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able to show that the high early Holocene levels of Lakes Nakuru, Elmenteita and
Naivasha in the Kenya Rift would have required a significant increase in precipitation
over these lake basins.
A further reason for the final demise of the East African glacial-pluvial chronology
was the gradual realisation that the simple fourfold concept of Pleistocene Alpine
glaciations embodied in the terms Gunz, Mindel, Riss and Wurm was greatly over-
simplified and that in reality there had been at least ten glacial-interglacial cycles in
the last million years (Williams et al.,
1998
, pp. 23-106).
12.6 Pluvial lakes in Asia
Geologists, explorers and scientific travellers in the 1860s had observed evidence that
the vast inland lakes of central Asia, such as the Caspian Sea, the Aral Sea, Lake
Balkhash and Lop Nor, had once been even larger in what became known as the
pluvial age(s). In the hyper-arid Badain Jaran Desert of Inner Mongolia, north-west
China, there are at present more than 100 permanent lakes among the very high
dunes of that desert. Many of these lakes are flanked by higher shorelines, some
of them dated by
14
C and by thermoluminescence (TL) (see
Chapter 6
) to early to
mid-Holocene in age, when they were far less saline than they are today, and mean
annual precipitation was probably at least twice that of today, that is, 200 mm rather
than 100 mm, with desiccation setting in about 4,000 years ago (Yang and Williams,
2003
). Similar climatic histories are apparent frommany sites surrounding this region
and were discussed in
Chapter 11
. All were characterised by relatively arid late glacial
climates.
In the Thar Desert of Rajasthan in north-west India, Gurdip Singh analysed the
pollen contained in lake core sediments along an east-west transect from wetter to
drier. He and his colleagues studied four lakes in particular and concluded that follow-
ing a long spell of late Pleistocene aridity, these now saline lakes were full and fresh
during the early to mid-Holocene, drying out soon after about 4,000
14
C years ago,
with the most westerly lakes drying out a few centuries before the lakes in the less
arid east of the desert (Singh et al.,
1972
; Singh et al.,
1974
; Singh et al.,
1990
).
Singh (
1971
) speculated that the demise of the Indus Valley Culture resulted from
climatic desiccation around 4,000
14
C years BP. This was also about the time of the
putative Aryan invasion of India from the north-west - a topic much in dispute. This
migration, if indeed it did occur, may itself have been triggered by extreme drought in
Persia, Afghanistan and Mesopotamia at that time, for which there is some indepen-
dent evidence (Cullen et al.,
2000
; Weiss,
2000
).
Later archaeological surveys by V.N. Misra (
1983
MS) led him to question Singh's
climatic desiccation hypothesis for the abandonment of Mohenjo-Daro situated on
the Indus River and Harappa situated on the Ravi River. A number of the Indus Valley
sites were located alongside a once active branch of the Ghaggar-Hakra River, fed
