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Geology 305 > Midterm One > Flashcards

Midterm One Flashcards

1
Q

Rock Types

A

1) Shale
2) Sandstone
3) Limestone
4) Granite
5) Rhyolite
6) Basalt
7) Gabbro
8) Slate > Phyllite > Schist > Gneiss
9) Marble
10) Quartzite

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2
Q

Shale

A
  • Sedimentary, clastic (particles, terrestrial rocks), fine-grained, deeper water
  • Made of clay and silt-size grains
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3
Q

Sandstone

A
  • Sedimentary, clastic, medium-grained,

- Shallower water, sand-size grains

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4
Q

Granite

A
  • Igneous, cools from magma underground,
  • Larger-size crystals, slow cooling
  • Continental Rock
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5
Q

Rhyolite

A

– Igneous, volcanic equivalent to granite

- Continental Rock

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6
Q

Basalt

A
  • Igneous, volcanic, dark-coloured lava flows,

small-size crystals

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7
Q

Gabbro

A

– igneous, plutonic equivalent to basalt

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8
Q

Slate > Phyllite > Schist > Gneiss

A

• Metamorphic. Progressive meta of shale.
• Increase of T and P due to burial, regional
compression (directed stress)
- Significantly deformed
- Looks smooth & liquid BUT solid state the whole time
- Layers been struck together
- These are the rocks that differentiate Omenica from Foreland
- Too much heat & pressure > melting = granite
—- magma > new rock

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9
Q

Marble

A

metamorphic, protolith (T &P applied) is a limestone

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10
Q

Quartzite

A

– metamorphic, protolith is a sandstone

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11
Q

Mountain

A

Any part of the Earth’s crust higher than a hill,
sufficiently elevated above the surrounding land surface
to be considered worthy of a distinctive name, and
characterized by a restricted summit area.

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12
Q

Cordillera

A

An extensive series of more or less parallel
ranges of mountains (together with their associated
valleys, basins, plains, plateaus, rivers and lakes),
the component parts having various trends but the
mass itself having one general direction….
- Series of mountains
- Mountain ranges in one direction
- Alaska to Chile

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13
Q

Canadian Cordillera

A

The name for the mountains of
western Canada, includes not only the mountainous
and plateau regions, but also the submerged regions
on the continental shelf and slope.
- Includes plates in ocean

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14
Q

Ben Gadd

A

“Old rock, middle-ages mountains, young landscape”

  • Mt. that expose rocks = teenagers
  • All formed at different times > complex
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15
Q

Orogeny

A

The process of formation of mountains. The
process by which structures within fold-belt
mountainous areas were formed, including thrust
faulting, folding, metamorphism and plutonism (intrusive magma body exposed) in the
inner and deepest layers.

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16
Q

Morphogeological Belt

A

A continental or oceanic area
characterized by a distinctive combination of land
forms, rock types, metamorphic grade and structural
style.
- 5 major morphic belts > subdivided into terranes

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17
Q

Terrane

A

A terrane in geology is a short-hand term for a
‘tectonostratigraphic’ terrane, which is a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or ‘sutured’ to crust lying on
another plate.
- The crustal block or fragment preserves its own distinctive geologic history, which is different from that of the surrounding areas – hence the term ‘exotic terrane’
- Batch of rock w/ own history
- Multiple terranes in each Belt

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18
Q

5 belts of Canadian Cordillera

east to west

A

1) Foreland
2) Omineca
3) Intermontane
4) Coastal
5) Insular

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19
Q

Belts

A
  • zones with distinguishing/ diagnostic rock types and tectonic history
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20
Q

Foreland and Omineca

A 
North
American rock (sedimentary in
Foreland; metamorphosed in
Omineca Belt) 
- North American Craton
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21
Q

Intermontane and Insular

A

“Exotic (from elsewhere)
terranes” igneous and sedimentary
rock

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22
Q

Coastal

A

Subduction-related igneous rocks

- intrusive and extrusive

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23
Q

Major Mountain Building Events

A

1: Accretion of first set of volcanic islands to the
western margin of North America
• Sedimentary and igneous rocks involved in the accretion
zone are folded, faulted and metamorphosed

2: Accretion of more volcanic islands to the ‘new’
western margin of North America
• Sedimentary and igneous rocks of the volcanic islands are
folded, faulted and metamorphosed. Previously accreted
volcanic island rocks and sedimentary rocks are refolded, refaulted and re-metamorphosed.

3: Mountain building ceases. Erosion and glaciation
shape the land surface.

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24
Q

Following the rifting of the supercontinent Rodinia at 750Ma, what type of environment was found along the coastline?

A
  • Passive Margin
  • Warm env’t
  • Reefs (organic life, material, carbonates)
  • Not coral reef though!
  • No mountains being formed
  • Gentle continental shelf (slope is low)
  • No subduction zones
  • No volcanic islands
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25
Q

During the same time period, what types of rocks were forming further off the coast, in deeper water?

A
  • Shales, sand, clay, silt > carried by rivers
  • Further into deep ocean > siltstone and clay (Fine grain & sedimentary rocks)
  • — compressed into shale (single most common rock on planet)
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26
Q

Passive Margin

A
  • Old faults down below, used to be active
  • Rivers run off continent (more sediment, life) & dumps into ocean
    • Unto deep marine env’t
    • Deep marine sediment comes from rivers (dust, dead particles) or volcanoes
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27
Q

A line through the towns of
Prince George, Salmon Arm,
and Penticton, B.C., was the coastline up until about _______
million years ago.

A

180

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28
Q

What is some evidence that a terrane was once part of a chain of volcanic islands?

A
  • Dark mountains = Basalt, Igneous rock, rhyolite (extrusive igneous), granite (intrusive igneous)
  • Islands constantly being eroded & built
  • –Forming sedimentary units by the break down of igneous rocks
  • – Typically contains sedimentary rocks like limestone & mudstone
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29
Q

What is some evidence that a terrane was once part of the sea floor?

A
  • Contains sea floor rocks like basalt, chert, siltstone, sandstone
    • Sometimes these sea floor rocks preserve fossils
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30
Q

Foreland Fold and Thrust

A 
- Deformed sedimentary
 rocks
• Weak to no metamorphism
- Yumnuska
--- fossils, limestone, sedimentary, old rock smeared above young rock
- Mostly sedimentary
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31
Q

Omineca Belt

A
  • Deformed and metamorphosed sedimentary rocks
    – ductile deformation
  • Polyphase deformation & metamorphism
  • Parent rocks are the same as Foreland
  • More stressed applied to them > metamorphic
  • NOT exotic
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32
Q

Ductile deformation

A
  • Bends / folding occurring in high pressure as opposed to fault
  • Sign. pressure in order to occur
  • Rocks at surface of Mt.s today where not there when uplifting occurred > erosion
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33
Q

Polyphase deformation

A
  • Multiple phase occurred to form

- Several phases of metamorphism

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34
Q

Intermontane Belt

A

“Exotic Rocks”

  • Volcanic and sedimentary rock (volcanic islands)
  • Did not originate above the N.A. Craton
  • These are exotic not N.A.
  • Rocks from island arcs smeared on N.A.
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35
Q

Coast Belt

A 
"Exotic rocks intruded by igneous rocks"
- Intrusive rocks (~80%) & minor sedimentary (erosion rocks) and
metamorphic
– Granite
– Diorite
– Gabbro
- Volcanic rocks 
- Most from intrusively & then get eroded (uplifted)
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36
Q

Insular Belt

A

“Exotic Rocks”

  • Volcanic and sedimentary rocks (island arc
    terranes) – deformed and metamorphosed
  • Most recent terrane accreted NOT most recent event
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37
Q

Jurassic

A
  • Start metamorphism
  • Omenica Belt
  • 1st accretion event
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38
Q

Precambrian

A

90% of earth’s history happened here

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39
Q

1st Accretion Event

A

Terrane rocks found in Intermontane Belt

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40
Q

2nd Accretion Event

A

Terrane rocks found in Insular Belt

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41
Q

1st Period of Deformation

A

Intermontane rocks

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42
Q

2nd Deformation

A

Intermontane and Omineca rocks

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43
Q

1st Metamorphism

A

Omineca Belt rocks

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44
Q

2nd Metamorphism

A

Omineca Belt rocks

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45
Q

Results of Mountain Building

A
  • Folding and buckling of rock layers due to
    compressive forces
  • Metamorphism
  • Deformation
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46
Q

Deformation

A

Folding and Faulting

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47
Q

Metamorphism

A

Changing of original rock

forms in response to pressure and temperature conditions

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48
Q

Bugaboose

A
  • Omenica Belt
  • Radium hot springs
  • Metamorphic rocks, instead of sedimentary
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49
Q

Subduction Zone Rocks

A
  • Melting plate
  • Volcanic
  • Intrusive
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50
Q

Tectonic Melange

A
  • Cache Creek, BC
  • Glue
  • Jumble
  • Variety of rocks
  • Not strong
  • Relatively easily eroded
  • Intermontane super terrane contains ancient melange
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51
Q

Why subduction to the right?

A
  • B/c oceanic plates are denser than continental plates

- Ocean going beneath continent

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52
Q

Temperature and Precipitation

A
  • Effects the erosion rates
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53
Q

Why some mountains on the coast the same size as come interior?

A
  • inner = limestone, sedimentary (soft rocks)

- coast = igneous (hard rocks) > resistant to erosion

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54
Q

Rocks of Coast Belt

A

Sedimentary:

  • young
  • erosion of igneous rocks

Continental arc igneous rocks:

  • 80%
  • Basalt (melted oceanic plates)
  • Phelsic (Granite and Rhyolite)

Terrane:
-Associated with collision

55
Q

Coast Mountains

A

Almost all extrusive igneous rocks

56
Q

Continental arc rocks

A
  • Granite fractures
  • Chain of volanoes
  • Magma cutting through plutonic to get to top
57
Q

Plutonic

A

pocket of magma hardened & uplifted
> erosion & isostatic rebound
- glaciers

58
Q

Cascade Volcanic Arc

A 
- superimposed on older
plutonic rocks that have
been uplifted and exposed
at the surface 
- ACTIVE (long over due)
---But no active magma
- Mt. St. Helens = phelsic > explosive
59
Q

Insular Belt

A
  • Almost all of Vancouver Island

Sedimentary rock:
-Modern / recent sedimentary

Terrane rock
(Wrangellia):
- volcanic, some plutonic, sedimentary
- formed elsewhere

60
Q

Farallon Plate

A
  • Juan De Fuca is the last remanent element of this (renamed)
  • Made Coastal Belt
  • Subdivided into Juan de Fuca and Cocos
61
Q

Zircon mineral

A
  • In sedimentary rock
  • Incredibly resistant to erosion
  • Evidence of these old rocks from Baja in the basins
62
Q

Geological evidence for Plate Tectonics

A
  • Paleomagnetism
  • – Role changes direction (reversal) over geological time
  • Rock Ages
63
Q

Geochemistry of igneous rocks

A

Orientation of minerals

64
Q

Geophysical

A

Paleomagnetism

- Lithoprobe project

65
Q

Zircon

A
  • Used as geological clock
66
Q

U-Th/He thermochronology

A

technique that has been employed to date quickly cooled volcanic rock

67
Q

Helium Diffusion

A
  • Diffusion of atoms out of a mineral grain is thermally activated
68
Q

Glacial

A
  • An interval of time (thousands of years) within an ice age

that is marked by colder temperatures and glacier advances

69
Q

Glacial Ice

A
  • Erosive force
  • Active
  • Mobile
  • Moves like fluid
  • Noisy
70
Q

Interglacial

A
  • a period of warmer climate between glacial periods
  • We are currently living in the Holocene epoch, which is an
    interglacial
  • Glaciers are receding
71
Q

Stadial

A
  • a period of lower temperatures
    during an interglacial (warm period)
    e.g. Little Ice Age
72
Q

Glaciated Landscapes

A
  1. Duration of the Wisconsin Glacial : 110,000 yrs, peaked ~
    20-30,000 yrs ago, ended ~ 11,000 yrs ago
  2. During Wisconsin maximums valleys in the Cordillera were buried under 1-2 kilometres of ice
  3. Many of the large scale landforms (e.g. U-shaped valleys) were created during the Wisconsin Glacial
  4. Holocene interglacial began ~ 11,000 yrs ago
  5. Little Ice Age stadial terminated in the Southern Canadian Rockies ~ 1840AD
  6. We are currently in an Ice Age but in the Holocene interglacial, and having just come out of the LIA stadial
73
Q

Ice Age

A
  • NOT glacial
  • Refers to a Ice Sheet
    • Antartica and Greenland
  • Not something noticeable but on time chart
74
Q

Current state of world

A

Interglacial but, also, Ice Age

B/c ice sheets are present around world

75
Q

Ice

A
  • Best climate date

- Determines sea level

76
Q

Glaciers and Sea Level

A

Glaciers > sea level down
Glaciers melted > seal level up
- Antartica > melted > Florida underwater
- Wisconsin Glacier > sea level down significantly

77
Q

Glacial Tilt

A
  • Mixed sedimentary

- “Marine” - deposit of tilt as glacier moves

78
Q

Glacial Landscapes

A

U-shapes valleys = Glaciers

V-shaped valleys = Streams

79
Q

Glacial Landscapes:

Erosional features

A
  • Sculpting of the mountains
  • Horn
  • Arete
  • Alpine Cirque
  • Cirque w/ tarn Lake
80
Q

Glacial Landscapes:

Glacial deposits

A

Layers of sediment moved by glacial activity

81
Q

Movement of Glacial Ice

A

“Plastic Flow”
-The lower layers of glacial ice flow and deform plastically under the pressure, allowing the glacier as a whole to move
slowly like a viscous fluid
- Middle faster b/c friction

82
Q

Glacial Budget

A

Accumulation < ablation
Accumulation = ablation
Accumulation > ablation

  • Glacier will “advance” when accumulation is greater than ablation > mass increase
  • Ice moves down like water
  • – No matter if toe moving or receding/ retreating (moving up)
83
Q

Glacial Budget:

Accumulation dominate

A

Snowfall, snow turning to ice

84
Q

Glacial Budget:

Ablation dominate

A
  • Sublimation

- Melting and iceberg calving

85
Q

Ablation

A 
- refers to melting,
runoff, evaporation or
sublimation of the ice,
resulting in a thinning of
the ice if it is not
replenished by some
other process
86
Q

Sublimation

A
  • transformation from solid

to gaseous state

87
Q

Erosional Features: Horn

A
  • A high mountain peak that forms when the walls of three or more glacial cirques intersect
88
Q

Erosional Features: Arete

A
  • A sharp-edged ridge of rock formed between adjacent cirque glaciers
89
Q

Erosional Features: Cirque

A
  • A bowl-shaped depression carved out of a mountain by an alpine glacier
90
Q

Rock Flour

A
  • Extremely fine powder
    ground from the underlying rock by the glacier’s movement
  • Found in Glacial meltwaters
91
Q

Glacial Moraines

A
  • are usually composed of linear mounds of till, a non-sorted mixture of rock, gravel
    and boulders within a matrix of a fine powdery material
  • The till is deposited directly by the glacier as it erodes
    rocks that it passes over
  • Big ridges of sediment
  • Determine where glaciers end
92
Q

Glacial: Depositional Features

A
  • Moraine deposits = till
  • Big Rock Erratic, Okotoks
  • Outwash plain
  • Gravel deposits
93
Q

Drumlins

A
  • an elongated whale-shaped hill formed by
    glacial action. Its long axis is parallel with the movement
    of the ice, with the blunter end facing into the glacial
    movement. Drumlins may be more than 140 ft high
    and more than ½ mile long,
  • Drumlins are often found in drumlin fields of similarly
    shaped, sized and oriented hills
94
Q

How are drumlins formed?

A
  • many theories and plenty of
    controversy among geologists. Some consider them a
    direct formation of the ice, while others theorize
    catastrophic flooding underneath the glacial ice
95
Q

Glacial Abrasion

A
  • occurs when the ice and the load of rock
    fragments slide over the bedrock and function as
    sandpaper that smooths and polishes the surface
    situated below
96
Q

Causes of Ice Ages

A

1) Precession (23,000) = wobble on axis
2) Tilt (41,000) = effects amount of sunlight on earth
3) Eccentricity (100,00) = Incoming solar radiation

  • Different variations determine sun variation
  • Earth’s orbit drives Ice Ages
97
Q

Canadian Rocky Mountains (CRM)

A
  • Eastern margin of the
    Canadian Cordillera

• Chain of mountains and
foothills oriented NNWSSE

• >1,500 km length
(Glacier National Park,
Montana to Liard River
near Yukon – B.C.
border)

• ~150 km width (Rocky
Mountain Trench –
Foothills-Plains
boundary)

  • The REAL “Rockies”
98
Q

Southern CRM

A
  • Parts of the Southern Canadian Rockies
    are co-located with the Great Divide
    — One side water goes to Hudson’s Bay & and other flows to Pacific
- Subdivided into
sub-provinces based on character of topography, structure and stratigraphy
1) Foothills
2) Eastern Ranges
3) Western Ranges
4) Front Ranges 
-----Based on structure, rocks &amp; age
99
Q

Plate Tectonics

A
  • Crust is thicker because of pressure

- Old continental crust

100
Q

Fault

A
  • The suture zone between a terrane and

the crust it attaches to

101
Q

What is the big draw to the Rockies?

A
  • Rock-walls, waterfalls, glaciers, iridescent turquoise
    coloured lakes and fossils

• the Canadian Rocky Mountain Parks World Heritage Site
(UNESCO 1984)

• just an hour’s drive from Calgary

102
Q

Rockies: Physiological Character

A

Foreground: low relief Plains

Midground: forest covered moderate relief Foothills

Background: snow-capped large relief Front Range

• Rugged relief (great relief per map length)
- steep!

• elevation difference between valley floor to peak often exceeds 1000m and as much as 3000m

  • Relief and elevation play role in H2O & like around those mt.s
103
Q

Rockies: Basic Rock Types

A

• Canadian Rockies are comprised of layered (stratified) sedimentary rocks (mostly)

• strata are deformed; tilted
- AND folded, faulted and tilted

  • Layered down horizontally
  • Carbonates (marine life) > different env’t
  • Tilt head and see layers of sea beds
  • -Geological slices on time
104
Q

Rockies: Structures

A

• strata are deformed
- folded (diff types & degrees)

  • faulted (2 diff time intervals, Old rock sitting on top of young rock)
  • folded &/or transported and uplifted
  • — Significant amount of stress
  • — Rocks near surface> stress = break
  • — Rocks buried> stress = deform. Plastic.
  • — This has formed underground and then eroded to be exposed
105
Q

Fossiliferous Sedimentary Rocks

A
  • Devonian age corals,
    brachiopods, crinoids, etc.
  • Fossilized marine organisms found at elevation of 2,000 metres
  • Canadian Rocky Mountains contain sedimentary rocks and fossils
106
Q

Glaciated Landscapes

A
  • Landscape has been shaped by the Quaternary Ice Age:
    moraines, hanging valleys,
    cirques, tarns, etc.
  • The surface is always glaciated after structure has been formed
107
Q

Glaciated Landscapes: Water

A
  • CRM source of fresh, clean, reliable drinking water
  • A lot is glacially driven
  • Renewed resource (snow)
  • Some underground H20
108
Q

Canadian Rockies Facts:

A

• CRM composed mostly of layers of sedimentary rocks

• Rocks deformed; tilted, folded and faulted by tectonics –
stratigraphy before deformation was simple “layer-cake”, tectonic events developed structural complications

• Minimal metamorphic overprint and not obscured by
outpourings of volcanic material

• CRM can be distinguished from adjacent mountain
systems by its stratigraphic, structural and physiographic
style

• Older sediments were deposited along the edge of
ancestral North America – sediments were deposited in
shallow to deep marine environments; younger sediments were deposited in an inland sea or lower-most coastal
plain

  • CRM contains an excellent exposed record of Phanerozoic environments preserved in the sedimentary rocks
109
Q

Foothills West of Calgary

A
  • Low topographic relief

•Weaker less indurated rocks

110
Q

West of Chain Lakes

A
  • Moderate relief

•Moderately indurated rocks

111
Q

Longview (Highwood River)

A
  • Low topographic relief

* Weaker less indurated rocks

112
Q

Foothills Facts

A
  1. Numerous closely-spaced linear ridges (hogbacks)
    and valleys (with low to moderate relief) that parallel
    the mountains to the west.
  2. Linear ridges are capped by moderately hard
    sandstone, valley bottoms with softer shale
  3. Sediments were deposited between the Jurassic and
    Paleogene time periods (but mostly Cretaceous)
  4. Sediments were deposited in lower-most coastal plain
    to shallow inland sea environments
  5. Sediments were sourced from rising topography to
    the west
113
Q

Front Ranges

A
  • Large topographic relief
  • Broadly spaced linear valleys
  • Mountain peaks capped with strong older strata, younger weaker strata outcrop in valley floors

-Cross-sectional view of the Front Ranges near Canmore
Sedimentary rock layers are repeated and stacked
imbricate style, dipping to the SW

  • This geometry is produced by the development of thrust faults
  1. High relief; >1000m elevation difference between valley
    floor an mountain peak
  2. Older, stronger, Carboniferous - Devonian age rocks cap the mountain ranges whereas younger, softer, Jurassic – Cretaceous rocks outcrop in valley floors
  3. The outcrop pattern has a repeating striped fabric
    (congruent to the mountain ranges) that reflects the
    presence of widely-spaced, large-scale thrust faults
  4. Southwest dipping strata creates asymmetric mountain
    profiles; SW dip-slope and NE stair-stepped profiles
  5. Spectacular folds are often associated with thrust faults
114
Q

Main Ranges

A
  • Gentle dipping broadly folded strata
  • Castellated Peaks
  • Gentle dipping strata
  • Platformal Carbonates
  • Normal Faulting
  1. Gently dipping to horizontal, broadly folded, well indurated
    rocks
  2. The outcrop pattern follows topography
  3. Castellated peaks; horizontal strata best orientation that
    resists erosion
  4. Highest relief; up to 3000m elevation difference between
    valley floor an mountain peak
  5. Co-located with continental divide
  6. Cambrian - Ordovician age platformal carbonate and
    sandstone rocks forming mountain ranges and NeoProterozoic age rocks forming valley bottoms
  7. Very few thrust faults (Simpson Pass thrust) and little
    apparent deformation
  8. Fossiliferous sedimentary rocks
115
Q

Ice River Complex

A
  • Igneous intrusion occurred between latest Devonian and earliest Carboniferous
116
Q

Igneous Dykes

A

Igneous rocks are rare in the CRM but are exposed along

the TransCanada Highway

117
Q

Western Main Ranges

A
  • Increased shale content
  • Weaker rocks easily fold
  • Increased burial depth
  • Low-grade metamorphic over-print
    1. Intensely folded and cleaved argillaceous (clay rich) rocks
    2. Low-grade metamorphism (green schist grade)
  1. Cambrian - Ordovician age deep-water basinal rocks (shale
    and debris)
  2. Exquisitely preserved fossils providing a window into the
    “Cambrian Explosion”
  3. Minor amounts of igneous rocks age ~ Ordovician –
    Carboniferous age
118
Q

Walcott Quarry

A
  • Perhaps the most famous
    shale in the world
  • The Burgess Shale hosts
    exquisitely preserved fossils that lived at the end of the
    Cambrian Explosion
  • Located at edge of paleo-continent
119
Q

Principle of original horizontality

A
  • states that layers of sediment are originally deposited horizontally under the action of gravity . It is a relative dating technique.
120
Q

Principle of later continuity

A
  • States that layers of sediment initially extend laterally in all directions; in other words, they are laterally continuous.
  • As a result, rocks that are otherwise similar, but are now separated by a valley or other erosional feature, can be assumed to be originally continuous.
121
Q

Principle of Superposition

A
  • Stating that in any undisturbed sequence of rocks deposited in layers, the youngest layer is on top and the oldest on bottom, each layer being younger than the one beneath it and older than the one above it.
122
Q

CRM Architecture

A
  • Principle of original horizontality
  • Principle of lateral continuity
  • Principle of superposition
  • The stratigraphy of the CRM is simple; the complexity is in the structuring
123
Q

CRM Structure

A
  • All thrust faults are linked to one basal fault that lies
    immediately above the crystalline basement.

• Thrust faults branch off the basal fault, cut up-section and
eventually emerge at the surface

• Each thrust fault carries the sheets of rock that lie above the fault surface

• The overlying sheets of rocks slide along the thrust fault
surface from hinterland (SW) to foreland (NE)

• As thrust sheets slide foreland-ward they climb up-section and place older rocks above younger rock units

• Individual rock units are shortened horizontally and
thickened (duplicated) vertically

• The total shortening across the CRM is about 2:1. The width
of the CRM is about 150km so the original width of the
sedimentary layers was about 300km

• The rocks at the Foothills-Plains boundary have moved very little. The rocks at the Rocky Mountain Trench have moved ~
+150km towards the foreland (continent).

• Major thrust faults can be traced on the ground for hundreds of kilometres; their maximum displacement is tens of kilometres

• The total shortening across the Canadian Rockies varies
little or slowly along its length; as one fault dies out another fault picks up the shortening

124
Q

Thin-skinned tectonics

A
  • The sedimentary rocks have been delaminated and scraped
    off the crystalline basement and shoved further onto the
    continent.
125
Q

CRM: Stratigraphy

A

• the lower 2/3 of the stratigraphy are primarily
sedimentary rocks deposited on or adjacent to a
continental platform. These sediments were sourced
from the continent.

• The upper 1/3 of the stratigraphy (along the eastern
portion of the Rocky Mountains) are primarily
sedimentary rocks deposited in a foreland trough created in front of an advancing mountain front. These sediments are sourced from the elevated sedimentary
rocks that were deposited on or adjacent to the platform. These older rocks are scavenged from the west to create the younger foreland fill rocks.

126
Q

Geological History of the CRM:

A
  • Paleoproterozoic
  • Neoproterozoic
  • Lower Cambrian
  • Middle Cambrian to Triassic
  • Jurassic
  • Cretaceous
  • Paleogene
  • Material continued to erode off the mountains. Repeated
    glaciations have “rejuvenated” the mountains by deepening and gouging out the valleys and sharpening
    the peaks.
127
Q

Paleoproterozoic

A
  • igneous and sedimentary activity deposited/formed the rock units that became the crystalline basement. These rock units were buried to great depths and then denuded for 1
    billion years.
128
Q

Neoproterozoic

A
  • The supercontinent Rodinia rifted apart and the land mass that was west of present-day Alberta moved away. The rifting process heated the crust, uplifting and stretching it and creating large scale grabens that filled in with sediments that became the Miette Group.
129
Q

Lower Cambrian

A
  • The continental crust gradually cooled and sea level rose transgressing the land and deposited the Gog Group
130
Q

Middle Cambrian to Triassic

A
  • The continent continued to subside and sea-level rose creating conditions ideal for the development of a carbonate platform. At the edge of the platform marine organisms were preserved as fossils in special conditions. Off in the deeper water clay, silt, and debris were deposited. A brief period of uplift during the Silurian to Early Devonian beveled off some of the
    sediments.
131
Q

Jurassic

A
  • North America began colliding with Terranes
    creating an elevated landmass along its west coast. The
    elevated land shed its eroded sediments onto the North
    American continent. These sediments are the lowest part
    of the foreland basin.
132
Q

Cretaceous

A
  • continued collisions with Terranes to the west deformed the sedimentary rocks of the carbonate platform. These rock units were uplifted, eroded and deposited as foreland sediments on the North American continent
133
Q

Paleogene

A

-collision with Terranes ceased and the elevated mountains relaxed and developed minor normal faults.

Geology 305 (1 decks)

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