Module 2 Flashcards
(132 cards)
1
Q
are derived from pre-existing rock masses formed from consokidation of loose sediments or chemical precipitation fron solution or an organic matter consisting of secretion remains of plabts and animals
A
Sedimentary rocks
2
Q
They are also called as secondary rocks
A
Sedimentary rocks
3
Q
They are
formed due to decay and disintegration of pre-existing rocks by natural agencies
like ocean, running water, glacier, lake, wind etc. in the depressions that occurred
on the land area
A
Sedimentary rocks
4
Q
The surface of the Earth, including its seafloor, is covered with sediments
and sedimentary rocks. They form a surface _______ or ‘______’ on bedrock ranging
in thickness from practically non-existent (in places where bedrock crops out at the
Earth’s surface) to few kms.
A
veneers or cover
5
Q
________, loosened materials that ultimately formed
sedimentary rocks, are usually deposited in layers one on top of the other. They
record the conditions that existed at the time of deposition and subsequent
changes.
A
Sediments
6
Q
_____________ can infer the sources and the environment of deposition
of the sediments using evidences provided by the study of its texture, structure
and mineral content.
A
Sedimentologists
7
Q
two main groups of sedimentary rocks are classified on the basis of their origin
A
Clastic Sedimentary Rocks
Chemical/Biochemical Sedimentary Rocks
8
Q
formed as a result of the weathering
or fragmentation of pre-existing rocks and minerals and classified on the basis of their textures, primarily the sizes of the grains.
A
Clastic Sedimentary Rocks
9
Q
Sedimentary rocks can be coarse-grained, medium-grained, and fine-grained. Give examples for the three
A
coarse-grained: conglomerates medium-grained: sandstones
fine-grained: siltstones, mudstones, and shales
10
Q
Within each textural
category, clastics are further subdivided by ______________ which reflects the
parent rock, for example, a quartz-rich sandstone or a feldspar-rich
sandstone.
A
mineralogy
11
Q
formed as a result of chemical processes
A
Chemical or Biochemical Sedimentary Rocks
12
Q
results from the precipitation and deposits formed by plants and animals that utilize
carbonates in their life processes.
A
Primary carbonate deposition
13
Q
The most abundant mineral chemically
or biochemically precipitated in the oceans is ______, most of it the shelly
remains of organisms and the main constituent of limestone.
A
calcite
14
Q
a calcium-magnesium carbonate
precipitated during lithification.
A
dolomite
15
Q
are formed by the
chemical precipitation during the evaporation of seawater
A
Gypsum and halite
16
Q
Five types of sedimentary rocks that are important in the production of
hydrocarbons:
A
Sandstones
Carbonates (limestones and dolomite)
Shales
Evaporites
17
Q
are clastic sedimentary rocks composed of mainly sand size particles
or grains set in 2 matrix of silt or clay and more or less firmly united by a cementing
material (commonly silica, iron oxide, or calcium carbonate).
A
Sandstone
18
Q
The sand particles
usually consist of _______, and the term “sandstone”, when used without
qualification, indicates a rock containing about _____% _____.
A
Quartz
85-90% quartz
19
Q
are sediments formed by a mineral compound characterized by a
fundamental anionic structure of CO3-2.
Calcite and aragonite CaCO3, are
examples of these
A
Carbonate
20
Q
are sedimentary rocks consisting chiefly of
the mineral calcite (calcium carbonate, CaC03), with or without magnesium
carbonate.
A
Limestone
21
Q
are the most important and widely distributed of the
carbonate rocks
A
Limestones
22
Q
is a common rock forming mineral with the formula
CaMg(CO3)2 or calcium magnesium carbonate
A
dolomite
23
Q
A sedimentary rock will be named dolomite if that rock is composed
of more than __% mineral dolomite and less than __% mineral calcite.
A
90
10
24
Q
is a type of detrital sedimentary rock formed by the consolidation of fine-grained material including clay, mud, and silt and have a layered or stratified
structure parallel to bedding.
A
Shale
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formed by the consolidation of fine-grained material and have a layered or stratified structure parallel to bedding.
Shale
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have a layered or stratified
structure parallel to bedding.
Shale
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Shales are typically ____ and contain hydrocarbons
but generally exhibit no ___________. Therefore, they typically do not formreservoirs but do make excellent ________. If a shale is _______, it would have
the potential to be a reservoir
Porous
Permeability
Cap rocks
Fractured
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do not form reservoirs like limestone and sandstone, but are veryimportant to petroleum exploration because they make excellent cap rocks and
generate traps.
Evaporites
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is used for all deposits, such as salt deposits,
that are composed of minerals that precipitated from saline solutions concentrated
by evaporation.
Evaporites
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On evaporation the general sequence of ________ is: calcite
gypsum or anhydrite, halite, and finally bittern salts.
precipitation
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Evaporites make excellent cap rocks because they are ___________ and, unlike
lithified shales, they deform plastically, not by fracturing
impermeable
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The formation of _______ structures can produce several different types of traps. One
type is created by the folding and faulting associated with the lateral and upward movement of it through overlying sediments.
salt structures
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They occur on the upper and lower
surfaces of beds as well as within beds. They can be used to deduce the processes
and conditions of deposition, the directions of the currents which deposited the
sediments.
Sedimentary structures
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are large-scale features which show variety of interesting and significant
geometries that are produced by physical, chemical and biological processes
operating on sediments during and after their deposition
Sedimentary Structures
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Depending on the kind of mechanism of formation and relative time of
deposition, the structures are classified into:
Primary or Mechanical Structures
Secondary Structures (can be Chemical or Organic)
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are formed during the deposition of the constituent sediments
Primary Structures
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_____________ operating during the deposition develop these
structures like bedding, cross stratification, ripple marks, etc. and therefore they
are also termed as mechanical structures. They are _____ in nature
Physical (or mechanical) processes
inorganic
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Primary structures are significant and may help us in determining:
- paleocurrent conditions
- rate of supply of sediments
- mode of transportation
- environment of deposition
- top and bottom of beds
39
Primary sedimentary structures Include the folowing:
1. Bedding and Stratification
2. Cross Bedding
3. Graded Bedding
4. Ripple Marks
5. Mud Cracks
6. Raindrop Imprints
7. Sole Structure
40
are generally layered rocks because of the deposition of similar
or dissimilar in colour, grain size or mineral composition, sediments one over
another in a basin.
Sedimentary Rocks
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Individual layer of a sedimentary rock is called
Bed
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is the linear deposition of constituent sediments like small fragments of
parent materials.
Layering
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If the individual layers are less than one cm thick, they are called
lamination
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is a characteristic structure of fine-grained sedimentary rocks like clays and shales.
Lamination
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in cm
>100
30-100
10-30
3-10
1-3
0.3-1
<0.3
Very thickly bedded
Thickly bedded
Moderately bedded
Thinly bedded
Very thinly bedded
Thickly laminated
Thinly laminated
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Individual layers are called _______. They may be parallel or nonparallel,
continuous or discontinuous and curved, either wavy or planar
laminae
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is an umbrella term which is used to cover both bed and laminae.
Stratum (PI. strata)
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Stacking up process of strata one over another is known as
stratification
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It consists of sets of bedded material deposited by wind or water and
inclined at angles even upto 35° from the horizontal
Cross Bedding
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Cross Bedding consists of sets of bedded material deposited by wind or water and
inclined at angles even upto __° from the horizontal
35 degrees
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usually show truncated top and asymptotic bottom beds
assuming some horizontality. I
Crossed beds
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Ilt is formed due to change in the velocity
and/or direction of flow of streams.
Crossed Beds
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_______ lines of a cross bedded layer always meet the upper bedding at a higher angle and lower portion
tangentially. In _____________________, the laminations are curved
and of larger magnitude. Cross stratification is also referred as ______________.
Oblique
wind formed current beddings
current-bedding or false bedding
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Cross bedding consists of inclined dipping bedding, bounded by sub
horizontal surfaces and each of these units is termed a _____.
Set
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A group of similar sets
are termed ______.
cosets
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Three sets of beds (or _______) i.e. ____ (upward), _________
(towards sole) and _________ (inclined bedding in between the above two) comprises crossbedding or Cross lamination
laminae
topset
bottomset
foreset
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When the top and bottom beds show convergence at point, it is said to be _____ cross stratification.
wedge
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In _______ cross
bedding top and bottom sets are more or less parallel, but when the top and bottom
sets tend to meet, they form ______ cross bedding.
tabular
lensoid
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The angles of truncation of fore sets and the nature of lower bounding
surfaces of the sets, they are of following types:
Simple
Planar
Trough
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The angle of truncation is at 15° with non-erosional lower
bounding surfaces
Simple
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The angle of truncation is over 15 having lower bounding
surfaces as erosional plane
Planar
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The angle of truncation is less than 15° and have curved
erosional surfaces.
Trough
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The attributes of top and bottom sets, they are:
Tabular
Lenticular
Wedge
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Cross beds having the top and bottom surfaces of the deposit
are essentially parallel, indicating better sorted sediments.
Tabular
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When all the layers in Cross beds show an extreme
irregularity in their shape and disposition and may be intersected by
many other beds at different angles
Lenticular
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In this type of cross beds the individual layers exist in well-
defined sets of parallel layers but bears angular relationship with each other.
Wedge
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They show progressive variation of grain size from coarser at the bottom to
finer towards the top of a bed , in a gradational manner
Graded Bedding
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a wavy structure characterized by a crest and a trough.
Ripple Marks
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they are very small dune like features of sand or silt whose
long dimension is at right angles to the direction of current movement.
Ripple Marks
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generally result from interplay of wind and wave action during
the process of deposition of sediments in shallow waters.
Ripple Marks
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Two types of Ripple Marks
Current ripple marks
Wave-formed ripple marks
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are asymmetrical in nature, having parallel,
long, more or less equidistant ridges trending in straight lines at right
angles to the direction of flow lee-ward side.
Current ripple marks
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are the
commonest bedforms encountered within the lower flow
unidirectional regime
Current ripples
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_________ ripples contain finer materials at the crest and coarser
material at the troughs, but in the case of _________ ripples coarser
materials are found at crests
Aqueous
Aeolian
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also known as symmetrical ripples form
when the water moves back and forth, such as tidal action
Wave-formed ripple marks
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These are
shallow water features and are indicative of a stagnant body of water
frequently agitated by waves
Wave-formed ripple marks
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They are common structural features typically develop in clayey sediments due
to prolonged exposure to the atmosphere
Mud Cracks
79
Mud cracks are also known as
shrinkage cracks
or sun cracks
80
In plan view, they are polygonal and are generally about 0.5 m
across. It indicates that the sediment was exposed at the
surface shortly after deposition, since drying of the sediments would not occur
beneath a body of water
Mud cracks
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These are irregular, small crater-shaped depressions with slightly
raised edges seen on fine-grained dried soft sediment surfaces.
Raindrop imprints
82
________ falling on the surface of fine-grained compacted clays often makes crater
like depressions
Rain drops
83
Thus, they are shallow depressions surrounded by low
ridges formed by the impact of hailstones, etc. These may get dried
up and subsequently preserved under another layer of mud above them
Raindrop imprints
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are good indicators of subaerial
exposure but are not exclusive to arid climates, though they may have a higher preservation potential in such conditions
Rain prints
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These structures are preserved on the base of bed which is sharply
differentiated lithologically from the bed below.
Sole structure
86
They usually occur at the
interface of two different lithologies.
They are found most commonly
in turbidite deposits.
Sole imprints
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Sole marks also include ______ which are grooves eroded by turbulent flow and later flled with coarse sediments.
flute cast
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are elongated
depressions that form on the bottom of the body water as the current
erodes.
Flutes
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are a
characteristic structure of turbidites and are excellent indicators of current
direction and tops/ bottoms of bed.
Flute marks
90
The rounded
part of the flute is at the ____ current end. The flared end points are ____ current.
Up
Down
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Flutes are characterized by ( _____) and (______) . Similar features, but when parallel grooves are oriented in the flow direction, term ___________ are used.
up stream bulbous end
downstream flattening
groove casts
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are formed sometime after deposition.
Secondary sedimentary structure
93
These
structures are products of chemical action or biological activity contemporaneous
with sedimentation or shortly thereafter.
Secondary sedimentary structures
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Secondary structures classification
Chemical structures
Organic structures
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originates due to chemical action, e.g.concretions
stylolites, dendrites and solution structure,.
Chemical structures
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are formed due to biological activity of organisms
e.g. track and trails,
Organic structures
97
They are the product of chemical action contemporaneous with sedimentation
or shortly thereafter
Chemical structures
98
Different chemical structures
Concretions
Solution action
Stylolites
Dendrites
99
They are spherical to elliptical usually small bodies of diverse
chemical nature than the rocks in which they occur.
Concretions
100
They are developed on
accretion and subsequent precipitation of the dissolved carbonate material derived from the pre-existing rock.
Concretions
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When the accreted material is precipitated in an open space
like cavity or vug, it is referred to as _____
Secretion
102
_________ are structureless
irregular shaped bodies in a rock, such as chert in carbonates. They vary in
size.
Nodules
103
Radiating cracks flled in by carbonate materials in large and oblate
nodules are termed _________.
Septaria
104
are spherical to sub-spherical
hollow shell of chalcedony with an internally lined minerals commonly
quartz but sometimes crystals of aragonite, chalcopyrite or sphalerite may
as well project.
Geodes
105
They are
formed as a result of solution activity commonly in calcareous rocks.
solution action
106
Caves
stalactites and stalagmites are its features.
Solution action
107
Any material that is
soluble, can be deposited as a colloid, or is in suspension and is capable of
being melted may form a _________ at the roof of cave or cavern (the letter
'__' in it refers to ceiling from where stalactites hang).
stalactite
c
108
The saturated water
dripping from the end of a stalactite falls to the floor of a cave and deposits
more calcite into a mound forms a __________ at the bottom of the cave or
cavern (the letter '___' refers/points to ground where stalagmites are formed)
in a cone like shape.
stalagmite
g
109
sketch of solution action
stalactite
dripstone
stalagmite
110
These are serrated surfaces within a rock mass along which
mineral material has been removed by interstratal solution dissolution circulating under pressure.
Stylolites
111
The pattern produced by stylolites
resembles the pattern that of a _______
heartbeat
112
The term "________" is used to describe branched projections of
neurons.
dendrite
113
A nerve cell that receives and sends electrical signals over long distances within the body.
neurons
114
The ________ that mimics the function of the
human brain and nerves built on the so-called neurons. These are also known as __________.
dendrites
pseudofossils
115
They form when water
rich in manganese and iron flows along fractures and bedding planes giving
rise to deposition in branch-like dendritic pattern.
Dendrites
116
They include fossil impressions or structures produced by biological activities
of organisms, as well as petrified remains of animals or plants. These structures
commonly met in intrabasinal sediments but sometimes they are also reported
from extrabasinal sediments
Organic structures
117
Different organic structures
Tracks and Trails
Burrow Marks
Stromatolite
Coral Reefs
Cast and Mold
118
These markings are indicative of activity of organism
over soft sediments. They may be due to feeding, crawling, dwelling
-grazing, resting heir bodies over soft sediments.
Tracks and Trails
119
Traces preserved wholly
within the bed are called '________'. Those occurring at the interface of two layers of rocks are called '_____________' . When occurring at the upper surface
of a sandy bed are termed '__________' and those occurring on the lower
surface (sole) of a rock layer are termed '______'
full relief
semirelief
epirelief
hyporlief
120
They are also known as bioturbation marks.
Burrow Marks
121
These
sedimentary structures are remnants of burrows and tunnels excavated by
worms and many other marine organisms that live on the bottom of the sea.
Burrow Marks
122
Bedding in
many sedimentary rocks is broken or disrupted by roughly cylindrical tubes a few cms in diameter that extend verticaly through several beds.
Burrow Marks
123
also known as algal stromatolites are
sedimentary structures and are composed of sand-silt and clay sized
sediment particulates.
Stromatolites
124
They are
laminated structures produced by the finer sediment trapping usually by an
algal mat, binding, and precipitating activity of phototropic microbes
including cyanobacteria / blue-green algae. They may shape like
small mound or be columnar, concentrically structured.
Stromatolite
125
Types of stromatolite
-almost flat along the bedding,
-arched hemispherical,
-cabbage like,
-a pile of stacked inverted vertical column like tumbles,
-expanding upward club like.
126
They are dome to elongate, massive to bedded forms
accumulate largely as a result of organic buildups within otherwise horizontal or nearly flat-lying strata.
Coral Reefs
127
They are built during carbonate
deposition by organisms that biogenetically precipitate carbonate materials.
Coral Reefs
128
Organisms buried in sediment slowly decay, leaving a
hollow space that contains an exact imprint of the organisms' shape and
size.
Casts and Molds
129
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