Geology Reference
In-Depth Information
in the Karewa aquifers are mostly Mg(Ca)-HCO
3
type and have characters
of interaction with volcanics indicating their reservoir in Panjal Traps (Jeelani
2004, 2005).
2. Alluvium
The central part of the Valley, which mostly covers the flood plains of the
river Jhelum and adjoining streams, is filled with Recent alluvium. These
deposits include alluvial tracts, flood plains, river terraces and talus and
scree fans. The deposits are mostly water logged. The groundwater at some
places along Jhelum River has evolved to chloride type and the total dissolved
solids have increased to ~1500 mg/L. Besides, the groundwater is mostly
associated with methane gas. The wells sunk in these deposits were abandoned
by the people. However, towards the periphery the quality of groundwater
is excellent of Ca-HCO
3
type. The groundwater in these areas has signatures
of interaction with carbonates reflecting Triassic Limestone as the reservoir.
The exploratory drilling operations carried out by ONGC, CGWB and
Directorate of Geology and Mining, Jammu & Kashmir, suggest that the
aquifers are highly erratic, mostly lenticular with lesser aerial and vertical
extent.
HARD ROCK AQUIFERS
The soft rocks are surrounded and underlaid by hard rocks. Broadly hard
rocks of Kashmir can be divided on the basis of their distribution and
dimensions into two broad divisions; Panjal Traps and Triassic Limestones.
These rocks have been subjected to tectonic disturbances through geological
time with the evolution of Himalayas, resulting into the deformation in the
form of fractures. The fractures in the Triassic Limestone have progressively
developed to karst due to solution action.
1. Panjal Traps
The Panjal Traps are upper Middle Carboniferous to Permian basic volcanic
rocks of Kashmir. These are fine grain, generally light coloured, massive and
hard block lavas with columnar and conjugate joints (Middlemiss, 1910;
Bhat et al., 1881). The Panjal Traps are extensively developed with estimated
thickness of about 2500 m. Active tectonics have developed the secondary
porosity in the Formation, making it a productive aquifer. A number of
perennial springs with a discharge of not exceeding 20 L/s emanate through
it. The perennial and less fluctuating discharge of the springs reflects the
productivity of the aquifer. The famous Chashma-Shahi spring emanate
through this aquifer. The water is sweet and digestive, and was used by
people from time immemorial. Pandit Jawahar Lal Nehru used to get this
water to Delhi. The groundwater of this formation is really a mineral water
