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exam 2 Flashcards

(74 cards)

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1
Q

what is a facies? (start of river lakes notes)

A

In sedimentology (or natural sciences more broadly) we use it as the name for a group of deposits with shared characteristics. (Similar lithology, grain size, sorting, sedimentary structures, color, composition, biogenic content)

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2
Q

what is an erg?

A

sand seas (eolian environments)

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3
Q

describing river channels: sinuosity

A

deviation from a straight path (lower sinuosity = straighter river. higher sinuosity = curvier river)

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4
Q

describing river channels: braiding

A

braiding is caused by bars within the river channel. bars are like little islands of gravel and whatnot that make the river look like a hidden side lego piece. they migrate downstream. often poorly sorted

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5
Q

what controls meandering vs braiding?

A

Slope to some degree, but mostly bank cohesion. Cohesive banks meander, non-cohesive channels braid. bank cohesion is the property of soil that affects the stability of river banks

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6
Q

describing river channels: anastomosing(ness)

A

simply means connections or openings between things. kind of like a roads merging and overlapping with eachother

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7
Q

What happens, in terms of transport, when a river meets an open body of water? (start of delta marginal marine 1 notes)

A

Energy is lost as the river channel empties into an open body of water

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8
Q

what is a delta?

A

where rivers meet a sea (or a lake). looks like tree branches entering into ocean from land. it is a landform with river roots. looks like broccoli

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9
Q

describe waves

A

-in deep water, waves have constant wavelength
-approaching shore, waves touch bottom and wavelength decreases
-in the surf zone, waves break (or “breakers” form) (this is where the wave forms a c shape and crash. like that one ocean pic they made a lego mosaic out of)

wave height increases and velocity decreases as it approaches shore

Wave energy depends on the distance wind blows across the ocean basin and the orientation of the shoreline.

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10
Q

tides are driven by?

A

gravitational forces

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11
Q

what is an estuary?

A

the “not” deltas. partially enclosed body of water where freshwater from rivers mixes with salt water from the ocean. different from delta because it is where the river poops out water to the ocean

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12
Q

what is a lagoon?

A

an embayment without a river (landlocked pool of water by the river that no longer has a connection to the river)

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13
Q

what is the walther’s law? (start of marginal marine continued notes)

A

lithologies that conformably overlie one another must have accumulated in adjacent depositional environments. in stupid terms its when a sedimentary environment moves laterally, the vertical sequence of sediments produced is the same as the original lateral sediment pattern.

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14
Q

relative sea level change (what sea level is doing locally) is due to?

A

tectonics, sediment loading/compaction

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15
Q

global (eustatic) sea level change (what sea level is doing globally) is due to?

A

glacial cycles, seafloor spreading

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16
Q

the peak of the sea level rise (transgression) is called the?

A

highstand

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17
Q

the peak of the sea level fall (regression) is called the?

A

lowstand

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18
Q

explain glacioeustatic sea level change

A

more ice in water = sea level is low. less ice in water = sea level is high

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19
Q

what is the littoral zone?

A

No precise definition sedimentologically but it is generally the nearshore zone within the active tidal, swash, surf, shoaling zones, down to normal or storm wave base (pretty much from the beach to the offshore zone)

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20
Q

what is the surf zone?

A

Surf zone: Area near the coastline where waves break (breaker zone) (think of where waves near the end of a pier would break on the ocean like in san diego)

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21
Q

what is the swash zone

A

The part of a beach that is alternately inundated and exposed by wave runup located at the landward edge of the surf zone. Characterized by a turbulent layer of water that washes up on the beach after an incoming wave has broken. (think of the area where the sand is always wet and occasionally has a wave hit)

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22
Q

what are rip currents?

A

Powerful, channeled currents of water flowing away from shore. They typically extend from the shoreline, through the surf zone, and past the line of breaking waves. (think of the current that drags you out to sea if you go to far)

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23
Q

what is longshore transport?

A

Movement of sediment along the shore due to oblique wave approach

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24
Q

what is a beach?

A

A landform alongside a body of water which consists of loose particles

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25
what is a barrier island?
Long, narrow, offshore deposits of sand or sediments that parallel the coast line and are detached from the mainland (think of a hump of sand parallel to the land and the sea)
26
what is a marsh?
a wetland that is dominated by herbaceous plants rather than by woody plants. More generally, the word can be used for any low-lying and seasonally waterlogged terrain (swamps have trees).
27
explain barrier island migration: rollover
Storms wash sediment from the front of the island to the back. This process allows the barrier island to migrate landward even as sea level rises
28
list the three different tidal zones
-supratidal zone (land) -intertidal zone (from land to beginning of sea. salt marshes then mid upper intertidal then lower intertidal) -subtidal zone (pretty much the sea)
29
what are tidal inlets?
where the tides come in and out. It is pretty much a doorway between the ocean an an area of water behind a barrier island or along the coast. Lobate features called flood and ebb “deltas” might develop on one or both sides of the inlet. flood tidal faces the shoreline and ebb tidal faces the ocean
30
explain tidal range/tidal prism
The height and volume of water that moves in and out with the tides. The larger the tidal prism and the smaller/fewer the tidal inlets, the higher the current energy flowing through those inlets.
31
what is a tidal flat?
Low-gradient coastal areas that are covered and uncovered by the tide (they are usually muddy though not always). sometimes called mudflats. In low- to midlatitude areas, they are often vegetated with things like mangroves.
32
what are tidal couplets?
pair(s) of sedimentary structures of different grain sizes with different transport directions deposited during flood, slack, ebb, slack cycles. Each couplet represents one full tidal cycle, showing evidence of both the rising and falling tides within a given day.
33
what is the offshore zone? (start of the deep marine notes)
the zone past the littoral zone.
34
what is a continental shelf?
The edge of a continent that lies beneath the ocean, or simply the low slope bit offshore. Typical slope: 0.1˚. This is the area across which sea level transgresses and regresses. Sometimes its marine, sometimes its marginal marine or even terrestrial. Ravinement (eroding flat) over multiple sea level cycles keeps the shelf low-gradient
35
what is a continental slope?
steeply sloping region of the seafloor that lies between the continental shelf and the deep ocean floor. Typical slope: 2-5˚. It is virtually always submarine. The shelf and slope are often cut by submarine canyons and gullies
36
what is continental rise?
Also called the “toe of slope” it has depositional slope/topography. area between continental slope and abyssal plain
37
what is the abyssal plain/basin floor
The flat bit extending across the rest of the basin (until you hit a mid-ocean ridge). The geometry/width/slope of this environment is inherited from tectonics. Tectonically active margins tend to have narrow shelves and rifted margins tend to have wide shelves.
38
Why are (offshore) marine/deep-marine rocks so common in the sedimentary rock record?
-Most of the Earth is a marine basin. -The marine realm, particularly the deep-marine realm, is the end of the line from source to sink -The marine realm, particularly the deep-marine realm, has very high preservation potential because there no more current or gravitational potential energy to transport sediment further
39
describe the marine sub environments: divisions of the shelf (talking about continental shelves)
-inner shelf (initial third of the continental shelf) -mid shelf (middle third of the continental shelf) -outer shelf (final third of the continental shelf) -shelf edge (area right before the drop off of the shelf. think of a lego macaroni piece) -upper slope (slope leading to continental shelf)
40
describe deep marine transport and deposition: sediment gravity flows
mixtures of water and sediment particles where the gravity acting on the sediment particles moves the fluid. debris flows and turbidity currents
41
what are debris flows?
supported by internal cohesion come in many forms at many scales. Large debris flows that may include other processes like soft-sediment faulting and slumping are called mass transport complexes. it is pretty much a type of fast-moving landslide that carries a mix of rocks, mud, soil, and sometimes even trees and other debris downhill. Imagine a thick, sludgy river of all kinds of materials mixed together—it’s very different from clear water flowing in a stream.
42
what are turbidites?
Turbidites are a type of sedimentary rock formed from underwater landslides or mudflows, known as turbidity currents, that occur on the slopes of the ocean floor, typically near continental shelves.
43
where do carbonates occur? (start of carbonates notes)
Carbonate factories are where calcium carbonate can form (either through biological processes (like organisms making shells or skeletons) or chemical precipitation from water). these include pelagic carbonate factories (often open sea, around littoral zone), shallow water carbonate factories (often warm shallow seas) skeletal carbonate factories (often in marine environments)
44
describe the types of carbonate grains: skeletal fragments/bioclasts
carbonate grains that come from whole organisms or pieces of organisms
45
describe the types of carbonate grains: ooids
spherical clasts made of concentric spheres of chemical precipitates. They form in high current energy zones where grains are rolled and agitated.
46
describe the types of carbonate grains: peloids
spherical to oval aggregates of fine carbonate. Often interpreted as fecal pellets
47
describe the types of carbonate grains: limeclasts/intraclasts
bits of cemented or partially cemented carbonate material ripped up by currents
48
describe the types of carbonate grains: pisoids
small, round or oval grains, usually made of minerals like calcium carbonate
49
describe the types of carbonate grains: oncoids
Oncoids are small, rounded structures that are made of layers of minerals, usually calcium carbonate, similar to pisoids but with a key difference. Oncoids grow by rolling around in water, and they often have a bumpy or irregular surface because they form around something like a sand grain or a tiny shell.
50
what is stratigraphy? (start of stratigraphy notes)
the study of sequences of sedimentary rocks/deposits
51
what is lithostratigraphy?
studying the rock types (including sedimentary structures, textures, etc.)
52
what is biostratigraphy?
studying the fossil assemblages hosted in sedimentary rocks/deposits
53
what is chemostratigraphy?
studying changes in environmental/source rock chemistry recorded in sedimentary rocks/deposits
54
what is chronostratigraphy?
defining the absolute time periods recorded in sedimentary rocks/deposits
55
what is sequence stratigraphy?
interpreting the sequences of stratigraphy
56
explain steno's laws of stratigraphy
-law of superposition: younger layers of rock sit atop older layers -law of original horizontality: layers of sedimentary rock are originally deposited flat -law of cross-cutting relationships: rock layers A (top) and B (bottom) must be older than the intrusion C that disturbs them. (cant bake cookies by starting with chocolate chips) -law of lateral continuity: layers of rock are continuous until they encounter other solid bodies that block their deposition or until they are acted upon by agents that appeared after the deposition took place
57
what are conformable contacts?
no evidence of significant periods of nondeposition between units/beds
58
what are unconformable contacts?
evidence of significant periods of nondeposition between units/beds
59
what is a disconformity?
layers above and below an erosional boundary have the same orientation
60
what is a nonconformity?
sediments are deposited on top of an eroded surface of igneous or metamorphic rocks
61
what is a paraconformity?
strata on either side of the unconformity are parallel, there is little apparent erosion
62
what is an angular unconformity?
strata is deposited on tilted and eroded layers
63
what is a bed?
named distinctive layer in a member or formation.
64
what is a member?
named lithologic subdivision of a formation.
65
what is a formation?
primary unit of lithostratigraphy.
66
what is a group?
two or more formations.
67
what is a supergroup?
two or more groups
68
what is a sedimentary formation?
a distinct mappable unit. Formations are divided by differences in lithofacies
69
what is a sedimentary sequence?
is a record of deposition through time. Sequences are divided by unconformities(ish)
70
what are sequence boundaries?
internally, all stratigraphic contacts are conformable. Unconformable surfaces define the boundaries between sequences.
71
what is a sedimentary basin? (start of basins intro notes)
A sedimentary basin is an area of accommodation. Accommodation is space for sediment to fill. It is generated or lost by changes in sea level and subsidence/uplift. Thick sedimentary basins can form without ever being flooded by marine waters (like a bowl of sediment cereal). created by tectonic plate movement
72
what are the mechanism for subsidence?
-Compaction -Loading -Thermal -Crustal thinning -Sub-crustal processes
73
what is sediment compaction?
decrease in sediment thickness due to burial/weight of overlying sediment. Sediment becomes more tightly packed and de-waters. This generates local surface subsidence. It does not cause basin basement subsidence.
74
what is loading?
When mass accumulates on the lithosphere, it depresses

geos 3421 (3 decks)

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