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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

WWI

A

Echosounding helped to hear enemy subs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

German meteor expedition

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Maurice Ewing

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Bruce Heezen and Mary Tharp

A

Map of the entire ocean floor published in 1977

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Alvin

A

Research Sub

built in 1964

Max depth 14,000ft (4000m)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Deep Sea Vent Communities

A

Discovered in 1977

Pacific

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

JOIDES

A

Joint Oceanographic Institues of Deep Earth Sampling

1960s-1980s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Glomar Challenger

A

Drilled 624 sites

confirmed valididty of seafloor spreading and plate tectonics

continued with Ocean Drilling Program (ODP) in 1985

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Deepsea Drilling Project

A

1960s

started with Glomar Challenger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Integrated Ocean Drilling Program

A

IODP

2003-2013

multiple platforms

refurbished JOIDES Resolution, Chickyu

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

GPS

A

Fully operational in 1994

DOD funded for missile launches

degraded until 2000, then available to everyone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

GLONASS

A

Russian Global Navigation Satellite system

incomplete coverage until about 2004

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Sampling the bottom

A

grab sample

gravity core and Kasten core

Piston core

vibracore

Pneumatic hammer coring

rotary drill core

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Grab sampler

A

Not representative of the bottom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

gravity corer

A

top of the core gets disturbed, good for bottom seds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Vibracoring

A

Deep water or shallow

vibrations liquify material and buries it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

pneumatic hammer coring

A

tower of power

very efficient- 20 in one day

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
IODP coring
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
26
Bathymetric and Side-Scan Sonar
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
27
Microbathymetry Sonar
have to move it around to stitch it together and get rid of shaddows
28
echodistance
determined by time Distance = (2-way travel time X sound Velocity)/2
29
speed of sound in water
1500 m/s variable depending on water pressure, temp, and salinity
30
Side scan data
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
31
Side Scan vs mutibeam
elevation vs details
32
multi channel seismic data
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)
33
air gun data
lower frequency lower resolution but can see deeper into seafloor
34
Convergent Margin
35
single channel seismic data
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)
36
hyperbolic trace or diffractions
generated by features that have dimensions comparable to the wavelength of the acoustic signal end of a fault plane, rough topographic, boulders
37
sparker vs airgun
sparker attenuates faster than airgun
38
Vertical resolution
affected by frequency 1/4 lamda = vertical resolution ex. dominant frequency is 1.5khz, velocity is 1500m/s (1500/1500)/4 = 0.25m
39
Layers of Earth
Crust (5-70 km) Mantle (2900 km) Core (3486 km) Earth is mostly mantle Like a Ferrero Roche
40
P- waves
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
41
S-waves
Secondary waves perpendicular to wave propogation cannot travel through liquids squiggly like a slinky
42
Mohororvicic Disontinuity/ Moho
Between crust and the mantle Changes is P-wave velocity can get depth
43
Age of Earth?
4.6 Billion years
44
How did Earth form layers?
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
45
What is Earth made up of?
Primarily Fe, O, Si, Mg
46
Radioactivity of young earth
5x more than present
47
frequency of meteorite impact?
every million years one as big as Kazahkastan meteor
48
Earth's core is primarily made up of
Nickle and Iron Controls Earth's magnetic field
49
Earth's mantle is made up of
Mostly Mg
50
Crust is composed of lighter materials
K, Na, Si
51
Differentiation
formation of magnetic field formation of ocean and atmosphere formation of layers
52
Convection Overturn
heat from the interior transferred to crust via convection dissipates heat rapidly and it cools quickly
53
Where are oceanic ridges located?
above convection and upwelling in the mantle
54
deep ocean trenches
descending limb of convection currents
55
Alfred Wegner
developed theory of continental drift in 1915 supercontinent Pangaea
56
Evidence for continental drift
continental fit fossil evidence Rock sequences and mountain ranges paleoclimatic- past glacial deposits
57
age of oceanic crust
older farther from MOR and younger near the middle oldest is 180 million years old
58
Earth's magnetic field
strongest near the poles displaced ~11.5degrees from actual poles
59
Geodynamo theory
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
60
paleomagnetism
when magma cools, iron bearing minerals align with Earth's magnetic field
61
Seafloor spreading theory
Harry Hess in 1962- continental and ocean crust must move together confirmed with geomagnetic reversals- normal and reverse
62
reversals around MOR
should be symmetrical
63
thickness of sediments decrease near
Ocean ridges
64
age of oldest ocean crust
less than 180 million years
65
age of oldest continental crust
3.96 billion
66
plates move
1-10cm per year begins with subduction, causes divergent zones (current theory)
67
Divergent plate boundaries
constructive margins ocean ridges and seafloor spreading have axial magma chambers
68
What is the longest topographic feature on Earth's surface?
Mid Ocean Ridge 70,000 km
69
continental rifting
divergent plate boundaries that develop within a continent landmass splits in two ex. East africa rift/Red sea How the oceans were formed
70
Convergent boundaries
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
71
deep ocean trench is how deep?
8-12km
72
Transform fault boundaries
where two plates grind past each other without production or destruction of lithosphere accommodates for sphere shape of Earth
73
Fracture Zones
include active transform faults and inactive extensions into plates interior EX. San Andreas
74
Steno's Laws
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
75
Law of Horizontality
Beds of sediment deposited in water form as horizontal (or nearly horizontal) layers due to gravitational settling.
76
Law of Superposition
In undisturbed strata, the oldest layer lies at the bottom and the youngest layer lies at the top.
77
Law of Lateral Continuity
Horizontal strata extend laterally until they thin to zero thickness (pinch out) at the edge of their basin of deposition.
78
Law of Cross-Cutting Relationships
An event that cuts across existing rock is younger than that disturbed rock. This law was developed by Charles Lyell (1797-1875).
79
Principle of Inclusion
Fragments of rock that are contained (or included) within a host rock are older than the host rock.
80
Unconformities
A surface that represents a very significant gap in the geologic rock record (due to erosion or long periods of non-deposition).
81
Steps to form an ocean basin
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
82
Disconformity
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.
83
horst and graben
graben- low place where sediment is deposited during continental rifting horst- block that's been pushed up Hoarst and grabben are blocky
84
Why are rift margins important to oil companies?
they're prime places for the buildup of Carbon and formation of oil and gas
85
How Salt domes form
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
86
Nonconformity
A contact in which an erosion surface on plutonic or metamorphic rock has been covered by younger sedimentary or volcanic rock.
87
Paraconformity
A contact between parallel layers formed by extended periods of non-deposition (as opposed to being formed by erosion). These are sometimes called "pseudounconformities").
88
Where did the water come from?
From within! with a little help from comets (10-20%) The Earth outgassed and condensed as the Earth cooled after formation (80-90%)
89
Offlap
Progradation into deeper water
90
Stratal Patterns (Slug Diagram)
91
How much water came from comets?
10-20%
92
When did the oceans form?
~4 billion years ago
93
Offlap break
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
94
Eustatic Sea Level
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
95
What is the continental crust made up of?
Si, and granite
96
What is the oceanic crust made up of?
Basalt and Mg
97
Sir John Murray
Published 50 volumes of data from HMS Challenger Expedition 23 years to publish
98
Geoid
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
In the Archaen
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
Ophiolite
consists of layers representing part of the upper mantle and the oceanic crust Key to detecting old subduction zones
101
Ophiolite Sequence
Pillow basalt Gabbro- amphibole basaltic dykes peridotite- mantel rock didn't melt all the way
102
mantle is primarily composed of conglomerates known as...
Peridotite zenoliths
103
zenoliths
hitches a ride with the melt
104
Blueschist
subduction of oceanic crust first appeared in proterozoic
105
Isostatic Sea Level
More localized Affected by changes such as glacial rebound
106
when did plate tectonics start to occur and how do we know?
late proterozoic (1000-545 mya) ophiolites, first appearrance of bluescists and high pressure metamorphic rocks
107
What can gravity tell us?
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
Causes of sea level change
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
Gravity anomalies
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
When was the highest historic sea level?
~95 mya Late Cretaceous (the WIS!)
111
Boug
Changes in density of rock between you and the center of the earth
112
fe
Free air has to do with elevation
113
Sequence Chronostratigraphy (record of sea level changes)
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
Why does the MOR have relief?
Because it's hot, the relief lessens as it cools
115
What can spreading rates do to sea level?
Fast- increase sea level Slow- decrease sea level
116
Last Glacial Maximum
18,000 years ago Sea level was 125m lower than today Laurentide ice sheet (3-4 km thick)
117
How is subsidence increased?
Increasing thickness of sediments and decreasing temperature
118
What is the most important mode of heat transfer?
Advection of water through rock
119
How long does it take the entire volume of the oceans to circulate through the crust at spreading ridges?
10 million years
120
Cesare Emiliani
In 1955 discovered that fluctuations in the oxygem isotope composition of forams in deep sea cores record glacial and interglacial stages.
121
Oxygen isotope ratio
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
Orbital Eccentricity
The degree to which Earth's orbit departs from a circle 100,000 year cycle
123
Axial Tilt
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
Precession of the equinoxes
Changes in the timing of the equinoxes resulting for a wobble in the Earth's axial tilt. 22,000 year cycle
125
Glacial Isostatic Adjustment (GIA)
Glaciers created fore bulges and a depression loss of heavy mass means bulges go down and middle comes back up
126
Using corals for paleo-sea level reconstruction
coral data and isotope data agrees also basal peat data (louisiana) agrees with corals (gulf of mexico)
127
Increase in rate of sea-level rise
Risen from 0.82 +- 0.02 mm/yr 4,000 years ago to today at 2.8 mm/yr over the last century.
128
Formation of continents
During the Archean (4.0-2.5 Bya) intense meteorite impacts, cooling allowed crustal blocks to form, low density first (granites, silicates)
129
Clinoform
130
regressive
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
transgressive
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
Low stand
sedimentation moves basinward, creation of deep sea fans
133
High stand
Sedimentation moves landward, deep sea sedimentation is more pelagic, no erosion from exposed shelves.
134
Passive Margin Morphology
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
Abyssal Plain
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
Hot Spots
Stationary in upper mantle mantle plumes burn through plates while plates move over top E.g. Hawaii, Iceland, Yellowstone Indicate movements of plates
137
Atolls
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
Sediment locations
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
Types of sediments
Terrigenous, biogenic, authigenic, volcanogenic, cosmogenic
140
Terrigenous sediments
Produced by weathering and erosion of rocks on land Transported by rivers, wind (dominant), and icebergs
141
Biogenic sediments
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
CCD
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
Mechanisms for deep-sea sedimentation
Settling from water column Bottom transport by gravity flows Transport by geostrophic bottom currents Chemical and biochemical precipitation on the ocean floor
144
Authigenic Sediments
formed by precipitation of minerals in seawater manganese nodules are concentric layers accreting 1.7-8.7 mm per million years
145
Lysocline
The depth at which the rate of calcite dissolution rapidly increases. Due to increased corrosiveness of water High pressure, low temperature, high CO2
146
Volcanogenic sediments
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
Cosmogenic Sediments
Pieces of meteorites that survive the trip through the atmosphere microtektites small glassy meteorites not a big component at all
148
Sediment thickness is controlled by what? Rates of deposition of Lithogenic, biogenic, abyssal clays, and Mg nodules?
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
Distribution and average thickness of marine sediments
150
High latitude shelf topography
Very deep rugged topography landward sloping profile
151
glacio-isostatic imbalance
Accounts for 150m of the continental shelf depression at the grounding line (~25%)
152
When was the Messinian Salinity Crisis?
End of the Miocene, about 5 Mya
153
How much of the Antarctic ice sheet discharges into the Ross Sea
25%
154
What's the average shelf depth in Antarctica
500m
155
What was the Messinian Salinity Crisis?
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
What's the maximum shelf depth in Antarctica
1200m
157
Is the inner shelf or outer shelf deeper at high latitudes
inner shelf
158
Why are glaciers difficult to deal with?
Hard to date They're efficient at removing the sedimentary record map geologic units around the continent
159
Messinian Crisis setting
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
drumlins
streamlined hills made of till; steeper on the side from which the ice came
161
Evaporite deposition sequence
CaCO3--\> CaSO4 (gypsum)--\> NaCl--\> K and Mg
162
How much of the west antarctic ice shee (WAIS) drains into Pine Island Bay
1/3
163
Mega Scale glacial lineations
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
How much evaporites are produced from 1000 m of seawater?
15 m
165
Evaporiates turn into...
Salt diapirs, domes, and turtle structures Low density so they migrate up in high pressure areas
166
Evidence for the Messinian Crisis
Rivers cut canyons on the shelf when dried, velocity increased, and eroded the steeper slope.
167
Heinrich Event
Armadas of the N Atlantic huge influx of iceburgs More lithic during heinrich events, more forams between heinrich events
168
What did Heinrich events due to thermohaline circulation?
Shut it down
169
How large were iceburgs during heinrich events?
keel depths 50-310m megaburgs were \>650m
170
What happens when 6% of the Earth's salt is removed?
Lower freezing point of water More sea ice lower sea level moves CCD up because CaCO3 saturation lowers
171
Refilling the Mediterranean
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
Walther's Law
Depositional environments beside each other in map view will be superimposed on top of each other in a conformable vertical succession of strata.
173
where do glaciers form?
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
Valley glaciers
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
Ice Sheets
continental glacier covers vast areas and are unconstrained by underlying topography Greenland, WAIS, EAIS Found in polar regions
176
Facies
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
Glacier movement
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
Zone of accumulation
snow accumulates and forms ice
179
Zone of ablation
general term for loss of ice or snow from a glacier sublimation, melting, evaporation, calving
180
Controls on facies
1. Sedimentary processes 2. Sediment supply 3. Climate 4. Tectonics 5. Sea level change
181
Glacial budget
182
Delta
Delta is at the end of a river and is the sedimentary record of deposition into deeper water
183
plucking
loosen and lift blocks of rock- mechanical weathering
184
Abrasion
sediment in ice acts as giant sandpaper creates rock flour and striations
185
Rock flour
very fine-grained material
186
Striations
grooves scratched in bedrock that indicate direction of ice movement
187
Drift
general term applied to any deposit associated with glaciers
188
Till
sediment deposited directly from melting ice; till is unsorted and massive
189
Stratified drift
deposits from glacial meltwater streams
190
Moraines
ridges made of till that form at margins of a glacier
191
End (terminal) moraine
forms at the bottom end of glacier
192
lateral moraine
forms at side of glacier
193
Medial moraine
when two glacial valleys merge
194
What is sequence stratigraphy?
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
East Antarctic Ice Sheet
Continental ice sheet
196
Ice Stream
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
Ice shelf
Floating platform of ice forms where ice sheet flows onto ocean surface thickness ranges from 100-1000m NOT sea ice
198
Grounding line
The boundary between floating ice shelf the grounded ice that feeds it (resting on rock)
199
What is limestone composed of
CaCO3 Calcite, Aragonite
200
control of carbonate sediment production
Temperature- warm water (18-36 degrees C) Salinity- normal salinities (27-40 ppt) Light intensity- abundant light (shallow water), clear water
201
What kind of slopes can carbonates hold? Why?
Steep they bind themselves together much more easily- lithify into rock
202
Clinoforms
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
Carbonate banks are isolated platforms that are surrounded by deep or shallow water? Do they receive terrigenous clastic supply?
Deep Yes
204
Carbonate atoll is a type of carbonate bank formed above what?
A subsiding volcanic island
205
Isolated Platforms
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
Base level
The level above which deposition is temporary and erosion occurs Is an imaginary surface everything above erodes, below deposits
207
Platform Evolution
Response to sea level rise
208
Accommodation
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
Keep-up reefs
maintain their crests at or near sea level
210
catch-up reefs
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
Depositional Sequence
Cycle of deposition bounded above and below by erosional unconformities (disconformities).
212
Controls on durations of sequence
Creation and destruction of accommodation Tectonics, subsidence, and eustacy
213
Prograding deposits
Once builtup to sea level, reefs can only grow through prograding
214
Sediment supply
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
Give-up reefs
first grew as others did but stopped b/c changes in envrionmental conditions ex. dropping below the photic zone
216
ooids
spherical carbonate grains requires carbonate supersaturation- presence of nuclei and agitation Usually in shallow depths b/c of wave agitation
217
Rimmed Carbonate shelf
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
Controls on volume and types of sediments
* Hinterland physiography * Tectonics * Climate * Drainage basin area * Erosion rate (climate, relief, rock type)
219
Spur and Groove
passive response of corals to wave action near edge of a platform
220
Progradation
* 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
black mangroves
occupy drier ground
222
pneumatophores
roots that turn around and come back out at the surface
223
Once carbonate becomes subaerial
desiccation occurs
224
Carbonate ramp
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
Aggradation
* 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
Retrogradation
* 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
Submarine Fans and Canyon-Channel System
Sediment transfer zone b/n terrestrial source area and deep-sea depositional sink
228
Classic slug diagram
Changes in base level and sediment supply through time creates these types of repeating patterns.
229
How often to deep sea fans get sediment
Not continuously during mass wasting events gravity drive
230
Deep sea fan morphology
Radial, cone, fan
231
Canyon -channel system
232
Climatic forcing of deep sea fan formation
subglacial meltwater monsoonal pulses
233
Information gained from deep sea fan sedimentology
tectonic formation climate change erosion
234
How much of the global burial of organic carbon is the Bengal Fan responsible for?
10-20%
235
Slide
large intact blocks moving on a well-defined slippage plane
236
Slumps
break up into smaller blocks and exhibit some internal deformation of original bedding
237
Debri flows and turbidity currents
sedimetary gravity flows mixtures of sediment and water
238
Turbidites
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
What does a turbidite sequence look like?
Fining upward | (not like cereal, more like nuts)
240
Too much sediment for accomodation space
deposition occurs past the slope and onto the deep sea fan
241
Contourites
Sediment deposite by contour currents or thermohaline-induced deep water bottom currents and geostrophic currents Continental rise to lower slope
242
Horizontal Resolution
affected by trigger rate, speed of boat, wavelength of source
243
Maurice Ewing's 5 divisions of Lamont Geological Survey
1. Bathymetry 2. Siesmics 3. Gravity 4. Heat Flow 5. Magnetics