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Page 1: Eduncle...According to Weller (1960), Stratigraphy is defined as the branch of the geology that deals with the study and interpretation of stratified and sedimentary rocks …

Eduncle.comMPA 44, 2nd Floor, Rangbari Main Road, Mahaveer Nagar 2nd, KotaRajasthan, 324005

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Page 2: Eduncle...According to Weller (1960), Stratigraphy is defined as the branch of the geology that deals with the study and interpretation of stratified and sedimentary rocks …

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According to Weller (1960), Stratigraphy is defined as the branch of the geology that deals withthe study and interpretation of stratified and sedimentary rocks and with the identification, description,sequences (vertical and horizontal), mapping and correlation of stratigraphic rock units. The word �stratified�means layered metamorphic as well as volcanic rocks. Sedimentary rocks and the fossils they containare the fundamental materials for understanding the stratigraphic concept.

Stratigraphy is the study of sequential arrangement of layered rocks according to their time offormation on the surface of the Earth. It deals with succession of rocks and their mutual relationships.

The stratigraphy aims, grouping of naturally, occurring rocks and establishing the age of suchgroup and further correlation of these groups of different areas. The organic remains found preservedin certain rocks play special significance for their immense utility in assigning precise age to the rocks.At the end these all information are used to understand the evolutionary history of the Earth.

1. PRINCIPLES OF STRATIGRAPHY

Stratigraphic Laws are basic principles that all geologists use in deciphering the spatial andtemporal relationships of rock layers. These laws were developed in the 17th to 19th centuries basedupon the work of Niels Steno, James Hutton and William Smith and others. By 1900, all the intellectualtools needed to establish the description, sequence, and correlation of strata were in place.

Steno established three cardinal principles of stratigraphic analysis and then used these toreconstruct the geological history of Tuscany. Steno�s principles are as follows :

1. Original Horizontality : unconsolidated sediments deposited on a solid base must haveoriginally formed horizontal layers since the sediment particles would have �slithered� tothe lowest point. Thus, consolidated strata inclined at some angle must have becometilted after consolidation.

2. Original Continuity : layers of unconsolidated sediments deposited on a solid basewould have formed continuous sheets of material. Thus, bands of consolidated sedimentswhose ends have been broken must have experienced this breakage and erosion afterconsolidation.

3. Superposition : Since each layer of unconsolidated sediment deposited on a solid basemust form after the basal layer has been deposited, layers of sediment that overly otherlayers are younger than the other layers.

The Scottish lawyer-gentlemen farmer James Hutton (1726�1797) made the next significantcontribution to stratigraphic principles in 1785

4. Doctrine of Uniformitarianism : Uniformitarianism, in geology, the doctrine suggestingthat Earths geologic processes acted in the same manner and with essentially the sameintensity in the past as they do in the present and that such uniformity is sufficient toaccount for all geologic change. This principle is fundamental to geologic thinking andunderlies the whole development of the science of geology. This law can be summarizedin following two lines :

The present is the key to the past

Sometimes there are environments/conditions that do not have good modernanalogues

Stratigraphy

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Geology (Sample Theory)

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In the earliest 1800s, and Georges Cuvier in France used the successions of faunas instratified rocks for mapping. This led to the development of another principle called lawof faunal succession

5. Law of Faunal Succession : It is based on the observation that sedimentary rock stratacontain fossilized flora and fauna, and that these fossils succeed each other vertically ina specific, reliable order that can be identified over wide horizontal distances. A fossilizedNeanderthal bone will never be found in the same stratum as a fossilized Megalosaurus,for example, because Neanderthals and megalosaurus lived during different geologicalperiods, separated by many millions of years. This allows strata to be identified and datedby the fossils found within.

Note : To Hutton, these erosion-deposition-uplift cycles had been repeated endlessly in Earthhistory, implying that (1) the Earth itself is very old, (2) the processes we see working today (e.g.,erosion, deposition, gradual uplift) operated in the past, (3) that the power for uplift came fromthe heat generated by compaction, supplemented by heat at depth left over from the Earth�s initialformation, and (4) the ultimate purpose of this system was to produce a self-renewing Earth thatwas �adapted to the purposes of man.� In particular, Hutton denied that fossils provided anyevidence for the directional passage of time because each uniformitarian cycle�s biota was�perfect�.

6. Law of Inclusion : The law of inclusion is a method of relative dating in geology.Essentially, this law states that clasts in a rock are older than the rock itself. One exampleof this is a xenolith, which is a fragment of country rock that fell into passing magma asa result of stopping. Another example is a derived fossil, which is a fossil that has beeneroded from an older bed and redeposited into a younger one.

This is a restatement of Charles Lyell's original principle of inclusions and componentsfrom his 1830 to 1833 multi-volume Principles of Geology, which states that, withsedimentary rocks, if inclusions (or clasts) are found in a formation, then the inclusionsmust be older than the formation that contains them. For example, in sedimentary rocks,it is common for gravel from an older formation to be ripped up and included in a newerlayer. A similar situation with igneous rocks occurs when xenoliths are found. Theseforeign bodies are picked up as magma or lava flows, and are incorporated, later to coolin the matrix. As a result, xenoliths are older than the rock, which contains them.

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Geology (Sample Theory)

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7. Law of Cross Cutting : Cross-cutting relationships is a principle of geology that statesthat the geologic feature which cuts another is the younger of the two features. It is arelative dating technique in geology. It was first developed by Danish geological pioneerNicholas Steno in Dissertationis prodromus (1669) and later formulated by James Huttonin Theory of the Earth(1795) and embellished upon by Charles Lyell in Principles ofGeology (1830).

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2. DEFINITIONS

1. Stratigraphy : Stratigraphy, from Latin stratum + Greek graphia, is the description of allrock bodies forming the Earth's crust and their organization into distinctive, useful, mappableunits based on their inherent properties or attributes in order to establish their distributionand relationship in space and their succession in time, and to interpret geologic history.

2. Stratum (plural = strata) : Layer of rock characterized by particular lithologic propertiesand attributes that distinguish it from adjacent layers.

3. Stratigraphic Classification : The systematic organization of the Earth's rock bodies, asthey are found in their original relationships, into units based on any of the properties orattributes that may be useful in stratigraphic work.

4. Stratigraphic Unit : A body of rock established as a distinct entity in the classification ofthe Earth's rocks, based on any of the properties or attributes or combinations thereof thatrocks possess.

Stratigraphic units based on one property will not necessarily coincide with those basedon another.

5. Stratigraphic Terminology : The total of unit-terms used in stratigraphic classification.It may be either formal or informal.

(a) Formal stratigraphic terminology uses unit-terms that are defined and namedaccording to guidelines conventionally established.

(b) Informal stratigraphic terminology uses unit-terms as ordinary nouns in a descriptivesense, not as a part of a specific scheme of stratigraphic classification. The useof informal terms in published documents is strongly discouraged.

6. Stratigraphic Nomenclature : The system of proper names given to specific stratigraphicunits.

7. Zone : Minor body of rock in many different categories of stratigraphic classification. Thetype of zone indicated is made clear by a prefix, e.g. lithozone, biozone, chronozone.

8. Horizon : An interface indicative of a particular position in a stratigraphic sequence.

The type of horizon is indicated by a prefix, e.g. lithohorizon, biohorizon, chronohorizon.

9. Correlation : A demonstration of correspondence in character and/or stratigraphic position.The type of correlation is indicated by a prefix, e.g., lithocorrelation, biocorrelation,chronocorrelation.

10. Geochronology : The science of dating and determining the time sequence of the eventsin the history of the Earth.

11. Geochronologic Unit : A subdivision of geologic time.

12. Geochronometry : A branch of geochronology that deals with the quantitative (numerical)measurement of geologic time. The abbreviations ka for thousand (103), Ma for million(106), and Ga for billion (milliard of thousand million, 109) years are used.

13. Facies : The term "facies" originally meant the lateral change in lithologic aspect of astratigraphic unit. Its meaning has been broadened to express a wide range of geologicconcepts: environment of deposition, lithologic composition, geographic, climatic or tectonicassociation, etc.

14. Caution against Preempting General Terms for Special Meanings : The preemptingof general terms for special restricted meanings has been a source of much confusion.

The preferable procedure is to conserve the original general meaning of a term and to seek amore precise and less ambiguous word for the special meaning.

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Geology (Sample Theory)

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Stratotypes and Type Localities (Definitions)

Standard Definitions : Named stratigraphic units must be defined or characterized at a specifiedlocality where they are well exposed and developed in order that there will be a common, materialstandard of reference for their identification.

Reference to a Specific Rock Section : The particular sequence of strata chosen as a standardof reference of a layered stratigraphic unit is called a stratotype. In the case of nonlayered rocks thestandard of reference is a type locality. It may be an area of exposure (or well or mine) and is an essentialpart of the establishment of a formal stratigraphic unit. In cases where the written description and thestratotype are not the same, the data from the stratotype take precedence.

For some stratigraphic units, such as biostratigraphic range zones, the standard of the unitcannot be tied to a specific stratigraphic section or area because the stratigraphic scope of the unit mayvary with increasing information.

However, the characterization and description of these and other biostratigraphic units can beenhanced by the designation of one or more specific reference sections.

1. Stratotype (Type Section) : The designated exposure of a named layered stratigraphicunit or of a stratigraphic boundary that serves as the standard of reference. A stratotypeis the specific stratal sequence used for the definition and/or characterization of thestratigraphic unit or boundary being defined.

2. Unit-Stratotype : The type section of a layered stratigraphic unit that serves as thestandard of reference for the definition and characterization of the unit.

3. Boundary-Stratotype : The specified sequence of strata that contains the specific pointthat defines a boundary between two stratigraphic units.

4. Composite-Stratotype : A unit-stratotype formed by the combination of several specifiedintervals of strata combined to make a composite standard of reference.

5. Type Locality : The specific geographic locality was the stratotype of a layered stratigraphicunit is situated. The name also refers to the locality where the unit was originally describedand/or named. In the case of units composed of nonlayered igneous or metamorphicrocks, the type locality is the specific geographic locality where the unit was originallydefined.

6. Type Area or Type Region : The geographic area or region that encompasses thestratotype or type locality of a stratigraphic unit or boundary.

7. Holo-, para-, neo-, lecto-, and hypostratotypes.

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Geology (Sample Theory)

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3. PRINCIPLES OF STRATIGRAPHIC CLASSIFICATION

Stratigraphic classification encompasses all rocks of the crust of the Earth. Rocks have manytangible and measurable properties and may be classified according to any of them. Rocks may alsobe classified by their time of origin or interpreted attributes, such as environment or genesis.

The stratigraphic position of change for any property or attribute does not necessarily coincidewith that for any other. Consequently, units based on one property commonly do not coincide with thosebased on a different property. Therefore, it is not possible to express the distributions in the rocks of allof the different properties with a single set of stratigraphic units. Different sets of units are needed.

However, all the different classifications are closely related because they express different aspectsof the same rock bodies and they are used to achieve the same goals of stratigraphy: to improve ourknowledge and understanding of the Earth's rock bodies and their history.

Categories of Stratigraphic Classification

Rock bodies may be classified according to many different inherent properties. Each classificationneeds its own distinctive nomenclature. The following kinds of formal units are best known and mostwidely used :

(A) Lithostratigraphic Units : units based on the lithologic properties of the rock bodies. Theseare strictly empirical, based on observable lithologic features including composition and grain-size andpossibly including certain basic sedimentological information, such as types of sedimentary structuresand cyclic successions.

A hierarchy of units has been developed based on the formation, which is the primarylithostratigraphic unit (NACSN 2005).

Supergroup

Group

Formation (Primary Unit) :

(I) Mappability at a scale of 1:50,000

(II) Formations should not contain major unconformities, although minor disconformitiesmay be acceptable

(III) The contacts of the formation should be established at obvious lithologic changes(sharp or gradational)

(IV) Unconformity is a logical choice for a formation contact Member Tongue or lentilBed.

Fig. : A correlation table for a hypothetical basin fill, drawn to illustrate the various ways in whichlithostratigraphic terminology may be adapted to best capture existing stratigraphic variability.

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(B) Unconformity-Bounded Units : bodies of rock bounded above and below by significantdiscontinuities in the stratigraphic succession. They may consist of any kinds of rocks, igneous,metamorphic or sedimentary. Unconformity-bounded sedimentary successions may be formalized usingthe empirical, descriptive classification procedures of Allostratigraphy (see NACSN 2005), but increasinglygeologists now employ the interpretive procedures and models of sequence stratigraphy as the mainbasis for subdivision and mapping of the basin fill.

(C) Biostratigraphic Units : Units based on the fossil content of the rock bodies. Descriptive orempirical biostratigraphy is used in erecting zones for local or regional stratigraphic correlation and formsthe basis for a global system of chronostratigraphic subdivision.

Fossil content varies through a stratigraphic succession for two main reasons: evolutionarychanges and ecological differences, such as changes in climate or depositional environment.Biostratigraphy should be based only on evolutionary changes, but it is always difficult to distinguishthese from changes that take place in a biostratigraphic assemblage as a result of ecological modifications,and this problem is a cause of continuing controversy for many fossil groups.

The work of the early stratigraphers, following Smith, had clearly established the value of fossilassemblages for the establishment of stratigraphic order and for the purposes of comparison betweenstratigraphic sections. The similarity of the succession of faunas or floras between sections in differentbasins, even different continents termed homotaxis was well established. In the absence of a clearunderstanding of how faunas and floras changed with time, and without the tools to establish numericalage, it remained a legitimate question whether homotaxis could be equated with synchrony. Eventuallythis philosophical dilemma was resolved by developments in the understanding of the processes ofevolution, coupled with the establishment of ever more detailed systems of zonation and correlation,which left little room for doubt regarding the reality of the principle of relative age and time correlationbased on fossil content. It is now universally accepted that formally established biozones representspecific intervals of time. The appearance of a successful evolutionary step requires a discrete periodof time for it to spread throughout its full range. A biozone may not, therefore, have exactly the same agerange everywhere.

Concept of Zone

Albert Oppel in France (1856) defined �zones� that are characterized by more than two taxa andhaving boundaries based on two or more documented first and/or last occurrences of the includedcharacterizing taxa. This zone is now named �Oppel zone� or �concurrent range zone�. It is a type ofassemblage zone (see below). The concept of zone allowed subdivision of stages into two or more,smaller biostratigraphic units. �Zones� constitute the basic unit of biostratigraphic classification.

Fig. : Oppel Zone

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Geology (Sample Theory)

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Biostratigraphic Units

(i) Interval Zone : Interval zone is a body of strata between two specific, documented lowestand/or highest occurrences of single taxa. There are three basic types of interval zones :

Taxon Range Zone : (International Stratigraphic Guide [ISG], Salvador, 1994, Fig. a as shownbelow) : The interval between the lowest and highest occurrences of a single taxon.

Concurrent Range Zone and Partial Range Zone (ISG, Fig. b and c): The interval between thedocumented lowest occurrence of one taxon and the documented highest occurrence of another taxon.Concurrent range zone is used when the fossil occurrence results in stratigraphic overlap of the taxa(Fig. b). When such occurrences do not result in stratigraphic overlap, the interval zone may be calleda partial range zone (Fig. c).

Interval Zone : The interval between documented successive lowest occurrences (Fig. d) orsuccessive highest occurrences of two taxa (Fig. e).

(ii) Assemblage Zone : An assemblage zone is a biozone characterized by the association ofthree or more taxa. If the zone is characterized by taxa without regard to their range limits, it is calledan assemblage zone. If, on the other hand, it is characterized by more than two taxa and is furthercharacterized by having boundaries based on two or more documented first and/or last occurrences ofthe included characterizing taxa, it is called an Oppel zone. Note that the Oppel zone is no longerrecognized as a biozone in the International Stratigraphic Guide (Salvador,1994).

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(iii) Abundance Zone : An abundance zone is a body of strata in which the abundance of aparticular taxon or specified group of taxa is significantly greater than is usual in the adjacent parts ofthe section. The term �acme zone� is no longer used by ISG.

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(iv) Magnetostratigraphic Polarity Units : Units based on changes in the orientation of theremanent magnetization of the rock bodies. Magnetic reversal scale based on recent volcanic rocks, isshown in image.

(v) Chronostratigraphic Units : units based on the time of formation of the rock bodies.

Chronostratigraphic units comprise groups of strata recognized as being formed during a specificinterval of geological time. While chronostratigraphic terms are conceptual rockstratigraphic units, theirclassification is mirrored by the geochronologic or time-stratigraphic classification scheme. To understandthe difference between these two scales, consider and hourglass. Sand falling through the neck of thehourglass is deposited in the lower reservoir over a certain time interval (1 hour). A chronostratigraphicunit is equivalent to the sand deposit while the associated geochronologic unit is equivalent to the amountof time over which the sand deposit accumulated (1 hour). The chronostratigraphic unit accumulatedover a the time interval and can be said to represent that interval in terms of the deposit is thicknessand extent. But the sand deposit itself cannot be said to be time. Table lists the chronostratigraphic andgeochronometry unit equivalents.

Application of chronostratigraphic unit classification may be illustrated by the chronozone (equivalentto a geochronologic chron). All stratigraphic intervals represent potential chronozones/chrons as do alllithostratigraphic and biostratigraphic units For example, the Exus alphus biozone represents a chronozonethat begins with the stratigraphic horizon time equivalent with the speciation event of this (hypothetical)species and ends with the stratigraphic horizon that is time-equivalent its global extinction event (Fig).This chronozone corresponds to the chron which is defined as the time interval between this speciesglobal speciation and extinction events. Both the chronozones and chrons are worldwide in extent,though it may not be possible to recognize either in localities remote from the geographic range of thespecies. The chronozones and chrons will also be estimates (at least for biostratigraphic zones) andsubject to revision as outlined above.

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Table : Chronostratigraphic and geochronologic unit equivalents with an example.

Stages (equivalent to a geochronologic age) are the most common chronostratigraphic unit andare usually defined on the basis of the chronozones of a series of biozones (e.g., the MaastrichtianStage/Age). Note that biozone boundaries themselves cannot be used to achieve a true chronostratigraphicsystem because they are inherently diachronous. Stages may be subdivided into substages.

Systems (equivalent to a geochronologic period) are composed of a sequence of stages. Forexample, the Indian, Olenekian, Anisian, Laningian, Carnian, Norian, and Rhaetian stages/ages, all ofwhich are defined on the basis of biochronozones, combine to form the Triassic System/Period. Similarly,Erathems (equivalent to a geochronologic era) are composed of a sequence of systems/periods. Threeerathems eras are currently recognized, the Palaeozoic, Mesozoic, and Cenozoic. Finally, Eonathems(equivalent to a geochronologic eon) are composed of a sequence of ears. Thus, the Palaeozoic,Mesozoic, and Cenozoic combine to form the Phanerozoic Eonathem/Eon. This was preceded in geologicaltime successively by the Proterozoic and Archean eonathems/eons.

Fig. : An example of the use of biostratigraphic units to zone a classic Upper Cretaceous suite of deep-marine sediments in north-central Texas on the basis of their planktonic foraminiferal content. Notechronostratigraphic series unit (Maastrichtian) and that not all subbiozones are divided into zonules.

Many other properties and attributes may be used to classify rock bodies and the way is opento use any that show promise. Whenever this is the case, the unit-terms being used should be defined.

Though each kind of stratigraphic unit may be particularly useful in stratigraphic classificationunder certain conditions or in certain areas or for certain purposes, chronostratigraphic units offer thegreatest promise for formally-named units of worldwide application because they are based on their timeof formation. Lithostratigraphic, biostratigraphic, and unconformity-bounded units are all of limited arealextent, and thus unsatisfactory for global synthesis.

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Magnetostratigraphic polarity units, though potentially worldwide in extent, require extrinsic datafrom the other units for their recognition, and dating. For these reasons, chronostratigraphic units havebeen chosen for international communication among stratigraphers with respect to position in thestratigraphic column.

Distinguishing Terminologies for each Category

Appropriate distinguishing terms are needed for each of the various categories of stratigraphicunits. Some of the classifications are best suited to a hierarchical classification whereas in others allcategories are of equal rank.

Table : Summary of Categories and Unit-Terms in Stratigraphic Classification

Table gives terms here recommended for various categories of stratigraphic units.

Chronostratigraphic and Geochronologic Units

Chronostratigraphic units are tangible stratigraphic units because they encompass all the rocksformed during a defined interval of time.

Geochronologic units are units of time-an intangible property-and thus intangible units, not inthemselves stratigraphic units.

Incompleteness of the Rock Record

The rock record of any one area is far from continuous or complete. It is commonly interruptedby innumerable diastems, discontinuities, and unconformities.

Short interruptions of the record, in fact, exist in layered rocks at every bedding plane. Theevidence which the rocks carry of these missing intervals is in itself a part of stratigraphy and a veryimportant contribution to the understanding of Earth history.

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4. THE SIX STEPS INVOLVED IN DATING AND CORRELATION

1. Identification of the units or stratigraphic events to be correlated, and development ofregional correlation frameworks, including the mapping of hiatuses, unconformities andother key surfaces. Local correlations may be based on lithostratigraphy, but sequencestratigraphic concepts and methods are now practically universal.

Correlations may be guided or constrained by supplementary data, such as biostratigraphiczonation. Determining the position of events such as sequence boundaries may or maynot be a straightforward procedure, and requiring the application of facies mapping andsequence mapping techniques.

2. Determining the extent and chronostratigraphic significance of unconformities.Unconformities, including sequence boundaries, represent finite time spans which varyin duration from place to place. In any given location this time span could encompassthe time span represented by several different sedimentary breaks at other locations.Resolving such problems may require that some of the other steps be completed,particularly step 3.

3. Determination of the biostratigraphic framework. One or more fossil groups is used toassign the selected event to a biozone framework, and zones are defined and correlatedfrom section to section. Error and uncertainty may be introduced because of theincompleteness of the fossil record. Graphic correlation or other quantitative techniquesmay be employed.

4. Assessment of relative biostratigraphic precision. The length of time represented bybiozones depends on such factors as faunal diversity and rates of evolution. Durations ofbiozones vary considerably through geological time and between different fossil groups

5. Correlation of biozones with the global stage framework. Much of the existing stageframework was initially, with notable exceptions, built from the study of macrofossils inEuropean type sections, although microfossils have become increasingly important forsubsurface work and for global studies (McGowran 2005). Correlation with this frameworkraises questions of environmental limitations on biozone extent, our ability to inter-relatezonal schemes built from different fossil groups, and problems of global faunal and floralprovinciality and diachroneity.

6. Assignment of numerical (�absolute�) ages. The use of radiometric and magnetostratigraphicdating methods, plus the increasing use of chemostratigraphy (oxygen and strontiumisotope concentrations) permits the assignment of numerical ages in years to thebiostratigraphic framework. Such techniques also constitute methods of correlation intheir own right, especially where fossils are sparse. The Geological Time Scale (GTS) hasbecome an instrument of considerable geological importance and practical utility in recentyears, contributing to the emergence of what Miall (2013) termed �SophisticatedStratigraphy�).

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Fig. : Steps in the correlation and dating of stratigraphic events. e = typical range of error associatedwith each step. a In the case of the sequence framework, location of sequence boundaries maynot be a simple matter, but depends on interpretation of the rock record using sequence principles.b Assignment of the boundary event to the biozone framework. An incomplete record of preservedtaxa (almost always the case) may lead to ambiguity in the placement of biozone boundaries. cThe precision of biozone correlation depends on biozone duration. Shown here is a simplificationof Cox�s (1990) summary of the duration of zones in Jurassic sediments of the North Sea Basin.d The building of a global stage framework is fundamental to the development of a global timescale. However, global correlation is hampered by faunal provincialism. Shown here is asimplification of the faunal provinces of Cretaceous ammonites, shown on a mid-Cretaceousplate-tectonic reconstruction. Based on Kennedy and Cobban (1977) and Kauffman (1984). e Theassignment of numerical ages to stage boundaries and other stratigraphic events contains inherentexperimental error and also the error involved in the original correlation of the datable horizon(s)to the stratigraphic event in question. Diagrams of this type are a standard feature of any discussionof the global time scale (e.g., Haq et al. 1988; Harland et al. 1990). The establishment of a globalbiostratigraphically-based sequence framework involves the accumulation of uncertainty oversteps a�d. Potential error may be reduced by the application of radiometric, magnetostratigraphicor chemostratigraphic techniques which, nonetheless, contain their own inherent uncertainties(step e)

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Geology-GG (MSP)

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Geology (GG)Model Solved Paper

Duration : 180 minutes Maximum Marks : 100

Read the following instructions carefully.

1. This test paper has a total of 60 questions carrying 100 marks. The entire question paper

is divided into Three Sections A, B and C. All sections are compulsory. Questions in

each section are of different types.

2. Section � A contains Multiple Choice Questions (MCQ). Each MCQ type question has

four choices out of which only one choice is the correct answer. This section has 30

Questions and carry a total of 50 marks. Q.1 � Q.10 carry 1 mark each and Questions

Q.11 � Q.30 carry 2 marks each.

3. Section � B contains Multiple Select Questions (MSQ). Each MSQ type question is

similar to MCQ but with a difference that there may be one or more than one choice(s)

that are correct out of the four given choices. The candidate gets full credit if he/she

selects all the correct choices only and no wrong choices. This section has 10 Questions

and carry 2 marks each with a total of 20 marks.

4. Section � C contains Numerical Answer Type Questions (NAT). For these NAT type

questions, the answer is a real number which needs to be entered using the virtual

numerical keypad on the monitor. No choices will be shown for these type of questions.

This section has 20 Questions and carry a total of 30 marks. Q.1 � Q.10 carry 1 mark

each and Questions Q.11 � Q.20 carry 2 marks each.

5. In all sections, questions not attempted will result in zero mark. In Section � A (MCQ),

wrong answer will result in NEGATIVE marks. For all 1 mark questions, 1/3 marks will

be deducted for each wrong answer. For all 2 marks questions, 2/3 marks will be

deducted for each wrong answer. In Section � B (MSQ), there is NO NEGATIVE and NO

PARTIAL marking provisions.There is NO NEGATIVE marking in Section � C (NAT) as

well.

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SECTION-(A) MULTIPLE CHOICE QUESTIONS (MCQ)

1. The planet having density less than 1.0 g/cm3 is

(A) Jupiter (B) Neptune

(C) Saturn (D) Uranus

2. Low velocity zone (LVZ) occurs globally at the base of

(A) Asthenosphere (B) Crust

(C) Lithosphere (D) Mantle

3. Which of the following minerals is harder than knife blade ?

(A) Calcite (B) Fluorite

(C) Gypsum (D) Quartz

4. The type of dentition found in Hippurites is

(A) Schizodont (B) Taxodont

(C) Dysodont (D) Pachydont

5. Rift valleys are bounded by

(A) Normal fault (B) Reverse fault

(C) Strike-slip fault (D) Transform fault

6. The Si : O ratio is phyllosilicates is

(A) 1 : 3 (B) 1 : 4

(C) 2 : 5 (D) 1 : 2

7. The plutonic equivalent of dacite is

(A) Diorite (B) Granite

(C) Gabbro (D) Granodiorite

8. Composition of a sandstone is :

Quartz � 55%, Feldspar � 25%;

Rock fragments � 3% Matrix � 17%

The sandstone is classified as

(A) Arkose (B) Arkosic wacke

(C) Lithic arenite (D) Quartz wacke

9. Age of Neyvelli lignite is

(A) Paleocene (B) Miocene

(C) Cretaceous (D) Eocene

10. An igneous rock containing 50% olivine, 25% orthopyroxene and 25% clinopyroxene by mode is

(A) Dunite (B) Harzburgite

(C) Lherzolite (D) Wehrlite

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11. Arrange these events from oldest to youngest :

P. Rajmahal Volcanics Q. Deccan Volcanics

R. Panjal Volcanics S. Malani Volcanics

(A) Q P S R (B) S R Q P

(C) S R P Q (D) Q P R S

12. Which of the following statements are true for porosity of sandstone?

P. Porosity increases with sorting

Q. Porosity decreases with sorting

R. Porosity increases with mud content

S. Porosity decreases with mud content

(A) Q (B) P, S

(C) P, R (D) S

13. The {0001} section of an uniaxial mineral can be distinguished from an isotropic mineral in thinsection by

(A) Extinction angle (B) Pleochroism

(C) Relief (D) Interference figure

14. On crystallization of anorthite, Sr concentration in the magma will

(A) decrease (B) increase

(C) increase and then decrease (D) remain same

15. Match the following

List-I List-II

P. Olivine 1. Sorosilicate

Q. Quartz 2. Nesosilicate

R. Epidote 3. Phyllosilicate

S. Biotite 4. Tectosilicate

Codes :

P Q R S

(A) 2 4 1 3

(B) 2 4 3 1

(C) 2 3 1 4

(D) 4 3 2 1

16. Quartz can be optically distinguished from nepheline based on

(A) Relief (B) Birefringence

(C) Optic Sign (D) Extinction angle

17. Which of the following is an ore mineral of iron?

(A) Manganite (B) Magnesite

(C) Malachite (D) Magnetite

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18. Which one of the following deposits is associated with glaciers ?

(A) Dune (B) Fanglomerate

(C) Moraine (D) Point bar

19. The second sillimanite isograd is marked by

(A) Absence of Muscovite and Presence of Sillimanite

(B) Absence of both Muscovite and Sillimanite

(C) Presence of both Muscovite and Sillimanite

(D) Presence of Muscovite and Absence of Sillimanite

20. Match the following :

List-I : (Locality) List-II : (Mineral)

P. Zawar 1. Chromite

Q. Hutti 2. Magnesite

R. Sukinda 3. Lead-Zinc

S. Almora 4. Gold

Codes :

P Q R S

(A) 1 2 4 3

(B) 3 2 4 1

(C) 4 2 3 1

(D) 3 4 1 2

21. A clay core is an essential part of

(A) Arch dam (B) Buttress dam

(C) Gravity dam (D) Earth dam

22. The maximum curvature of a cylindrically folded surface occurs at

(A) Axial plane (B) Fold axis

(C) Hinge (D) Limb

23. This type of structure is shown by

(A) Biotite (B) Garnet

(C) Diopside (D) Orthoclase

24. Which of the following is a texturally immature but mineralogically matured sandstone ?

(A) Arkose (B) Quartz wacke

(C) Lithic wacke (D) Quartz arenite

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25. Point group 4 2 m belongs to

(A) Isometric (B) Tetragonal

(C) Orthorhombic (D) Monoclinic

26. Match the following :

List-I List-IIP. Opisthoparian 1. Cephalopoda

Q. Micropygus 2. Gastropoda

R. Ceratitic Suture 3. Trilobite suture

S. Spire 4. Pygidium

Codes :P Q R S

(A) 4 2 1 3

(B) 3 4 1 2

(C) 3 1 4 2

(D) 2 1 4 3

27. Which of the following minerals are/is found in supergene enrichment zone ?

P. Chalcocite Q. Sphalerite

R. Galena S. Covellite

(A) P (B) P, Q, R, S

(C) P, S (D) Q, R

28. The ratio of Earth�s total magnetic field at Equator to that at North Pole is

(A)13

(B)12

(C)23

(D)34

29. Which of the following features are used to describe a lineation?

(A) Strike (B) Dip

(C) Hade (D) Plunge

30. Match the following :

List-I : (Mineral) List-II : (Si:O ratio)P. Beryl 1. 1 : 4

Q. Amphibole 2. 1 : 3

R. Olivine 3. 2 : 7

S. Zoisite 4. 4 : 11

Codes :P Q R S

(A) 2 4 1 3

(B) 2 4 3 1

(C) 4 3 2 1

(D) 3 4 1 2

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SECTION-(B) MULTIPLE SELECT QUESTIONS (MSQ)

1. Which of the following are/is correctly matched ?

(A) Cuddapah Supergroup � Paleoproterozoic

(B) Vindhyan Supergroup � Neoproterozoic

(C) Burgess Shale Formation � Cambrian

(D) Siwalik Group � Jurassic

2. Which of the following flora belong to lower Gondwana ?

(A) Gangamopteris (B) Williamsonia

(C) Bucklandia (D) Buriadia

3. Which of the following elements are incompatible ?

(A) Ni (B) Cr

(C) La (D) K

4. Which of the following statements are NOT true about 4 2 2m m m

crystal class ?

(A) There are 5 mirror planes

(B) There are 4 diads

(C) There is no centre of symmetry

(D) This crystal class belongs to tetragonal system

5. Out of the 10 minerals present in Mohs scale of hardness, which of the following minerals are�silicates� ?

(A) Talc (B) Apatite

(C) Topaz (D) Corundum

6. Which of the following indicate(s) pre-kinematic crystals ?

(A) Foliation wrapped around porphyroclast

(B) Pressure shadow zone

(C) Helicitic folds in internal schistosity

(D) Kink bands or folds

7. Which of the following textures are metamorphic textures ?

(A) Porphyroblastic texture (B) Mortar texture

(C) Porphyritic texture (D) Cumulate texture

8. Which of the following minerals weather faster than K-feldspar ?

(A) Pyroxene (B) Amphibole

(C) Biotite (D) Muscovite

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9. Which of the following represents closed crystallographic forms ?

(A) Tetragonal disphenoid (B) Tetragonal pyramid

(C) Tetragonal trapezohedron (D) Tetragonal scalenohedron

10. Which of the following igneous bodies are concordant ?

(A) Laccolith (B) Dyke

(C) Phacolith (D) Lopolith

SECTION-(C) NUMERICAL ANSWER TYPE QUESTIONS (NAT)

1. The S-wave velocity in the lower continental crust is 6800 m/s and its density is 3380 kg/m3. Findits rigidity in GPa (upto 2 decimal places)

2. On a 1:10000 scale map, length of a fault trace is 5 cm. What is its length on a 1:25000 map?

3. If a radioactive isotope has a decay constant of 1.55 × 10�10 year�1, its half life is ___________× 109 years.

4. The dip of a plane is 30°. Calculate its hade (in degrees)

5. An aquifer has a thickness of 10 m and transmissivity of 0.75 m2/day. Its hydraulic conductivityis ______ m/day.

6. The energy released by an earthquake of magnitude 8 is _____________ times the energyreleased by an earthquake of magnitude 6.

7. Structure contours of a bedding plane at 100 m interval are spaced in such a manner thathorizontal equivalent is also 100 m. Find its dip (in degree).

8. If a planet revolves around the sun with a period of 8 years, then its distance from the sun is__________ times the distance between the Earth and sun.

9. The dip slip of a fault is 200 m. The dip amount is 30°. The throw of the fault is _______ m.

10. After decaying through 7 half life periods, the original amount of radioactive substance that

reduces to an amount of 1

64 g is ________ g. (Give answer upto 2 decimal places)

11. The P-wave velocity is twice that of S-wave velocity in a medium. Calculate Poisson�s ratio (upto

2 decimal places)

12. The Fe-O bond length in Fe2O3 is 2.05 Å. The ionic radius of anion is 1.32 Å. Calculate

coordination number (CN).

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13. A radioactive substance decays to one-third of its original value in 6 hours time. What is the halflife (in hours) ? [2 decimal places]

14. A mineral assemblage consists of fayalite, ferrosilite and quartz in equilibrium. Find the no. ofdegrees of freedom in P-T space.

15. A basaltic lava flow is found to have 87

86

SrSr

ratio of 0.720 and 87

86

Rb

Sr ratio of 0.750. If initial value

of 87

86

SrSr

ratio is 0.704, the age of the flow is ___________ × 109 years.

Given that = 1.42 × 10�11 year�1. (Answer upto 2 decimal places).

16. Consider this reaction :

3 cordierite = 2 garnet + 4 sillimanite + 5 quartz

S = �0.0984 kJ/K

V = �15.973 kJ/Kbar

If equilibrium pressure at 25°C is 3.6 Kbar, what is the equilibrium pressure in Kbar at 650°C?

(Answer in 2 decimal places)

17. The length of a fossil increases from 5.6 cm to 7 cm due to tensional force. Calculate the�stretching� value (upto 2 decimal places)

18. Given the difference in arrival time of S and P waves recorded at a station to be 10 seconds,find the epicentral distance in km if Vp = 6.5 km/s and Vs = 3.6 km/s.

(Answer in 2 decimal places)

19. No. of mirror planes present in 2

3m

crystal class are ___________ .

20. A silt loam has bulk density of 1.2 g/cm3 and particle density of 2.6 g/cm3. Find porosity.

(Answer in 2 decimal places)

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ANSWER KEY

SECTION-(A) MULTIPLE CHOICE QUESTIONS (MCQ)

1 2 3 4 5 6 7 8 9 10C C D D A C D B B C11 12 13 14 15 16 17 18 19 20C B D A A C D C A D21 22 23 24 25 26 27 28 29 30D C C B B B C B D A

SECTION-(B) MULTIPLE SELECT QUESTIONS (MSQ)

1 2 3 4 5 6 7 8 9 10B,C A,D C,D A,B,D A,C A,B,D A,B A,B,C A,C,D A,C,D

SECTION-(C) NUMERICAL ANSWER TYPE QUESTIONS (NAT)

1 2 3 4 5 6 7 8 9 10156.29 2 4.47 60 0.075 900 45 4 100 2.00

11 12 13 14 15 16 17 18 19 200.33 6 3.78 1 1.50 7.45 1.25 80.65 3 0.54

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SOLUTIONSSECTION-(A) MULTIPLE CHOICE QUESTIONS (MCQ)

1. (C) Planet Name Density (g/cm3)

Mercury 5.4

Venus 5.2

Earth 5.5

Mars 3.9

Jupiter 1.3

Saturn 0.7

Uranus 1.3

Neptune 1.6

Hence, (C) is the correct answer.

2. (C) Low velocity zone is present between the lithosphere and asthenosphere. So, LVZ occursat the base of lithosphere.

Hence, (C) is the correct answer.

3. (D) Mineral Mohs Scale of Hardness

Talc 1

Gypsum 2

Calcite 3

Fluorite 4

Apatite 5

Orthoclase 6

Quartz 7

Topaz 8

Corundum 9

Diamond 10

Hardness of knife blade = 5.5.

(D) is the correct answer.

4. (D) Taxodont � Arca, Nucula

Schizodont � Trigonia Unio

Dyrodont � Mytilus

Pachydont � Hippurites

(D) is the correct answer.

5. (A)

Valleys

Rift valleys are formed due to extension and are bounded by normal faults as shown.

(A) is the correct answer

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6. (C) Talc is a phyllosilicate.

Formula of talc is Mg3 Si4 O10 (OH)2

Si:O = 4:10 = 2:5

Hence, (C) is the correct answer.

7. (D) Volcanic Rock Plutonic Rock

Andesite Diorite

Rhyolite Granite

Basalt Gabbro

Dacite Granodiorite

Hence, (D) is the correct answer.

8. (B) Since matrix > 15% rock is �wacke�. As the rock contains 25% feldspar, its composition

can be termed as �arkosic�.

Rock is �Arkosic Wacke�

Hence, (B) is the correct answer.

9. (B) Neyveli lignite is found within Cuddalore Sandstone of Mis-Pliocene

age. So, (B) is the correct answer.

10. (C)

Olivine

90

40

Clinopyroxene

Wehrlite

Lherzolite

Dunite

Harzburgite

OrthopyroxeneWebsterite

Hence, (C) is the correct answer.

11. (C) S. Malani Volcanics � Neoproterozoic

R. Panjal Volcanics � Permian

P. Rajmahal Volcanics � Late Jurassic to Early Cretaceous

Q. Deccan Volcanics � Late Cretaceous

Hence, (C) is the correct answer.

12. (B) Porosity increases with sorting. If mud content in a sandstone increases, the pore spacesbetween the sand grains get occupied by the finer mud particles. Hence, the porosity ofsandstone decreases with mud content.

Hence, (B) is the correct answer.

13. (D) {0001} section of an uniaxial mineral displays interference figures as this section isperpendicular to the optic axis or c-axis.

However, extinction angle, pleochroism and relief can�t be observed.

But for an isotropic mineral, everything appears dark and we can�t observe interference

figure, pleochroism extinction angle and relief.

14. (A) Sr can replace Ca and in this way Sr enters anorthite (CaAl2Si2O8) So, Sr concentrationin the magma will decrease.

Hence, (A) is the correct answer.

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15. (A) P. Olivine (Mg2SiO4) Nesosilicate

Q. Quartz (SiO2) Tectosilicate

R. Epidote Sorosilicate

S. Biotite (KMg3Si3AlO10(OH)2) Phyllosilicate

(A) is the correct answer.

16. (C) Quartz Optically (+)ve

Nepheline Optically (�)ve

Hence, (C) is the correct answer.

17. (D) Manganite Ore mineral of Mn

Magnesite MgCO3

Malachite Cu2CO3(OH)2

Magnetite Fe3O4

Hence, (D) is the correct answer.

18. (C) Dune is formed due to deposition of sediments by air and running water. Fanglomerate

is formed in alluvial faus due to the deposition by river. Point bars are also formed in the

concave side of meandering rivers. Moraines are formed as a result of deposition by

glaciers.

Hence, (C) is the correct answer.

19. (A) Second sillimanite isograd is marked by the following reaction :

Muscovite + Qtz Kfs + Sillimanite + H2O

In this reaction, Sillimanite appears at the cost of Muscovite.

Hence (A) is the correct answer.

20. (D) Zawar (Rajas than) Lead-Zine

Hutti (Karnatake) Gold

Sukinda (Orissa) Chromite

Almora (Uttarakhand) Magnesite

P-3, Q-4, R-1, S-2

Hence (D) is the correct.

21. (D)

Structure of Earth dam

Clay core

Fine earth material

Rock Cover

BoulderPitch

Hence, (D) is the correct answer.

22. (C) Hinge is the point of maximum curvature. At hinge, 2

2

d ydx

is maximum.

Hence, (C) is the correct answer.

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23. (C) In the given structure,

Si : O ratio is 2 : 6 = 1 : 3

Mineral Si : O ratio

Biotite 2 : 5

Garnet 1: 3

Diopside 1: 3

Orthoclase 1: 2

Garnet is a cyclosilicate but the given structure represents single chain silicate. Pyroxenehave single chain structure.

Diopside (CaMgSi2O6) is a clinopyroxene.

Hence, (C) is the correct answer.

24. (B) Textural Immaturity Includes :

1. High Matrix Content

2. Poor Sorting

3. Presence of angular grains.

Mineralogical Maturity means presence of robust minerals like quartz and absence offragile minerals like feldspar.

Hence, (B) is the correct answer.

25. (B) Crystal classes of tetragonal system include :

4 Tetragonal pyramid

4 Tetragonal disphenoid

4m

Tetragonal disphenoid

422 Tetragonal trapezohedron

42m Tetragonal scalenohedron

4mm Ditetragonal pyramid

4 2 2m m m

Ditetragonal dipyramid

Hence, (B) is the correct answer

26. (B) Types of Trilobite Suture :

i. Protoparian ii. Proparian

iii. Gonatoparian iv. Opisthoparian

v. Hypoparian

Types of Pygidium :

i. Micropygus ii. Heteropygus

iii. Isopygus iv. Macropygus

Types of Cephalopod Suture :

i. Orthoceratitic ii. Nautilitic

iii. Goniatitic iv. Ceratitic

v. Ammonitic

Spire - Part of the gastropod shell except the body whorl.

P-3, Q-4, R-1, S-2 Option (B).

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27. (C) Oxidation zone minerals are Tenorite (CuO), Cuprite (Cu2O), etc.

Supergene enrichment zone minerals are chalcocite (Cu2S), covellite (CuS), etc.

Option (C) is correct.

[Galena and Sphalerite are very rarely present in supergene sulphide enrichment zone]

28. (B) B = 2K 1 3cos

where = Colatitude

= Colatitude

= Latitude

For equation, = 90

For poles, = 0°

Bequator = K and Bpoles = 2K

Hence, (B) is correct.

29. (D) Strike, dip and hade are used to describe a plane.

Plunge, pitch, trend are used to describe a lineation.

Option (D) is correct.

30. (A)

Mineral Type of Silicate Si : O ratio

Beryl Cyclosilicate 1: 3

Amphibole Double chain silicate 4 :11

Olivine Nesosilicate 1: 4

Zoisite Disilicate 2 : 7

P-2, Q-4, R-1, S-3

Option (A) is correct.

SECTION-(B) MULTIPLE SELECT QUESTIONS (MSQ)

1. (B,C) Cuddapah Supergroup � Mesoproterozoic

Vindhyan Supergroup � Neoproterozoic

Burgess Shale Formation � Cambrian

Siwalik Group � Tertiary

Hence (B) and (C) are correct.

2. (A,D) Lower Gondwana Flora

Glossopteris, Gangamopteris, Barakaria, Buriadia, Vertebraria, Dadoxylon,Noeggerathiopsis, Glossotheca, etc.

Upper Gondowana Flora

Ptilophyllum, Pterophyllum, Otozamites, Dictyosomites, Bucklandia, Dicroidium,Williamsonia, Pentoxylon, etc.

Hence, (A) and (D) are correct.

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3. (C,D) Incompatible elements prefer melt over solid and have KD < 1. Compatible elements

prefer solid over liquid and have KD > 1.

Compatible elements � Ni, Cr, Co, V etc.

Incompatible elements � K, Rb, U, Th, La, etc.

Hence, (C) and (D) are correct.

4. (A,B,D)

4 2 2m m m

belongs to tetragonal system and the name of this crystal class is ditetragonal

dipyramid.

The properties of this crystal class are -

i. 1 tetrad (A4) at c-axis

ii. 4 diads (A2) 2 of them are at a and b axes while the other 2 are at the diagonals

iii. 5 mirror planes.

iv. Centre of symmetry (i) present.

Hence, (A), (B) and (D) are correct.

5. (A,C) Talc � Mg3Si4O10(OH)2

Gypsum � CaSO4.2H2O

Calcite � CaCO3

Fluorite � CaF2

Apatite � Ca5(PO4)3 (OH, F)

Orthoclase � KAl Si3O8

Quartz � SiO2

Topaz � Al2SiO4 (OH, F)2

Corundum � Al2O3

Diamond � C

Hence, (A) and (C) are correct.

6. (A,B,D)

If a crystal is formed before an episode of deformation, then foliation that forms later

wraps around the crystal and pressure shadow zone is formed.

Pre-kinematiccrystal

Foliation formedafter the crystal

Pressure shadow zone

Kink bands also indicate pre-kinematic crystals formed prior to deformation.

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Helicitic folds in internal schistosity characterize post-kinematic crystals.

Internal Schistority

This crystal has beenformed after foliation

External Schistosity

Hence, (A), (B) and (D) are correct.

7. (A,B) Porphyroblastic Texture : Metamorphic texture in which certain large grains are formedby recrystallization and these grains are larger than surrounding groundmass.

Mortar Texture : Metamorphic texture formed due to increased pressure. In this texture,robust grains are set in a growd-down matrix.

Porhyritic TextureIgneous Textures

Cumulate Texture

Hence, (A) and (B) are correct.

8. (A,B,C)

Olivine

Ca plagioclase

Pyroxene

Amphibole

Na plagioclase

Biotite

k feldspar

Muscov ite

Quartz

Increasing resistance

to weathering

So, pyroxene, amphibole and biotite weather faster than k-feldspar

Hence, (A), (B) and (C) are correct.

9. (A,C,D)

Tetragonal disphenoid has 4 faces and can inclose space.

Tetragonal pyramid has 4 faces but does not enclose space.

Tetragonal trapezohedron has 8 faces and encloses space.

Tetragonal scalenohedron has 8 faces and encloses space.

[All trapezohedrons and scalenohedrons enclose space].

Hence, (A), (C) and (D) are correct.

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10. (A,C,D)

Laccolith Lopolith

Dyke

Phacoliths

So, laccolith, lopolith and phacolith are concordant while dykes are discordant (custacross strata)

Hence, (A), (C) and (D) are correct.

SECTION-(C) NUMERICAL ANSWER TYPE QUESTIONS (NAT)

1. 156.29 Velocity = Shear Modulus( )

Density( )

(6800)2 = 3380

m = 156.29 GPa

2. 2 Actual length of fault trace

= (5 × 10000) cm

Length of the fault trace on

1 : 25000 scale map

= 5 10000

25000

cm = 2 cm

3. 4.47 = 1.55 × 10�10 year�1

Half life = 10ln 2 0.693 10

1.55

years

= 4.47 × 109 years

4. 60 Hade of a plane

= (90 � dip amount)

= (90 � 30)° = 60°

5. 0.075 Hydraulic conductivity × Thickness = Transmissivity

Hydraulic conductivity

= 0.7510

m/day

= 0.075 m/day

6. 900 Ans = 308�6 = 302 = 900

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7. 45 AB = horizontal equivalent

AC = contour difference

= dip.

BA

C

= tan�1 ACAB

= tan�1 100100

= 45°

8. 4 We know, T2 R3

R T2/3 [T = time period]

Hence, answer = 82/3 = (23)2/3 = 22 = 4

9. 100 AB = heave

BC = throw

AC = dip slip = 200 m

BA

C

= dip amount = 30°

sin = BCAC

sin 30° = BC200

BC = 100 m

10. 2.00 Let original amount be �x� g

7

7

x 1 2x x 2

64 642

11. 0.33 Poisson�s ratio ()

=

2

p

s2

p

s

v2

v12 v

1v

vp = p-wave velocity

vs = s-wave velocity

=

2

2

1 2 2 1 2 12 2 3 32 1

= 0.33

12. 6 Anionic radius = 1.32 Å

Cationic radius = (2.05 � 1.32) Å = 0.73 Å

Radius ratio = 0.731.32

= 0.553

Since radius ratio is between 0.414 and 0.732, coordination no. = 6

13. 3.78 N = N0

1/ 2t / t12

N = present no. of atoms

1/ 2

tt

0

N 1N 2

N0 = initial no. of atoms

1/ 2

6t1 1

3 2t1/2 = half life

Log1/ 2

1 6 1log

3 t 2

t1/2 = 3.78 hours

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14. 1 Forsterite + Quartz = Ferrosilite

No. of components = 2

No. of phases = 3

F = C � P + 2 F = 2 � 3 + 2 = 1

15. 1.5087 87 87

86 86 86ri

Sr Sr Rb. t

Sr Sr S

0.720 = 0.704 + 0.750 × 1.42 × 10�11 × t

0.016 = (1.065 × 10�11).t

t = 110.016 10

1.065

years

= 1.50 × 109 years

16. 7.45 We know,

dP SdT V

x 3.6 0.0984

650 25 15.973

x = 7.45

[x is the new pressure in kbar]

17. 1.25 Stretching (s) = 1 + e

where e(elongation) = 0

0

S = 1 + 0

0 0

[ = new length; 0 = original length]

S = 7

5.6 = 1.25

18. 80.65 Let the epicentral distance be �x� km.

x x

3.6 6.5 = 10

1 1

x 103.6 6.5

x × 0.124 = 10

x 80.65

19. 3 Properties of 2

3m

crystal class :

i. 3 diads

ii. 3 mirror planes

iii. 4 no. of 3

iv. Centre of symmetry (i)

Hence, the answer is 3.

20. 0.54 Porosity = 1 � Bulk density

Particle density

= 1 � 1.22.6

= 0.54

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