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Marine Geology > Final Exam > Flashcards

Final Exam Flashcards

1
Q

Heinrich Events

A

Characterized by finding higher percentage of coarse grained material thought to have been transported by ice-rafted debris and deposited when the debris melts

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2
Q

What can Iceberg tracks or striations tell us

A

How far the ice-bergs got before they melted

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3
Q

What size is an iceberg

A

>5m across

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4
Q

Bergy bits

A

5-2m across

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5
Q

Growlers

A

<2m across

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6
Q

Red beds

A

hematite-stained grains

from heinrich events

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7
Q

Flux

A

the rate of flow of a property per unit area

[quantity]*[time]-1*[area]-1

Hardest part of flux is time

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8
Q

Ice-rafted debris in the North Atlantic

A

appears in marine sediments for several thousand years

events correlated with Greenland ice core

Where they show up is related to currents and rates of calving

Armadas of icebergs

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9
Q

foraminifera as a temperature indicator

A

left coiling (sinistral) = cold

right coiling (dextral) = warm

distribution also affected by temperature (latitude)

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10
Q

Mg/Ca

A

based on the idea that Mg is substituted for Ca in foraminifera lattice- reflects temperatures

Higher Mg/Ca ratios correlate with higher calcification temperatures

More Mg = higher temperatures

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11
Q

Oxygen isotopes at equilibrium

A

depend only on the temperature of precipitation and 18O/16O of the ambient water

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12
Q

Range of foram delta 18O values

A

0ºC = +4 per mil

20ºC = -2 per mil

colder temps means more positive

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13
Q

Paleo-temperature Equation

A

T°C = 16.9-4.2*(d18OCaCO3 - d18Owater )+0.1*(d18OCaCO3 - d18Owater )2

This is one of several equations available. Can change per species.

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14
Q

Vienna Standard Mean Ocean Water (VSMOW)

A

distilled ocean water collected from around the globe

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15
Q

Pee Dee Belemnite (PBD)

A

Carbonate from a fossil from the Pee Dee formation in South Carolina

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16
Q

CLIMAP

A

Climate: Long range Investigation Mapping, and Prediction

major project in 70s and 80s to produce map of climate conditions during the last glacial maximum

Most data from atlantic, lacking in Pacific. Not good for global representation.

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17
Q

Surface currents during LGM according to CLIMAP

A

surface currents were stronger

driven by winds which are dependent on horizontal temperature gradients

ice rim and polar front much closer to equator, temperature difference between ice and tropics was compressed into much shorter distance than present

Steeper temperature gradient = strong winds = stronger ocean currents

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18
Q

Currents during LGM according to CLIMAP

A

Coastal and equatorial upwelling was intensified

Productivity decreased at high latitudes because of ice cover

Productivity increased at mid latitudes because of intensified mixing

Productivity increased in the subtropics because of upwelling

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19
Q

Tertiary Oxygen Isotope Record

A

Overall cooling since the Cretaceous- from 18O benthic foram record

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20
Q

MM and EO on graph show what?

A

about where the cooling periods occurred involving high latitudes and deep ocean water masses

MM = midmiocene

EO = Eocene/oligocene

Cooling steps increase in frequency closer to present

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21
Q

Tertiary period

A

66Ma- 2.58Ma

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22
Q

Planktonic and Benthic foram records

A

planktonic is the top, benthic is the bottom

shows separate trends for low latitudes, but similar trends for high latitudes

So- cooling is high latitude and deep water phenomenon

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23
Q

Temperature gradients during Tertiary

A

increased since Oligocene (30-35mya)

caused stronger winds which increased coastal and equatorial upwelling

Evidence in increasing diatom supply in N Pacific and Antarctic

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24
Q

Ocean Hemisphere Partitioning

A

Plate tectonics affect configuration and circulation of the oceans

creation and destructions of gateways

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25
Q

Effects of ocean hemisphere partitioning during Tertiary

A

restriction of Southern Ocean- cold box

Average ocean has to be cold

Deep sea and cold-water fauna become global

Tropical and subtropical fauna become localized (closed off)

Antarctica glaciated

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26
Q

Albedo and ocean hemisphere partitioning

A

whitening of Antarctic continent

effect of pushing climatic zones northward

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27
Q

Northward movement of large continental masses during tertiary

A

set up monsoonal regimes favorable for northward heat transfer

himalayas intensified the monsoons

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28
Q

Uplift of Tibet and the Himalayas during the Tertiary

A

strengthened monsoons and increased weathering helping move heat north

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29
Q

Geographic configuration of Atlantic and Pacific during Tertiary

A

deflected westward-flowing equatorial currents sending them North strengthening/creating the Gulf Stream and Kuroshio currents

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30
Q

Effect of Panama straights closing during the Tertiary

A

Before- arid continent

After- warm air could move towards the poles, condense as snowfall feeding land glaciers

Big difference between Pleistoncene and Pliocene in amplitude of ocean temperature

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31
Q

Overall Results of Ocean Hemisphere Partitioning

A

Southern Hemisphere robbed of heat

Ice age preceeded in Antarctic, not in Northern latitudes

overall cooling

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32
Q

Overall cooling caused Earth to begin what cycles?

A

glacial/interglacial cycles

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33
Q

What was Earth like when it was warmer?

A

Stagnant ocean

Organic-rich sediments indicating either high supply or reduced losses b/c of low oxygen content in deep ocean (anoxia)–> Perhaps both

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34
Q

Black Sea and Baltic Sea- Modern Analogs for Tertiary warm period

A

restricted basins

little estuarine circulation

high supply of OM

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35
Q

How to get “black deposits”

A

increase productivity while keeping the oxygen supply constant, or decrease the oxygen supply, keeping productivity constant

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36
Q

During the Cretaceous, what was productivity and oxygen like?

A

No evidence for high productivity

low oxygen supply

Lots of OM deposited

distinct positive delta C-13 excursions

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37
Q

The continental shelf

A

Shallow, submerged extension of the continent

Extends from shoreface toe to shelf break

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38
Q

Sea level fluctations and the continental shelf

A

sometimes shelf is dry land

What dominates today doesn’t mean it dominated in the past

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39
Q

What processes impact the shelf during a sea-level cycle?

A

Erosion

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40
Q

Types of erosion on the continental shelf

A

Subaerial erosion (shelf exposed, rivers)

wave erosion- transgressive and regressive ravinements

Current erosions- deep sea currents, tides, storms

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41
Q

Two primary shelf classifications

A

Supply dominated

Accomodation dominated

(Interplay between water depth and sediments)

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42
Q

Progradational shelves

A

Sediment supply > rate of accomodation creation

Supply dominated shelf

Regressive sequence

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43
Q

Transgression

A

Sediment supply < Rate of accomodation creation

Accomodation dominated shelf

Little preservation of deposition

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44
Q

Subclassifications for shelves

A

Tide

Storm

Wave

Ocean-current

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45
Q

Classifying shelves based on hydraulic regime (qualitative)

A
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46
Q

Percentage of each subcategory of shelf dominated regimes

A

80% by storm waves

17% by tidal currents

3% by ocean currents

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47
Q

Examples of ocean current dominated shelves

A

Pennell coast- Antarctica

Campos margin- Brazil

South Africa margin (Agulhas Current)

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48
Q

Palimpsest shelf sediment

A

reworked older sediment, not new seds

align subparallel with tidal currents (example in North Sea)

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49
Q

Examples of Tide Dominated Shelves

A

North Sea, Celtic Sea, Georges Bank, East China Sea

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50
Q

What is a major feature on tide dominated shelves?

A

Tidal sand ridges

Dunes migrate

ridges on top of ridges

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51
Q

Wave and storm dominated shelves

A

longshore transport

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52
Q

Huthnance model for sand ridge formation

A

initial protruberance grows upwards then outwards

Then it migrates across the shelf

start with a bathymetric high, creates a pressure gradient and spurs deposition

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53
Q

Where did the term “delta” come from?

A

The Nile delta was triangular- looked like a delta

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54
Q

Types of Rivers

A

Meandering

Braided

Enastomosing

Straight

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55
Q

Anastamosing river

A

meandering on steriods

very sinuous

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56
Q

What does a dam do to a stream profile

A

causes a notch- upstream deposition, downstream erosion

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57
Q

What happens when you expose the continental shelf

A

rivers incise and deposit more to the deep sea

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58
Q

Braided Rivers

A

high gradient

large sediment load

small channel capacity

forms moving islands or bars

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59
Q

Meandering rivers

A

low gradient

humid areas

low sediment supply

large channel capacity

lots of vegetation in flood plain, stabilizes

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60
Q

Helicoidal flow

A

flow isn’t just straight downriver

think of Tony’s corkscrew dance

areas of maximum velocity shift from side to side

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61
Q

Homopycnal flow

A

river and basin water have same densities

rapid deposition of sediment load

forms a channel mouth bar

commonly found in rivers discharging into lakes

lobate and symetrical

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62
Q

Hypopycnal flow

A

River is less dense so it floats on top

can extend plume much farther offshore

delta is more spread out

river influence extends into deeper water

clays settle out futher into the bay (flocculation)

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63
Q

Hyperpycnal flow

A

Density of river water is greater than basin water

could be colder or heavy in sediments

plume hugs the bottom, carrys far, clear water on top

nepheloid layer (created at flood stage of a river, high seds)

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64
Q

Flocculation

A

clay-particle aggregation

physio-chemical processes: electrostatic force

clays are negatively charged, attracted to salts in seawater, flock together

Tides enhance process

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65
Q

wave dominated deltas

A

Ex: Nile

wings on either side of the delta

Waves breaking on muddy plume, not shallow topography

bar welds to shore creating beach ridges

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66
Q

In a wave dominated delta, what do beach ridges indicate?

A

Severe floods, not necessarily sea level fall

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67
Q

Tide-dominated deltas characterized by

A

tidal sand bodies along direction of tidal flow

shoreline has perpendicular sand bars and distributary channels that don’t link b/c they’re tidal channels- perpendicular channel mouth bars

These channels only carry water during flood stage

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68
Q

River dominated deltas

A

ex: Mississippi

long distributary channels extending seaward

large sediment supply

channels get choked on mouth bar and bifurcates

Lobes

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69
Q

delta lobe shifting

A

river shifts - avulsion - caused by flooding events and lack of accommodation space

waves rework front as the delta subsides

destructive process

  1. Reoccupation (form delta front)
  2. Abandonment (bay)
  3. Subsidence (lagoon to shallow marine)
70
Q

how many orders of branching have been identified in the Mississippi River Delta?

A

at least 3

71
Q

What percent of sediment discharge makes it to the Bengal Fan?

A

30%

72
Q

How fast is the Ganges delta foreset advancing seaward?

A

50 meters/year

73
Q

Dual clinoforms are present where?

A

large rivers discharge onto an energetic marine shelf

subaerial and subaqueous regions

74
Q

Where are estuaries prevalent?

A

Along passive margins

75
Q

What are 4 important considerations when talking about estuaries?

A

Sea level

coastal morphology

continental shelf morphology

tectonics

76
Q

Definition of an estuary?

A

“a semi-enclosed coastal body of brackish water with one or more rivers or streams flowing into it and with a free connection to the open sea” (Pritchard, 1967)

77
Q

What does the Pritchard 1967 definition of an estuary include (types of estuaries)?

A

drowned river mouth estuaries,

bar-built estuaries,

deltas,

tectonic estuaries,

fjords

78
Q

definition and examples of drowned river mouth estuaries

A

It is what it is

galveston bay, north carolina

79
Q

Bar-built estuary definition and examples

A

Bogue and Core sounds

oriented parallel to coast and have no major rivers discharging into them

80
Q

estuarine component of Deltas

A

inter-distributary bay (like Barataria Bay, LA)

81
Q

tectonic estuary

A

found along fault lines

Many of them are really drowned river mouth estuaries, but tectonics drives the drainage basin

Lots of mini basins, oddly shaped

82
Q

Fjords

A

has brackish water

glacial feature

83
Q

What is the Pritchard 1967 definition of an estuary based on?

A

Salinity

Very oceanographic

84
Q

What is Dalrymple 2006 definition of an estuary?

A

“a transgressive coastal environment at the mouth of a river, that receives sediment from both fluvial and marine sources, and that contains facies influenced by tide, wave, and fluvial processes. The estuary is considered to extend from the landward limit of tidal facies at its head to the seaward limit of coastal facies at its mouth”

85
Q

What is estuarine formation intimately tied to?

A

Sea level fluctuations

drives valley incisions

86
Q

In estuarine formation, what does sea level fall, drainage basin, and maring morphology drive?

A

valley incision

That valley inundates during sea level rise to form estuaries

87
Q

Stream power

A

increases across break in slope

Ω=ρgQS

Ω= Stream Power

ρ = density of water (1000 kg/m3)

g= acceleration due to gravity (9.8 m/s2)

Q= discharge (m3/s)

S= channel slope

88
Q

Wave dominated estuaries

A

High energy at the mouth and head of the estuary

Width increases in middle bay

Barrier islands at mouth with inlet

89
Q

Tide dominated estuaries

A

Missing middle bay and barrier island complex

Now you have sandbars perpendicular to shoreline

Generally have extensive salt marsh

90
Q

Bayhead deltas

A

the landward side of estuaries

(Eg Roanoke)

91
Q

Forcing mechanisms of change in estuarine evolution

A

Sediment accomodation

Sediment accumulation

92
Q

Sediment accomodation

A

the space available for sediments to accumulate

aka base level

93
Q

allogenic

A

external environment, global

ex: sea level rise, tectonics

94
Q

autogenic

A

intrinsic, localized

ex: topography of land being inundatd, sediment compaction

95
Q

Relationship between sea level rise and accomodation space

A

Can have steady sea level rise, but episodic changes in sea level because of accomodation space

96
Q

Sediment accumulation

A

volume of sediment filling accomodation

97
Q

What does sediment accumulation depend on?

A

sediment flux and sequestration

98
Q

sediment flux

A

the amount of sediment delivered to the estuary over time

99
Q

sources of sediment

A

fluvial

marine

bay-shore erosion

100
Q

How do changes in climate and sea level impact sediment flux?

A

vegetation and discharge

storm frequency and magnitude

where sediments are deposited

101
Q

Sediment sequestration

A

the ability of the estuary to trap sediments

102
Q

How do climate and sea level affect sediment sequestration?

A

Storm frequency and magnitude

tidal inlet dynamics- number of inlets and tidal amplitude

barrier width

103
Q

how does wave base modulate sedimentation rates in estuaries?

A

High tide, high wave base, large accomodation space

104
Q

How does the shape of the estuary affect sedimentation rates

A

wider and deeper- more fetch, higher energy

105
Q

Drainage basin characteristics

A

Interfluves

Drainage divide

Valley

Outflow has to do with precipitation, size of watershed, and climate

106
Q

Deposition of sediments at river mouth

A

Larger settle out first

form a channel mouth bar, part of the delta front

friction dominated

107
Q

Prodelta

A

composed mostly of silts and clays

below and basinward of delta front

108
Q

Ages of Mississippi River lobes

A

Oldest lobe formed 7500 years ago

Newest is 1000 years old

109
Q

Landscape topography and accommodation space

A

V-shaped - flat with steep sides; accommodation space creation almost linear with SLR

Flat - gets inundated quickly; creates accommodation space immediately

Terraced - slow beginning for accommodation space, floods one part then increases space quickly, then slows back down as upper part floods

110
Q

Parts of a beach

A

Foreshore, backshore, dunes, berms, high intertidal, middle intertidal, low intertidal, and subtidal

111
Q

Tributary Junctions

A

Width of tributaries equals the width of the secondary channel

Promote stabilization of estuaries because gradients increase in a non-linear way

112
Q

What is a barrier island?

A

A narrow, elongate sand ridge rising slightly above the high-tide level and extending generally parallel with the shore, but separated from it by a lagoon, estuary, or marsh (Shepard, 1952)

theories of formation all include sea level rise

113
Q

Strandplain Shoreline

A

Open ocean shoreline lacking a marsh or lagoon between it and the mainland. Commonly defined by beach ridges.

114
Q

Chenier Plain

A

A strand plain with mudflats between the beach ridges. The ridges are trangressive, but the mudflats are regressive.

115
Q

Shoreline processes

A

Tides

waves

currents

wind

116
Q

Tides review

A

Response to gravitation of moon and sun

twice daily

Flood = rising

Ebb = falling

Dominated by moon

Affected by continents and shoreline configurations

117
Q

Lunar tide

A

moon revolves around earth every 28 days

24:50 cycle

118
Q

Spring tides

A

when sun and moon are aligned every two weeks

20% higher than average

119
Q

Neap tides

A

when sun and moon are at right angle to each other

20% lower than average

120
Q

Causes of wave generation

A

displacement by landslides, seafloor faulting, volcanoes

wind (velocity, fetch, duration)

121
Q

Wave base

A

the depth the waves first are influenced by the bottom = L/2

122
Q

Shoaling waves

A

wave height increases

wave length decreases

waves change direction due to refraction

123
Q

Types of wave breaks

A

Surging

plunging

spilling

collapsing

124
Q

Surging breakers

A

happen on steep slopes, wave doesn’t actually break, rolls onto steep beach, destructive

125
Q

Plunging breakers

A

Happen on moderately steep beaches, normally curls over a tunnel until wave breaks, surfer waves.

126
Q

Spilling breakers

A

occur on gentle slopes, break far from shore, surf gently rolls over the front of the wave

127
Q

Beach morphology

A

not just a product of the waves interacting with the sand, underlying geology is important (outcrops, scarps)

128
Q

Longshore currents

A

result from waves striking the shoreline at an angle

slow parallel to shoreline

transport and deposit large quantities of sand in the nearshore

129
Q

Wave refraction

A

the bending of waves so that they more nearly parallel the shoreline

130
Q

Longshore drift

A

the movement of sand along a shoreline by longshore currents

primary mechanism for distributing sand along a shoreline

131
Q

Rip currents

A

narrow surface currents that flow out to sea through the breaker zone

mechanism for returning water that has built up in the breaker zone back out to sea.

waves approach parallel to shore

132
Q

Types of barrier islands

A

attached

wave-dominated

mixed-energy

(no tide-dominated exist)

133
Q

Wave-dominated barrier islands

A

long and narrow with few inlets

washover fans are common

inlets are unstable, have small or no ebb-delta, large flood deltas

134
Q

Mixed-energy barrier islands

A

“drumstick barrier”

dominant longshore sediment transport

sediment transport reversal

135
Q

Barrier classifications based on evolution

A

Transgressive

progradational (regressive)

aggradational

136
Q

Delta morphologies

A
137
Q

Theories on barrier island origin

A

buildup of an offshore bar

longshore transport, spit elongation, inlet breaching

drowning of coast-parallel antecedent topography

initiated on shelf, migrated landward, presently cut-off from origins

138
Q

Attached barrier islands

A

Spit accretion

139
Q

Barrier evolution

A

Sea-level rise and sediment supply are not the only forcing mechanisms

also storm climate, geologic framework, anthropogenic influence

140
Q

stratigraphy of a beach ridge

A
141
Q

Equilibrium Shoreface model

A

h = Ay2/3

h = water depth

A = scaling parameter based on sediment characteristics

y = distance offshore

142
Q

Brunn Rule

A

Assumes that with a rise in sea level, the equilibrium profile of the beach and shallow offshore moves upward and landward.

R = S[L/(B+h)] = (S)1/tanØ

R = Recession

S = Sea level rise

B = berm height

Ø = active profile slope

h = depth of active profile base

L = width of active profile

143
Q

Brunn Rule part 2

A

the upper beach is eroded due to landward translation of the profile

material eroded from the upper beach is transported immediately into the offshore and deposited (equal volumes, conservation of mass)

the rise in the nearshore bottom is equal to the rise in sea level, thus maintaining a constant water depth in the offshore

Response to sea level rise is instantaneous

144
Q

Successive shoreface profiles

A
145
Q

What is the preservation potential of shoreline deposits with sea level rise?

A

Movement of sediment from shoreline to inner shelf implies there is no preservation

may be preserved in deep facies, look at sediment type down core, indicates environment

146
Q

CVI

A

Coastal Vulnerability Index

147
Q

V Datum tool

A

Can look at maps and switch between MLLW and NAD83 elevation models

148
Q

Rip-rap revetment

A
149
Q

OGZ

A

Optimal growth zone

Oysters have to be in and our of tidal range

20-40% aerial exposure for a growing reef

150
Q

Connection between wave climate and beach morphology

A
151
Q

Ways to engineer the coast

A

Build hard structures (groins, jetties, seawalls)

beach nourishment

152
Q

Groins

A

Groins are shorter and typically built in the middle of a beach

meant to be buried and bypassed by sand

153
Q

Jetties

A

Built to protect waterways

154
Q

Beach nourishment

A

important to consider compatible sand for wildlife and preservation of beach

155
Q

Breakwaters

A

Tires make bad breakwaters

156
Q

Geotubes

A

Large “soft” structures to protect against flooding and storm surges

filled with sand

157
Q

Rate of sea-level rise and preservation potential

A

Depends on slope of beach

In figure, the lower photo has a higher rate of sea level rise, even though Za=Zb

Over time the upper figure will be impacted by storm waves because of longer exposure = lower preservation potential

THE HIGHER THE RATE OF SLR THE GREATER THE PRESERVATION POTENTIAL

Preservation can be enhanced by sediment lithification or diagenesis

158
Q

How is preservation potential affected by gradient?

A

The lower the gradient, the higher the preservation potential

159
Q

How is preservation potential affected by the rate of sea level rise?

A

Higher rate of sea level rise, the higher the preservation potential

160
Q

Two ways to change the properties of sediment to make the shoreline more durable

A

lithification

digenesis

161
Q

What does lithification do for the preservation of a shoreline?

A

Increases preservation

162
Q

Impact of storms on barrier islands

A

Very important!! Will probably be on exam!

Waves and wave reworking needs to be factored in

You never return to inital state

163
Q

Dynamic equilibrium

A

Overwash and shoreface fluxes sufficiently high and equivalent to maintain morphology of barrier during landward migration

SLR leads to increase in overwash flux

As barrier narrows, overwash flux increases

164
Q

Height drowning

A

When overwash fluxes can’t maintain landward migration rate required to keep pace with SLR, barrier drowns, even though it maintains width

165
Q

Width drowning

A

When onshore sediment transport is insufficient to maintain barrier geometry during landward migration

rate of shoreline migration exceeds dynamic equilibrium

166
Q

Discontinuous retreat

A

Barrier undergoes rapid transgression and experiences large rates of overwash

Onshore fluxes from shoreface toe can’t compensate for overwash fluxes, barrier narrows as shoreface flattens

shoreface slope gets flat so barrier width increases

barrier widens to critical value and overwash flux to back-barrier shuts down

barrier stops landward migration - aggradational phase begins

Close to what’s happening in reality

Movement pauses, jumps landward, grows upward during pause, jumps again, etc. (has a recovery period)

167
Q

What was the large-scale inlet activity during MWP and LIA due to?

A

increased hurricane activity and nor’easter’s

168
Q

Washover fan stratigraphy

A

Fans continue to evolve long after storm subsides

169
Q

When did most of the inlets of NC close?

A

over the last 300 years bceause of a more stable climate

170
Q

Ripple scour depression

A

Sediment starved

Found along North Carolina coast

Gravel and Sand depressions

not good for beach nourishments

Common on storm dominated shelves

Marine Geology (2 decks)

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