Match the features in Column 1 to the most appropriate description in Column 2.Column 1Column 2P. Ash layeri. Part of a turbidite sequenceQ. Graded beddingii. Subaerial episode in the sedimentary recordR. Hiatusiii. Dating of sedimentary rocksS. Soil profileiv. Missing faunal zone

The correct matching is P-iii; Q-i; R-iv; S-ii.An ash layer contains volcanic crystals such as zircon and sanidine that can be dated radiometrically, so it is used for dating sedimentary rocks (iii).Graded bedding is the Ta division at the base of a Bouma sequence, so it is part of a turbidite (i).A hiatus is a gap in the record, recognised biostratigraphically as a missing faunal zone (iv).A soil profile (palaeosol) forms only at the land surface, so it records a subaerial episode (ii).Option B makes graded bedding the dating tool and ash the turbidite, and option C swaps the hiatus and the soil profile.

Sedimentary Processes and Environments Questions and Answers

Q: Which one of the following primary structures can be used for paleocurrent measurement?

The structure used for paleocurrent measurement is the flute cast.A flute is a scour cut into mud by a turbulent, one-way current; sand filling it leaves a cast on the base of the overlying bed. Each flute has a deep, rounded upcurrent end and flares out downcurrent, so its shape gives the actual direction the current flowed, not just a line. Flute casts on turbidite soles are the classic paleocurrent indicator.Oscillation ripples are symmetric, formed by waves moving water to and fro, so they record only the trend of the wave crests. Hummocky cross-strata are built by storm-wave oscillatory flow and have no consistent dip direction. Load and flame structures are soft-sediment deformation caused by dense sand sinking into wet mud, a vertical process that says nothing reliable about current direction.

Q: Which one of the following is characteristic of a point bar succession?

A point bar succession shows an upward gradation from sandstone to shale.Point bars build out sideways on the inner bank of a meander as the channel migrates. The deepest, fastest part of the channel lays down coarse sand and gravel at the base; higher up the bar the flow is slower, so the grain size falls; and at the top come fine overbank silt and mud. The result is a fining-upward succession, typically with trough cross-bedding passing up into ripple lamination and then mudstone.Upward gradation from shale to sandstone is a coarsening-upward succession, typical of a prograding delta front or shoreface. Thick homogeneous sandstone and thick laminated shale lack the vertical grain-size trend that defines a point bar.

Q: In an arid environment, winds of similar intensity blow in nearly opposite directions in alternate seasons. Which dune type is most likely to form in such an environment?

The dune most likely to form is the seif.Seifs are long, sharp-crested linear (longitudinal) dunes. They grow where winds of similar strength blow from two directions at an angle to each other, often alternating with the season: each wind builds the dune on its lee side in turn, so the crest stays fixed and lengthens parallel to the mean wind direction.Barchans (barkhans) and lunate dunes are the same crescent form, built by one dominant wind blowing over limited sand, with horns pointing downwind. Transverse dunes are long ridges at right angles to a single dominant wind where sand is plentiful. None of these needs a reversing wind.

Q: Which of the following are the typical marine biogenic sediment types ?

The typical marine biogenic sediments are Calcareous Ooze & Siliceous Oozes.A biogenic sediment is made mostly of the skeletal remains of organisms; an ooze contains at least 30% such material. Calcareous ooze is built of the calcium carbonate shells of foraminifera and coccolithophores, and siliceous ooze of the silica tests of diatoms and radiolarians.Pelagic muds (red clays) and turbidites are lithogenous, derived from land, and turbidites are deposited by density currents. Calcareous sandstone and sandy limestone are lithified rocks, not the typical deep-sea biogenic sediments, so 'none of the above' is also wrong.

Q: The surface features of .................. are those of three-dimension circular to elliptical draping humps and swals of about 01 meter in length 10s cm in heights.

The description fits hummocky cross stratification.Hummocky cross stratification consists of gently curved laminae forming low, three-dimensional domes (hummocks) and hollows (swales), roughly circular to elliptical, a metre or more across and only some tens of centimetres high. It forms in shallow marine sand below fair-weather wave base under storm waves, and is a key indicator of storm deposits.Trough cross stratification forms by migrating three-dimensional dunes and has scoop-shaped sets cut into one another, simple (planar) cross stratification comes from straight-crested bedforms, and ripple drift (climbing ripple) lamination forms where ripples migrate while sediment rains out. None produces the draping humps and swales described.

Q: ........................ are the areas of deposition within a meandering stream channel producing ridge-and-swale topography at the surface.

They are point bars.In a meandering river, flow is fastest on the outside of a bend, which erodes the cut bank, and slowest on the inside, where sand and gravel are deposited as a point bar. As the meander migrates, successive bars are added, leaving curved ridges separated by low swales, the ridge-and-swale (scroll bar) topography of the floodplain.Crevasse splays are fans of sediment deposited on the floodplain where a levee is breached, levees are ridges built along the channel banks by overbank flooding, and alluvial fans form where a stream leaves a mountain front. None lies within the meandering channel itself.

Q: A normal curve in sediment size analysis is defined in term of the Mean and the ...........................

A normal curve is defined by the mean and the standard deviation.The normal (Gaussian) distribution is fully described by two parameters: the mean, which fixes its centre, and the standard deviation, which fixes its spread. In grain size analysis the standard deviation of the phi values measures sorting.In a normal curve the mode equals the mean, so it adds nothing; skewness is zero, since the curve is symmetric; and kurtosis has the fixed normal value. These describe departures from normality, not the normal curve itself.

Q: In Phi(\(\phi\)) grain size scale :(a) Increasing absolute value of negative Phi numbers indicate increasing millimetre size(b) Increasing positive Phi numbers indicate decreasing millimetre size(c) Increasing positive Phi numbers indicate increasing millimeter size(d) Increasing absolute value of negative Phi numbers indicate decreasing millimeter size

Statements a and b are correct, so the answer is (a), (b).The phi scale is defined as \(\phi = -\log_{2} d\), with d the grain diameter in millimetres. So 1 mm is 0 phi, 2 mm is -1 phi, 4 mm is -2 phi, and 0.5 mm is +1 phi, 0.25 mm is +2 phi.Larger negative phi values (bigger absolute value) mean coarser grains, as in a (and not d), and larger positive phi values mean finer grains, as in b (and not c). Statements c and d reverse the scale.

Which one of the following primary structures can be used for paleocurrent measurement?

A.Oscillation ripple
B.Hummocky cross-strata
C.Flute cast
D.Load and flame structures

Exam Year(s)

IIT JAM - 2026,

Answer: C

The structure used for paleocurrent measurement is the flute cast.

A flute is a scour cut into mud by a turbulent, one-way current; sand filling it leaves a cast on the base of the overlying bed. Each flute has a deep, rounded upcurrent end and flares out downcurrent, so its shape gives the actual direction the current flowed, not just a line. Flute casts on turbidite soles are the classic paleocurrent indicator.

Oscillation ripples are symmetric, formed by waves moving water to and fro, so they record only the trend of the wave crests. Hummocky cross-strata are built by storm-wave oscillatory flow and have no consistent dip direction. Load and flame structures are soft-sediment deformation caused by dense sand sinking into wet mud, a vertical process that says nothing reliable about current direction.

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Which one of the following is characteristic of a point bar succession?

A.Thick homogenous sandstone
B.Upward gradation from sandstone to shale
C.Upward gradation from shale to sandstone
D.Thick laminated shale

Exam Year(s)

IIT JAM - 2026,

Answer: B

A point bar succession shows an upward gradation from sandstone to shale.

Point bars build out sideways on the inner bank of a meander as the channel migrates. The deepest, fastest part of the channel lays down coarse sand and gravel at the base; higher up the bar the flow is slower, so the grain size falls; and at the top come fine overbank silt and mud. The result is a fining-upward succession, typically with trough cross-bedding passing up into ripple lamination and then mudstone.

Upward gradation from shale to sandstone is a coarsening-upward succession, typical of a prograding delta front or shoreface. Thick homogeneous sandstone and thick laminated shale lack the vertical grain-size trend that defines a point bar.

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In an arid environment, winds of similar intensity blow in nearly opposite directions in alternate seasons. Which dune type is most likely to form in such an environment?

A.Barkhan
B.Transverse dunes
C.Seif
D.Lunate

Exam Year(s)

IIT JAM - 2026,

Answer: C

The dune most likely to form is the seif.

Seifs are long, sharp-crested linear (longitudinal) dunes. They grow where winds of similar strength blow from two directions at an angle to each other, often alternating with the season: each wind builds the dune on its lee side in turn, so the crest stays fixed and lengthens parallel to the mean wind direction.

Barchans (barkhans) and lunate dunes are the same crescent form, built by one dominant wind blowing over limited sand, with horns pointing downwind. Transverse dunes are long ridges at right angles to a single dominant wind where sand is plentiful. None of these needs a reversing wind.

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Match the features in Column 1 to the most appropriate description in Column 2.

Column 1	Column 2
P. Ash layer	i. Part of a turbidite sequence
Q. Graded bedding	ii. Subaerial episode in the sedimentary record
R. Hiatus	iii. Dating of sedimentary rocks
S. Soil profile	iv. Missing faunal zone

A.P-iii; Q-i; R-iv; S-ii
B.P-i; Q-iii; R-iv; S-ii
C.P-iii; Q-i; R-ii; S-iv
D.P-iii; Q-iv; R-i; S-ii

Exam Year(s)

IIT JAM - 2026,

Answer: A

The correct matching is P-iii; Q-i; R-iv; S-ii.

An ash layer contains volcanic crystals such as zircon and sanidine that can be dated radiometrically, so it is used for dating sedimentary rocks (iii).
Graded bedding is the Ta division at the base of a Bouma sequence, so it is part of a turbidite (i).
A hiatus is a gap in the record, recognised biostratigraphically as a missing faunal zone (iv).
A soil profile (palaeosol) forms only at the land surface, so it records a subaerial episode (ii).

Option B makes graded bedding the dating tool and ash the turbidite, and option C swaps the hiatus and the soil profile.

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Which of the following are the typical marine biogenic sediment types ?

A.Pelagic muds & turbidites
B.Calcareous Ooze & Siliceous Oozes
C.Calcareous sandstone and sandy limestone
D.none of the above

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: B

The typical marine biogenic sediments are Calcareous Ooze & Siliceous Oozes.

A biogenic sediment is made mostly of the skeletal remains of organisms; an ooze contains at least 30% such material. Calcareous ooze is built of the calcium carbonate shells of foraminifera and coccolithophores, and siliceous ooze of the silica tests of diatoms and radiolarians.

Pelagic muds (red clays) and turbidites are lithogenous, derived from land, and turbidites are deposited by density currents. Calcareous sandstone and sandy limestone are lithified rocks, not the typical deep-sea biogenic sediments, so 'none of the above' is also wrong.

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The surface features of .................. are those of three-dimension circular to elliptical draping humps and swals of about 01 meter in length 10_s cm in heights.

A.Simple cross stratification
B.Trough cross stratification
C.Hummocky cross stratification
D.Ripple drift stratification

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: C

The description fits hummocky cross stratification.

Hummocky cross stratification consists of gently curved laminae forming low, three-dimensional domes (hummocks) and hollows (swales), roughly circular to elliptical, a metre or more across and only some tens of centimetres high. It forms in shallow marine sand below fair-weather wave base under storm waves, and is a key indicator of storm deposits.

Trough cross stratification forms by migrating three-dimensional dunes and has scoop-shaped sets cut into one another, simple (planar) cross stratification comes from straight-crested bedforms, and ripple drift (climbing ripple) lamination forms where ripples migrate while sediment rains out. None produces the draping humps and swales described.

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........................ are the areas of deposition within a meandering stream channel producing ridge-and-swale topography at the surface.

A.Creuasse-splay
B.Levees
C.Point bar
D.Alluvial fans

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: C

They are point bars.

In a meandering river, flow is fastest on the outside of a bend, which erodes the cut bank, and slowest on the inside, where sand and gravel are deposited as a point bar. As the meander migrates, successive bars are added, leaving curved ridges separated by low swales, the ridge-and-swale (scroll bar) topography of the floodplain.

Crevasse splays are fans of sediment deposited on the floodplain where a levee is breached, levees are ridges built along the channel banks by overbank flooding, and alluvial fans form where a stream leaves a mountain front. None lies within the meandering channel itself.

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A normal curve in sediment size analysis is defined in term of the Mean and the ...........................

A.Mode
B.Skewness
C.Standard deviation
D.Kurtosis

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: C

A normal curve is defined by the mean and the standard deviation.

The normal (Gaussian) distribution is fully described by two parameters: the mean, which fixes its centre, and the standard deviation, which fixes its spread. In grain size analysis the standard deviation of the phi values measures sorting.

In a normal curve the mode equals the mean, so it adds nothing; skewness is zero, since the curve is symmetric; and kurtosis has the fixed normal value. These describe departures from normality, not the normal curve itself.

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The change over from laminar to turbulent flow during sedimentation by water at 20°C takes place at a critical Reynolds Number of around ...................

A.300
B.500
C.700
D.900

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: B

The changeover occurs at a critical Reynolds number of around 500.

The Reynolds number compares inertial to viscous forces, \(Re = \rho V L/\mu\). For flow in open channels, as in sediment transport, the flow is laminar below about 500 and becomes turbulent above it, with a transitional range above that. (For pipe flow, using diameter as the length scale, the familiar figure is about 2,000.)

300 is still in the laminar range, while 700 and 900 lie beyond the critical value usually quoted for open-channel flow.

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10.

In Phi(\(\phi\)) grain size scale :

(a) Increasing absolute value of negative Phi numbers indicate increasing millimetre size
(b) Increasing positive Phi numbers indicate decreasing millimetre size
(c) Increasing positive Phi numbers indicate increasing millimeter size
(d) Increasing absolute value of negative Phi numbers indicate decreasing millimeter size

A.(a), (b)
B.(c), (d)
C.(d), (a)
D.(b), (c)

Exam Year(s)

MH SET - 2019, SET Exam - 2019,

Answer: A

Statements a and b are correct, so the answer is (a), (b).

The phi scale is defined as \(\phi = -\log_{2} d\), with d the grain diameter in millimetres. So 1 mm is 0 phi, 2 mm is -1 phi, 4 mm is -2 phi, and 0.5 mm is +1 phi, 0.25 mm is +2 phi.

Larger negative phi values (bigger absolute value) mean coarser grains, as in a (and not d), and larger positive phi values mean finer grains, as in b (and not c). Statements c and d reverse the scale.

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