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EAS 100 > L10: Sedimentary Rock > Flashcards

L10: Sedimentary Rock Flashcards

1
Q

Define sedimentary rock

A

Composed of compacted or cemented grains which have become lithified

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2
Q

Coarser material carried in from a river get deposited _________. , while finer _____ and _______ are carried into deeper waters

A
  • First

- Silts and clays

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3
Q

What are clastic sedimentary rocks?

A
  • Formed from the products of mechanical weathering of pre-existing rocks
  • The grains are then transported by gravity, water, ice, or winds to accumulate as sediments in streams, lakes, oceans, soils, or deserts
  • BASICALLY: The transport of existing rock from pre-existing particles
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4
Q

What are chemical sedimentary rocks?

A
  • Do not form from the mechanical break-up and transport of grains. Instead, they derive from the precipitation of minerals from supersaturated solutions
  • Precipitate out of sea/lakewater
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5
Q

Examples of chemical sedimentary rock

A
  • Limestone = from calcite
  • Chert = silica
  • Evaporites = gypsum and halite
  • Iron formations = iron oxides
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6
Q

What are biological sedimentary rocks?

A
  • Formed biologically from the shells of plankton

- Ex.: diatoms and foraminifera

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7
Q

What are the 3 types of sedimentary rocks?

A
  • Clastic
  • Chemical
  • Biological
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8
Q

What do currents reveal?

A

A propensity to change flow speed

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9
Q

What is sorting?

A

The tendency for variations in current velocity to segregate sediment according to size

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10
Q

What happens the longer transport processes are and when particles are exposed to more abrasion?

A
  • The more rounded and the smaller the grains become

- Sedimentary rock also give clues to how far the grains have travelled from their source

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11
Q

Sedimentary structures include all the features that are formed at the time of __________.

A

depositions

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12
Q

What is strata

A

Individual beds nearly horizontal when deposited

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13
Q

What can be found within sedimentary rocks?

A

Oil and gas

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14
Q

What is cross-bedding?

A
  • Consists of bedded material deposited by wind or water and inclined at angles as large as 35o from the horizontal, the angle of repose
  • They form when grains are deposited on the steeper, downcurrent slopes of sand dunes on land or on sandbars in rivers and under the sea
  • Common in sandstones
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15
Q

What is the precursor for oil and gas?

A
  • Plankton

- Organic carbon

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16
Q

What is graded bedding?

A
  • Abundant in continental slope and deep-sea sediment deposited by dnse, muddy “turbidity currents”
  • Hug the bottom of topography of the oceans as they move downhill
17
Q

Turbidites

A

Accumulations of many graded-beds in this manner

18
Q

Continental shelf

A

Water thats 150 m deep in the ocean then drops off to BP

19
Q

Bissell plank

A

The depth past continental shelf; drops down

20
Q

What are ripples?

A
  • Very small dunes of sand or silt whose long dimensions are at right angles to the current or wave direction
  • Ripples are present in shallow water bc current is present to move the water along
  • Help us identify what the environment was like at that time
21
Q

What is bioturbation?

A
  • Bedding in structures thats broken down by the burrowing activity of animals
  • Appear as cylindrical tubes that represent burrowing
22
Q

What occurs when pressure and temperatures change?

A
  • Cause pre-existing sediment to dissolve, such that the water which does seep through the buried sediment carries dissolved minerals
  • Common cementing agents = silica and calcite
23
Q

Lithification is . . .

A

Turning loose sediment into rock

24
Q

What is diagenesis?

A

Changing loose sediments (a rock) composition

25
Q

What is the process of maturation?

A
  • Process by which organic matter is transformed into various forms of petroleum
  • Occurs when the temperature reaches a certain point and the element becomes unstable
26
Q

Clastic rocks are . . .

A
  • Carried from land back to the ocean
  • Based on particle size
  • High flowing water needs more energy to move big particles along fine particles, coarse grained
27
Q

If rocks are fine grained, where can we assume they formed?

A

Fine grained particles are formed further offshore

28
Q

How are clastic rocks formed?

A

Most rocks are made up of mud bc most sediments around keep getting recycled

29
Q

What is biomass useful for?

A

Finding fossil fuels

30
Q

Carbonate sediments are best examples of . . .

A
  • Chemical and biological participates

- Form mostly from the accumulation of carbonate minerals that are directly formed by organisms

31
Q

What is caused by seawater evaporation?

A

Causes the precipitation of an ordered sequence of minerals of increasing solubility

32
Q

Evaporites

A

Highly soluble; easy to weather bc formed in extreme environments

33
Q

Place the following in order: Limestone, halite, patash, gypsum

A
  1. Limestone
  2. Gypsum
  3. Halite
  4. Potash
34
Q

What is banded iron formation?

A
  • Formed during the precambrian period
  • 95% of earth’s iron reserves come from this
  • Precipitate out of seawater
  • From BIF we know that oceans used to be full of iron, indicating the change in earth’s composition
35
Q

Limestone

A
  • Brine reaches 2x the concentration of seawater

- Calcite the first mineral to precipitate out

36
Q

Gypsum

A
  • Reaches approximately 5x the concentration of seawater

- More soluble than limestone

37
Q

Halite

A
  • 10-12x original seawater concentration
  • Halite precipitates out of brine
  • A highly soluble salt; will dissolve in a natural environment
38
Q

Potash

A
  • Bittern starts to precipitate
  • Major potassium source
  • Concentration of brine reaches the viscosity of honey

EAS 100 (17 decks)

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