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Marine Geology > Geology > Flashcards

Geology Flashcards

1
Q

Lt. Matthew Fontaine Maury

A

1842-1870s Head of US Navy hydrographic office First marine geologist First deep marine bathymetric map (N Atlantic) MAR circa 1855 Telegraph Plateau Soundings for laying telegraph line

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2
Q

Challenger Expedition

A

1872-1876 Charles Wyville Thomson, prof @ Edinburgh convinced royal society of London to let them go Circumnavigated globe 362 stations 500 (492) soundings dredge, cored rock and sediments collected water samples measured temperature, salinity, currents

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3
Q

WWI

A

Echosounding helped to hear enemy subs

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4
Q

German meteor expedition

A

1925-1927 First to use continuous recording echosounding to study the seabed

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5
Q

Maurice Ewing

A

in 1948 Founded Lamont-Doherty Geological Observatory (LDGO) led to theory of plate tectonics

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6
Q

Bruce Heezen and Mary Tharp

A

Map of the entire ocean floor published in 1977

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7
Q

Alvin

A

Research Sub

built in 1964

Max depth 14,000ft (4000m)

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8
Q

Deep Sea Vent Communities

A

Discovered in 1977

Pacific

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9
Q

JOIDES

A

Joint Oceanographic Institues of Deep Earth Sampling

1960s-1980s

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10
Q

Glomar Challenger

A

Drilled 624 sites

confirmed valididty of seafloor spreading and plate tectonics

continued with Ocean Drilling Program (ODP) in 1985

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11
Q

Deepsea Drilling Project

A

1960s

started with Glomar Challenger

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12
Q

JOIDES Resolution

A

successor of the Glomar Challenger

operated in the International Ocean Drilling Program (ODP)

1985

Can drill 5 miles below ocean surface

500 wells

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13
Q

Integrated Ocean Drilling Program

A

IODP

2003-2013

multiple platforms

refurbished JOIDES Resolution, Chickyu

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14
Q

GPS

A

Fully operational in 1994

DOD funded for missile launches

degraded until 2000, then available to everyone

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15
Q

GLONASS

A

Russian Global Navigation Satellite system

incomplete coverage until about 2004

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16
Q

Satellites

A

have a clock set to exactly the same time and know their exact position

trasmits position and time signal

GPS recieves signal, delayed by distance travelled- difference is calculated and the distance to each satellite is calculated

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17
Q

for precise GPS location

A

need 4 satellites

the atomic clock is on the satellite, not on handheld.

the 4th satellite provides the atomic clock component

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18
Q

Sampling the bottom

A

grab sample

gravity core and Kasten core

Piston core

vibracore

Pneumatic hammer coring

rotary drill core

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19
Q

Grab sampler

A

Not representative of the bottom

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20
Q

gravity corer

A

top of the core gets disturbed, good for bottom seds

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21
Q

Kasten core

A

type of gravity core, but rectangular

has a liner

have to process on the ship

much larger sample and less disturbance

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22
Q

Piston Coring

A

method of choice

Freefalls a known distance dependent upon material

creates a vacuum right at sample at the surface so the core isn’t disturbed

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23
Q

Vibracoring

A

Deep water or shallow

vibrations liquify material and buries it

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24
Q

pneumatic hammer coring

A

tower of power

very efficient- 20 in one day

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25
Q

IODP coring

A

Riserless drilling- uses seawater to remove cuttings from the bottom to the top

Giant push core

wireline drilling

concrete re-entry cone

Riser drilling- similar to riserless, uses mud instead of water

casing around drill pupe pumps mud down hole, can go much deeper. Mud keeps the hole from collapsing

Closed system

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26
Q

Bathymetric and Side-Scan Sonar

A

Corrects for:

Salinity, instrument offset from GPS, boat movement, tide

swath is 10x water depth

“mowing the lawn”

sends out an array

depth is proportionate to swath size (shallow: narrow, deep: wide)

mosaiced together

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27
Q

Microbathymetry Sonar

A

have to move it around to stitch it together and get rid of shaddows

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28
Q

echodistance

A

determined by time

Distance = (2-way travel time X sound Velocity)/2

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29
Q

speed of sound in water

A

1500 m/s

variable depending on water pressure, temp, and salinity

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30
Q

Side scan data

A

won’t give you depth info

give you info about targets on seafloor- position and height above the bottom

will give you real time info about height of fish above the bottom

can be used for seafloor classification

has a swatch that’s not depth dependent, like a multibeam

low amplitude with smooth bottoms

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31
Q

Side Scan vs mutibeam

A

elevation vs details

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32
Q

multi channel seismic data

A

multiple hydrophones

each hydrophone is a channel

low frequency, they travel through the seafloor and reflect off different strata

can have multiples of the same reflection (look for twice the height of the water surface)

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33
Q

air gun data

A

lower frequency

lower resolution

but can see deeper into seafloor

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34
Q

Convergent Margin

A
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35
Q

single channel seismic data

A

used for high res studies of upper few meters of sediment

boomer with a hydrophone streamer

Chirper uses a swept frequency, hydrophone built in

best of both worlds, high res and deep penetration (ew)

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36
Q

hyperbolic trace or diffractions

A

generated by features that have dimensions comparable to the wavelength of the acoustic signal

end of a fault plane, rough topographic, boulders

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37
Q

sparker vs airgun

A

sparker attenuates faster than airgun

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38
Q

Vertical resolution

A

affected by frequency

1/4 lamda = vertical resolution

ex. dominant frequency is 1.5khz, velocity is 1500m/s

(1500/1500)/4 = 0.25m

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39
Q

Layers of Earth

A

Crust (5-70 km)

Mantle (2900 km)

Core (3486 km)

Earth is mostly mantle

Like a Ferrero Roche

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40
Q

P- waves

A

Primary waves

travel faster

pressure waves

shear waves

same direction as wave propogation

can travel through liquids and go faster when this occurs, but refracted by the core

compress like a slinky

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41
Q

S-waves

A

Secondary waves

perpendicular to wave propogation

cannot travel through liquids

squiggly like a slinky

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42
Q

Mohororvicic Disontinuity/ Moho

A

Between crust and the mantle

Changes is P-wave velocity

can get depth

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43
Q

Age of Earth?

A

4.6 Billion years

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44
Q

How did Earth form layers?

A

Single step

1) Cold Accretion of unsorted materials (homogenous) 500-800K
2) Solar Winds- contraction due to gravity, boiled away lighter elements
3) Heated up because of contraction, radioactive decay, and meteorite impacts- and different densities differentiated forming layers

Molten iron and nickel sank to the center

Ocean and atmosphere formed because of differentiation

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45
Q

What is Earth made up of?

A

Primarily Fe, O, Si, Mg

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46
Q

Radioactivity of young earth

A

5x more than present

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47
Q

frequency of meteorite impact?

A

every million years one as big as Kazahkastan meteor

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48
Q

Earth’s core is primarily made up of

A

Nickle and Iron

Controls Earth’s magnetic field

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49
Q

Earth’s mantle is made up of

A

Mostly Mg

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50
Q

Crust is composed of lighter materials

A

K, Na, Si

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51
Q

Differentiation

A

formation of magnetic field

formation of ocean and atmosphere

formation of layers

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52
Q

Convection Overturn

A

heat from the interior transferred to crust via convection

dissipates heat rapidly and it cools quickly

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53
Q

Where are oceanic ridges located?

A

above convection and upwelling in the mantle

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54
Q

deep ocean trenches

A

descending limb of convection currents

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55
Q

Alfred Wegner

A

developed theory of continental drift in 1915

supercontinent Pangaea

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56
Q

Evidence for continental drift

A

continental fit

fossil evidence

Rock sequences and mountain ranges

paleoclimatic- past glacial deposits

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57
Q

age of oceanic crust

A

older farther from MOR and younger near the middle

oldest is 180 million years old

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58
Q

Earth’s magnetic field

A

strongest near the poles

displaced ~11.5degrees from actual poles

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59
Q

Geodynamo theory

A

The magnetic field is generated in the liquid metal region of the outer core

flows for several km/yr

Convecting metal (Fe) creates electrical currents, which creates the magnetic field

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60
Q

paleomagnetism

A

when magma cools, iron bearing minerals align with Earth’s magnetic field

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61
Q

Seafloor spreading theory

A

Harry Hess in 1962- continental and ocean crust must move together

confirmed with geomagnetic reversals- normal and reverse

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62
Q

reversals around MOR

A

should be symmetrical

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63
Q

thickness of sediments decrease near

A

Ocean ridges

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64
Q

age of oldest ocean crust

A

less than 180 million years

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65
Q

age of oldest continental crust

A

3.96 billion

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66
Q

plates move

A

1-10cm per year

begins with subduction, causes divergent zones (current theory)

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67
Q

Divergent plate boundaries

A

constructive margins

ocean ridges and seafloor spreading

have axial magma chambers

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68
Q

What is the longest topographic feature on Earth’s surface?

A

Mid Ocean Ridge

70,000 km

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69
Q

continental rifting

A

divergent plate boundaries that develop within a continent

landmass splits in two

ex. East africa rift/Red sea

How the oceans were formed

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70
Q

Convergent boundaries

A

two plates move together

ocean lithosphere goes under plate

eventually re-absorbed into the mantle or collision b/n two continental blocks- mtn building

create deep trenches, slumps

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71
Q

deep ocean trench is how deep?

A

8-12km

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72
Q

Transform fault boundaries

A

where two plates grind past each other without production or destruction of lithosphere

accommodates for sphere shape of Earth

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73
Q

Fracture Zones

A

include active transform faults and inactive extensions into plates interior

EX. San Andreas

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74
Q

Steno’s Laws

A

1) Law of Horizontality
2) Law of Superposition
3) Law of Lateral Continuity

Not Steno, but still important…

4) Law of Cross-Cutting Relationships
5) Principle of Inclusion

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75
Q

Law of Horizontality

A

Beds of sediment deposited in water form as horizontal (or nearly horizontal) layers due to gravitational settling.

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76
Q

Law of Superposition

A

In undisturbed strata, the oldest layer lies at the bottom and the youngest layer lies at the top.

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77
Q

Law of Lateral Continuity

A

Horizontal strata extend laterally until they thin to zero thickness (pinch out) at the edge of their basin of deposition.

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78
Q

Law of Cross-Cutting Relationships

A

An event that cuts across existing rock is younger than that disturbed rock. This law was developed by Charles Lyell (1797-1875).

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79
Q

Principle of Inclusion

A

Fragments of rock that are contained (or included) within a host rock are older than the host rock.

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80
Q

Unconformities

A

A surface that represents a very significant gap in the geologic rock record (due to erosion or long periods of non-deposition).

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81
Q

Steps to form an ocean basin

A
  1. Extension and formation of normal faults
  2. Extension and uprise of upper mantle which melts due to heat from increased pressure and volcanism (creates magma)
  3. Extension, crustal thinning and formation of a graben
  4. Rifting apart of continents and formation of new ocean crust (MORB- mid ocean ridge basalt)
  5. Seafloor spreading and rift sequence is buried
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82
Q

Disconformity

A

A contact representing missing rock between sedimentary layers that are parallel to each other. Since disconformities are parallel to bedding planes, they are difficult to see in nature.

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83
Q

horst and graben

A

graben- low place where sediment is deposited during continental rifting

horst- block that’s been pushed up

Hoarst and grabben are blocky

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84
Q

Why are rift margins important to oil companies?

A

they’re prime places for the buildup of Carbon and formation of oil and gas

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85
Q

How Salt domes form

A

Tons of organic matter deposited via rivers on the shelf

then salt deposited on top of that forming a cap

Then more sediment is buried on top, but salt is low density so it rises through sediment layers towards the surface- pathway through hydrocarbons can move

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86
Q

Nonconformity

A

A contact in which an erosion surface on plutonic or metamorphic rock has been covered by younger sedimentary or volcanic rock.

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87
Q

Paraconformity

A

A contact between parallel layers formed by extended periods of non-deposition (as opposed to being formed by erosion). These are sometimes called “pseudounconformities”).

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88
Q

Where did the water come from?

A

From within! with a little help from comets (10-20%)

The Earth outgassed and condensed as the Earth cooled after formation (80-90%)

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89
Q

Offlap

A

Progradation into deeper water

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90
Q

Stratal Patterns (Slug Diagram)

A
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91
Q

How much water came from comets?

A

10-20%

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92
Q

When did the oceans form?

A

~4 billion years ago

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93
Q

Offlap break

A

A break in the slope on the depositional clinoform, most often occurring at fairweather wave base.

About equal to the shoreline, indicator of base level activity

separates sediments deposited in shallow water from those deposited in deep water

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94
Q

Eustatic Sea Level

A

Relative to a fixed datum

Global level that includes tectonics (shape of the bathtub) and volume of water (filling the bathtub)

Longterm changes (thousands to millions of years)

NOT RELATIVE SEA LEVEL <–more localized

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95
Q

What is the continental crust made up of?

A

Si, and granite

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96
Q

What is the oceanic crust made up of?

A

Basalt and Mg

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97
Q

Sir John Murray

A

Published 50 volumes of data from HMS Challenger Expedition

23 years to publish

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98
Q

Geoid

A

The equipotential surface of the Earth’s gravity field that fits best, in a least squares sense, global mean sea level.

Irregular shape

Make measurements to the ellipsoid (regular shape), then adjust to fit the geoid

99
Q

In the Archaen

A

Large meteorite impacts ceased (much lower frequency)

cooling allowed crustal blocks to form

amount of continental crust increased

series of collisions of mini continents making fewer but larger continents

100
Q

Ophiolite

A

consists of layers representing part of the upper mantle and the oceanic crust

Key to detecting old subduction zones

101
Q

Ophiolite Sequence

A

Pillow basalt

Gabbro- amphibole

basaltic dykes

peridotite- mantel rock didn’t melt all the way

102
Q

mantle is primarily composed of conglomerates known as…

A

Peridotite

zenoliths

103
Q

zenoliths

A

hitches a ride with the melt

104
Q

Blueschist

A

subduction of oceanic crust

first appeared in proterozoic

105
Q

Isostatic Sea Level

A

More localized

Affected by changes such as glacial rebound

106
Q

when did plate tectonics start to occur and how do we know?

A

late proterozoic (1000-545 mya)

ophiolites, first appearrance of bluescists and high pressure metamorphic rocks

107
Q

What can gravity tell us?

A

Structures that exist on the boundaries between oceans and continents

dimensions of MOR magma chambers

the presence and dimensions of offshore sedimentary basins

processes that lead to rifting and formation of ocean basins

108
Q

Causes of sea level change

A

Tectonic changes (10-100 Ma; 10-100 m)

Glacial melting/freezing (100 ka; 100 m)

Water storage on continents (lakes, groundwater) (1 day-1 year; 1 cm-1 m)

Temperature (100-1000 years; 1 cm - 1 m)

109
Q

Gravity anomalies

A

Difference between measured and expected values

1) expect increase with latitude- g(lat)
2) expect decrease with increasing elevation above sea level- g(fe)
3) expect increase due to the mass of rock between sea level and observation point- g(Boug)

G = g(lat) + g(fe) + g(Boug)

change in g = g(measured) - g(predicted)

110
Q

When was the highest historic sea level?

A

~95 mya

Late Cretaceous (the WIS!)

111
Q

Boug

A

Changes in density of rock between you and the center of the earth

112
Q

fe

A

Free air

has to do with elevation

113
Q

Sequence Chronostratigraphy (record of sea level changes)

A

Regressions (basinward movements) are shown to happen really quickly, but is an artifact of the data. The shelf is commonly eroded and open when sea level is low, creating disconformities in the stratigraphy (erases record). Sea level fluctuations began to increase around 37 Mya when Antarctica became glaciated (moved to the south pole).

114
Q

Why does the MOR have relief?

A

Because it’s hot, the relief lessens as it cools

115
Q

What can spreading rates do to sea level?

A

Fast- increase sea level

Slow- decrease sea level

116
Q

Last Glacial Maximum

A

18,000 years ago

Sea level was 125m lower than today

Laurentide ice sheet (3-4 km thick)

117
Q

How is subsidence increased?

A

Increasing thickness of sediments and decreasing temperature

118
Q

What is the most important mode of heat transfer?

A

Advection of water through rock

119
Q

How long does it take the entire volume of the oceans to circulate through the crust at spreading ridges?

A

10 million years

120
Q

Cesare Emiliani

A

In 1955 discovered that fluctuations in the oxygem isotope composition of forams in deep sea cores record glacial and interglacial stages.

121
Q

Oxygen isotope ratio

A

geologic proxy for sea level change

Oxygen has two stable isotopes, 18 (0.2%) and 16 (99.8%)

Rainfall and ice are very depleted in 18 because 16 evaporates from ocean easiest

Oceans are heavier in 18 when lots of ice/glaciers

benthic forams record ocean water composition in shells

122
Q

Orbital Eccentricity

A

The degree to which Earth’s orbit departs from a circle

100,000 year cycle

123
Q

Axial Tilt

A

The angle between Earth’s axis and a line perpendicular to the plane of the ecliptic shifts, about 1.5 degrees from its current value of 23.5.

41,000 year cycle

124
Q

Precession of the equinoxes

A

Changes in the timing of the equinoxes resulting for a wobble in the Earth’s axial tilt.

22,000 year cycle

125
Q

Glacial Isostatic Adjustment (GIA)

A

Glaciers created fore bulges and a depression

loss of heavy mass means bulges go down and middle comes back up

126
Q

Using corals for paleo-sea level reconstruction

A

coral data and isotope data agrees

also basal peat data (louisiana) agrees with corals (gulf of mexico)

127
Q

Increase in rate of sea-level rise

A

Risen from 0.82 +- 0.02 mm/yr 4,000 years ago to today at 2.8 mm/yr over the last century.

128
Q

Formation of continents

A

During the Archean (4.0-2.5 Bya)

intense meteorite impacts, cooling allowed crustal blocks to form, low density first (granites, silicates)

129
Q

Clinoform

A
130
Q

regressive

A

seaward movement of shoreline

incisions in sequence boundary means erosion from exposure from low sea level, river channels

can be with stable (offlap break moves out, but not up or down), rise (offlap break moves out and up), or fall (offlap break moves out and down) of sea level

Sediments coarsen upwards

131
Q

transgressive

A

landward movement of shoreline

with SLR sequence backsteps with sediment supply (offlap break moves up and in)

Stable SL shoreline transgression is not preserved (eroded by waves) or with rising sea level but no sediment supply

sediments fine upwards

132
Q

Low stand

A

sedimentation moves basinward, creation of deep sea fans

133
Q

High stand

A

Sedimentation moves landward, deep sea sedimentation is more pelagic, no erosion from exposed shelves.

134
Q

Passive Margin Morphology

A

Continental Shelf- 75 km wide 0.1⁰

Continental Slope- 10-100 km wide, 4.0⁰

Continental Rise- 0-600 km wide, 0.05⁰-0.6⁰

Abyssal Plain- 0.05⁰

Canyons are conduits for sediment flows

135
Q

Abyssal Plain

A

Flat, nearly level

Thick sediments blanketing the rugged ocean crust

Sedimentation through lateral movement or snowing down

Sediments thicken towards the margins

Very little mixing because of no waves, but there are distal turbidite deposits

136
Q

Hot Spots

A

Stationary in upper mantle

mantle plumes burn through plates while plates move over top

E.g. Hawaii, Iceland, Yellowstone

Indicate movements of plates

137
Q

Atolls

A

Volcano–> fringing reef–> barrier reef–> atoll–> guyot–> seamount

reef gets larger, is bigger at atoll stage than fringing

islands subside due to cooling

reefs affected by sea level and erosion

138
Q

Sediment locations

A

Neritic: Shoreface or shelf

Pelagic: fine-grained accumulating in open ocean far from land through settling particles

Hemipelagic: >25% of the fraction coarser than 5 um is of terringenous volcanogenic and/or neritic origin

139
Q

Types of sediments

A

Terrigenous, biogenic, authigenic, volcanogenic, cosmogenic

140
Q

Terrigenous sediments

A

Produced by weathering and erosion of rocks on land

Transported by rivers, wind (dominant), and icebergs

141
Q

Biogenic sediments

A

CaCO3 and SiO2 oozes composed of hard parts of organisms

Fine grained, make up <30% of pelagic sediments

controlled by productivity and dissolution

Ocean is never saturated with SiO2, highest deposition in areas of upwelling and high productivity

CaCO3 oozes cover about 50% of the ocean floor

142
Q

CCD

A

Calcite Compensation Depth

The depth where the rate of supply and dissolution of CaCO3 are in balance

Below CCD Calcite dissolves

Aragonite dissolves at shallower depths than calcite

CCD is more shallow in the Pacific (4200-4500 m) than Atlantic (5000 m) because of higher CO2 (old water)

Buried CaCO3 (forams) do not dissolve

143
Q

Mechanisms for deep-sea sedimentation

A

Settling from water column

Bottom transport by gravity flows

Transport by geostrophic bottom currents

Chemical and biochemical precipitation on the ocean floor

144
Q

Authigenic Sediments

A

formed by precipitation of minerals in seawater

manganese nodules are concentric layers accreting 1.7-8.7 mm per million years

145
Q

Lysocline

A

The depth at which the rate of calcite dissolution rapidly increases.

Due to increased corrosiveness of water

High pressure, low temperature, high CO2

146
Q

Volcanogenic sediments

A

Stuff ejected from volcanoes

Ash and tephra

Can use as a dating marker, creates a layer in the sediment record

only helpful near volcanoes

147
Q

Cosmogenic Sediments

A

Pieces of meteorites that survive the trip through the atmosphere

microtektites

small glassy meteorites

not a big component at all

148
Q

Sediment thickness is controlled by what?

Rates of deposition of Lithogenic, biogenic, abyssal clays, and Mg nodules?

A

Lithogenic: 1 m/1000 years

Biogenic: 1 cm/1000 years

Abyssal clays: 1mm/1000 years

Manganese nodules: 0.001 mm/1000 years

Controlled by age of underlying crust, tectonics, structure of basement, nature and location of sources, sediment delivery process.

149
Q

Distribution and average thickness of marine sediments

A
150
Q

High latitude shelf topography

A

Very deep

rugged topography

landward sloping profile

151
Q

glacio-isostatic imbalance

A

Accounts for 150m of the continental shelf depression at the grounding line (~25%)

152
Q

When was the Messinian Salinity Crisis?

A

End of the Miocene, about 5 Mya

153
Q

How much of the Antarctic ice sheet discharges into the Ross Sea

A

25%

154
Q

What’s the average shelf depth in Antarctica

A

500m

155
Q

What was the Messinian Salinity Crisis?

A

Global salinity dropped

Mediterranean Sea was isolated from the rest of the ocean

1 million km3 of evaporites deposited over

Took about 1000 years to dry up, 700k years to form

Shoreline moved basinward rapidly, noticeable at human time scales

Evaporated ~40 times

156
Q

What’s the maximum shelf depth in Antarctica

A

1200m

157
Q

Is the inner shelf or outer shelf deeper at high latitudes

A

inner shelf

158
Q

Why are glaciers difficult to deal with?

A

Hard to date

They’re efficient at removing the sedimentary record

map geologic units around the continent

159
Q

Messinian Crisis setting

A

20 Mya Arabian plate impinged upon the Eurasian plate blocking connection to the Indian Ocean

Connection to Atlantic temporarily closed when Africa moved North

Led to drier climate in entire region

5 Mya Combined effects of uplift in west

sea levels fell, not all tectonic driven

Evaporite history varies per basin in the Mediterranean

160
Q

drumlins

A

streamlined hills made of till; steeper on the side from which the ice came

161
Q

Evaporite deposition sequence

A

CaCO3–> CaSO4 (gypsum)–> NaCl–> K and Mg

162
Q

How much of the west antarctic ice shee (WAIS) drains into Pine Island Bay

A

1/3

163
Q

Mega Scale glacial lineations

A

corrugation ridge formation

sediment squeezed into ridges by the trailing edge of a portion of a broken up ice shelf rising and settling to the sea floor under tidal influence as it drifts seaward

164
Q

How much evaporites are produced from 1000 m of seawater?

A

15 m

165
Q

Evaporiates turn into…

A

Salt diapirs, domes, and turtle structures

Low density so they migrate up in high pressure areas

166
Q

Evidence for the Messinian Crisis

A

Rivers cut canyons on the shelf when dried, velocity increased, and eroded the steeper slope.

167
Q

Heinrich Event

A

Armadas of the N Atlantic

huge influx of iceburgs

More lithic during heinrich events, more forams between heinrich events

168
Q

What did Heinrich events due to thermohaline circulation?

A

Shut it down

169
Q

How large were iceburgs during heinrich events?

A

keel depths 50-310m

megaburgs were >650m

170
Q

What happens when 6% of the Earth’s salt is removed?

A

Lower freezing point of water

More sea ice

lower sea level

moves CCD up because CaCO3 saturation lowers

171
Q

Refilling the Mediterranean

A

Sea level rose >10 m a day

90% of water transferred in a short period ranging from months to two years

Discharge of ~10^8 m3 s-1 (3-orders of magnitude larger than the present Amazon River).

172
Q

Walther’s Law

A

Depositional environments beside each other in map view will be superimposed on top of each other in a conformable vertical succession of strata.

173
Q

where do glaciers form?

A

precipitation as snow, snow must accumulate

high latitutes and high elevations

ice is flowing

efficient agent of erosion

interrupts hydrologic cycle by locking up water

174
Q

Valley glaciers

A

colder conditions in high altitude mtns keep snowfall from melting away during summer

Found in mountainous areas

lengths greater than widths

only cover a small region

transform V-shaped river valleys to U-shaped

175
Q

Ice Sheets

A

continental glacier

covers vast areas and are unconstrained by underlying topography

Greenland, WAIS, EAIS

Found in polar regions

176
Q

Facies

A

The aspect, appearance, and characteristics of a rock unit, usually reflecting the conditions of its origin.

Transitions between subenvironments

May shift so that the deposits of an adjacent environment lies directly on top of a laterally related environment.

Use modern environments to evaluate facies

177
Q

Glacier movement

A

Gravity primary force

Entire ice sheet moves 5-50 m/yr

Plastic flow and basal slip

fastest movement in the center

friction slows down the slides

178
Q

Zone of accumulation

A

snow accumulates and forms ice

179
Q

Zone of ablation

A

general term for loss of ice or snow from a glacier

sublimation, melting, evaporation, calving

180
Q

Controls on facies

A
  1. Sedimentary processes
  2. Sediment supply
  3. Climate
  4. Tectonics
  5. Sea level change
181
Q

Glacial budget

A
182
Q

Delta

A

Delta is at the end of a river and is the sedimentary record of deposition into deeper water

183
Q

plucking

A

loosen and lift blocks of rock- mechanical weathering

184
Q

Abrasion

A

sediment in ice acts as giant sandpaper

creates rock flour and striations

185
Q

Rock flour

A

very fine-grained material

186
Q

Striations

A

grooves scratched in bedrock that indicate direction of ice movement

187
Q

Drift

A

general term applied to any deposit associated with glaciers

188
Q

Till

A

sediment deposited directly from melting ice; till is unsorted and massive

189
Q

Stratified drift

A

deposits from glacial meltwater streams

190
Q

Moraines

A

ridges made of till that form at margins of a glacier

191
Q

End (terminal) moraine

A

forms at the bottom end of glacier

192
Q

lateral moraine

A

forms at side of glacier

193
Q

Medial moraine

A

when two glacial valleys merge

194
Q

What is sequence stratigraphy?

A

A method to impose the dimension of time on the relationships of rock units in space (area and depth)

By understanding how rock units are related in time and space, we can better interpret how they are connected.

Basically transgressive and regressive cycles

195
Q

East Antarctic Ice Sheet

A

Continental ice sheet

196
Q

Ice Stream

A

corridors of fast flow within an ice sheet

They discharge most of the ice and sediments from ice sheets

fed by tributaries that extend up to 1000km into interior of ice sheet

197
Q

Ice shelf

A

Floating platform of ice

forms where ice sheet flows onto ocean surface

thickness ranges from 100-1000m

NOT sea ice

198
Q

Grounding line

A

The boundary between floating ice shelf the grounded ice that feeds it (resting on rock)

199
Q

What is limestone composed of

A

CaCO3

Calcite, Aragonite

200
Q

control of carbonate sediment production

A

Temperature- warm water (18-36 degrees C)

Salinity- normal salinities (27-40 ppt)

Light intensity- abundant light (shallow water), clear water

201
Q

What kind of slopes can carbonates hold? Why?

A

Steep

they bind themselves together much more easily- lithify into rock

202
Q

Clinoforms

A

Topset <0.1 degree, alluvial, deltaic, and shallow marine

Foreset >1.0 degree deeper water depositional processes

Bottomset, low gradients, deep water depositional systems

Offlap break, break in slope between topset and foreset

Controlled by the rate of sediment supply vs. rate of creation of accommodation space on the shelf.

203
Q

Carbonate banks are isolated platforms that are surrounded by deep or shallow water? Do they receive terrigenous clastic supply?

A

Deep

Yes

204
Q

Carbonate atoll is a type of carbonate bank formed above what?

A

A subsiding volcanic island

205
Q

Isolated Platforms

A

Have flat tops, steep sides

can be several km thick

can extend over many 100s of km^2

Margins are strongly influenced by wind-driven currents- usually grow higher than reef interior

206
Q

Base level

A

The level above which deposition is temporary and erosion occurs

Is an imaginary surface

everything above erodes, below deposits

207
Q

Platform Evolution

A

Response to sea level rise

208
Q

Accommodation

A

The space available for sediment to accumulate at any point in time. Below base level, above sed surface. Controlled by base level.

Δ accommodation = Δ eustasy + Δ subsidence + Δ compaction.

Δ water depth = Δ eustasy + Δ subsidence + Δ compaction - sediment deposited.

209
Q

Keep-up reefs

A

maintain their crests at or near sea level

210
Q

catch-up reefs

A

either began as shallow reefs that get deeper when they couldn’t keep up with slr, but then later grew fast OR

started deep and quickly grew upward

211
Q

Depositional Sequence

A

Cycle of deposition bounded above and below by erosional unconformities (disconformities).

212
Q

Controls on durations of sequence

A

Creation and destruction of accommodation

Tectonics, subsidence, and eustacy

213
Q

Prograding deposits

A

Once builtup to sea level, reefs can only grow through prograding

214
Q

Sediment supply

A

The rate controls both how much and where accommodation is filled.

Rivers are the principle means of transporting material from the continental interior to the depositional basin.

215
Q

Give-up reefs

A

first grew as others did but stopped b/c changes in envrionmental conditions ex.

dropping below the photic zone

216
Q

ooids

A

spherical carbonate grains

requires carbonate supersaturation- presence of nuclei and agitation

Usually in shallow depths b/c of wave agitation

217
Q

Rimmed Carbonate shelf

A

Energy decreases from outer shelf to shoreline- reefs and CaCO3 sand bodies occur along high energy shelf margin, restricting circulation on the shelf lagoon

Debris from rimmed-shelf margin is shed onto adjacent slope and into the basin

Ex. Belize, Queensland, Australia, Florida

218
Q

Controls on volume and types of sediments

A
  • Hinterland physiography
  • Tectonics
  • Climate
  • Drainage basin area
  • Erosion rate (climate, relief, rock type)
219
Q

Spur and Groove

A

passive response of corals to wave action near edge of a platform

220
Q

Progradation

A
  • Occur when sediment supply exceeds the rate of creation of accommodation space on the shelf.
  • Basinward migration of the offlap break.
  • Regression - basinward movement of the shoreline.
221
Q

black mangroves

A

occupy drier ground

222
Q

pneumatophores

A

roots that turn around and come back out at the surface

223
Q

Once carbonate becomes subaerial

A

desiccation occurs

224
Q

Carbonate ramp

A

gently sloping to deeper water with no break in slop

shoreline might be a beach barrier-tidal delta complex with lagoons and tidal flats behind, or a beach-ridge/strandplain system

225
Q

Aggradation

A
  • Occur when sediment supply and rate of creation of accommodation space on the shelf are roughly balanced.
  • Facies belts stack vertically, offlap break does not migrate landward or basinward.
226
Q

Retrogradation

A
  • Occur when sediment supply is less than the rate of creation of shelfal accommodation space.
  • Facies belts migrate landward.

Former offlap break becomes a relict feature

227
Q

Submarine Fans and Canyon-Channel System

A

Sediment transfer zone b/n terrestrial source area and deep-sea depositional sink

228
Q

Classic slug diagram

A

Changes in base level and sediment supply through time creates these types of repeating patterns.

229
Q

How often to deep sea fans get sediment

A

Not continuously

during mass wasting events

gravity drive

230
Q

Deep sea fan morphology

A

Radial, cone, fan

231
Q

Canyon -channel system

A
232
Q

Climatic forcing of deep sea fan formation

A

subglacial meltwater

monsoonal pulses

233
Q

Information gained from deep sea fan sedimentology

A

tectonic formation

climate change

erosion

234
Q

How much of the global burial of organic carbon is the Bengal Fan responsible for?

A

10-20%

235
Q

Slide

A

large intact blocks moving on a well-defined slippage plane

236
Q

Slumps

A

break up into smaller blocks and exhibit some internal deformation of original bedding

237
Q

Debri flows and turbidity currents

A

sedimetary gravity flows

mixtures of sediment and water

238
Q

Turbidites

A

A turbidite is the geologic deposit of a turbidity current, which is a type of sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean.

239
Q

What does a turbidite sequence look like?

A

Fining upward

(not like cereal, more like nuts)

240
Q

Too much sediment for accomodation space

A

deposition occurs past the slope and onto the deep sea fan

241
Q

Contourites

A

Sediment deposite by contour currents or thermohaline-induced deep water bottom currents and geostrophic currents

Continental rise to lower slope

242
Q

Horizontal Resolution

A

affected by trigger rate, speed of boat, wavelength of source

243
Q

Maurice Ewing’s 5 divisions of Lamont Geological Survey

A
  1. Bathymetry
  2. Siesmics
  3. Gravity
  4. Heat Flow
  5. Magnetics

Marine Geology (2 decks)

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