The Other Side of Eye Candy


  1. Geographical Analysis of Islamabad 

    By Aneeqa Abrar

    1.       Geographic Extension

Islamabadlies on the East of Khyber Pakhtunkhwa. Kotli Sattian, Murree and Kahuta are situated in the Northeast of Islamabad and the city is surrounded by Taxila and Attock district on the Northwest.  In theSouth Rawalpindi, Gujar Khan and Rawat mark the boundary.

 

  1. 2.     Hydrogeology

Hydrogeologically, the study area is situated on the Soan river basin which forms a part of Indo-Gangetic synclinorium. The area is mainly drained bySoanRiverandKurangRiverand the perennial streams emerging from Margalla hills are Gumrah Kas, Tanawala Kas, Bedarwali Kas and Lei Nala. The three artificial reservoirs which regulate the drainage system ofIslamabadare Rawal, Simli and Khanpur Dam. The Soan andKurangRiversare the main streams drain­ing the area. Their primary tributaries are theLingRiver, draining northwestward into the Soan; Gumreh Kas, draining westward into the Kurang from the area between the Kurang and Soan; and Lei Nala, draining southward into the Soan from the mountain front and urban areas. The Kurang andSoanRiversare dammed at Rawal andSambliLakes, respec­tively, to supply water for the urban area (Sheikh et.al, in press).

  1. 3.     Stratigraphy

The rocks found in this area are mostly of sedimentary origin; limestone, shale and dolomitize limestone being the main constituent. These rocks belong mainly to Eocene and Paleocene ages. The major Formations which come under these ages are Margalla Formation, Patala Formation, Hangu Formation, Lockhart Formation and Kawagarh Formation. The table below summarizes the stratigraphy found in this region.

 

Figure 1: Map showing stratigraphy of the study area source: modified from Latif

AGE

FORMATION

DESCRIPTION

Pleistocene

Lei Conglomerates

Carbonate-cemented cobble conglomerate consisting of sub-angular limestone clasts intercalated with and grading laterally into weakly consolidated silt, sand, and clay.

Pleistocene

Soan

Conglomerate and subordinate inter beds of sandstone, siltstone, and clay stone.

Pliocene

Dhok Pathan

Light gray, fine to medium grained, medium bedded and cross-bedded sandstone.

Miocene

Nagri

Gray, greenish gray, and brownish gray; medium to coarse grained, thick bedded; cross-bedded; and calcareous.

Miocene

Chinji

Brick red, friable, hard, and intercalated clay ­stone with dark gray to brownish gray and cross-bed­ded sandstone.

Miocene

Murree

Sandyshale, siltstone, sandstone, conglomerate, fossiliferous limestone at the base.

Early-middle Eocene

Kuldana

Variegated, multicolored and maroon to magenta silt and shale, and yellowish to bluish grey, marly well banked limestone and cellular limestone.

Early Eocene

Chorgali

Alternating well banked limestone and brownish to greenish marl. The limestone has chert lenses in places.

Early Eocene

Margalla hills limestone

Well banked, usually dark grey but light grey weathering limestone, occasionally nodular, massive and cliff-forming.

Late Paleocene

Patala

Medium to dark brown shale with marly limestone layers.

Middle Paleocene

Lockhart

Well banked, usually dark grey and dark grey weathering limestone, occasionally nodular inliers; massive and cliff-forming; caves.

Early Paleocene

Hangu

Oxidized sandstone, while clay, iron-crusts, rusty weathering limestone, pisolitic gossans.

Early-middle Cretaceous

Kawagarh

Dark brown weathering limestone, partly dolomitic.

Early Cretaceous

Lumshiwal

Dark brown weathering thickly banked sandstone of dark grey to black color with an occasional greenish tint, glauconitic.

Late Cretaceous

Chichali

Black shale, thinly bedded, brown, often rusty, weathering.

Middle- Late Jurassic

Samana Suk

Well banked limestone, partly oolitic, often rich in fossils, yellowish tints, partly dolomitic.

Table 1: Stratigraphy of the study region, their age and description

  1. 4.     Geological Structures

Main boundary thrust (MBT)

It is a long feature extending for several hundred kilometers (about 270 km) along the Himalayan front. West of the Hazara- Kashmir syntaxes, it takes several bends and is concealed under the alluvial sediments at many places and therefore its structural continuity cannot be established. It passes at a close distance of about 1 km from Margalla hills and is the main fault present in the area of study (Ahmed, 2005).

Margalla Hill Anticlinorium

 The major regional structure is the anticlinorium that extends over entire Kala Chitta andMargallaRange. It is known as anticlinorium because the major regional anticline of the area underwent a series of further deformations that created further folds on the existing anticline. Therefore the region under the observation underwent great deformation. It is built by multivergent folds of Margalla hill limestone and Lockhart limestone (Ahmed, 2005).

 

Figure 2: Tectonic Feature of the Study Area source: Ahmed (2005)

  1. 5.     Tectonic Settings

Areas in Margalla hills are an intensely deformed and tectonised belt which along-with the Attock-Cherat range and Kala Cheta range represents the uplifted Southern margin ofPeshawarbasin. It is part of active Himalayan fore land – fold and thrust belt region in the collision zone between Indo-Pakistan and Eurasian plates. The plate boundary is characterized both by northward under thrusting plate margin and southward abduction of upper crustal rocks and sediments.

This has resulted in dramatic horizontal tectonics and crustal shortening since initial collision of the Indian Plate with the Kohistan Island Arc in latest Cretaceous to middle Eocene developing local micro faults and thrusts. Continental thrust transferred or distributed southward to a zone of weakness defined as Main Boundary Thrust (MBT) that also represents the frontal thrust of Margalla Hills and Kala Chitta. However, the deformation within these hills fold and thrust belt predates its thrusting to south over Kohat-Potwar plateaus (Ahmad, 2005).

* The Author is currently doing her MS in Remote Sensing and GIS from NUST Islamabad

* If you want to make a contribution email us at admin@islamabadthecapital.com

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