Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Sedimentology and Stratigraphy > (S8) Clastic Coasts and Estuaries > Flashcards

(S8) Clastic Coasts and Estuaries Flashcards

1
Q

What three features determine whether a coastline is depositional or erosional?

A

Morphology, wave energy and sediment budget

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

What is an erosional coastline and what is it’s main feature?

A

A coastline where material is reflected back into the sea - usually has a characteristic steep graident

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

What is a depositional coastline and what is it’s main characteristic?

A

A coastline which is accumulating sediment - usually genetle gradient

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

Why is a gentle gradient key for a depositonal coastline?

A

Wave energy is dissapated over the shallow water

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

What four weathering processes takes place on a cliff exposure on an erosional coastline?

A

Oxidation, Hydration, Salt growth, Physical impact

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

What is the name for the feature left behind when a cliff is eroded?

A

Wave-cut platform

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

What type of sediment is accumulated along a depositional coastline? (2)

A

Terrigenous clastic detritus or bioclastic debris

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

What are the three modes of transportation to a depositional coastline, not including fluvial/aeolian?

A

Tidal currents, windblown currents, geosptrophic currents

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

What are the four controls on longshore drift?

A

Sediment supply, wave energy, tidal range, climate

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

What is the main control on carbonate and evaporite deposition along depositional coastlines?

A

Climate

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

What does barrier and lagoon formation depend upon?

A

Tidal range

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why does the backwash wave have less energy on a gravel beach?

A

Water percolates into the porous gravel

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

What is a storm ridge?

A

Formed on gravel beackhes when clasts wash up at the top of the foreshore

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

What are the three sources of clasts found on a gravelly beach?

A

Terrigenous clastic, Volcaniclastic, Bioclastic

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

What is the name for the ridge which divides the foreshore and backshore?

A

Berm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Where would we expect to find sedimentary structures on a beach and under what formation conditions?

A

Behind the Berm, when waves wash over to the landward side during storm events

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the backshore and what are it’s two features?

A

Collonised by plants, loose sand reworked by aeolian processes

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

Wave ripples may be preserved as __-___ ___ ___, or they may also be destroyed by ___.

A

Wave-ripple cross-lamination, Bioturbation

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

What are the typical dimensions of beach dune ridges?

A

10’s m high, 100’s m inland

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

What is the main limiting factor of beach dune ridges?

A

Suplly of sediment from the beach

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What two type of coasts do beach dune ridges usually form along?

A

Coasts with barrier systems + strand plain coasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the main difference in beach dune ridges and aeolian dunes in the geological record?

A

Beach dune ridges are less likely to show preservation of cross-bedding due to the later stabilization of vegetation

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

What are the four processes likley to be found on a coastal plain?

A

Fluvial, Alluvial, Aeolian, Pedogenic

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

What type of material is usually deposted on the coastal plain after a storm event? (2)

A

Bioclastic debris, Marine fauna

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is a strand plain?

A

Ajacent to the coastal plain as a sandy beach, where sediment is deposted on foreshore and backshore and backshore merges onto the coastal plane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What are the typical dimensions of a strand plain?

A

10’s - 100’s km long

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are two pieces of evidence which determine the subaerial conditions of a coastal plain?

A

Plant colonisation and aeolian dune formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the main purpose of a barrier?

A

Seperates sea from a lagoon by sand/gravel buildup

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is a beach spit?

A

A partially attached barrier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is a welded barrier?

A

A wholly attached barrier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is a barrier island?

A

A unattached barrier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is the range of lengths of a barrier?

A

100’s m to 10’s km

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is the maximum width a barrier could be?

A

100’s m wide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Where are the largest barriers found?

A

Open coasts of large oceans where wave energy is high and tidal range is small

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What does the seaward margin of a barrier look like?

A

Beaches and dune ridges where aeolian processes rework the sand and vegetation stabilizes dunes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What does the landward margin of a barrier look like?

A

Sand deposted during storms, pinches out to mud deposits at edge of lagoon margin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What would the deposit after a storm surge look like over a barrier?

A

Washover deposits form a low-angle cone of stratified sands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What are the three conditions of barrier formation?

A

Abundant sand/gravel supply, Tidal range small, Slow relative sea level rise

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Why does a macrotidal range prevent barrier formation?

A

Restricted inlet is not big enough for high flow from rate of macrotidal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Why is slow relative sea level rise benificial in barrier formation?

A

Coastal plain behind the ridge may be lower than top of the ridge - becomes flooded and sediment is continually added

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

If a lagoon is fed by a river, what may the lagoon be considered?

A

Part of an estuary system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

How deep is a typical lagoon?

A

Few m’s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What is the fetch like in a lagoon and what does this mean for bedforms?

A

Usually limited, ripples only form in very shallow water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What vegetation regeme would be expected in a tropical lagoon?

A

Aerial root systems - mangraves which aid progradation into the lagoon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What vegetation regeme would be expected in a temerate lagoon?

A

Saline tolerent grasses, trees and shrubs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What processes are likely to form a brackish lagoonal system?

A

High rainfall, local runoff, small streams

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What processes are likely to form a hypersaline lagoonal system?

A

Evaporation, arid environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What are the three characteristics of a lagoonal succession?

A

Mudstone, organic-rich, thin wave-rippled sand beds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What is the distinguishing feature between lake and lagoonal successions?

A

Presence of marine fossil assemblages in lagoons or brackish/hypersaline fauna

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What is a typical feature of a microtidal coast?

A

Barrier system with widely speaced inlets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

What would the barrier system on a mesotidal coast look like?

A

More inlets than microtidal, thus likley that barrier islands were present

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

What is a possible effect of mesotidal regeme on a lagoon?

A

Currents may be strong enough to redistribute sediment in a lagoon - higher energy environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

What is a flood tidal deposit/delta?

A

A deposit from sediment brought through the inlet by a mesotidal regeme and deposited suddenly due to drop in energy forming low angle, thin cone

54
Q

What is an ebb tidal deposit/delta?

A

A deposit of sediment brought back through an inlet from the lagoon to create a low angle, thin cone on the sea-ward side of the barrier

55
Q

What is the direction of paleocurrents on a flood tidal delta?

A

Landwards

56
Q

What does the barrier system on a macrotidal coastline look like and why?

A

No barrier system - tidal currents are stronger control on sediment distribution than waves are

57
Q

What is a common feature of a macrotidal coastline?

A

Intertidal mudflats and saltmarches

58
Q

What is the name for dry-tolerent vegetation?

A

Xerophytes

59
Q

What is a tidal creek?

A

A small channel of stronger flow which cuts into a tidal flat

60
Q

What sedimentary structures may form on the lower parts of a tidal mudflat?

A

Flaser/lenticular bedding, ripple laminated sands interbedded with mud-drapes

61
Q

What does a prograding barrier succession look like?

A

Barriers become wider, inner margins become stabilized by vegetation

62
Q

What does a retrograding barrier succession look like?

A

Loss from erosion as supply is too low, reduces in width and height - more susceptable to washovers, lagoon becomes partially filled in, beach moves landwards

63
Q

What would a coastal succession for slow relative sea level rise look like?

A

Landwards movement of beach and lagoonal fill

64
Q

Breifly state what the succession of a barrier system would look like

A

Coastal plain deposits at base, lagoon facies, capped by beach deposits

65
Q

Breifly state what the succession of a strand plain system would look like

A

Coastal plain deposits overlain by beach deposits

66
Q

What is the definition of a estuary?

A

Marine influenced portion of river valley which becomes flooded with seawater

67
Q

Where does sediment come from in an estuary?

A

Marine and Fluvial sources

68
Q

Where does all of the sedimentation occur in an estuary?

A

Drowned valley

69
Q

When do estuaries form?

A

During and immediately after a transgression - hence modern examples after the holocene

70
Q

What are the two categories of estuary?

A

Wave dominated and tide dominated

71
Q

What are the four main variables affecting the form of an estuary?

A

Sediment supply volume, relative importance of marine/fluvial, size of valley, depth of flooding

72
Q

What is the range of dimensions for modern estuaries?

A

1-100km long, 0.1-10km wide

73
Q

What is the equilibrium of a estuary system?

A

Drowned valley will eventually fill to sea level and the area will cease to have an estuarine character

74
Q

After equilibrium has been reached in an estuary system, what is the next phase for a high sedimentary supply?

A

Deltaic system forms at the mouth

75
Q

What will occur after a estuary ceases to exist in a marine, tidal dominated system?

A

Tidal flats will form at the mouth

76
Q

What will occur after a estuary ceases to exist in a marine, wave dominated system?

A

Strand plain will form at the mouth

77
Q

What are the three main features found in a wave dominated estuary?

A

Bay-head delta, Central lagoon, Beach barrier

78
Q

How and why does a bay-head delta form?

A

Fluvial processes dominate and sudden deceleration into a lagoon forms a delta - barrier protected from wave energy

79
Q

What is the process of formation and progradation of a central lagoon in a wave dominated estuary?

A

Fill with sediment, becomes salt water marsh which is crossed with channels

80
Q

What determines the relatvie thickness of a wave-dominated estuary succession?

A

The balance between fluvial and marine supply

81
Q

What would be the dominating factor in a fluvial dominated wave-estuary succession?

A

Bay head delta facies

82
Q

What would be the dominating factor in a marine dominated wave-estuary succession?

A

Barrier deposits

83
Q

What are the three main features found in a tide-dominated estuary?

A

Tidal channels, Tidal flats, Tidal bars

84
Q

What are the characteristics of a typical tidal channel? (3)

A

Low gradient, Meandering, Point-bar formation

85
Q

What is the main difference between tidally influenced meandering channels and normal meandering channels?

A

More than one grainsize on point bar deposits

86
Q

What is the name for more than one grainsize on a point bar deposit?

A

Inclined heterolithic straitifcation

87
Q

What is a typical characteristic of a tidal flat?

A

Seawater covers at high tide and exposed at low tide, saltmash

88
Q

What determines tidal bars from fluvial bars? (3)

A

Mud-drapes, reactivation surfaces, herringbone cross stratification

89
Q

What is the orientation of a dune bedform on a tidal bar?

A

Elongate to flood-tide direction

90
Q

What could cause herringbone cross-stratification in a tidal bar? (2)

A

Overlap of banks of beds with different directions, Current changes position

91
Q

What would the sedimentary structure for the strongest of tidal currents be?

A

Upper flow regime plane beds - horizontally laminated sands

92
Q

What do the proportions of tidal channel, tidal flat and tidal bar deposits depend on in succession?

A

Strength of the tidal currents, Amount of mud/sand/gravel

93
Q

What would a typical succession of a tide dominated estuary look like?

A

Base of channel, scouring and lag - fining up, cross-bedded sands, mudrapes, Inclined heterolithic stratifcation

94
Q

What is the main difference between a delta and estuary in succession?

A

Delta is progradational, estuary is aggradational

95
Q

What is the benefit of having a sea level change on hydrocarbon formation?

A

Beach sands a very good reservoir potential, change in sea level could result in trapping of sands under mud

96
Q

What are the typical lithologies associated with beach/barrier system deposits?

A

Sand and conglomerate

97
Q

What would be expected of the mineralogies of beach/barrier system deposits?

A

Mature quartz sand and shelly sands

98
Q

What would be expected of the texture of beach/barrier system deposits?

A

Well sorted, well rounded clasts

99
Q

What would be expected of the bed geometry of beach/barrier system deposits?

A

Elongate lenses

100
Q

What sedimentary structures would be expected in beach/barrier system deposits?

A

Low-angle strata + wave reworking

101
Q

What paleoflow would be expected in beach/barrier system deposits?

A

Mainly wave-formed structures

102
Q

What fossils would be expected in beach/barrier system deposits?

A

Robust shelly debris

103
Q

What would be expected of the sedimentary colouring of beach/barrier system deposits?

A

Not diagnostic

104
Q

What are the facies associations of beach/barrier system deposits?

A

Coastal plain, lagoonal, shallow marine

105
Q

What are the typical lithologies associated with lagoonal system deposits?

A

Mainly mud, some sand

106
Q

What would be expected of the mineralogies of lagoonal system deposits?

A

Variable

107
Q

What would be expected of the texture of lagoonal system deposits?

A

Fine-grained to moderately to poorly sorted

108
Q

What would be expected of the bed geometry of lagoonal system deposits?

A

Thinly bedded mud with thin sheets and lenses of sand

109
Q

What sedimentary structures would be expected in lagoonal system deposits?

A

May be laminated wave ripples

110
Q

What paleoflow would be expected in lagoonal system deposits?

A

Rare, not diagnostic

111
Q

What fossils would be expected in lagoonal system deposits?

A

Often monospecific assemlages of hypersaline or brackish tolerent organisms

112
Q

What would be expected of the sedimentary colouring of lagoonal system deposits?

A

May be dark due to anerobic conditions

113
Q

What are the facies associations of lagoonal system deposits?

A

Coastal plains, beach barrier deposits

114
Q

What are the typical lithologies associated with tidal-channel system deposits?

A

Mud, sand and less commonly conglomerate

115
Q

What would be expected of the mineralogies of tidal-channel system deposits?

A

Variable

116
Q

What would be expected of the texture of tidal-channel system deposits?

A

May well be sorted in high energy settings

117
Q

What would be expected of the bed geometry of tidal-channel system deposits?

A

Lenses with erosional bases

118
Q

What sedimentary structures would be expected in tidal-channel system deposits?

A

Cross bedding and cross laminations and inclined heterolithic stratification

119
Q

What paleoflow would be expected in tidal-channel system deposits?

A

Bimodal in tidal estuaries

120
Q

What fossils would be expected in tidal-channel system deposits?

A

Shallow marine

121
Q

What would be expected of the sedimentary colouring of tidal-channel system deposits?

A

Not diagnostic

122
Q

What are the facies associations of tidal-channel system deposits?

A

May be overlain by fluvial, shallow marine, continental or delta facies

123
Q

What are the typical lithologies associated with tidal-mudflat deposits?

A

Mud and sand

124
Q

What would be expected of the mineralogies of tidal-mudflat deposits?

A

Clay and shelly sand

125
Q

What would be expected of the texture of tidal-mudflat deposits?

A

Fine-grained, not diagnostic

126
Q

What would be expected of the bed geometry of tidal-mudflat deposits?

A

Tabular muds with thin sheets and lenses of sand

127
Q

What sedimentary structures would be expected in tidal-mudflat deposits?

A

Ripple cross-lamination and flaser/lenticular bedding

128
Q

What paleoflow would be expected in tidal-mudflat deposits?

A

Bi-modal in tidal estuaries

129
Q

What fossils would be expected in tidal-mudflat deposits?

A

Shallow marine fauna and salt marsh vegetation

130
Q

What would be expected of the sedimentary colouring of tidal-mudflat deposits?

A

Often dark due to anaerobic conditions

131
Q

What are the facies associations of tidal-mudflat deposits?

A

Shallow marine or continental

Sedimentology and Stratigraphy (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions