CHAPTER by rocks of Nari and Gaj formation of

CHAPTER
# 1

Introduction

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The
following report provides knowledge about correlation of upper Gaj carbonate
with the help of its petrography, geochemistry and sedimentology. That are much
helpful for predicting the depositional environment and its provenance.

As
carbonates have very much significance in different industries and is available
in vast amount in our country, so that is much important to study about it and
gain benefit from this natural resource.  For the following purpose the Carbonate rocks
of Upper Gaj formation, Miocene age are selected for study and to construct
their correlation in Sona Pass area and Hub Dam area. Both the areas are
covered by rocks of Nari and Gaj formation of Oligocene and Miocene
respectively, having major lithologies are Sandstone, Limestone and shale.

Physiography of Area

The
field area is a part of semi-arid to arid region at the boundary of Sindh and Baluchistan
near the coast of Arabian Sea, with one major stream i.e. Hub River. As the
average rainfall is low so mechanical weathering is dominant. Relief is
generally moderate. In summer the temperature ranges from 30°C to 40°C and in
winter it ranges from 15°C to 25°C (mean climate of 2007 by Pakistan
metrological department).

 

Location of Area

The
first area is located East of Baluchistan and West of Hub River. It is part of
Sokran district. Second area which is of Sona Pass is located in the south western
side of Karachi. Structurally it is on the common flank of Cape Monze Anticline
and Lalji Syncline, in the South of Hub River.

 

 

 

 

 

 

 

Previous Work

 
Geochemistry
and sedimentology of Jhill limestone of Gaj formation, in Cape Monze and
adjoining area, Karachi (Shahid Naseem, Shamim Ahmed Sheikh, M. Qadeeruddin);

 

Objective

To
study the chemical and petrographic properties of Jhill limestone of Gaj
formation, for correlation of the area, to predict depositional environment and
provenance and most importantly for the determination of its capability in the
generation of hydrocarbon in future.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CHAPTER
# 2

Instrumentation
and Methodology

The
area of Hub Dam site and Sona Pass was selected for the sampling due to easy
accessibility, vast exposure and presence of maximum characters of the
formation units.

 

Thin Section Preparation

·        
Start by cutting an 8-10 mm piece from
your main stone sample by using Geoforms’s left side cutting station. Grind the
glass slide to make its surface rough to fix the stone sample onto the slide.
Rub the stone sample’s flat surface with Silicone carbide water to make its
surface rough.

·        
Fix the sample to the glass slide using
KEPT epoxy resins then the samples can be placed in the Geofix to assist in
bonding the sample to the glass slide under pressure.

·        
Using the Geoforms’s left side station,
put the glass slide to the Vacuum chuck, and then cut your samples up to
approx. 2.0 mm thickness by using the special slide cut mechanism on the
Geoform.

·        
Then place the sample to the right
station of the Geoform, using the vacuum you can precisely grind your sample.
Touch the stone with the micrometer and adjust the digital positioning of the
micrometer to zero, then start grinding the stones surface with the grinding
cup from approx. 2.0mm to 80 microns. You can grind with 50 mic steps when the
samples thickness is 200 micron

·        
Set the Kemtech vacuum jig to the
required final thickness and then mount the uniformly ground samples to the
vacuum jig face.

·        
Lap on the Kemtech III machine using a Silicon
carbide/water mix until the jigs diamond faced stop ring fully contacts the
cast iron lapping plate. There is a change in sound when this point is reached.
This means the slides have been lapped to the set thickness.

·        
Remove the slides from the jig and clean
and inspect. The slides are now ready for polishing on the Kemtech III.

·        
Clean the Vacuum jig in an ultrasonic
cleaner to ensure all lapping slurry contamination has been removed and adjust
the diamond stop ring so that it is above the vacuum face plate.

·        
Change the cast iron lapping plate to
the aluminum lift off disc and mount a PSU-M polishing pad.

·        
Charge the Aku-Disp slurry pump
(separate pump heads are available) with Diamond suspension and program the
pump to dispense a 2 second supply of slurry every 8-10 seconds.

·        
Mount the now lapped samples to the clean
vacuum jig and polish on the PSU & MBL cloths working down the Diamond
suspension micron size to the required thickness and surface finish, approx.
30micron. Remove the samples and clean.

·        
The slides are now ready for analysis.

 

 

Geochemical Analysis of the Sample:

1.      Loss On Ignition (LOI)

·        
Red hot the crucibles on mason burner.

·        
Cool the crucibles in desiccator up to
room temperature.

·        
Weigh crucibles and number them with
permanent glaze.

·        
Add approximately 1gram of sample in
crucibles and put them in Furness at 950oC to 1000oC for
one hour.

·        
Remove sample from Furness and place
them in desiccator until they get cool.

·        
Weight the sample again.

(Loss-on-Ignition
Standard Operating Procedure, Lac Core, National Lacustrine core facility, 2013)

 

2.      Insoluble Residue (IR)

 

·        
Take exact 1 gram sample of limestone in
250ml beaker.

·        
Add 5-10 ml of hydrochloric acid, and
heat.

·        
Add 50ml distilled water in to the
beaker.

·        
Now filter the solution, from filter
paper no 41 in to 250ml flask.

·        
Take a crucible, red hot it on burner, then
put in desiccator up to room temperature and weight it.

·        
Put the filter paper in the crucible and
burn it on mason burner.

·        
Put the crucible in desiccator up to
room temperature.

·        
Weight the sample and subtract the
crucible weight.

 

 

3.     
Neutral,
Viscous, Crystal Retardant or Refractory Oxides (r2o3)

 

·        
Take the filtered solution obtained
after the IR test in flask.

·        
Fill the distilled water up to mark.

·        
Pipit out 100ml of solution into the
250ml beaker.

·        
Add few drops of Nitric acid (HNO3),
a small piece of litmus paper, then Ammonium Chloride (NH4CL) with
spatula and few drops of Ammonia.

·        
Heat the solution and leave for 24
hours.

·        
Filter the solution in to 250ml flask.

·        
Take a crucible, red hot it on burner,
then put in desiccator up to room temperature and weight it.

·        
Put the filter paper in the crucible and
burn it on mason burner.

·        
Put the crucible in desiccator up to
room temperature.

·        
Weight the sample.

4.     
Titration
by Ethylenediaminetetraacetic acid disodium salt (EDTA) for Calcium (Ca)

·        
Take the filtered solution obtained
after the r2o3 test in flask.

·        
Fill the distilled water up to mark.

·        
Pipit out 50ml of solution into the
250ml beaker.

·        
Add a pinch of Potassium Syenite (KCN)
and Ascorbic acid with spatula in solution.

·        
Add Peten & reader indicator.

·        
Then add few drops of precipitator (i.e.
Buffer 12).

·        
Titrate the solution by EDTA and mark
the reading on burette.

 

5.     
Titration
by Ethylenediaminetetraacetic acid disodium salt (EDTA) for Magnesium (Mg)

·        
Take the filtered solution obtained
after the r2o3 test in flask.

·        
Fill the distilled water up to mark.

·        
Pipit out 50ml of solution into the
250ml beaker.

·        
Add a pinch of Potassium Syenite (KCN)
and Ascorbic acid with spatula in solution.

·        
Add Eochrom Black T as indicator.

·        
Then add few drops of precipitator (i.e.
Buffer 10).

·        
Titrate the solution by EDTA and mark
the reading on burette.

 

 

 

 

 

 

 

 

CHAPTER
# 3

General Geology

Regional
Tectonics and Stratigraphy:

In
global tectonic perspective, Pakistan is situated at junction of three plates,
the Indian plate, Arabian plate and Eurasian plate (Kazmi and Jan 1997). The
Indus basin is situated on north western corner of Indian plate. The Indian
plate after separating form African plate during Jurassic-Early Cretaceous
started drifting in north east direction and collided with Eurasian plate in
Paleocene. The collision is characterized by continent-continent collision,
obduction and thrusting is considered the prototype Alpine –Himalayan orogeny
(Powell 1979).

This
tectonic activity related Himalayan orogeny continued through the Oligocene to
Pleistocene and in between there was change in climate in clastic in shallow
water carbonates were deposited in the southern Indus Basin. Upper Indus Basin
was uplifted as a result of collision between Indian and Eurasian plate. Nari
formation is developed in these localized basins and exposed extensively in the
Kirther and Suleiman region and out crop scattered in the tectonised thrust
blocks in the Baluchistan ophiolite and thrust belt (Blanford 1876, Williams
1859).

 

Tectonically the study
area is the part of Karachi embankment, geographically and
geologically, Karachi embayment is situated in the southernmost part of
Pakistan and Indus Basin respectively. Precisely, it is a part of southernmost
continuation of Kirthar fold belt and south-western margin of lower Indus
Basin. It is bounded by Ornachnal Fault in west and Hyderabad in east. The
southern part of Karachi embayment is submerged in the sea presently. The
Trough is characterized by thick Early Cretaceous sediments and also mark the
last stages of marine sedimentation. It contains large number of narrow chain
like anticlines, some of which contain gas fields (Sari, Hundi and Kothar). The
Early, Middle and Late Cretaceous rocks are well preserved in the area. It has
been a trough throughout the geological history. The Upper Cretaceous is marked
by westward progadation of a marine delta. The most interesting feature of
Karachi Trough is the reportedly continued deposition across the Cretaceous /
Tertiary (K/T) boundary wherein Korara Shales were deposited.

 

The
western part of Central and Southern Indus Basin was uplifted, though locally
marine conditions persisted in parts of the Karachi Trough and the present
Indus Offshore area. The Oligocene Nari Formation developed in these localized
basins consists of high energy limestone, ferruginous sandy siltstones and some
local shales. In the Offshore area, reefs have been recognized near the
shelf-slope break. Miocene/ Pliocene sediments were deposited in the depression
areas of the Siwalik Basin which was formed as a result of the development of
the proto-Indus drainage system. This is characterized by fluvial
sedimentation.

Tectonics of Pakistan

The Indian Ocean and the Himalayas, two of
the most pronounced global features surrounding the Indo-Pakistan subcontinent,
have a common origin. Both are the product of the geodynamic processes of
sea-floor spreading, continental drift and collision tectonics. A plate of the
earth’s crust carrying the Indo-Pakistan landmass rifted away from the
supercontinent Gondwanaland followed by extensive seafloor spreading and
opening up of the Indian Ocean. Propelled by geodynamic forces the Indian Plate
travelled 5,000 km northward and eventually collided with Eurasia. The
subduction of the northern margin of the Indian plate finally closed the Neotethys
and the Indian Ocean assumed its present widespread expanse. This collision
formed the Himalayas and the adjacent mountain ranges (Kazmi and Qasimjan,
1997).

In the Himalayas the main uplift began in
mid-Miocene time. Coincident with the Himalayan uplift, mid Miocene deformation
affected the Khojak flysch in the transform belt thus initiating transpressive
subduction along what became the Chaman Fault zone. In the Pliocene the most
significant event was the collision between the Zagros portion of Arabia and
Eurasia (Pakistan Hydrocarbon Habitat).

Tectonics of Pakistan is characterized by the
two convergent boundaries:

In the northeast there is an active
continent-island arc continent collision boundary, the west end of the Himalaya
Origen.

In the southwest, there is an active boundary
of oceanic lithosphere subducting beneath the arc trench gap, sediment and
continental sediments, the oceanic part of the Arabian plate passing under the
Makran arc-trench gap and afghan micro plate.

Pakistan comprises two main
sedimentary basins, Indus Basin and Baluchistan Basin which evolved through
different geological episodes and finally welded together during
Cretaceous-Paleocene along Ornach Nal/Chaman Strike slip faults.

The main feature that
control the sedimentation of proto-Indus basin up to Jurassic was Pre-Cambrian
Indian Shield whose topogrpahic highs exist in the form of Kirana Hills.
Following the classification of  Indus
Basin:

Upper Indus Basin
(Kohat sub-basin, Potwar sub-basin)

Lower Indus Basin
(Central Indus basin, Southern Indus basin)

Lower Indus Basin

It is mainly comprises
of Central and Southern Indus Basin. The Cape Monze Area is a part of Southern
basin, therefore only the Southern Indus Basin description is given below.

Southern Indus basin

This basin is located
just south of Sukkur rift. A divide between central and southern basin it
comprises the following five main units (Qadri, 1995).

1.     
Thar Platform                              

2.     
Kirthar Foredeep       

3.     
Karachi Trough   

4.     
Offshore Indus

5.     
Kirthar fold belt

 

Structure of the Area

 The Kirther formation is underlain by Nari and
Gaj Formation of Oligocene-Miocene ages respectively deposited on the
northwestern edge of the Indian continental shelf. Structures are
northeast-southwest oriented with folds plunging mainly towards southwest. Pir
Mangho Anticline and Lalji Syncline are the major structures of the region.
Both are fault induced folds indicated by their double hinges and kink
geometries. Thrust is blind and not exposed in the region; however several
sinistral strike slip faults transect the areas which are antithetic to the
tectonic transport of the Karachi arc.

Major folding of the
strata has taken place on frontal ramps while at places oblique ramps are also
the cause of some folding. Pir Mangho Dome is a consequence of thrusting on
such a pair of ramps. Structural vergence indicates tectonic transport towards
southeast. However, structures of the region may have been initially north
south oriented and may have been rotated clockwise, evidenced by the presence
of some extensional structures to the south of the area. However, partly
structural geometry of the Karachi arc is original, evidenced by the presence
of en-echelon folds. Eastward tectonic transport of the Karachi arc is post Miocene
in a thin skinned fashion as a result of India -Arabia convergence.

These structural
geometries extend towards north and northeast all along the Karachi arc and the
Kirther fold belt.

 

 

 

 

 

 

 

 

Stratigraphy of
Lower Indus Basin

 

 

 

 

 

General Stratigraphy
of Gaj Formation

The term Gaj series was first introduced
by Blanford (1876, 1878, and 1879) for sequence of shale and sandstone with
subordinate limestone (Cheema et al., 1977). Williams (1959) referred
this series as Gaj Formation which is synonymous to lower and upper Gaj
(Pascoe, 1963).

The
Miocene is represented by the Gaj formation and occurs in two separate areas in
a narrow zone between Karachi and Quetta, generally coinciding with the eastern
portion of Nari distribution.

Lithology:

The formation consists of shale with subordinate sandstone
and limestone. The shale is variegated greenish grey and gypsiferous. The
sandstone is brown greenish grey calcareous ferruginous and cross-bedded. The
limestone is brown or yellowish white argillaceous and fossiliferous.

Thickness:

At type locality (Gaj river) it is 650 meters thick. In
subsurface, offshore Karachi it is 50-65 meters thick  and 90 meters in Quetta.

Contact:

 Its
upper contact with Siwaliks Group and lower contact with Nari Formation is
transitional and conformable. Gaj/Nari contact is exposed north of karachi.

The Gaj formation has three units

·        
Meetan Clay

·        
Jhill Limestone

·        
Talawa Limestone

·        
Drig Clay

 

 

 

 

 

Metan Clay

Metan
is the oldest unit of Gaj formation. The dominant lithology of Metan is shale
which is inter bedded with thin layer of limestone. Fresh color of shale is
brownish grey and also have clay content with shale.

Jhill Limestone

Jhill
is second unit of Gaj formation. It is composed with limestone. Generally it is
very hard massive nodular limestone of creamy white color, with very high
fossil content.

Talawa Limestone

This
unit is composed with yellow color limestone which is hard and compacted and is
highly fractured.

 

ERA

PERIOD

EPOCH

FORMATION

MEMBER

LITHOLOGY

CENOZOIC
 

 
Quaternary
 
 

Recent

 

 

Alluvium

Sub-Recent

 

 

Alluvium

 
 
 
Pliocene-Pleistocene

 
 
Manchar

 

 
Sand, Shale & Subordinate
conglomerate.

 
Tertiary

 
 
 
Miocene
 
 

 
 
Gajj
 
 

Drig

Clay

Talawa

Limestone

Jhill

Limestone

Metan

Clay

 

 

 

 

 

 

 

CHAPTER
# 4

Correlation of
Upper Gaj Carbonates in Sona Pass and Hub Dam Area on the basis of their
Petrography and Geochemistry

 

 

CHAPTER
# 5

Economic
Importance

As
carbonates are chemically precipitated rocks and contains different kinds of
fossils that generates the hydrocarbon through the time and can preserve this
as a fossil fuel, so they can be used as a source rock as well as a good
reservoir rock and can be beneficial for petroleum industries. The world’s
largest oil and gas fields are mostly contained in porous limestone.

Most carbonate rocks
are made into crushed stone and used as a construction material. It is used as
a crushed stone for road base and railroad ballast. It is used as an aggregate
in concrete. It is fired in a kiln with crushed shale to make cement.

Some varieties of
carbonates perform well in these uses because they are strong, dense rocks with
few pore spaces. These properties enable them to stand up well to abrasion and
freeze. It is much easier to mine and does not exert the same level of wear on
mining equipment, crushers, screens, and the beds of the vehicles that
transport it.

Some additional but
also important uses of limestone include:

·        
Dimension Stone: Limestone is often cut
into blocks and slabs of specific dimensions for use in construction and in
architecture. It is used for facing stone, floor tiles, stair treads, window
sills, and many other purposes.

 

·        
Roofing Granules: Crushed to a fine
particle size, crushed limestone is used as a weather and heat-resistant
coating on asphalt-impregnated shingles and roofing. It is also used as a top
coat on built-up roofs.

 

·        
Flux Stone: Crushed limestone is used in
smelting and other metal refining processes. In the heat of smelting, limestone
combines with impurities and can be removed from the process as a slag.

 

·        
Portland cement: Limestone is heated in
a kiln with shale, sand, and other materials and ground to a powder that will
harden after being mixed with water.

 

·        
Ag Lime: Calcium carbonate is one of the
most cost-effective acid-neutralizing agents. When crushed to sand-size or
smaller particles, limestone becomes an effective material for treating acidic
soils. It is widely used on farms throughout the world.

 

·        
Lime: If calcium carbonate (CaC03) is
heated to high temperature in a kiln, the products will be a release of carbon
dioxide gas (CO2) and calcium oxide (CaO). The calcium oxide is a powerful
acid-neutralization agent. It is widely used as a soil treatment agent (faster
acting than aglime) in agriculture and as an acid-neutralization agent by the
chemical industry.

 

·        
Animal Feed Filler: Chickens need
calcium carbonate to produce strong egg shells, so calcium carbonate is often
offered to them as a dietary supplement in the form of “chicken
grits.” It is also added to the feed of some dairy cattle who must replace
large amounts of calcium lost when the animal is milked.

 

·        
Mine Safety Dust: Also known as
“rock dust.” Pulverized limestone is a white powder that can be
sprayed onto exposed coal surfaces in an underground mine. This coating
improves illumination and reduces the amount of coal dust that activity stirs
up and releases into the air. This improves the air for breathing, and it also
reduces the explosion hazard produced by suspended particles of flammable coal
dust in the air.

·        
Limestone has many other uses. Powdered
limestone is used as a filler in paper, paint, rubber, and plastics. Crushed
limestone is used as a filter stone in on-site sewage disposal systems.
Powdered limestone is also used as a sorbent (a substance that absorbs
pollutants) at many coal-burning facilities.