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The
Alwar quartzites of Delhi system exposed in the area belong to Pre-
Cambrian age. The quartizites are pinkish to grey in colour,
hard, compact, highly jointed, fractured and weathered. These occur
with interbeds of mica- schists and are intruded locally by pegmatites
and quart veins. The strike of these rocks varies north east - south
- west to north northeast – south southeast with steep dips towards
south east and east except for some local variations due to folding.
The prominent joint sets are strike joints, bedding joints and dip
joints. Quartzites are ferruginous and gritty types on weathering
and subsequent disintegration give rise to coarse sand
(Badarpur sands). Chemical weathering of deer horizons is also common.
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The
exploratory drilling undertaken has brought out the subsurface configuration
of rock formation and depth to bedrock is different parts of NCT of
Delhi. The nature of bedrock topography is rendered uneven due to
existence of sub surface ridges. Thickness of alluvium overlying the
quartzites increases away from the outcrops. The thickness of alluvium
is 300m or more in most parts of Najafgarh, Kanjhawala and Alipur
blocks while in the south eastern parts of Alipur block, it varies
from 100m to 300m. In the eastern parts of Najafgarh Block, the thickness
range is from 50m to 300m. In the city block, west of the ridge, the
alluvium thickness increases away from the ridge to 300m or more.
East of the ridge, in the area upto river Yamuna, the alluvium thickness
is comparatively less to about 165 m. East of river Yamuna covering
parts of city and Shahdara blocks, the thickness ranges from 48 to
240 m. In the Chattarpur basin of Mehrauli block, the alluvial thickness
varies from a few metres near the periphery to 115m around Satbari
bund.
|
Location |
Nature
of bedrock |
Depth
to bedrock in m. below land surface |
| Willingdon
Hospital |
Quartzites |
35.66 |
| Lady
Harding Hospital |
Mica
schist |
42.00 |
| Silver
Jublee Hospital |
-do- |
145.00 |
| Irwin
Hospital |
-do- |
22.86 |
| Vikas
Bhawan |
-do- |
107.30 |
| Ranbaxy
Laboratory,Okhla |
-do- |
39.01 |
| Okhla
Industrial Area |
-do- |
46.93 |
| West
Patelnager |
-do- |
63.70 |
| Malaria
Institute |
-do- |
24.38 |
| Swiss
Embassy Diplomatic Enclave |
-do- |
33.35 |
| Australian
High Commission |
-do- |
30.48 |
| Swatantra
Bharat Mills |
-do- |
150.87 |
| Delhi
Transport Undertaking Depot Vinaynagar |
-do- |
28.95 |
| Indra
Prastha College for Women,Alipur Road |
-do- |
25.3
to 28.35 |
| National
Physical Laboratory,Pusa |
-do- |
8.23
to 13.41 |
| S.O.C.
Petrol Pump,Mathura Road, Palam Airport |
-do- |
16.46 |
| Karewal
nagar(Shahadra Block) |
Quartzite
associated with mica-shist |
198.8 |
| Kichripur(-do-) |
-do- |
105.93 |
| Madanpur(-do-) |
-do- |
137.00 |
| Manduli(-do-) |
-do- |
42.67 |
| Dhansa(Najafgarh
block) |
Quartzite
associated with schist |
297.00 |
| Pindwala
Kalan(-do-) |
Quartzite |
300.10 |
| Chitorni(Chatter
basin) |
Weathered
quartzite |
64.00 |
| Rajpur(-do-) |
-do- |
90.83 |
| Satbari
bund(-do-) |
Quartzite |
125.00 |
Source: CGWB, New Delhi
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