreal evapotranspiration effect is observed. During the last interglacial optimum, the abundant trees and shrubs possibly consumed a significant part of the precipitation. Consequently, small water volumes were supplied to the Dead Sea, resulting in extremely low lake levels and massive halite deposition. A reverse scenario might explain the contrast between the coeval occurrence of low woodland coverage and high lake stands during glacials.
A synthesis of regional records (pollen, lacustrine sediments, and speleothems) indicates that the environment of the southern Levant at 128–122 ka was unstable, marked by generally low vegetation cover, intensified fire activities, and extensive flood-induced erosions. There were signs of moisture contribution from the sub-tropics during this episode, despite the dominant control of the Mediterranean rains during the whole investigated interval. In the southern Dead Sea drainage area, the sub-tropical atmospheric systems brought short-lived rainstorms that led to the delivery of numerous coarse detritus to the Dead Sea.
Archaeological evidence from the Israeli caves proves the occupation of anatomically modern human during 130–90 ka. This period was characterized by activated hydrological systems in the Sahara and the Negev Desert, as well as increased vegetation cover in the Sahara and the southern Levant. Hence, the present desert barrier between Africa and Asia was probably turned into a migrational corridor. In the southern Levant, the diverse ecosystems provided shelters and potential food resources for the residence and further dispersal of the hominins.
In the whole eastern Mediterranean region, a comparatively high abundance of trees and shrubs was characteristic of the last interglacial and vice versa for the glacials. This condition disapproves former hypothesis that an anti-phase relationship existed between the southern Levant and the rest of the Mediterranean region in terms of glacial-interglacial climate. The Mediterranean-wide phenomenon of sclerophyllous expansion during the early phase of the last interglacial points to the boreal summer insolation maximum as the trigger. It further questions the possibility of delayed arboreal expansion in the southern Levant that is based on the current age-depth model of the Dead Sea 5017-1A pollen record.
This study fills the gap of vegetation history during 147–89 ka in the southern Levant. The independent paleobotanical reconstructions add information to the paleoenvironment and gain new insights into resolving the controversies indicated by existing paleorecords. It improves our understanding of the environmental setting for early modern human dispersal, as well as the close association between the Mediterranean vegetation changes and the Atlantic-Mediterranean atmospheric-oceanic circulations.
Universitäts- und Landesbibliothek Bonn Accessed 150 times | Last updated 04.01.2018
Chen, C. (2017): Dead Sea Pollen Reveal the Paleoenvironment of the Southern Levant during 147–89 ka from the Paleobotanical Perspective. University of Bonn
|Title||Dead Sea Pollen Reveal the Paleoenvironment of the Southern Levant during 147–89 ka from the Paleobotanical Perspective|
|Publisher||University of Bonn|