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THE SAHARA

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Author Topic: THE SAHARA  (Read 4014 times)
Bianca
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« on: August 10, 2008, 08:19:44 am »









While there is a high degree of homogeneity in the Saharan palaeoclimatic record on multi-millennial
timescales (Jolly et al., 1998; Lezine, 1989; Petit-Maire et al., 1997), the timings of arid episodes and the onset of environmental desiccation are not identical at all locations (Alley et al., 1997; Gasse and vanCampo, 1994; Goodfriend, 1991; Smith, 1998).

This may be explained by a combination of geographical differences in the nature of the principal rain-bearing systems (particularly at the extremities of the Sahara), and the mediation of climate change impacts by local surface environments. The impacts of the final climatic desiccation of the Sahara on human populations would have been strongly mediated by the rapidity and nature of the corresponding environmental desiccation. Where surface water disappeared rapidly,human populations would have been forced to migrate to wetter areas; however, in certain areas populations undertook local adaptation to gradual desiccation by exploiting refugia in which water remained as a consequence of the near-surface geology or occasional rainfall resulting from local topography
(Di Lernia et al., 2002; Mattingly et al., 2003).

The area investigated during the 2002 field survey in Western Sahara is situated between the present
day zones of westerly Atlantic rain-bearing systems to the north-west and monsoonal rainfall to the south, and is characterised by numerous ephemeral river channels. While further research is necessary to develop a detailed environmental chronology for the study area, two radiocarbon dates indicate wetter conditions in the region in the seventh millennium BP, with water present in one of the now-dry lakes in the fifth millennium BP
(Brooks et al., 2003).

These preliminary results are broadly consistent with data from the central Sahara indicating an early-middle Holocene humid episode followed by middle-late Holocene desiccation
(Petit-Maire et al., 1997).
« Last Edit: August 10, 2008, 08:22:05 am by Bianca » Report Spam   Logged

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