Deck 6: Sedimentary Processes, Environments, and Rocks

Question 1

Which of the following statements about dolostone is NOT true?

A) It forms in tropical or semitropical climates in which extensive evaporation of seawater occurs.
B) It is similar to limestone except for the inclusion of magnesium in its chemical composition.
C) A sulfate- consuming bacteria has been shown to be associated with dolomite precipitation.
D) Marine evaporative processes are currently converting extensive areas of limestone to dolostone.

Answer 1

D

Question 2

Which of the following transport media generally results in the most well- sorted sediments?

A) Rivers.
B) Landslides.
C) Wind.
D) Glaciers.

Answer 2

C

Question 3

The term "sedimentary facies" refers to:

A) the geographic location of outcrop surfaces or "faces" of sedimentary rock units.
B) differences in the mineral composition of sedimentary rock units located in the same area.
C) contacts between distinct layers of sedimentary rocks deposited at different times.
D) characteristics that distinguish one sedimentary rock unit from another.

Answer 3

D

Question 4

Which one of the following may reveal the direction of a stream current?

A) Mudcracks.
B) Asymmetrical ripple.
C) Graded bedding.
D) Symmetrical ripple.

Question 5

Sedimentary rocks constitute approximately of the rocks exposed at the Earth's land surface.

A) 50%
B) 75%
C) 20%
D) 5%

Question 6

Processes that affect sedimentary rocks after burial, but before or during lithification, are:

A) sedimentation.
B) metamorphism.
C) erosion.
D) diagenesis.

Question 7

Which process causes an increase in the roundness of sedimentary particles?

A) Abrasion.
B) Sorting.
C) Lithification.
D) Solution.

Question 8

A sandstone containing quartz and feldspar grains in a fine- grained clay matrix is probably a(n):

A) quartzite.
B) graywacke.
C) quartz arenite.
D) arkose.

Question 9

All of the following statements concerning conglomerates and breccias are true EXCEPT:

A) they are coarse grained.
B) their grain shapes indicate relative transport distances.
C) they are chemical sedimentary rocks.
D) they may contain fine matrix material.

Question 10

A thinly layered rock composed of clay- sized particles is a:

A) shale.
B) limestone.
C) siltstone.
D) sandstone.

Question 11

The amount of calcium carbonate dissolved in water is directly proportional to:

A) the number of organisms that have lived in the water.
B) the amount of carbon dioxide dissolved in the water.
C) the depth of the water.
D) the temperature of the water.

Question 12

Which of the following sedimentary structures might indicate that deposition had occurred in a shallow lake during cycles of drought?

A) Cross- bedding.
B) Mudcracks.
C) Graded bedding.
D) Ripple marks.

Question 13

Common cementing agents include all of the following EXCEPT:

A) iron compounds.
B) olivine.
C) silica.
D) calcium carbonate.

Question 14

The main difference between a breccia and a conglomerate is:

A) color.
B) mineral composition.
C) particle shape.
D) particle size.

Question 15

The degree to which sediment particles are rounded depends on all of the following EXCEPT:

A) the amount of time that has elapsed since the particle was attached to the parent rock.
B) the hardness of the minerals.
C) the distance over which particles are carried by a transport medium.
D) the energy of collisions between particles.

Question 16

All of the following were present in ancient environments of dolostone formation EXCEPT:

A) oxygen- rich environments.
B) magnesium ions.
C) sulfate- consuming bacteria.
D) calcium carbonate crystals.

Question 17

Biogenic limestones that represent deep- marine environments are characterized by:

A) sponge skeletons.
B) foraminifera skeletons.
C) radiolaria skeletons.
D) diatom skeletons.

Question 18

In filling the dry Mediterranean salt basin, world ocean levels dropped about:

A) 10 meters.
B) 2000 meters.
C) 100 meters.
D) There was no change in world ocean levels.

Question 19

All of the following statements about cross- bedding are true EXCEPT:

A) cross- bedding is usually formed by deposition of sediments from wind or water.
B) cross- beds form when particles drop from still water.
C) changes in direction of wind or water currents are recognizable within cross- beds.
D) cross- beds are formed when a sedimentary layer is deposited at an angle to the underlying bed.

Question 20

Graded beds are commonly formed by:

A) lateral migration of a sand dune.
B) drying and cracking of mud.
C) particles settling at different rates.
D) small waves or ripples.

Question 21

Which of the following statements about various kinds of limestone is NOT true?

A) Tufa is an inorganic limestone formed when underground water loses carbon dioxide.
B) Chert is an biogenic limestone formed from carbonate secretions of microorganisms.
C) Travertine is a limestone that forms in the interior of caves.
D) Gypsum is a lithified biogenic ooze formed when saltwater evaporates.

Question 22

Sediments are classified as either detrital sediment or chemical sediment on the basis of:

A) particle size.
B) whether they react to chemicals such as hydrochloric acid.
C) the amount of fluid within the sediments.
D) the source of the sediments.

Question 23

Shales containing high amounts of organic matter are typically what color?

A) Orange.
B) Red.
C) Black.
D) Green.

Question 24

Sedimentary rocks are important for all of the following reasons EXCEPT:

A) they contain large amounts of+ groundwater.
B) they contain fossil fuels such as coal, oil, and natural gas.
C) they contain most of our precious gems, such as diamonds and emeralds.
D) they provide information about Earth's ancient environments.

Question 25

A sandstone with more than 25% feldspar and poorly sorted, angular grains is probably a(n):

A) quartz arenite.
B) quartzite.
C) arkose.
D) graywacke.

Question 26

Detrital sediment texture is identified on the basis of:

A) the mineral composition of the particles.
B) the way the sediments clump together in the formation of sedimentary rocks.
C) the relative percentages of each of the three categories of particle sizes.
D) the size, shape, and arrangement of the particles.

Question 27

Oolitic limestone forms as the result of:

A) the precipitation of silica in concentric coats around particles of calcium carbonate.
B) calcium carbonate precipitated as pearls by oysters around invading sand particles.
C) organic secretions of silica around calcium carbonate particles.
D) the precipitation of calcium carbonate in concentric coats around grains of sand.

Question 28

Which of the following statements concerning the formation of coal is NOT true?

A) Organic matter changes from peat, to lignite, to bituminous coal, and finally into anthracite coal.
B) Coal forms from the decomposition of organic matter in the absence of oxygen.
C) Coal is composed primarily of the remains of microorganisms.
D) The environment for deposition of coal is usually a swamp.

Question 29

Sedimentary structures allow a geologist to determine:

A) the age of detrital sediments.
B) the composition of detrital sediments.
C) the depositional environment of detrital sediments.
D) the source of detrital sediments.

Question 30

Which of the following sediment- moving processes is most effective in delivering sediment from the transitional environments to the subduction zone?

A) Turbidity currents.
B) Wind.
C) River currents.
D) Waves, tides, and ocean currents.

Question 31

Continental sedimentary environments are characterized by:

A) biogenic cherts.
B) biogenic limestones.
C) detrital sediments.
D) dolostone deposits.

Question 32

Sedimentary layers, or beds, indicate all of the following EXCEPT:

A) a change in depositional energy between beds.
B) a change in sediment composition between beds.
C) a change in grain size between beds.
D) disturbance of sediments by organisms.

Question 33

Inorganic chemical sedimentary rocks are derived from:

A) the dissolved products of chemical weathering that precipitate from solution.
B) igneous rock exposures.
C) sedimentary rock exposures.
D) metamorphic rock exposures.

Question 34

Sedimentary structures such as graded bedding, cross- bedding, and ripple marks are formed:

A) after lithification.
B) during lithification.
C) during or after deposition, but before lithification.
D) during any of the above stages.

Question 35

Sandstones are classified on the basis of:

A) color.
B) cleavage.
C) mineralogy of sand grains.
D) shape of their constituent particles.

Question 36

Most sediments are:

A) chemical, resulting from organisms that have extracted the materials from water.
B) detrital, composed of solid fragments of other rocks that have undergone mechanical weathering.
C) detrital, resulting from solid particles precipitating from solution in water.
D) chemical, resulting from precipitation from solution in water.

Question 37

A sandstone composed predominantly of quartz is a(n):

A) breccia.
B) quartz arenite.
C) arkose.
D) graywacke.

Question 38

Practical uses of shales include all of the following EXCEPT:

A) a source of energy.
B) clay for bricks and ceramics.
C) a component of cement.
D) a source of water in wells.

Question 39

Which of the following statements does NOT apply to all detrital sedimentary rocks?

A) They are composed of particles that have been cemented together.
B) They possess a clastic texture.
C) They have undergone compaction and recrystallization.
D) They are classified on the basis of their particle sizes.

Question 40

The vertical sequence of preserved sedimentary environments indicating a rising sea level would be:

A) deep marine, shallow marine, beach, river.
B) shallow marine, deep marine, beach, river.
C) river, beach, shallow marine, deep marine.
D) beach, shallow marine, deep marine, river.

Question 41

More than half of all sedimentary rocks are:

A) conglomerate and breccia.
B) mudstone.
C) limestone.
D) sandstone.

Question 42

Discuss the formation and behavior of turbidity currents.

Question 43

How does chert form?

Question 44

What is the difference between diagenesis and lithification?

Question 45

What information is supplied by a study of sediment grain size?

Question 46

How does cross- bedding form?

Question 47

What causes the coloration of sedimentary rocks?

Question 48

Ancient volcanic eruptions in the Caribbean region are recorded in cores of deep- sea muds as:

A) tephra layers.
B) disappearance of marine fossils above a certain level.
C) dust layers of fine clastic sediments.
D) coarse, ice- rafted debris.

Question 49

How do shifting sedimentary facies indicate changing sea level?

Question 50

List three possible environments of deposition for the three types of detrital sedimentary rocks.

Question 51

Describe what is known about the formation of dolostone.

Question 52

How do the particles of detrital sedimentary rocks become cemented together?