Geoscience Reference
In-Depth Information
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Fa
Fb
D
24°E
25°E
19
J M
20
4
fossil oil
palm leaf
impressions
15
2
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10
14°N
0
Kebkabiya
El Fasher
Barbis
10
m
Baya
D
JEBEL
0
m
MARRA
oil palm fossils
stone tools
Deriba
crater
5
basalt choppers
leaf and stem
fossils and
invertebrate tracks
sand, gravel
and stone
tools
finely
laminated
diatomite
Zalingei
13°N
Umm Mari
F
pala
e
osoll
terra
c
e: sand/silt
diatomaceous
ash
Kas
0
volcanic gravel
m
ash
pumice gravel
tuffaceous silt
bedrock
0
50
100
km
quartz sand
Nyala
A
quartz gravel
wadi floor
12°N
clay
B
basalt flow
Quaternary fluviatile, lacustrine and
aeolian sediments
D
Nubian (?) sandstone
Diatomite locality
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Tertiary volcanic rocks and
minor centres
Precambrian basement with
thin or sporadic sedimentary cover
F
Fossil oil palm locality
Figure 15.5. Paleosols associated with prehistoric artefacts and oil palm leaf fossils
in the piedmont zone of Jebel Marra volcano, north-west Sudan. (After Philibert et al.,
2010
.)
In the West Kenya Rift, a series of red clay paleosols formed from volcanic ash
occur in association with Middle Stone Age artefacts dated to at least 200 ka. Of
interest here is the fact that both wet and dry Munsell colours on these soils are
identical, which is not the case with younger soils in this region. The reason for this
phenomenon is not known but may imply that the soil peds become progressively
denser over time, as a result of pressure from overlying sediments and/or as a result of
the infilling of pore spaces with clay particles. The wet and dry colours of paleosols
in this region thus provide a relative age sequence.
Paleosols in the Middle Awash Valley of the Afar Desert range in age from early
Pliocene to late Pleistocene, and are intercalated between alluvial, lacustrine and
volcanic sediments (Williams et al.,
1986
; WoldeGabriel et al.,
2009
) that contain
plant microfossils (pollen, phytoliths) and vertebrate (including hominid) fossils (see
Chapter 17
). Analysis of the stable isotopic composition of pedogenic carbonates
