Deck 7: Pages of Earths Past: Sedimentary Rocks

Question 1

The sedimentary rocks breccia and conglomerate most commonly form in a ________ environment.

A) beach
B) lake
C) mountain stream
D) deep-ocean basin

Answer 1

C

Question 2

Chemical sedimentary rocks are classified primarily on the basis of

A) grain size.
B) degree of sorting.
C) angularity.
D) mineral composition.

Answer 2

D

Question 3

When limestone becomes chemically altered so that half of the calcium atoms are replaced by magnesium,the resultant rock is termed

A) agate.
B) dolostone.
C) jasper.
D) travertine.

Answer 3

B

Question 4

Which of the following is true regarding biochemical chert?

A) It is massive (lacking layers).
B) It is made of cryptocrystalline quartz.
C) It is made of aragonite shell fragments.
D) It is composed of the minerals calcite and dolomite.

Question 5

Biochemical limestones are dominated by carbonate mud and fragments of

A) siliceous shells of planktonic diatoms and foraminifera.
B) skeletons of marine invertebrates made of calcite and aragonite.
C) the phosphatic bones of fish.
D) the organic breakdown products of wood and leaves from trees.

Question 6

Grains become rounded primarily during

A) weathering at the outcrop.
B) lithification.
C) transportation.
D) deposition.

Question 7

What is the difference in the formation of chalk versus chert?

A) They have different grain sizes.
B) They are made of different source materials.
C) Chalk is terrestrial; chert is marine.
D) Chalk is biochemical; chert is chemical.

Question 8

The breakdown of exposed rock into small fragments and dissolved ions is termed

A) deposition.
B) erosion.
C) weathering.
D) lithification.

Question 9

The removal of detritus from weathered rock at an outcrop is termed

A) deposition.
B) erosion.
C) weathering.
D) lithification.

Question 10

The primary difference between breccia and conglomerate is that conglomerate

A) is finer-grained than breccia.
B) is coarser-grained than breccia.
C) possesses more angular grains than breccia.
D) possesses more rounded grains than breccia.

Question 11

Chemically precipitated limestone that forms in caves or around hot springs is termed

A) agate.
B) dolostone.
C) jasper.
D) travertine.

Question 12

Compaction and cementation of grains occurs during

A) erosion.
B) lithification.
C) transport.
D) weathering.

Question 13

Which of the following are most likely to preserve conditions of ancient environments on the Earth?

A) intrusive igneous rocks
B) extrusive igneous rocks
C) metamorphic rocks
D) sedimentary rocks

Question 14

Precipitation of gypsum due to evaporation of seawater produces which kind of sedimentary rock?

A) biochemical
B) chemical
C) clastic
D) organic

Question 15

The image below shows an outcrop of coarse-grained sedimentary rock.Note the rock hammer for scale.What is the name of this rock type?

A) sandstone
B) shale
C) breccia
D) conglomerate

Question 16

If water is the transport mechanism of sediment,the grain size of sedimentary deposits most closely indicates the

A) geographic extent of the weathering source rock at outcrop.
B) average velocity of the water from the time of erosion until deposition.
C) velocity of the water at the moment the sediment settled to the bottom.
D) climate conditions at the time of deposition.

Question 17

The majority of the rocks that form at the surface of the Earth are

A) intrusive igneous rocks.
B) foliated metamorphic rocks.
C) sedimentary rocks.
D) non-foliated metamorphic rocks.

Question 18

A shale differs from a mudstone in that it

A) breaks into platy sheets.
B) is compositionally richer in quartz.
C) has smaller grains.
D) has larger grains.

Question 19

Sedimentary rocks are most likely to form

A) near the Earth's surface.
B) in high-temperature conditions.
C) in high-pressure conditions.
D) in the upper mantle.

Question 20

Lithified detritus (breakdown products of preexisting rocks)forms which kind of sedimentary rock?

A) biochemical
B) chemical
C) clastic
D) organic

Question 21

Which of the following is NOT true? Sediments deposited in a beach environment are typically

A) well sorted.
B) medium-grained.
C) composed of angular grains.
D) composed of mostly quartz.

Question 22

Topset,foreset,and bottomset beds are indicative of ________ environments.

A) alluvial fan
B) lake bottom
C) delta
D) deep-marine

Question 23

Cemented shells of marine organisms form which kind of sedimentary rock?

A) biochemical
B) chemical
C) clastic
D) organic

Question 24

If a geologist found preserved mud cracks,he or she could conclude that the environment in which they formed

A) was once covered in wet mud.
B) was once covered by a glacier.
C) has been subjected to a major climate change event.
D) was the site of a mass extinction event.

Question 25

Stratification refers to

A) the development of layering within sedimentary rocks.
B) the act of deposition of sediment that will ultimately form sedimentary rock.
C) physical and chemical alterations,including compaction and cementation,that occur as sediment is transformed into rock.
D) the process of breaking down a source rock into smaller pieces called grains.

Question 26

It is unusual for ________ to carry grains larger than sand.

A) ice in glaciers
B) water in rivers
C) wind
D) water at a seaside beach

Question 27

Geologists call individual layers of sedimentary rocks ________,whereas several of them together are called ________.

A) beds; strata
B) strata; beds
C) laminations; graded beds
D) graded beds; laminations

Question 28

When graded beds are observed in a rock outcrop,this tells geologists that a

A) turbidity current deposited these beds,depositing finer material first.
B) turbidity current deposited these beds,depositing coarser material first.
C) slurry deposited these beds with little sorting.
D) glacier deposited these beds,depositing coarser material first.

Question 29

What type of sediment is typically found in lake bottoms?

A) gravel
B) sand
C) silt
D) clay/mud

Question 30

Thick accumulations of sediments and fossils in the deep ocean tend to be ___________-sized because of the low amount of energy in the environment.

A) cobble
B) gravel
C) sand
D) clay

Question 31

Consult the figure below.Here,distinct internal laminations are inclined at an angle to the boundary of the main sedimentary layers.These are termed

A) graded beds.
B) cross beds.
C) horizontal beds.
D) tilted beds.

Question 32

Which environment would most likely produce sedimentary deposits characterized by poorly to moderately sorted,angular to subangular grains that consist of feldspar,quartz,and lithics (rock fragments)?

A) river
B) glacier
C) beach
D) alluvial fan

Question 33

Two major sources of energy,coal and oil shale,are considered ________ sedimentary rocks.

A) clastic
B) biochemical
C) organic
D) chemical

Question 34

Large layers of cross-bedded sand can be indicative of a ____________ environment.

A) river
B) desert
C) shallow-marine
D) deep-marine

Question 35

Which environment would most likely produce sedimentary deposits characterized by very well-sorted,very well-rounded grains that are nearly pure quartz?

A) river
B) glacier
C) beach
D) alluvial fan

Question 36

Symmetric ripples form when

A) wind blows in a consistent direction and deposits sediment in an arid climate.
B) water flows in a consistent direction and deposits sediment in layers.
C) water deposits sediment in layers,but the direction of flow periodically changes.
D) a mountain stream reaches a flat basin and sediment is deposited in a fan-shaped pattern.

Question 37

Limestone is most likely formed in which of the following environments?

A) shallow-marine clastic
B) shallow-marine carbonate
C) marine delta
D) deep-marine

Question 38

Which transport medium carries the largest particles?

A) ice in glaciers
B) water in rivers
C) wind
D) water in lakes

Question 39

The image below shows a series of graded beds.How many graded beds are shown?

A) 1
B) 3
C) 6
D) 9

Question 40

The image below shows ancient dunes exposed in Zion National Park in Utah.Using the interpreted portion of the image at the left,what was the dominant wind direction that formed these sedimentary structures?

A) toward the right
B) toward the left
C) toward both the left and right
D) vertical,both up and down

Question 41

Pulling a block of clay apart,resulting in the middle portion thinning and sinking,is an adequate analogy for

A) passive margins and subsidence.
B) foreland basins and diagenesis.
C) rift basins and subsidence.
D) intercontinental basins and diagenesis.

Question 42

Diagenesis refers to

A) the development of layering within sedimentary rocks.
B) the act of deposition of sediment that will determine the characteristics of and,ultimately,form a sedimentary rock.
C) physical and chemical alterations,including compaction and cementation,that occur as sediment is transformed into rock.
D) the natural process of separating sediment by grain size.

Question 43

As compared with metamorphism,diagenesis

A) means exactly the same thing.
B) takes place at lower temperatures and pressures.
C) takes place at higher temperatures and pressures.
D) takes place at greater depths that are well within the mantle.

Question 44

Because the velocity of sediment settling (deposition)is positively related to grain size for waterborne sediments,fluvial deposits are more likely than glacial deposits to

A) be well sorted.
B) include coarse grains,such as cobbles.
C) include fine grains,such as clay.
D) have angular grains.

Question 45

How are a marine transgression and regression different? What happens to the shoreline in each?

Question 46

What are the steps involved in the formation of a clastic sedimentary rock?

Question 47

In which of the following three basin types might you be able to find oil forming and why? Rift basin,passive-margin basin,and foreland basin.

Question 48

Which of the following is true about regressions?

A) They are typically well preserved in the sedimentary record.
B) They occur when the climate warms and continental ice sheets melt.
C) They occur when the land is uplifted by tectonic processes.
D) Coastal environments will migrate landward.

Question 49

Sea level rises locally,and marine sediments are deposited on top of terrestrial sediments during events termed

A) transgressions.
B) regressions.
C) turbidity currents.
D) cross bedding.

Question 50

Notice the turbidity current in the image below.Briefly describe and sketch the deposit that will result.

Question 51

The image below of Death Valley,CA,shows a road that curves around a(n)

A) delta.
B) alluvial fan.
C) turbidite.
D) glacial till.

Question 52

Describe the difference between lithification and diagenesis.

Question 53

Basins that form on the continental side of mountain ranges are called _________ basins.

A) rift
B) passive-margin
C) foreland
D) intracontinental

Question 54

Limestone can be either a biochemical or a chemical sedimentary rock.Explain how both types of limestone are formed.Make sure to describe the environments in which they were formed.

Question 55

A well-sorted sandstone with asymmetric ripples was most likely deposited as sand by a

A) river (far from source).
B) glacier.
C) river (near source).
D) alluvial fan.

Question 56

Which of the three types of rock would you expect to be most abundant at the Earth's surface? Why? How does this relate to how these rocks form?

Question 57

Illustrate a rock formation that is bedded.How might this sequence have formed?

Question 58

Death Valley is currently sinking partly due to the weight of continuously accumulating sediment shed from the mountains that border the valley.What phenomenon is this an example of and what depositional environment is created by the sediment deposition?

A) regression and deltas
B) subsidence and deltas
C) regression and alluvial fans
D) subsidence and alluvial fans

Question 59

What attributes would a clastic sedimentary rock have if it had traveled far from its source and was carried in a current with uniform energy?

Question 60

What is an alluvial fan? How is it different from a marine delta?