stratigraphy and sedimentary rocks.pdf

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Assignment no.1

Student Name: Syed Nigah Haider

Enrollment Number: 01-161042-102

Course Code: Geol 220

Course Name: Geology of Pakistan

Teacher’s Name: Mr. Anwar Qadir

Due Date: February 24th

, 2006

Date of Submission: February 24th

, 2006

Faculty of Earth and Environmental Sciences,Bahria University, Islamabad.



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SerialNumber

Content PageNumber

01 Fundamental Laws of Geology 0402 Branches of Stratigraphy 0903 The Geological Time-scale 1104 Lithostratigraphical Units 15

05 Classification of Sedimentary Rocks 1606 Examples of Sedimentary Rocks 17



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FigureNumber

List of Figure PageNumber

01 Horizontal Layers of Sedimentary Rocks 0402 Photograph of the upper portion of the Grand Canyon 0503 Unconformity 0704 Angular unconformity 07

05 Disconformity 0806 Elements, their half life, and their daughter products 0807 Sedimentary Breccias 1708 Conglomerate 1809 Sandstone 1810 Arkose 1811 Mudstone 1912 Coquina 1913 Chalk deposits 2014 Limestone 2115 Dolomite 2116 Chert 2217 Coal 22



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Fundamental Laws o f Geology

Several principles or “laws” are fundamental to the geologic interpretation of a sequence of events. These principles are reviewed in the following sections.

1. Uniformitarianism,2. Original Horizontality,3. Superposition,4. Lateral Continuity,5. Crosscutting Relations,6. Components,7. Fossil Succession,8. Review of Unconformities,9. Nonconformity,10. Angular Unconformity,11. Radiometric Dating.

1. Uniformitarianism:

Uniformitarianism is the fundamental principle or doctrine that geologic processes and natural

laws now operating to modify the earth’s crust have acted in the same regular manner and withessentially the same throughout the same geologic time, and that past geologic events can beexplained by the phenomena and forces observable today; the classic concept that “the presentis the key to past”. This principle was first proposed by J ames Hutton in 1795 and waspopularized in 1830 by Charles Lyell.

2. Original Horizontality:

The law of original horizontality was conceived by Nicolas Steno (1638 – 1687) during the latterpart of seventeenth century. Steno observed that most sedimentary rocks are formed by theparticles that settle to the bottom of rivers, lakes, and oceans under the influence of gravity, andform essentially horizontally layers, or layers that are approximately parallel to the earth’s surface.

Therefore, Steno reasoned, if sedimentary rocks are found in an inclined or folded attitude, they

must have undergone movement after their deposition and Lithification.

Figure no.1: Horizontal layers of sedimentary rocks



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3. Superposition:

The law of superposition was also proposed by Steno in the latter part of seventeenth centuryand then effectively demonstrated by Hutton about 1975. Hutton had observed that sedimentaryrocks were formed by the accumulation of numerous layers. He concluded that in anyundisturbed sequence of strata the oldest or first – deposited layer would be on the bottom andthat the youngest or last – deposited layer would be on the top. A necessary aspect of thisprinciple is the assumption that the sedimentary strata have not overturned or inverted by foldingor faulting.

Figure no.2: The following is a photograph of the upper portion of the Grand Canyon. Exposed inthe canyon walls are successive layers of sedimentary rocks including red shale, sandstone andlimestone.

4. Lateral Continuity:

Steno also proposed the law of lateral continuity which states that most thick layer of thesediment were originally deposited over geographically extensive areas, then subsequentlycovered with overlying layers and lithified into sedimentary rocks. Uplift, erosion, faulting, andfolding have in many cases distributed the original lateral continuity of these layers.

5. Crosscutting Relations:

“The principle states that in any rock unit or fault that cuts across the other rocks units is youngerthan the rock units through which it cuts”.

6. Components:

“The principle of the components states that the components of a layering sedimentary rock areolder than the date of deposition of that rock layer”.

This principle is illustrated in an explanation of the formation of conglomerate. Assume, forexample, that preexisting granite (e.g., granite 150 million years old) had been weathered in themountains; the eroded fragments were transported and deposited in the bed of a stream thatflowed from those mountains 50 million years ago. The age of sedimentary deposit of gravel, now



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lithified as a conglomerate, is much younger than the age of the individual granite pebblescomposing it.

7. Fossil Succession:

William “Strata” Smith (1769 – 1839, often regarded as father of Historical Geology). He carefullyexamined fossils that were embedded in the rock strata. He then documented that each layer inthe succession of layer of rock strata could be identified by the distinctive fossils it contained. Onthe bases of these observations, Smith proposed the law of fossil succession, which states that:

“ The plant and animal fossil succeed one another in a recognizable order through the geologicrecord because the were layered in a stratigraphic sequence and throughout the sequence eachrock unit contained its characteristics group of fossils.

8. Review of Unconformities:

An unconformity is a surface of erosion or nondeposition that separates the younger strata fromolder once.

The older geologic units that a present below the unconformity may have undergone intrusion,

metamorphism, fo0lding, faulting, and erosion prior to accumulation of the younger overlyingstrata.

In most geologic interpretations, it is assumed that:

(a) Most sedimentary rocks of marine origin, in other words, that they were formed in anoceanic environment;

(b) Land areas must have been predominantly emergent (above sea level) before erosioncould have taken place;

(c) The lowering of the landmass relative to sea level (subsidence) must have proceeded tomarine deposition;

(d) Sedimentary rocks that appeared at steep angles or form noticeable dips must haveundergone folding and faulting.

9. Nonconformity:

Nonconformity is an erosional surface that separates older igneous and metamorphic (crystalline)rocks from younger overlying sedimentary strata.

Some of the criteria for identification of a nonconformable surface include:

(a) Incorporation fragments of the igneous or metamorphic material within the basal portionof the overlying sedimentary units,

(b) Erosional truncation or abrupt termination of an under lying igheous rock mass at theunconformable surface,

(c) Absence of contact metamorphism in the rocks immediately above the igneous or

metamorphic rocks.



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Figure no.3: Showing unconformity

10. Angular Unconformity:

An angular unconformity is an erosional surface that separates tilted or folded strata from fromoverlying beds of different attitude. This type of unconformity implies a definite sequence of geologic events.

Figure no.4: Steps involved in forming angular unconformity



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11. Disconformity:

A disconformity is an unconformable surface that separates essentially parallel sedimentarystrata. Beds above and below a disconformity must be nearly parallel, but the contact may exhibiterosional relief of considerable magnitude. The presence of disconformities implies that regionaluplift has occurred without severe deformation or a thermal event.

Figure no.5: Disconformity

12. Radioactive Dating:

Radioactive dating is the process by which the absolute age of a rock or geologic event isdetermined. Elements such as uranium, potassium, rubidium have both radioactive andnonradioactive isotopes. These radioactive isotopes are called Parent isotopes. In the decayprocess they transformed into the new isotopes of different elements called Daughter Isotopes.Some daughter products are themselves radioactive and decay to other daughter products.

Radioactive decay rate is expressed in terms of a length of time called “Half Life”. A Half Life isdefined as the amount of time necessary for half of the original parent atoms to decay to thedaughter product or atoms.

Uranium isotopes (U235

and U238

) have half life approximately 4.5 billion years and 713 millionyears respectively.

Figure no.6: Elements, their half life, and their daughter products



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Branches of Stratigraphy:

Following are the main branches of stratigraphy:

1. Biostratigraphy,2. Geophysical/Petrophys ical log Stratigraphy,3. Seismic Stratigraphy,4. Sequence Stratigraphy,5. Climate Stratigraphy,6. Event Stratigraphy,7. Magnetostratigraphy,8. Isotope Stratigraphy,9. Chemostratigraphy.

1. Biostratigraphy:

Biostratigraphy is the use of fossils in stratigraphy. It relies on the study of in situ fossildistributions to allow recognition of stratigraphically restricted and geographically widespreadpopulation, which enables subdivision and correlation of lithostratigraphical succession.

The basic unit of biostratigraphy is the biozone, which is formerly described in term of its fossilindices and content. Biozone are then ordered in stratigraphical position ultimately to allowcorrelation of lithostratigraphical units. They can be of any thickness or duration, and can be localto world-wide in scale.

2. Geophysical/Petrophys ical log Stratigraphy:

The borehole permit investigation of the strata drilled using various geophysical techniques,which allow the distinction and correlation of stratigraphically units and events, which is known asgeophysical/Petrophysical log stratigraphy.

Geophysical logs record continues digital wellbore Petrophysical data, the digital data aregenerated by a suite of tools with an output as a series of depth-matched digital values that can

also be displayed graphically, normally as linear traces. These data are integrated and used tocreate an interpreted lithological log.

3. Seismic Stratigraphy:

It is a method for delineating stratigraphical units from seismic reflection profiles.

Seismic reflections result from acoutis impedance contracts and are dependent upon abruptchanges in the density and/or velocity attributes of adjacent strata. Depending on the frequencyof seismic source used, seismic reflections can yield information about stratal arrangements fromdepths of a few meters to any kilometers. The stratigraphical information derived may be of two orthree dimensional.

4. Sequence Stratigraphy:

This type of stratigraphy is concerned with large scale, three-dimensional arrangement of sedimentary strata, and the major factors that influence their geometries, namely sea levelchanges, contemporaneous fault movements, basin subsidence and sediment supply. Theobservational basis of sequence stratigraphy is the ubiquitous arrangement of strata into unitsbounded above and below by unconformities that can be traced out into conformable surfaces ina basinward direction. These surfaces are defined as the sequence boundaries and the stratabetween them constitute a depositional sequence.



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5. Climate Stratigraphy:

For the quaternary there has been a tradition of dividing sediment sequence on the basis of climatic changes.

In the past, the preferred climate time-scale was that developed by Penck and Bruckner for theAlps. In recent decades it has been replaced by the oxygen isotopes record. Today, the burden of correlation lies in equating highly fragmentary, yet high resolution, terrestrial and shallow-marinesediments.

6. Event Stratigraphy:

Event stratigraphy comprises the study of stratigraphical traces of relatively short-lived eventscompared to those normally observed on the geological time scale. Events may be representedby depositional, erosional, or geochemical features. They may be of local significance (e.g. adebris flow), or more extensive (e.g. a volcanic ash deposit), or even global (flooding surface).

They may be random or regular.

7. Magnetostratigraphy:

Magnetostratigraphy exploits variations in the magnetic properties of rocks as a basis forgeological correlation. The most widely used property is the direction of primary remanentmagnetism, which records the geomagnetic field polarity at the time of formation of the rock. Setsof magnetic polarity reversal in sedimentary sequence can be correlated between sections.

8. Isotope Stratigraphy:

It is the method of determining relative ages of sediments based on measurement of isotopicratios of a particular element. It works on the principle that the proportions of some isotopesincorporated in biogenic minerals (calcite, aragonite, phosphate) change through time inresponse to fluctuating palaeoenvironmental and geological conditions. However, this primarysignal is often masked by diagenetic and alterations of sediments which have secondarily alteredthe isotopic ratios.

9. Chemostratigraphy:

In an oil field resvoir where fine correlation is required in sandstone that lack fossils. In suchcircumstances a variety of Chemostratigrapical methods can be employed with varying degree of success. These range from the recognition of distinctive heavy mineral suites to chemicalanalysis of vertical stratigraphical profiles. Such chemical analysis is relatively rapid, straightforward and requires very small samples.



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The Geologic Time Scale

Phanerozoic Eon

(544 million years ago - Present)

The period of time, also known as an eon, between the end of the Precambrian and today, ThePhanerozoic begins with the start of the Cambrian period, 544 million years ago. Itencompasses the period of abundant, complex life on the Earth.

Era Period or System Epoch or Series

Cenozoic (65 million years ago -

Present) "Age of Recent Life"

An era of geologictime from thebeginning of the

Tertiary period tothe present. Itsname is from Greekand means "newlife."

Quaternary (1.8 million years ago - Present)

The second period of the Cenozoicera. It contains two epochs: thePleistocene and the Holocene. It isnamed after the Latin word "quatern"(four at a time).

The several geologic eras wereoriginally named Primary, Secondary,

Tertiary, and Quaternary. The firsttwo names are no longer used.

Tertiary and Quaternary have beenretained but used as perioddesignations.

Holocene (8,000 years ago -

Present)

An epoch of theQuaternaryperiod. It isnamed after theGreek words"holos" (entire)and "ceno"(new).

Pleistocene (1.8 million - 8,000

years ago) "The Great Ice Age"

An epoch of theQuaternaryperiod. It isnamed after the

Greek words"pleistos" (most)and "ceno"(new).

Tertiary (65 - 1.8 million years ago)

The first period of the Cenozoic era(after the Mesozoic era and beforethe Quaternary period).

Pliocene (5.3 - 1.8 million

years ago)

Final epoch of the Tertiaryperiod. It isnamed after theGreek words

"pleion" (more)and "ceno"(new).

Miocene (23.8 - 5.3 million

years ago)

A epoch of theupper Tertiary



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period. It isnamed after theGreek words"meion" (less)and "ceno"(new).

Oligocene (33.7 - 23.8 million

years ago)

An epoch of theearly Tertiaryperiod. It isnamed after theGreek words"oligos" (little,few) and "ceno"(new).

Eocene

(55.5 - 33.7 millionyears ago)

An epoch of thelower Tertiaryperiod. Its nameis from the Greekwords "eos"(dawn) and"ceno" (new).

Paleocene (65 - 55.5 million

years ago)

Earliest epoch of the Tertiaryperiod. It isnamed after theGreek words"palaois" (old)and "ceno"(new).

Era Period or System Epochor

Series

Mesozoic (248 - 65 million years ago) "Age of Medieval Life"

An era of geologic timebetween the Paleozoicand the Cenozoic. Theword Mesozoic is fromGreek and means "middlelife."

Cretaceous (145 - 65 million years ago) "The Age of Dinosaurs"

The final period of the Mesozoic era. Thename is derived from the Latin word forchalk ("creta") and was first applied toextensive deposits of this age that formwhite cliffs along the English Channelbetween Great Britain and France.

Late orUpper

Early orLower



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Jurassic (213 - 145 million years ago)

The middle period of the Mesozoic era. It isnamed after the J ura Mountains betweenFrance and Switzerland, where rocks of thisage were first studied.

Late orUpper

Middle

Early orLower

Triassic (248 - 213 million years ago)

The earliest period of the Mesozoic era. Thename Triassic refers to the threefold divisionof rocks of this age in Germany.

The Break-up of the continent Pangea ...

Late orUpper

Middle

Early orLower

Era Period or System Epochor

Series

Paleozoic (544 - 248 million years ago)

"Age of Ancient Life"

An era of geologic time,from the end of thePrecambrian to thebeginning of theMesozoic. The wordPaleozoic is fromGreek and means "oldlife."

Development of theEastern Piedmont ...

Taconic Orogeny …

Permian (286 - 248 million years ago)

The final period of the Paleozoic era. It isnamed after the province of Perm, Russia,where rocks of this age were first studied.

Late orUpper

Early orLower

Carboniferous (360 - 286 million years

ago)

A period of time inthe Paleozoic erathat includes the

Pennsylvanian andMississippianperiods.

Pennsylvanian (325 - 286 million years

ago) "The Coal Age"

A period of thePaleozoic era. It isnamed after the stateof Pennsylvaniawhere rocks of thisage are widespread.

Late orUpper

Middle

Early orLower

Mississippian (360 - 325 million years

ago)

A period of thePaleozoic era. It isnamed after theMississippi Rivervalley, which containsgood exposures of rocks of this age.

Late orUpper

Early orLower

Devonian (410 - 360 million years ago)

A period of the Paleozoic era. It is named afterDevonshire, England, where rocks of this agewere first studied.

Late orUpper

Middle

Early orLower

Silurian (440 - 410 million years ago)

Late orUpper

Middle



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A period of the Paleozoic. It is named after aCeltic tribe called the Silures.

Early orLower

Ordovician (505 - 440 million years ago)

The second earliest period of the Paleozoic

era. It is named after a Celtic tribe called theOrdovices.

Late orUpper

Middle

Early orLower

Cambrian (544 - 505 million years ago)

The earliest period of the Paleozoic era. It isnamed after Cambria, the Roman name forWales, where rocks of this age were firststudied.

Late orUpper

Middle

Early orLower

Precambrian

(Beginning of earth - 544 million years ago)

All geologic time before the beginning of the Paleozoic era. This includes about 90% of allgeologic time and spans the time from the beginning of the earth, about 4.5 billion years ago,to 544 million years ago. Its name means "before Cambrian."



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Lithostratigraphical Units

A body of rock that is unified by consisting dominantly of certain lithologic types or combination of types, or by possessing other unifying lithologic features. It may consists of sedimentary, igneous,or metamorphic rocks, or of two or more of these. It may or may not be consolidated. The criticalrequirement is a substantial degree of overall lithologic homogeneity, it may also conforms thelaw of superposition.

Group:

It is the major/huge unit, it includes many formations such as J helum group includes:

(a) Baghanwala Formation,(b) J utana Formation,(c) Kussak Formation,(d) Khewera Formation.

Formation:

A persistent body of igneous, sedimentary, or metamorphic rock, having easily recognizable

boundaries that can be traced in the field without recourse to detailed paleontologic or petrologicanalysis, and large enough to be represented on a geologic map as a practical or convenient unitfor mapping and description; the basic cartographic unit in geologic mapping.

Member:

Member is a sub-division of formation; each formation can contain different number of members.For example, the salt range formation which is of Pre-Cambrian age, having thickness 825m at itstype locality i.e. Khewra Gourge. This formation has three members:

(a) Sahwal Marl Member (oldest Member salt range),(b) Bandar Kas Gypsum Member,(c) Billanwala Salt Member.

Bed:

The sedimentary rocks form as layers upon layers of sediment accumulates in variousdepositional environments; these layers are called Strata or beds.



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Sedimentary Rock Classification

Clastic and Bioclastic Textures

Texture Size ClastComposition

Rounding Sorting Rock Name Comments DepositionalEnvironment

C

l a s t i c

>2mm gravel Variable Angular Poor Sedimentarybreccia Largeangularclasts – lesstransport

Alluvial fans

>2mm gravel Variable Rounded Poor Conglomerate Largeroundedclasts – moretransport

Alluvial fans,stream, beach

2-1/16mmsand

Quartz Rounded Well Quartzsandstone

“clean”sandstone –moretransport

Dunes,streams

2-1/16mm

sand

Feldspar,

quartz, etc.

Angular Mod-

poor

Arkose “dirty”

sandstone –lesstransport

Alluvial fan,stream

<1/16mmmud

Well Mudstone May split apart alongbedding;easilyscratched

Floodplains,delta, shallowand deepmarine

B

i o c l a s t s

>2mm gravel Shells Poor Poor Coquina Poorly-cementedshellfragments

Beach

<1/16mmmud Shells Well Chalk Microscopicshells Shallow-deepmarine

Chemical and Biochemical Textures

Texture Composition Hardness

Colour Rock Name Comments DepositionalEnvironment

C

h e m i c a l

Calcite/CaCO3 3 Variable Limestone Can be scratched by a nail Shallow marine,lake

Dolomite/CaMg(CO3)2

3 Variable Dolomite Can be scratched by a nail Near shoremarine

Silica/SiO2 7 Variable Chert Cannot be scratched by a nail Deep seaHalite/NaCl,

Gypsum/CaSO4.2H2O

2.5

2

Clear

variable,whitevariable

Evaporite Soft, non-metallic minerals;

halite is “salty”

Playa

B i o

Altered organicremains

Sof t

Brown-black

Coal Light in weight swamps



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Some Examples of Sedimentary Rocks

Breccia:

Sedimentary breccias are a type of clastic sedimentary rock which are composed of angular to

subangular, randomly oriented clasts of other sedimentary rocks. They are formed by eithersubmarine debris flows, avalanches, mud flow or mass flow in an aqueous medium. Technically,turbidites are a form of debris flow deposit and are a fine-grained peripheral deposit to asedimentary breccia flow.

The other derivation of sedimentary breccia is as angular, poorly sorted, very immature fragmentsof rocks in a finer grained groundmass which are produced by mass wasting. These are, inessence, lithified colluvium. Thick sequences of sedimentary (colluvial) breccias are generallyformed next to fault scarps in grabens.

Figure no.7: Sedimentary Breccia

Conglomerate:

A conglomerate is a rock consisting of other stones that have been cemented together.Conglomerates are sedimentary rocks consisting of rounded fragments and are thusdifferentiated from breccias, which consist of angular clasts. Both conglomerates and brecciasare characterized by

Paraconglomerates consist of a matrix supported rock that containing at least 15% sand sized orsmaller grains (<2 mm); the rest being larger grains of varying sizes.

Orthoconglomerates are defined by texture. They are a grain supported rock that consistsprimarily of gravel sized grains (~256 mm) with less than 15% matrix of sand and finer particles.

In rock types such as paraconglomerates and orthoconglomerates, were the matrix to beremoved, the rock would collapse. This is because the larger grains are supported by the matrix,and without it there is nothing to hold the grains together. Therefore, the higher the percentage of matrix, the more unstable the rock.



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Figure no.8: Conglomerate

Sandstone:

Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock grains. Mostsandstone is comprised of quartz and/or feldspar because these are the most common mineralsin earth's crust. Like sand, sandstone may be any color, but the most common colors are tan,brown, yellow, red, gray, and white. Since sandstone beds often form highly visible cliffs andother topographic features, certain colors of sandstone may be strongly identified with certainregions.

Figure no.9: Sandstone

Arkose

Arkose is a kind of sandstone combining of quartz and with large amounts of feldspar.Sandstones with more than 25% feldspars are generally classified as Arkoses.

Figure no.10: Arkose



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Mudstone:

Mudstone is a fine-grained sedimentary rock whose original constituents were clays or muds.Grain size is up to 0.0625 mm (0.0025 in) with individual grains too small to be distinguished withthe naked eye. If it become finely bedded so that it splits readily into thin layers it is called shale.It tends to be found in older geological formations, being consolidated from muds and clays over

time.

Figure no.11: Mudstone

Coquina:

Coquina is an incompletely consolidated sedimentary rock of biochemical origin, mainlycomposed of mineral calcite, often including some phosphate, in the form of seashells or coral. Itis created in association with marine reefs. While not usually referred to as such, it is actually asubset of limestone.

Coquina is quarried or mined as a source of paving material. It is usually poorly cemented andeasily breaks into component shell or coral fragments, which can be substituted for gravel orcrushed harder rocks. Large pieces of coquina of unusual shape are sometimes used aslandscape decoration.

Because coquina often includes a component of phosphate, it is sometimes mined for fertilizer.

Figure no.12: Coquina



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Chalk:

Chalk is a soft, white, porous form of limestone composed of the mineral calcite. It is relativelyresistant to erosion and slumping compared to the clays that it is usually associated with, and soforms tall steep cliffs where chalk ridges meet the sea. Chalk hills, known as chalk downland,usually form where bands of chalk reach the surface at an angle.

Chalk is formed in shallow waters by the gradual accumulation of the calcite mineral remains of micro-organisms over millions of years. Embedded flint nodules are commonly found in chalkbeds.

Because chalk is porous, chalk downland usually holds a large water table, providing a naturalreservoir that releases water slowly through dry seasons.

Chalk has been quarried from prehistory, providing building material and marl for fields. Insoutheast England, deneholes are a notable example of ancient chalk pits.

The Chalk Formation is a European stratigraphic unit in the upper Cretaceous period. Thisincludes the famous White cliffs of Dover of Kent in England, which formed entirely of chalk

deposits.

Figure no.13: Chalk Deposits



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Limestone:

Limestone is the most abundant of the non-clastic sedimentary rocks. Limestone is producedfrom the mineral calcite (calcium carbonate) and sediment. The main source of limestone is thelimy ooze formed in the ocean. The calcium carbonate can be precipitated from ocean water or itcan be formed from sea creatures that secrete lime such as algae and coral.Chalk is another type of limestone that is made up of very small single-celled organisms. Chalk isusually white or gray in color.Limestone can easily be dissolved by acids. If you drop vinegar on limestone it will fizz. Put alimestone rock into a plastic jar and cover it with vinegar. Cover the jar and watch the bubbling of the calcium carbonate and also the disintegration of the rock over a few days.

Figure no.14: Limestone

Dolomite:

Dolomite is the name of both a carbonate rock and a mineral (formula: CaMg(CO3)2) consisting of a calcium magnesium carbonate found in crystals. Dolomite rock (also dolostone) is composedpredominantly of the mineral dolomite. Limestone which is partially replaced by dolomite is

referred to as dolomitic limestone, or in old U.S. geologic literature as magnesian limestone.

Dolomite mineral crystallizes in the trigonal - rhombohedral system. It forms white, gray to pink,commonly curved, crystals although it is usually massive. It has physical properties similar tothose of the mineral calcite, but does not rapidly dissolve or effervesce (fizz) in dilute hydrochloricacid. The Mohs hardness is 3.5 to 4 and the specific gravity is 2.85.

Figure no15: Lustrous, curved bright pearly pink dolomite crystals, measuring up to 5 mm (0.2")across

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