Late Quaternary palaeoenvironments of the Rub' Al Khali.
The Rub' al Khali desert of the Arabian Peninsula is a structural
basin which had filled with alluvium by the end of the Pliocene. During
the late Quaternary, intense arid wind activity transformed it into an
area of sand dunes. Occasional, brief rainfall periods gave rise to
shallow lakes scattered among the dunes. Stratigraphic examination of
the lake bed sites, combined with radiocarbon, sedimentary, geochemical,
geomorphological, and biological data, provides a framework for
interpreting late Quaternary climatic and geologic events in the region.
The clastic sediments of the lakes were derived by runoff from
surrounding sand dunes. Two distinct types of sand furnished the
substratum on which lakes were deposited. Carbonate precipitation
resulted from high rates of plant fixation and subsequent evaporation
and concentration. Gypsum was the usual end product of the evaporative
phase of the geochemical process, but dolomite was deposited in some
Radiocarbon dates on lake molluscs and mans indicate that
rainfall, probably of monsoon nature, filled the lakes during two
intervals, about 35,000 - 17,000 and 10,000 - 5, 000 years B.P. Lakes
lasted from a few years to hundreds of years, and their depths ranged
from about 2 meters to 10 meters. Temperatures were probably very warm
throughout most of the Pleistocene, and hot in the latest Pleistocene
and Holocene, with seasonality similar to that of today.
The evidence of geology, geomorphology, and flora and fauna
suggests that the Rub' al Khali evolved from a relatively subdued
Pleistocene landscape of longitudinally furrowed and gently rounded
dunes with lush grassland vegetation to a Holocene landscape of highly
crested longitudinal dunes and prominent interdunes with sparse grass
cover. The wind directions that prevailed throughout the Pleistocene
probably persist today, but their intensities may have varied.
The evidence from the Rub' al Khali is consistent with evidence
from other parts of the Arabian Peninsula and the Near East and
complements the low latitude record of other parts of the world, notably
Australia and East Africa.