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Geology 381 > Quiz 1 (-oct4) > Flashcards

Quiz 1 (-oct4) Flashcards

1
Q

What are the parts of the sedimentary rock cycle?

A

1) sediment source rock
2) weathering and erosion
3) transport
4)deposition and precipitation
5) diagenesis
6) uplift and erosion leading to another cycle

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2
Q

what is weathering?

A

The in-situ breakdown and alteration of bedrock by mechanical and chemical processes to creat regolith

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3
Q

What is denudation?

A

When the land surface is lowered by the combination of weathering and erosion

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4
Q

What is texture?

A

The grain-scale physical characteristics of sediments or sedimentary rocks

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5
Q

What is structure?

A

Refers to the characteristics at the scale of entire unites of a given sediment or rock and of their boundaries (contacts)
Ie. layers, laminae, beds

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6
Q

What are the textual elements?

A

1) grain size
2) sorting
3) shape
4)Surface texture is grains
5) fabric of grains

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7
Q

What is grain size?

A

Maximum grain diameter

Use the Udden-Wentworth scale

Closely related to flow velocity
Indicated. Intensity of transport

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8
Q

What is sorting?

A

Grain size distribution

Visual comparison

Well-poor

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9
Q

What is grain shape?

A

Roundness —- degree of sharpness of corner/ edges of grains

Sphericity —- degree to which a grain resembles a sphere

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10
Q

What is the fabric of grains

A

Produced by the packing and orientation of grains

Imbrication: flow leaving a fabric of long axes of clasts with a preferred orientation

Fissility: rock breaking along closely spaced, sub-parallel planes

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11
Q

Components of a siliclastic rock

A

Framework : clasts

Matrix

Cement

Pore space

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12
Q

What does textual maturity reflect

A

Shows degreee of transport

Intensity of reworking at the site of deposition

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13
Q

What is sediment?

A

Fragments (formed by weathering) of rocks or broken off minerals or shells over mineral crystals precipitated out of solution

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14
Q

What is bedrock

A

Solid rock underlying soils and/or surfacing sediments at the earth’s surface

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15
Q

What is erosion?

A

Transport of weathering products away from their site of origin

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16
Q

What are the two modes of weathering

A

Physical
‘Chemical

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17
Q

What are some examples of physical weathering ?

A

Freeze-thaw
Exfoliation
Roots
Salt crystal growth

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18
Q

What are some of the reaction types in chemical weathering ?

A

Simple solution
Hydrolysis
Oxidation and reduction
Hydration or dehydration
Biological processes

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19
Q

What is simple solution ( congruent dissolution)

A

Merials go into solution completely, without precipitation of other minerals

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20
Q

What is hydrolysis? (Incongruent dissolution)?

A

The rxn between H+ and OH- ions of water and the ions of silicate minerals; controlled by pH as by carbonic or humic acids for example

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21
Q

What are oxidation and reduction reactions?

A

Loss of an electron under oxygenated conditions

Gain of electrons can occur in water-sutured, oxygen-deficient conditions

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22
Q

What is hydration or dehydration reactions?

A

Add or subtract water from existing minerals

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23
Q

What are biological chemical processes?

A

When organisms induce reactions that ransom minerals or rocks or produce organic substances that react to decompose minerals/rocks

Ex. Chelation

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24
Q

What is chelation?

A

Chelating agents are released from decaying humus in the soil and cause a change in the chemical structure of the surrounding soil

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25
Q

What is karst topography?

A

A result of simple solution chemical weathering

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26
Q

The relative stability of minerals under surface weathering conditions is the inverse of what process?

A

Bowen’s reaction series

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27
Q

An increase in surface area leads to an increase in ———

A

Chemical weathering

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28
Q

What are the idealized soil profiles and horizons ?

A

O,A,E,B,C,R

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29
Q

What is soil?

A

Products of accumulated chemical and/or physical weathering of underlying bedrock or detritus

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30
Q

What is the O soil horizon?

A

Organic matter, (humus etc)

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31
Q

What is the R soil horizon ?

A

Unweathered bedrock or sediment

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32
Q

What affects the variability of soil profiles/horizons ?

A

Climate (laterite)
Rainfall
Type of substrate
Slope

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33
Q

What is laterite?

A

Soils with a very think A and B horizons, due to intense leaching by organic acids and resulting in Al and Fe oxides precipitation; some quartz remaining

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34
Q

What is the A soil horizon?

A

Organic and mineral matter

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35
Q

what is the B horizon?

A

Subsoil

Darker, enriched in organic matter, oxides, or clays

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36
Q

What are the controls on weathering ?

A

Water chemistry (acidity, salinity, oxidizing agents)
Water (availablity)
Temperature (reaction rate, fluctuations)
Climatic regime
Geomorphology (distribution of sediment and landforms)

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37
Q

What are the controls on erosion?

A

Wind exposure
Physiography (altitude)
Slope angle
Velocity of flow
Vegetation
Climate
Density of flowing movement

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38
Q

Media of erosion/transport ?

A

Water, wind, ice

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39
Q

What are the mechanisms of erosion/transport

A

Wind current s
Rock falls
Landslides
Slump
Debris flow
Turbidity current
Sheet wash
Rills, wgullies, streams

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40
Q

What are fluids vs plastic media?

A

Fluids— deform continuously when subjected to shear stress

Plastic media—- deform continuously only after a critical shear stress has been exceeded

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41
Q

What is traction on a sediment surface or bed?

A

Rolling, sliding, saltating (jumping) of particles below a fluid flow

Enabled by fluid shear with help from eddies and grains sticking out from the bed surface

Resisted by friction

Bed load

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42
Q

What are particles transported by traction called?

A

The bed load

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43
Q

What is suspension of particles in a fluid flow?

A

Initiated by lifted and enabled by flow velocity with help from fluid turbulence

Resisted by particles settling back down (stokes law)

Suspended load

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44
Q

Particles transported by suspension are called?

A

The suspended load

45
Q

What is stokes law?

A

Settling velocity is proportional to :
Acceleration due to gravity
Grain diameter
Density of the solid - density of teh fluid (contrast between the density of the grain and the density of the water)

Settling velocity is inversely proportional to viscosity

46
Q

What can be said abut the density of fresh water vs sea water?

A

Freshwater =1g/cm^3
Sea water = 1.028g/cm^3

Air is 700x less dense than water

47
Q

What is the buoyancy of particles?

A

Given by: Fg =v (density of solid-density of fluid) * g

Buoyancy not only influences the transport of particles, but the amount of shear stress on a. Bed surface.

Influence the ability of fluids to erode and transport sediment

48
Q

What is viscosity?

A

A measure of the ability of fluids to flow
The resistance of a fluid to deform with applied shear stress

Increasing viscosity suppresses turbulence, lowers erosion of the depositional surface, increase capacity to suspend grains, and lowers suspension and settling rates of sediment particles.

Dynamic and kinematic

49
Q

What is dynamic viscosity? (Mu u)

A

Shear stress = dynamic viscosity x the change in fluid velocity with distance from the sediment bed

50
Q

What is kinematic viscosity? (V)

A

Kinematic viscosity = fluid density / dynamic viscosity

51
Q

What is shear stress (t)

A

The shearing force per unit area which acts on the fluid (and the sediment bed) parallel to the boundary surfaces of the fluid body

52
Q

What is turbulence in fluids?

A

Disordered, circulating motions, at a variety of scales, in a flowing fluid. These motions transfer fluid at right angles to the mean direction of flow.

Results from friction between the fluid and/or substrate and suspended particles

Turbulence keeps sediment in suspension

53
Q

What is Reynolds’ number?

A

distinguishes laminar and turbulent flow

Re = flow velocity x (depth / kinematic viscosity)

Relationship b/w velocity to viscosity at a depth

54
Q

Reynolds number of turbulent vs laminar flows?

A

Turbulent: Re&raquo_space; 500
Laminar : Re ~ 10-20

55
Q

The subsections of a column of water?

A

Upper section

Boundary layer, where flow velocity starts to decrease due to the effects of friction within the sediment-water interface. Sediment transport takes place here

The viscous sublayer, this region at the base of the boundary layer where conditions approach laminar

56
Q

What is the Froude Number?

A

Relationship between inertial velocity and gravity forces

Fr = flow velocity / (g x water depth)^1/2

57
Q

What are froude’s different flows ?

A

Subcritical flow (fr</= 1) — velocity at which waves move is greater than the flow velocity, so waves can travel upstream.

Critical flow (fr=1)

Supercritical flow (Fr>/=1) — waves cannot be propagated upstream

Hydraulic jump is the jump formed when the depth of flow changes.

58
Q

What is the Bernoulli equation?

A

Shows that the total energy along laminar flow streamlines are constant

59
Q

What is entrainment ?

A

The process that lifts grains at feast from the bed, or otherwise putting them into motion

Fluid force must overcome gravity and frictional forces

60
Q

what is hjulstrom’s diagram ?

A

Flow velocity vs grain size

An idealized diagram hat illiterates the critical threshold for grain movement

61
Q

What criteria is used to calcify and name siliclastic sandstones?

A

Matrix % : (<15% = arenites) (15-50% = wackes) (>50% = Mudrock)

Composition of framework clasts: (Quartz, feldspars, and rock fragments)

62
Q

Quarts as framework clasts

A

Hard, concoidal fracture, no cleavage
Variety of colours
60-70% of the framework clasts

63
Q

Feldspars as framework clasts

A

Hard, mineral cleavage’s at ~90 degrees
Twin striations (in plagioclase)
Vitreous but not transparent
Commonly altered

64
Q

Rock or lithified fragments as framework clasts

A

Highly variable, depends on provenance
Chert: commonly dark
Shale clasts: fine grained and dark

65
Q

Why are rock fragments more commonly originated from the weathering of fine grained rocks ?

A

A plutonic rock will break don to make mineral grains

A fine-grained rock will break down into fine-grained rock fragments

66
Q

What does it mean to be epiclastic?

A

: formed at the surface of the earth by consolidation of fragments of preexisting rocks

Conglomerates typically

67
Q

How do breccias form?

A

Epiclastic

Solution (dissolved by solution creating angular shapes

Volcanic

Faulting

Impact (commonly meteor impacts)

68
Q

What is an oligomict?

A

Stable clasts of mainly a single type

Ie all quartz clasts

69
Q

What is a polymict?

A

A variety of stable clast types

Ie quarts, granite, quartzite

70
Q

What is a petromict?

A

A mixture of unstable or meta stable clasts such as limestone, shale, phyllite or basalt

71
Q

What is an orthoconglomerate?

A

Most clasts are in contact

Clast supported

72
Q

What is a paraconglomerate

A

Most clasts are floating in the matrix

Matrix supported

73
Q

What is extraformational?

A

Derived from the breakdown of other rocks

Conglomerates and breccias
(Rock type is very different from matrix)

74
Q

What is intraformational ?

A

Derived from approximately coeval units, often weakly consolidated

Rock type are very similar to the matrix

75
Q

What are primary sedimentary structures?

A

Structure formed just before, during or very shorty after deposition

76
Q

What are diagenetic or secondary structures?

A

NOT sedimentary structures

Structures formed during or after lithification

77
Q

What are beds?

A

Tabular or lenticular layers of sedimentary rick that have lithologic, textural or structural unity which distinguishes from the above strata

78
Q

What are laminae?

A

Layers in stats that are less than 1cm thick

79
Q

How does parallel laminae form?

A

Settling of very fine-grained particles from suspension or by traction transport in either air or water

80
Q

What are ripples?

A

Less than 5-6cm in heigh and have spacing from about 1m to tens of hundred of meters long

81
Q

What are bedforms?

A

Distinct topographic forms that develop on a surface of sediment due to specific conditions of fluid velocity and sediment transport/deposition

82
Q

What is Hummocky Cross Stratification? (HCS)

A

Dune scale bed forms with cross laminae dipping in all directions away from a high convex crystal area (hummock)
Thought to form under combined flow of string oscillatory currents (storm waves) and unidirectional flow

83
Q

How are herringbone cross bedding formed?

A

Consecutive flood and ebb tides produce unidirectional current structures but with opposite flow directions

84
Q

What is the effect of tides on bedding?

A

Slack-water periods allow mud deposition and result in dunes and ripples with alternating laminae of sand and mud (heterolithic bedding)

Tidal bundles of mud and sand Lamaze can form more sandy packages in strong tides (spring) and muddier package in weaker tides (neap)

85
Q

What is heterolithic bedding?

A

Interbedded mud laminar and sand

When there are variation in currents or sediment supply

Lenticular, wavy and flasher

86
Q

Lenticular vs wavy vs flaser bedding ?

A

Lenticular = more mud than sand, sand maleness in mud

Wavy = sand =mud

Flaser bedding = more sand than mud, mud lenses in sand

87
Q

What is a flute cast?

A

An erosion all structure formed by sediment filling in a depression which was scoured in cohesive sediment by turbulent eddies

Asymmetric depression, widens downcurrent

88
Q

What are tool marks?

A

Erosional structures that are elongated, irregularly shaped or straight ridges that result firm infilling of erosional relief produced by a tool being dragged or bounded along the bottom by current

89
Q

What are channels?

A

Elongate, continuous depressions that cut earlier-formed bedding

Not scours, which are smaller and more discontinuous due to hort lived events

90
Q

What is convolute bedding?

A

Soft sediment deformation where there is complex folding and intricate crumpling of laminae and beds

Induced by loading, dewatering or slumping (saturated rocks deform)

91
Q

What are flame structures?

A

Wavy or flamed shaped soft sediment deformations squeezed upward into an overlying layer

Results from loading a denser material on top of a less dense sediment that is saturated

92
Q

What are ball-and-pillow structures?

A

Hemispherical masses partially or complementary separated from the base of a unit, showing deformed lamination

Results from foundering and breakup of semi-consolidated sand bed due to partial liquefaction of underlying mud

93
Q

What are desiccation cracks?

A

Post depositional structures that look like downward tapering v shaped structures with a polygonal pattern

94
Q

What are synaeresis cracks?

A

Post depositional structures like desiccation cracks but with more variable orientation and more discontinuous. Shrinkage.

95
Q

What physical and chemical parameters control the distribution of living organisms?

A

Oxygen
Food availability (nutrients)
Environment (shelter/optimal living conditions)
Water (availability, temp, alkalinity, salinity)
Current velocity

96
Q

What is a biogenic sedimentary structure?

A

Structure produced or induced by activity of organisms

97
Q

What is a trace fossil?

A

Sedimentary structured formed and presented as a result of organism activity, including a variety of trails, depressions, open burrows, and borings in sediment produced by and organisms life activities (moving, resting feeding, etc)

98
Q

What is bioturbation?

A

Reworking of sediment by organisms modifying (or destroying) the primary sediment fabric and physical sedimentary structures

99
Q

What is the study of traces and trace fossils?

A

Ichnology

100
Q

What are borings vs burrows?

A

Borings — Holes/openings in hard/firm substrate

Burrows — soft/ loose substrate

101
Q

What are bioturbation structures?

A

Burrowing in soft/loose substrate, tracks, trails, resting traces, feeding traces, fecal pellets

102
Q

What is ichnogenera

A

The classification based on characteristics related to major behavioural traits of organisms, often reflected by trace fossil morphology and markings

103
Q

How do you describe/identify trace fossils ?

A

Mode of preservation — how were they preserved? E.g. within beds or bedding surfaces or above/below bedding surfaces

Morphology — shape, size, orientation, internal features, etc.

Behavioural interpretation — resting, feeding, grazing, escape, dwelling,

104
Q

How do we use morphology to classify trace fossils?

A

Track, trail, burrow or boring?

Shaft (sub vertical), tunnel (sub horizontal), furrow, depression, branched?

Length, width, diameter?

If burrows: type of fill, nature of wall or lining

What are the internal structures?

105
Q

What are facies?

A

Body of rock with specific characteristics that distinguish it from other facies

106
Q

What are ichnofacies? What are the recognized categories?

A

A group of trace fossils associated with particular environmental conditions such as energy levels, sedimentation rates, water salinity, etc.

Recognized ichnofacies are categorized as: soft ground marine, soft ground terrestrial, and substrate controlled.

107
Q

What is the soft ground marine ichnofacies?

A

In general, lever enegry setting wth normal marine salinity as well as plenty of oxygen and food.

Commonly dominated by traces that reflect a behavioural response o a physical process (high wave energy, high or low sedimentation process)

108
Q

Lee vs stoss side?

A

Lee = short upwards side

Stoss =. Long slope side

109
Q

During pressure dissolution diagenetic process, the chemical and physical changes occur primarily due to which of the following?

A

Extreme pressure is concentrated at the contact between grains within sediments.

Geology 381 (3 decks)

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