Abrupt Holocene Climatic Change in Northwestern India: Disappearance of the Sarasvati River and the End of Vedic Civilization - Abrupt Climate Change: Mechanisms, Patterns, and Impacts - page 183

Figure 3. Tectonic map of northwestern Rajasthan. After Sinha-Roy [1986].

groundwater agencies have been involved in the exploration
and extraction of the groundwater in this part of the country
during the last half century. Several deep as well as shallow
tube wells were drilled throughout region in different geo-
logical formations. Some of the groundwater samples were
sent to the Bhabha Atomic Research Centre for isotopic
dating [Nair et al., 1999]. It was noted that there are isolated
pockets of deep fresh groundwater. Tube wells dug in these
pockets show no indication of a lowering of water level
despite intense exploitation for the last 35 - 40 years. Most
of these pockets are located along the paleochannels of the
Sarasvati River system. In the Jaisalmer- Hanumangarh re-
gion, fresh groundwater has been located at a depth of 30 -
50 m and given a date of 1800 to 5000 years B.P. The fresh
groundwater located at a depth of 60 - 250 m gives a date of
6000 to 22,000 years B.P. [Nair et al., 1999]. In the area of
the Hakra floodplain a fresh groundwater pocket with a
100 m thick aquifer has yielded a radiocarbon date of 4700
to 12,900 years B.P. [Geyh and Ploethner, 1995]. These
dates indicate the existence of a large river system between
22,000 and 4700 years B.P.

4. NEOTECTONIC DISTURBANCES

Neotectonic disturbances in the region (Figure 3) have
been taking place for the last 5 million years. More conspic-
uous signatures of these disturbances have been recorded
during the Holocene period at (1) around 10,000 years B.P.,
(2) around 3000 - 3500 years B.P., and (3) around the elev-
enth/thirteenth centuries [Sridhar et al., 1999]. The trans-
form fault, a plate boundary of the Indo-Australian Plate
along the northwestern margin, gradually turned into a suture
zone. The Indus River has been flowing along the Indus
Suture, and maintaining almost the same path, for at least
last 5 million years. The geomorphologic map of the region
depicting the drainage pattern that existed about 5 million
years ago [Clift and Blusztajn, 2005], when compared with
the present geomorphologic setup (Figure 2), reveals that
there is no major change in the course of the Indus River for
the last 5 million years. However, there are some changes in
the pattern of its tributaries. The lowermost eastern tributary
changes its course remarkably and subsequently disappears
completely during this period. There is a possibility that this