Page 58

supply than today and ground water levels may have risen
whilst the valley floor aggraded.
7.3. Aridity and flow variability increased after ca. 20 ka.,
when climate changed significantly from a biostasic state,
with probably more frequent subtropical rains than today,
to an arid state similar to a mediterranean seasonnal-type
climate. After ca. 18,5 ka B.P., Unit 3 – shallow silty
sandy fans with aeolian imputs and sourced from the local
tributaries – was deposited over Unit 2. This period of reduced
vegetation, enhanced aridity and accelerated soil
erosion continued until ca 12 ka B.P. after which, in
OIS.1, the aggradation fills were deeply incised to their
present depths.
ACKNOWLEDGMENTS
This work was supported by the French CNRS programme
“ECLIPSE” and the French-moroccan cooperation agreement AI
87/03. The authors are greatly indebted to Martin Thorp (University
of Dublin, Ireland) for his helpfull criticism and comments, and his
entire rewriting of the englishmanuscript. Thanks are due also to another
anonymous rewriter and to Hassan Benhalima (University of
Agadir), who has always facilitated our studies in Morocco.
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