Midterm Flashcards
(171 cards)
1
Q
Are formed by consolidation and cementation of sediments deposited under water
A
Sedimentary Rocks
2
Q
Sediment Transport and Deposition
Ice, water, and wind can all transport particles of various sizes to another location
A
Formation of Sedimentary Rocks
3
Q
Conglomerates
Breccia
Sandstones
Shale/mudstones
A
Clastic Rocks
4
Q
Organic Rocks
Carbonated Rocks
Evaporated Rocks
A
Chemical and Organic Rocks
5
Q
Form due to decomposition of organic remains under temperature and pressure eg. Coal/Lignite etc.
A
Organic Rocks
6
Q
Form basically form CaCO3 - both by chemical leaching and by organic source (biochemical) eg. Limestone; dolomite
A
Carbonate Rocks
7
Q
These rocks are formed due to evaporation of saline water (sea water) eg. Gypsum, Halite (rock salt)
A
Evaporate Rocks
8
Q
- Weathering and erosion of pre-existing rock and minerals
- Transportation by water, ice, or wind
- Deposition (Sediments is laid down)
- Compaction
- Cementation by silica or calcite
- Recrystallization
- Lithification
A
Dignesis Process
9
Q
Cementation + Compaction =
A
lithification
10
Q
Made up of rounded or sub-rounded pebbles and cobbles eg. conglomerate, breccia
A
Rudaceous Rocks
11
Q
Made up of mainly sand eg. sandstone. These rocks are either accumulated by wind action or deposited under water action or marine or lake environment
A
Arenaceous Rocks
12
Q
Made up of clay size sediments eg. Shale, mudstones, siltstones
A
Argillaceous Rocks
13
Q
10mm & above - Conglomerate
A
Pebble
14
Q
2mm to 10mm - Conglomerate
A
Gravel
15
Q
0.1mm to 2mm - Sandstone
A
Sand
16
Q
0.01mm to 0.1mm - Silt Stone
A
Silt
17
Q
less then 0.01mm - Shale
A
Clay
18
Q
The most abundant carbonate are limestone and dolomite, which are formed by chemical precipitation of calcium carbonate from sea water.
A
Carbonate Rocks
19
Q
Evaporation is the major process involved in the deposition of chemical precipitate. The salt deposits formed by the evaporation of saline lakes are called evaporites the principal mineral of these deposits are chlorides and sulfates of Na, K, Mg & Ca. Example- Gypsum & Anhydrite
A
Salt Rocks
20
Q
These rocks are formed by chemical precipitation of iron oxide. Such rocks contains a high proportion of iron bearing minerals such as Siderite, Hematite & Pyrite.
A
Ferruginous Rocks
21
Q
These rocks are formed when silica is precipitated from water.
A
Siliceous Deposits
22
Q
The biochemical sediments are produced when plants and animals living under water, extract from it dissolved mineral matter usually calcite to form Shell or other hard parts. Example - Limestone
A
Biochemical Rocks
23
Q
Organic Rocks: Containing organic matter belongs this group. Example Coal these are called carbonaceous rocks.
A
Organic Rocks
24
Q
Origin of Grains
A
Clastic or Non Clastic
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Coarse grain
greater than 5mm
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Fine grain
less than 1mm
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Medium grain
1 - 5mm
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Shapes of Grains
Angular, Sub Angular, Rounded, Sub Rounded
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Opened packed / densely packed.
Related to litho stratigraphic pressure.
Packing of Sediments / Grains:
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Sedimentary rocks containing elongated particles and their orientation demarks the flows of sediments.
Example. Rhyolites: High degree of crystallization / parallel axis of grains.
Fabric of Grains
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The deposition of the sediments in to layer or beds are called Stratification. The plane dividing different beds are called bedding planes.
Stratification
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________ is most imp. Feature of a sed.
Bedding
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Rock Beds are usually > ______ Laminae< ______
1 cm
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________________ helps in knowing the paleo-current direction of the old rivers
Orientation of bedding
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The thin bedding less than 1 cm in thickness are called Lamination. Lamination is found in very fine grained rocks.
Lamination
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In this structure minor beds or laminations lie at an angle to the planes of the general stratification.
Cross bedding or current bedding
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____________________ is commonly found in shallow water and wind formed deposits. This structure shows rapid change in the velocity and direction of flow of streams or wind carrying sediments
Current bedding
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In ________________ each bed shows a gradation in grain size from coarse below to fine above. This results by rapid sedimentation in water.
Graded bedding
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The surface of some sedimentary deposits shows undulation on ripple marks. These are produced by the action of waves and current in shallow water, as well as on the surface due to wind action
Ripple Marks
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Some bedding planes shows minor structures such as mud crack, rain prints etc. these are found in fine grained sedimentary rocks.
Minor Structures
40
What cause the landscape to be different?
Weathering
Erosion
Deposition
41
____________ is the chemical and physical/mechanical processes that change the characteristics of rocks on the Earth's surface.
Occurs when rocks are exposed to the hydrosphere (water) and atmosphere (air)
These weathering agents can change the physical and chemical characteristics of rocks.
Weathering
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________________ occurs when rocks are broken in to smaller pieces without changing the chemical composition of the rock. Think of a physical change (e.g., ripping a piece of paper) where the sample will change in size but all its other characteristics will remain the same
Physical weathering
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____________ is the breakup of rock caused by the freezing and thawing (contracting and expansion) of water.
Water can seep into the cracks of a rock and as the climate cools the water freezes and expands breaking the rock apart. A very similar process occurs on roads, which causes potholes.
Frost wedging
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These are examples of ___________:
* Frost Wedging
* Exfoliation
* Abrasion
* Biological Activity
Physical weathering
45
_______________ is the peeling away of large sheets of loosened materials at the surface of a rock. Common in shale, slate, and mica.
Rocks formed deep in the Earth are made under high pressure.
When the pressure is released the rocks expand & crack.
May also be caused by alternate heating and cooling of rocks by weather conditions.
Exfoliation
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_______________is the physical wearing down of rocks as they rub or bounce against each other. This process is most common in windy areas, under glaciers, or in stream channels
Abrasion
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_________________ is where the rock material is changed into another substance by reacting with a chemical.
Chemical weathering
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These are examples of ___________:
* Oxidation
* Hydration
*Reaction to acid (Carbonation)
Chemical weathering
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When oxygen interacts chemically with minerals. (ex. when a nail rusts)
Oxidation
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When water interacts chemically with minerals. (ex: when hornblende and feldspar join with water they eventually form into clay)
Hydration
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when carbon dioxide interacts chemically with minerals. Forms carbonic acid--> ex: dissolves limestone creating caverns and caves. Karst Topography
Carbonation
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Occurs in limestone bedrock
limestone easily weathers chemically (carbonation) by weak acids in groundwater
landforms created:
-caverns
-sinkholes
-disappearing rivers
Karst Topography
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Weathering occurs on the surface. More surface exposed, the faster the weathering will occur.
Exposed Surface Area
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Some minerals are more resistant than others.
ex.: Quartz is resistant to chemical and physical weathering
Mineral composition
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Not only is quartz the most stable of the common rock forming minerals in chemical weathering, its high hardness and lack of cleavage make it quite resistant to mechanical weathering. Quartz is itself an agent of mechanical weathering in the form of blowing dessert sand.
Resistance to Weathering
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Cold and/or dry climates favor physical weathering.
Warm and wet climates favor chemical weathering.
Frost action works best in areas where the temperature fluctuates wildly.
Sent
Climate
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When rock particles are smaller, the total surface area per unit volume exposed to weathering is greater.
For example, granulated sugar dissolves faster than a sugar cube.
Particle Size
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- is a combination of particles of rocks, minerals, and organic matter produced through weathering processes.
- contains the necessary nutrients to support various forms of plant and animal life.
Soil
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As a result of weathering processes and biologic activity, _____________form.
Soil horizons (layers)
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Vary in depth depending on an areas climate and weathering rates
Soil horizons
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refers to the organic material on the upper most part of the profile (this layer is usually very thin).
Dominated by organic matter, leaf and stem litter
Present in dense forests and in is olated patches elsewhere.
O horizon
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commonly known as topsoil. this layer includes organic material (humus), such as fallen leaves, twigs, decaying plant and animal remains.
The material helps prevent erosion, holds moisture, and decays to form a very rich soil known as humus.
Provides plants with nutrients
Zone of accumulation of organic matter and nutrients (Most roots occur here)
A horizon -
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Zone of illuviation (accumulation of clays)
is known as the subsoil.
much less humus.
usually will contain a fair amount of clay and iron oxides, but also may contain some elements from horizon A because of the process of leaching.
Leaching resembles what happens in a coffee pot as the water drips through the coffee grounds. Leaching may also bring some minerals from horizon B down to horizon C.
B horizon
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Consists mostly of weatherized big rocks known as Parent material (the rock that the soil formed from).
C horizon
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Which is not shown in this illustration, usually contains solid bedrock.
D horizon
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_________ resembles what happens in a coffee pot as the water drips through the coffee grounds. Leaching may also bring some minerals from horizon B down to horizon C.
Leaching
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How does climate affect weathering?
Warm and moist climates favor chemical weathering
Cold and dry climates weather physical weathering
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____________ formed from rock that originated in that particular area and was weathered
Residual soil
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____________ formed from rock that weathered some place other than where it is found.
Transported soil
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____________ refers to the transportation of rock, soil, and mineral particles from one location to another.
Erosion
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Erosion is different from weathering since erosion has the ________ element.
Moving
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The main driving force behind all agents of erosion is
Gravity
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____________ is the primary agent of erosion on Earth.
Running water
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Most running water is found in
Streams and Rivers
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Sediments carried by a stream are almost always rounded due to the grinding action of the water on the rocks, a process called
Abrasion
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Influence a stream's velocity and the erosion and deposition of sediments
Gradient (slope), discharge, and channel shape
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are eroded by streams
V-shaped valleys
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are eroded by glaciers
U-shaped valleys
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deltas, flood plains, and meanders are results of what a ________ can form.
stream
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____________ is the area drained by a stream and its tributaries (smaller feeder streams).
The watershed of a stream
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is the final step in the erosional-depositional system.
Rock particles picked up and transported will ultimately be deposited (left behind) somewhere else.
Final deposition of particles (sediments) usually occurs at the mouth of a stream. This is due to the faster flowing stream emptying into a slower larger body of water.
* The sediments that were once carried down the stream are arranged from largest to smallest.
Deposition
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Factors affecting deposition
particle size, shape, density, and velocity
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Smaller particles settle more slowly than the larger particles, due to the pull of gravity.
The smaller particles tend to stay in suspension for longer periods of time.
This form of deposition is called graded bedding
Particle Size
84
A round sediment compared to a flat (skipping stone) sediment of equal size will settle faster in a body of water.
This is due to the resistance the flat particle will undergo as it settles through the water. The round particle will meet little resistance and settle at a must faster rate.
Particle Shape
85
If particles are the same size but have different densities the higher density particle will settle faster.
Density
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___________ of the transporting stream determines when sediments will be deposited.
- If the stream slows down, carrying power will decrease and the particle sizes carried and deposited will also decrease.
If a stream is flowing faster, then the carrying power of the stream will increase and the sizes of particles deposited will increase as well.
Velocity
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As glaciers move over the land they act as a "bulldozer" changing the view of the landscape
As glaciers pass over the land they leave distinct features
Glacial Deposition
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broken down by processes of weathering and erosion, and is transported by the action of wind, water, or ice, and/or by the force of gravity
Earth material
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part of the earth's surface which is physically, chemically and biologically distinct from adjacent areas
A sedimentary environment
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The characteristics of a sedimentary rock that can be observe
Lithology
Sedimentary structures
Fossils
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The characteristics of a sedimentary rock that are affected by its depositional environment are
Sedimentary Lithology (the minerals and texture of the rock)
Sedimentary Structures
Fossils
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Sedimentary structures and fossils are best found and examined in ________, where whole beds of sedimentary rocks are exposed in their undisturbed geological setting.
outcrops
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Terrestrial\Continental: Deposited on land or in fresh water
Fluvial Alluvial
Glacial
Eolian\Desert
Lacustrine
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Transitional: Deposited in an environment showing influence of both fresh water or air and marine water.
Deltaic
Esturine
Lagoonal
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Marine: Only influenced by sea water. Shallow marine clastic
Carbonate shelf Reefs
Continental slope
Deep marine
96
Confined water body moving downhill in channels
River
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Processes associated with rivers and streams, deposits and landforms created by them
Fluvial
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Fluvial processes:
Motion of sediments
Erosion
deposition
99
Almost straight, less bends
Consists of network of small channels
Separated by temporary islands called Bars
Straight Braided Rivers
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Straight Braided Rivers occurs in river with
high slope and large Sediments load
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Straight Braided Rivers Also typical in environments that dramatically decrease in
channel depth and channel velocity
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A sinuous river with bends
Forms as moving water erode stream at outer banks(widens the valley)
Deposition at the inner part of river
Snaking pattern as stream meanders back and forth
Meandering Rivers
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_________ lakes forms as meander gets cut off from main channel
Oxbow
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in this stage, High gradient, High velocity, Erosion, Tributaries, Straight\Braided, boulders mostly deposits
Young
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in this stage, Low Gradient, Erosion and Deposition, Meanders forms, Velocity decreases
Mature
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Boulders left at upstream in young age
Channel Lag
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in this stage, Very Low Gradient, Deposition, Low Velocity, Distributaries, Meanders
Old
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Sediments deposition in rivers
Bars
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Elongated naturally occurring ridges\walls of sediments which regulates water levels
Natural Levees
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Area of land adjacent to stream or river which experience flooding during high discharge
Flood Plain
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Formed when river breaks natural levees and deposits sediments on floodplain
Crevasse Splay
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Loose, unconsolidated (not cemented) soil or sediments
Eroded and reshaped by water in some form
Redeposited in a non-marine setting
Alluvium
113
Fan or cone shaped deposits of sediments built up by streams
Stream enters from high-land to low-land
Typically found where canyons draining from mountain enters flat area
Poorly sorted material
Caused by flash floods
Alluvial fan
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Absence of marine fossils (Typically Unfossiliferous)
Presence of plant fossils
Red beds (Oxidation)
Scoured channels
Unidirectional-flow
Lamination, Cross-lamination, Ripple marks, Graded beddings
Diagnostic criteria
115
Grain size, angularity decrease from source to mouth
Sorting, sphericity, roundness increases from source to mouth
Physical
116
Desert areas cover about 20-25 percent of land surface
Within latitudinal belts about 10-30 degrees north and south
These areas have dry climate with low air pressure and low rainfall (<25cm \10 inches)
These dry areas are dominated by wind activity and covered by sand
Desert
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the removal of loose, fine-grained particles by the turbulent action of the wind
Deflation
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the wearing down of surfaces by the grinding action by windborne particles
Abrasion
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these are perpendicular to the prevailing wind, and form a wave like pattern
Traverse
120
stretch parallel to the prevailing wind with rounded or pointed tops. These can reach 300m in height and range up to 300km in length.
Longitudinal (Seif) dunes
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A curved, arc shaped sand mound with horns facing downwind formed in arid regions.
Barchans
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These are U-shaped mounds that form in the reverse direction of a barchans. They consist of sand tails which may hold vegetation
Parabolic
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These are most commonly found on beaches, and are sandy depressions in a sand dune caused by the removal of sediments by win
Blowout
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These dunes are mounds that are subject to different wind directions, forming their star-like pyramidal structure.
Star
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This is the lightest material carried by the winds which form a so-called blanket covering the existing land. This blanket is easily eroded and rain penetrates through them rapidly
Losses
126
desert alluvial fan, broad surface area, fine graine
Bajada
127
Sand - Sandstone
Well sorted- large scale cross beds
terrestrial reptile traces
Vertebrates, pollen and spores (fossils)
Yellowish - brownish colour sediments
Hematite coating of grains
Diagnostic criteria
128
Land locked water body having its own drainage system
Lake
129
Still water in lakes permits very fine particles (fine sand, silt, and clay) to settle out and to form lacustrine deposits
These deposits get exposed by elevation of old lakebeds
Lacustrine deposits are very well sorte
Characterized by thin layers that reflect annual deposition of sediments
Environment
130
in upper layer, fine particles
Overflow
131
in between layers, medium size particles
Interflow
132
at the bottom, coarse particles
Underflow
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lakes are formed from crustal stretching also known as rifting. Sediment influx is typically dominated by precipitation runoff and discharge through channels migrating towards the depression
Rift graben
134
form lacustrine deposits from seasonal overbank flooding as well as precipitation runoff which refills these isolated basins with fresh water and new sediments.
Oxbow lakes
135
form when terminal moraines block water from escaping the newly carved valley from glacial erosion. As the glacier melts, the valley fills with melt water that creates a glacial lake.
Glacial lakes
136
can be meteoritic or of the caldera variety. Crater lakes sediments are provided from precipitation runoff descending their steep slopes
Crater lakes
137
are characterized by low nutrient values, which limits the lake's ability to support animal life, the water remains clear.
Oligotrophic lakes
138
are characterized by high nutrient values, which allows microorganisms and algae to grow in large numbers, which then allows animals that feed on those algae to also be supported
Eutrophic lakes
139
Lacustrine rocks appears circular to sub- circular in map
Fine sediments in middle
Turbidites
Rhythmic bedding (showing seasoning) Natron, Trona (salts)
Lamination (organic)
Siderite (Iron carbonate)
Diagnostic criteria
140
Gastropods, Bivalves, Ostracods, Green Algae (charophytes)
Fossils
141
Ice is a major transport process. Liquid water and wind can also transport sediment in these environments
Wind transport is common when there is little vegetation. Liquid water transport occurs when the ice melts
the high viscosity of ice makes all ice
transport of sediment laminar. grain
sizes are not sorted
All of the sediment is transported together, with the ice, and it is deposited when the ice melts
Glacial
142
is the area above the firn line, where snowfall accumulates and exceeds the losses from ablation
Zone of Accumulation
143
area of a glacier or ice sheet below firn with a net loss in ice mass due to melting
Zone of Ablation
144
separates the accumulation zone from the ablation zone
Firn line
145
type of snow that has been left over from past seasons and has been recrystallized into a substance denser than snow. It is ice that is at an intermediate stage between snow and glacial ice
Firn
146
cracks in glacier
Crevasses
147
___________ - glacier deposition making land features
Lateral: ridge of sediments along sides of glacier
Medial: ridges formed in middle of glacier
End\Terminal: ridges at the end (last stop of glacier)
Ground: thin sheet deposits
Moraines
148
spoon shaped sediment deposits formed due to streams
Drumlin
149
long sinuous deposition
Esker
150
small depression and cavity formed in bedrock due to glacier movement
Kettle
151
Half Bowled shaped valley formed by glacial erosion
Cirques
152
Sharp long narrow ridges at mountain tops formed by glacial erosion
Arête
153
sharpest and elevated point of Arête
Horn
154
Poorly sorted and unstratified deposits
Striations
Angular sediments with unspecific
origins
Oxidising environment with few fossils
Stroma
Stromatolites (fossils)
Diagnostic criteria
155
When river\stream enters still\standing water body, sediments are deposited in triangle shape
Delta
156
landward portion
Sand size particles, distributaries
Delta Plain
157
Delta Front:
Slightly grades into ocean, silt (sand and clay)
Delta Front
158
Submerged into ocean, majority clay(silt and sand also)
Pro-Delta
159
The shape of a delta is influenced by
sediment input, wave energy, and tidal energy
160
occur in micro tidal settings with limited wave energy,
river contribution > ocean
all three parts of delta developed
controlled by the water density difference between the inflowing river water and the standing water on the basin
River-dominated deltas
161
Deltas which undergo strong tidal interaction
ocean contribution > river
resembles bird's feet
High tides and flood tides confine sediment on the delta plain and low tides carry sediment seaward.
Sediment supply is over powered by strong tidal currents so the delta tends to be very small
Tide-dominated deltas
162
An open ocean basin accepts more water input so potential for greater wave energy, making wave- dominated deltas
High wave interference causes conflicted or deflected river mouths.
Less influence from fluvial sources
Breaking waves cause immediate mixing of fresh and salt water. Typically, the fresh water flow velocity decelerates rapidly.
Wave-dominated deltas
163
► Majority sand size particles - sandstone
► Cross-beddings, ripple marks, laminations
► Yellowish-brownish colour
► Best reservoir
► Particle size decreases towards ocean
► Forams, Brachiopods, Pelecopods, leaves, Gastropods (fresh + marine water)
Diagnostic Criteria
164
An partially 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
Less saline than lagoon due to fresh water
Inflows of sea and fresh water provide nutrients, so it is more productive
Estuary
165
_______ is a shallow body of water separated from a larger body of water by barrier islands or reefs
little or no fresh water inflow, and little or no tidal flow
More saline
Lagoon
166
► Mostly Evaporates
►Thin beds of carbonates
► Salt pseudo-morphs
Diagnostic Criteria
167
Regions near the mouths of rivers are usually clastic dominated because the critters that secrete CaCO3 tend to have trouble living in muddy water
Shallow marine clastic
168
Regions with clear water shallow enough to be penetrated by sunlight are often dominated by the skeletons of marine organisms
Carbonate shelf
169
Dominated by the deposition of submarine landslides
Continental slope
170
Very thin sediments formed by the slow accumulation of skeletons (Planktons ) and clasts (clay) dropped into the ocean by wind
Deep Marine
