Geology Reference
In-Depth Information
alluvial plains, preponderance of glaciers and patches of snow fields, plateau
like features developed in thick accumulations of the Pleistocene glacial
moraines (Karewas) and numerous glacial lakes”. Geomorphologically the
area is represented by a valley, high structural hills, small mounds of Karewa
in the valley portion and colluvial fans below the hill slopes (Singh and
Sharma, 1999). This complexity of physiographic units with numerous faults
gives rise to complex aquifer system. However, in this article an attempt is
made to describe the possibility of occurrence of groundwater in geological
formations on a broader scale.
Diversified geological formations, lithological variations, tectonic
complexity and geomorphological dissimilarities of Kashmir give rise to a
variety of groundwater situations. The Valley is filled with soft rocks,
unconsolidated sediments of Quaternary and Recent age, garlanded by and
rested on hard rocks mostly volcanics and limestones (Fig. 1). Being part of
the Himalayas, it has a complex tectonic history, consisting of diversified
rocks that are folded, faulted and jointed. Groundwater occurs in both soft
as well as hard rocks.
SOFT ROCK AQUIFERS
The Quaternary to Recent rocks comprising the alluvium and Karewa deposits
are the important continuous media or unconsolidated formations. These
sediments are comprised of clays, silts, sands, gravels etc. and may be good
aquifers.
1. Karewas
The Karewas preserve a record of sediment deposition in a lake formed
during the Late Neogene to Quaternary period (Bhatt, 1975, 1976; Singh,
1982; Burbank and Johnson, 1983) covering an area of about 5000 km
2
.
These unconsolidated fluvio-lacustrine deposits are exposed in the river valleys
and the plateau margins of the Kashmir Valley, comprising alternations of
clays, silts, sands with occasional boulder beds. The gravity surveys supported
by refraction surveys, carried out in the Valley, indicate their maximum
thickness as 2000 m resting on Triassic Limestone or Panjal Traps (Datta,
1983). Exploratory drilling carried out by ONGC in search of hydrocarbon;
at Chattargam (very close to Yachigam, Pulwama) where the Karewa
sediments encountered up to the depth of only 515 m below which 600 m
of Triassic Limestone have been drilled and at Narbal where Karewa sediments
directly overlie Panjal Traps at a depth of only 550 m. This indicates the
narrowing of the Karewas towards the peripheral areas. Isolated exposures
of Karewas form minor hillocks in the Valley. The frequent alternations of
clay with sand and boulders, sub-horizontal disposition, almost gradational
character and undulating nature of the Karewa deposits minimizes the
possibility of occurrence of potential aquifers in these deposits. Groundwater
