1
Q
What are sedimentary facies?
A
Bodies of sediment distinct from adjacent sediment that resulted from different depositional environments.
2
Q
What are the main types of fluvial systems?
A
Alluvial fans, braided rivers, and meandering rivers.
3
Q
What are the characteristics of alluvial fans?
A
Steep depositional slopes, cone-shaped, convex-up, and high relief with coarse gravelly deposits that fine down fan.
4
Q
What are the main types of alluvial fans?
A
Debris-flow dominated and stream-flow dominated fans.
5
Q
What are debris-flow dominated fans?
A
Fans with muddy matrix, poorly sorted sediments, typical of arid climates.
6
Q
What are stream-flow dominated fans?
A
Fans with channelized and sheetflood deposits, better sorted, typical of more humid climates.
7
Q
What are the two main river channel types?
A
Braided and meandering channels.
8
Q
What controls river sinuosity?
A
Discharge, slope, grain size, sediment load, and stability of channel banks.
9
Q
What are characteristics of braided rivers?
A
Multiple channels, moderate gradient, coarse sediments, and frequent bar shifting.
10
Q
What are characteristics of meandering rivers?
A
Single sinuous channel, low gradient, point bars, oxbow lakes, and overbank deposits.
11
Q
What are the main depositional features in fluvial systems?
A
Point bars, cross-beds, ripple marks, and fining-upward sequences.
12
Q
What percentage of Earth’s surface is covered by deserts?
A
About 25%.
13
Q
What are the main processes in desert environments?
A
Wind (aeolian) transport, flash floods, and evaporite formation.
14
Q
What is an erg?
A
A ‘sand sea’ covering more than 125 km² of area.
15
Q
What are the main aeolian depositional features?
A
Ripples, dunes, and cross-bedding.
16
Q
What is loess?
A
Silt deposits that accumulate far from their source.
17
Q
What is a deflation pavement?
A
A surface of gravel-sized particles left behind after finer material is blown away by wind.
18
Q
What are lacustrine systems?
A
Lake systems that cover 1–2% of Earth’s surface and are important for climate studies.
19
Q
What is an open lake?
A
A lake with an outflow of water, stable shorelines, and balance between inflow and outflow.
20
Q
What is a closed lake?
A
A lake without a major outflow where inflow < evaporation, leading to fluctuating shorelines.
21
Q
What are varves?
A
Thin alternating light and dark sediment layers deposited seasonally in cold climates.
22
Q
What do varves represent?
A
Summer: thicker, light-colored layers; Winter: thinner, dark organic layers.
23
Q
What percentage of Earth’s surface is covered by glaciers today?
A
About 10%, holding 80% of Earth’s freshwater.
24
Q
What are the main glacier environments?
A
Glacial (in contact with ice), proglacial (around the glacier), and periglacial (beyond glacier influence).
25
What are moraines?
Ridges of unsorted sediment deposited by melting glaciers.
26
What are the types of moraines?
End, lateral, and medial moraines.
27
What is till?
Unstratified, unsorted glacial sediment deposited directly by ice.
28
What is diamict?
A poorly sorted glacial deposit with a mix of large and fine sediments.
29
What is glaciofluvial sediment?
Sediment deposited by braided streams of meltwater near glacier fronts.
30
What is a glaciolacustrine deposit?
Sediment deposited in proglacial lakes, often varved.
31
What is a glaciomarine deposit?
Sediment deposited in marine settings influenced by glacial meltwater and icebergs.
32
What is a delta?
A discrete shoreline protuberance formed where a river enters a standing body of water.
33
What factors influence delta formation?
Climate, water and sediment discharge, river-mouth processes, wave power, tides, currents, winds, slope, subsidence, tectonics, and basin geometry.
34
What are the main types of deltas?
Fluvial-dominated, tide-dominated, and wave-dominated.
35
What is a fluvial-dominated delta?
Delta where river processes dominate and wave/tide reworking is minimal.
36
What are the three types of fluvial flow?
Homopycnal, hyperpycnal, and hypopycnal flows.
37
What is a Gilbert-type delta?
A coarse-grained delta with steep foreset beds between topset and bottomset strata.
38
What is a delta avulsion?
A channel switching to a new lobe location, forming coarsening-upward deltaic cycles.
39
What is a tide-dominated delta?
A delta shaped mainly by tidal currents with bidirectional sediment transport.
40
What is a wave-dominated delta?
A delta reworked by strong wave action and longshore currents, forming smooth delta fronts.
41
What is a fan delta?
A delta formed where an alluvial fan deposits sediment subaqueously into a basin.
42
What are the main subenvironments of a delta?
Delta top, delta front, and prodelta.
43
What is the typical vertical sequence in a delta?
Coarsening-upward succession as the delta progrades seaward.
44
What is an alluvial fan?
A cone-shaped deposit of sediment formed where a stream's velocity decreases rapidly at a mountain base.
45
Where are modern alluvial fans most commonly found?
In arid or semi-arid regions at the base of mountains or fault scarps.
46
What are the two main types of alluvial fans?
Debris-flow dominated fans and stream-flow dominated fans.
47
How do debris-flow deposits differ from stream-flow deposits?
Debris flows are poorly sorted with muddy matrices; stream flows are better sorted with laminated sands and gravels.
48
What does reverse grading in a debris-flow indicate?
That coarser material was deposited on top due to viscous flow mechanics.
49
What are sieve deposits?
Highly permeable gravel deposits that allow water to flow through, trapping coarse sediments.
50
How can vertical grain trends indicate fan activity?
Coarsening upward shows active progradation, fining upward indicates retrogradation or inactivity.
51
How do rivers differ from alluvial fans?
Rivers are continuous transport systems, while fans are depositional lobes from episodic flows.
52
What are the three main river channel types?
Meandering, braided, and anastomosing channels.
53
What factors influence whether a river meanders or braids?
Discharge, slope, sediment load, and bank stability.
54
Where does erosion occur in a meandering river?
On the outer bend of a meander where velocity is highest.
55
Where does deposition occur in a meandering river?
On the inner bend forming point bars with fining-upward sequences.
56
How can you recognize a braided river in the rock record?
Multiple channel sand bodies, poor sorting, cross-bedding, and unidirectional paleocurrents.
57
What are floodplain deposits?
Fine-grained sediments deposited when rivers overflow their banks.
58
What sedimentary structures are common in fluvial systems?
Planar and trough cross-bedding, ripple marks, and fining-upward successions.
59
What is fluvial architecture?
The large-scale pattern of channel and bar migration through time forming stacked sand bodies.
60
What are aeolian deposits?
Sediments transported and deposited by wind, typically well-sorted sands.
61
What is an erg?
A vast sand sea with dunes covering more than 125 km².
62
What are the main aeolian transport processes?
Traction, saltation, and suspension.
63
What are loess deposits?
Windblown silt layers found far from their source, typically from glacial regions.
64
What are lag deposits?
Residual coarse sediments left behind after finer material is blown away.
65
How can you distinguish dune cross-bedding from fluvial cross-bedding?
Dune cross-beds are large-scale with sweeping foresets; fluvial cross-beds are smaller and often bi-directional.
66
What are interdune deposits?
Sediments between dunes, often fine-grained or bioturbated by ephemeral lakes.
67
What does a drying-upward sequence in aeolian sediments suggest?
Increasing aridity and dune progradation.
68
What are varves used to indicate?
Annual lake deposition cycles useful for reconstructing past climate and time.
69
What are the typical minerals in arid lake deposits?
Evaporites like gypsum and halite.
70
How can you recognize a glacial deposit?
Poorly sorted diamictites, dropstones, and striated clasts.
71
What are moraines?
Ridges of unsorted glacial debris marking former glacier positions.
72
What are eskers?
Sinuous ridges formed by sediment deposition in subglacial meltwater tunnels.
73
What are varves in glacial lakes?
Thin annual layers alternating coarse summer and fine winter sediments.
74
What defines a delta?
A depositional system formed where a river enters a standing body of water, building outward with sediment.
75
What controls delta type?
The balance between fluvial, wave, and tidal energy.
76
What are the three main delta types?
Fluvial-dominated, tide-dominated, and wave-dominated.
77
What is a Gilbert-type delta?
A coarse-grained delta with topset, foreset, and bottomset beds formed by rapid sediment progradation.
78
What are distributary channels?
Branching channels that distribute river flow and sediment across a delta plain.
79
What are mouth bars?
Sediment mounds formed at river mouths due to loss of velocity and sediment deposition.
80
How do prodelta deposits differ from delta-front deposits?
Prodelta sediments are fine-grained clays; delta-front sediments are sands and silts.
81
What is delta switching?
When a river changes its course, abandoning one delta lobe and building another.
82
What sedimentary pattern indicates a prograding delta?
A coarsening-upward sequence from prodelta muds to delta-front sands.
83
How does a tide-dominated delta differ from a fluvial delta?
Tide-dominated deltas show bidirectional flow and sand ridges parallel to tidal currents.
84
How does a wave-dominated delta differ?
Wave energy reworks sediment into beach ridges and spits along the coast.
85
What is a fan delta?
A delta formed where an alluvial fan meets a standing body of water.
86
What processes dominate beach formation?
Wave action, longshore currents, and tidal fluctuations.
87
What is longshore drift?
Sediment transport along the shore caused by waves striking at an angle.
88
What are the three main tidal flat sub-environments?
Subtidal, intertidal, and supratidal zones.
89
What structures form on tidal flats?
Ripple marks, flaser bedding, wavy and lenticular bedding, and mud cracks.
90
What is a barrier island?
A sandy island separated from the mainland by a lagoon or marsh, parallel to the coast.
91
What are washover deposits?
Sand layers formed when storm waves breach barriers and wash sand landward.
92
What is transgression?
A landward shift of the shoreline due to sea-level rise.
93
What is regression?
A seaward shift of the shoreline due to sea-level fall or progradation.
94
What are lagoons?
Shallow water bodies separated from the sea by barriers, usually low energy and muddy.
95
What are estuaries?
Drowned river valleys with mixed fluvial and marine sediments formed during sea-level rise.
96
What differentiates an estuary from a delta?
Estuaries have net landward sediment movement, deltas have seaward deposition.
97
How can a geologist recognize a beach deposit?
Well-sorted fine to medium sand, planar lamination, and cross-bedding indicating wave action.
98
What is the continental shelf?
The submerged edge of a continent extending to the shelf break at ~130m depth.
99
What is the continental slope?
The steep incline from the shelf break down to the deep ocean basin.
100
What is the continental rise?
A gentle slope at the base of the continental slope formed by accumulated submarine fans.
101
What are relic sediments?
Old sediments reworked by newer marine processes, often coarse and irregularly distributed.
102
What processes transport sediments across shelves?
Waves, tides, storms, ocean currents, and density currents.
103
What are tempestites?
Storm-deposited layers showing graded bedding and hummocky cross-stratification.
104
What is hummocky cross-stratification?
Gently undulating lamination formed by storm wave oscillation in shallow marine settings.
105
What are tidal rhythmites?
Paired laminae of sand and mud deposited during successive tidal cycles.
106
What are contour currents?
Deep, density-driven ocean currents flowing parallel to continental margins.
107
What are turbidites?
Deposits from turbidity currents showing graded bedding from coarse to fine material.
108
How can you distinguish a storm-dominated shelf from a tide-dominated shelf?
Storm shelves show hummocky cross-stratification; tidal shelves show herringbone cross-bedding.
109
What is pelagic rain?
Slow settling of fine biogenic material from the water column to the seafloor.
110
What are oozes?
Deep-sea sediments composed mainly (>60%) of planktonic shells, such as forams and diatoms.
111
What is the calcium carbonate compensation depth?
The depth where carbonate dissolution equals deposition; below this, carbonates dissolve.
112
What is a submarine canyon?
A steep-sided valley cutting through the continental slope formed by turbidity currents or ancient rivers.
113
What is a submarine fan?
A cone-shaped accumulation of sediment at the base of the slope from turbidity currents.
114
What are abyssal plains?
Flat, deep ocean floors covered by fine sediment and pelagic deposits.
115
What is nepheloid flow?
A dense cloud of suspended fine particles transported above the ocean floor.
116
What are contourites?
Sediments deposited by contour currents; typically show both coarsening and fining upward sequences.
117
What are hemipelagic sediments?
Mixed biogenic and terrigenous fine-grained sediments found on slopes and rises.
118
How does sea level affect shelf sediments?
Transgression causes fining-upward sequences; regression causes coarsening-upward sequences.
119
What is the Calcium Carbonate Compensation Depth (CCD)?
The ocean depth where calcium carbonate dissolves as fast as it accumulates, preventing limestone formation below it.
120
How does ocean acidity affect carbonate deposition?
Increased acidity dissolves carbonate shells, reducing limestone preservation.
121
What are the main components of the ocean buffer system?
CO2, HCO3−, CO3²−; these regulate pH through equilibrium reactions with carbonic acid.
122
What happens to ocean pH if CO2 increases?
pH decreases as more carbonic acid forms, dissolving carbonate sediments.
123
What is the primary carbonate-producing organism in warm marine waters?
Coral, algae, and foraminifera that precipitate calcium carbonate skeletons.
124
What conditions favor carbonate deposition?
Warm, shallow, clear, low-clastic marine water with high biological activity.
125
How do carbonate platforms differ from siliciclastic shelves?
Carbonate platforms are biologically built and chemical; siliciclastic shelves are detrital.
126
What are reef structures composed of?
Framework-building organisms like corals, bound by lime mud and cement.
127
What are oolitic limestones?
Carbonate rocks made of ooids—tiny spherical grains formed by chemical precipitation in shallow warm water.
128
What happens during a transgressive carbonate sequence?
Deeper water carbonates overlie shallow reef or lagoonal facies, showing fining upward.
129
What is dolomitization?
The replacement of calcium carbonate by dolomite through magnesium-rich fluids.
130
What are lime mudstones?
Fine-grained carbonate sediments formed by chemical precipitation or settling of biogenic mud.
131
How do carbonates record environmental change?
Their textures, fossil content, and isotopic signatures reflect water chemistry and climate shifts.
132
Why are carbonate environments economically important?
They often host petroleum reservoirs and aquifers due to high porosity and permeability.
133
What role does CO2 play in carbonate equilibrium?
It shifts reactions between bicarbonate and carbonate ions, controlling precipitation or dissolution.
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