May 10, 2013

Lakes in SE Arabia ~60 thousand years ago

From the paper:
From the current archaeological evidence, it seems that after MIS 5, the different lithic traditions within Arabia develop along separate trajectories, with no indication of additional input from Africa. Recent genetic evidence (Fernandes et al., 2012) also indicates that the relict distribution of minor haplogroups N1, N2 and X, reflects an ancient ancestry of these groups within the Arabian Peninsula which, the authors conclude, then spread from the Gulf region toward the Near East and Europe between 55 and 24 ka. The potential occurrence of increased humidity within the Arabian interior during MIS 3 would, therefore, have been instrumental in determining the success and trajectory of the autochthonous development of early human communities within the region at this time. Although Rosenberg et al. (2012) may be correct in their description of Arabia between ca. 75 and 10.5 ka as a natural barrier for human dispersal, it is possible that indigenous inhabitants may have persisted in environmental refugia around Arabia, such as the Gulf Oasis (e.g. Rose, 2010). The occurrence of a pluvial phase during the early stages of MIS 3, therefore, may have facilitated a range expansion of early humans previously contained within such refugia. To address these important issues, we present a multiproxy record of an early MIS 3 wet phase from a palaeolake sequence within the continental interior of SE Arabia.
Quaternary International Available online 22 February 2013

An early MIS 3 pluvial phase in Southeast Arabia: Climatic and archaeological implications

Ash Parton et al.

Climatic changes in Arabia are of critical importance to our understanding of both monsoon variability and the dispersal of anatomically modern humans (AMH) out of Africa. The timing of dispersal is associated with the occurrence of pluvial periods during Marine Isotope Stage (MIS) 5 (ca. 130–74 ka), after which arid conditions between ca. 74 and 10.5 ka are thought to have restricted further migration and range expansion within the Arabian interior. Whilst a number of records indicate that this phase of aridity was punctuated by an increase in monsoon strength during MIS 3, uncertainties regarding the precision of terrestrial records and suitability of marine archives as records of precipitation, mean that the occurrence of this pluvial remains debated. Here we present evidence from a series of relict lake deposits within southeastern Arabia, which formed at the onset of MIS 3 (ca. 61–58 ka). At this time, the incursion of monsoon rainfall into the Arabian interior activated a network of channels associated with an alluvial fan system along the western flanks of the Hajar Mountains, leading to lake formation. Multiproxy evidence indicates that precipitation increases intermittently recharged fluvial systems within the region, leading to lake expansion in distal fan zones. Conversely, decreased precipitation led to reduced channel flow, lake contraction and a shift to saline conditions. These findings are in contrast to the many other palaeoclimatic records from Arabia, which suggest that during MIS 3, the latitudinal position of the monsoon was substantially further south and did not penetrate the peninsula. Additionally, the occurrence of increased rainfall at this time challenges the notion that the climate of Arabia following MIS 5 was too harsh to permit the further range expansion of indigenous communities.


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