Geoscience Reference
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Figure 1.8. Granite inselbergs, Jebel Kassala, eastern Sudan.
very young depositional landforms, together with the absence of vegetation and the
sharp breaks of slope, give desert landscapes their peculiar and somewhat paradoxical
character. These young landforms and sediments, whether eolian, fluviatile or lacus-
trine, contain the best record of past environmental changes, most notably the rapid
climatic fluctuations of the late Cenozoic that provide the focus of much of this topic.
1.4 Ambiguous quality of the evidence for climatic change in deserts
Early studies of desert regions tended to focus on specific desert landforms such as
dunes, alluvial fans, river terraces, playa lakes and deflation hollows. In the last thirty
years, particularly since the use of radiocarbon dating became widespread, paleocli-
matic research in deserts has focussed on using alluvial and lacustrine deposits and
their associated plant and animal fossils to reconstruct the history of desert rivers
and lakes (Cooke et al.,
1993
; Abrahams and Parsons,
1994
; Thomas,
1997
; Parsons
and Abrahams,
2009
; Thomas,
2011
; Goudie,
2013
). One of the problems inherent
in using high lake levels as evidence of formerly wetter climates lies in the complex
hydrology of many desert lakes. Some are fed primarily from groundwater and may
respond slowly to local changes in climate. Others may be fed solely from surface
run-off. If the rivers that flow into these lakes originate in some distant, well-watered
upland areas, the lake levels will fluctuate in response to distant changes in rainfall
and may again not accurately reflect local conditions. Where the lakes are full and
