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Fig. 16.6
(
a
) Spatial distribution of loess in Africa and the Middle East, active sand seas, and
Arenosols (sandy soils) (From Crouvi et al.
2010
and references therein). Near-surface dominant
wind directions for January and June are based on Breed et al. (
1979
). Red contours are content
of silt (24 m mode) in oceanic sediments off the West Africa coast deposited during the last
glacial maximum (Sarnthein et al.
1981
, see also Chap.
17
)
.
Black rectangles
mark the location of
well-studied loess sites in these regions mentioned in the text and in Crouvi et al. (
2010
): (
b
) Israel
(Negev), (
c
) Tunisia and Libya, (
d
) Nigeria, (
e
) Namibia, (
f
) Yemen, and (
g
) the UAE. Abbrevia-
tions:
GEO
Grand Erg Oriental,
HE
Hausaland Erg,
KS
Kalahari Sands,
RAK
Rub' al Khali
regions; (2) at most sites, loess covers an area of 10
3
-10
4
km
2
; (3) loess sediments
are dominated by coarse silt to very fine sand grains, with median grain size ranging
from50to80m; in some sites, the particle size distribution (PSD) is reported to be
tri- or bimodal; (4) the loess bodies are generally characterized by calcic soils; (5)
loess mineralogy is mostly quartz and feldspars, with various amounts of carbonate,
depending on the degree of soil development in the loess; (6) in most sites, the
underlying lithologies are inconsistent with the presence of quartz in the loess and
suggest an external source for the silt; (7) the shapes of particles are reported as
subangular to angular for most regions; and (8) most loess bodies were deposited
during the last glacial period (
110-10 ka).
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