Deck 7: Sediment and Sedimentary Rocks

Question 1

What are some of the characteristics of sedimentary rocks that are used in determining the depositional environment represented by a facies?

Answer 1

fossils/sedimentary textures/geometry of the facies/sedimentary structures

Question 2

Briefly explain how coal forms.

Answer 2

Coal forms from the accumulation of generations of dead plants in a swamp.The plants never decay fully because there is no oxygen for the decomposers to use.As the plants are buried by sediments and other plants,they are lithified and become coal.

Question 3

Explain how fossils,and especially microfossils,can be used to help determine ancient depositional environments.

Answer 3

Marine versus terrestrial organisms are relatively easy to distinguish,based on a comparison with their living counterparts.Strong invertebrate shells usually indicate a high energy environment,such as the intertidal zone; deep sea fossils are microscopic and fragile.Marine microfossils are particularly important because so many can be retrieved in a single core sample.Coral reef deposits are bounded in depth,as well as latitude,and are always marine.

Question 4

Under what conditions do carbonates form?

Question 5

What makes up a chemical sediment?

Question 6

What two sedimentary structures can be useful in determining paleocurrent directions?

Question 7

How are oil and gas trapped in rock strata? What are these traps called?

Question 8

What is an example of an evaporite sedimentary rock?

Question 9

Under what conditions does coal form?

Question 10

What are some examples of sedimentary structures?

Question 11

What are sedimentary facies?

Question 12

What can mud cracks tell us if we find them preserved in ancient rocks?

Question 13

Explain why understanding the depositional environments of sedimentary rocks are sometimes economically important.

Question 14

How do detrital sedimentary rocks differ from chemical sedimentary rocks?

Question 15

What are the two most common cements in sedimentary rocks?

Question 16

How does graded bedding form?

Question 17

Briefly explain why the study of sedimentary environments is important in the study of historical geology.

Question 18

What are the four major types of coal,and which is the most valuable?

Question 19

What are some ways in which fossils are useful?

Question 20

Briefly explain how dolostone is formed.

Question 21

Describe how compaction lithifies sediments.

Question 22

Rock units with sheet-like geometry were most likely deposited during marine ____________________ or ____________________.

Question 23

A vertical sequence of a(n)____________________ facies records the landward advance of the sea.

Question 24

The designation of sediment grain size,from largest to smallest,is _______,_______,_______,_______.

Question 25

____________________ ripple marks form in response to wind or water moving in one direction.

Question 26

Sedimentary deposits formed by wind tend to be very ____________________ sorted.

Question 27

What are the requirements for a rock body to serve as a reservoir rock for hydrocarbons?

Question 28

Is banded iron formation a chemical or detrital sedimentary rock? Explain.

Question 29

The basis for classifying detrital sediments and their rocks is ____________________.

Question 30

The steam channel,floodplain,lake,beach or deep seafloor where a sediment is laid down is known as its _______ _______.

Question 31

The two major types of sediments that may become sedimentary rocks are ____________________ and ____________________.

Question 32

What are three ways in which hydrocarbons can be trapped in reservoir rock?

Question 33

____________________form when layers are deposited at an angle to the surface and the layers dip in direction of ____________________.

Question 34

A vertical sequence of a(n)____________________ facies shows an offshore facies superposed on nearshore facies.

Question 35

A sedimentary rock with gravel-sized particles that are angular is a _______; a sedimentary rock with rounded particles is a _______.

Question 36

Sediment becomes sedimentary rock by the process known as _______.

Question 37

All detrital sedimentary rocks have a _______ texture.

Question 38

A vertical sequence of regressive facies shows _______ facies superposed on _______ facies.

Question 39

Two processes that can create a rock from sediment are _______,in which grains are squeezed and water is lost,and _______ in which material is precipitated in pore spaces and binds grains together.

Question 40

What is a fossil?

Question 41

What are the properties used to describe detrital sediment?

A) size
B) sorting
C) rounding
D) size and rounding
E) All of these

Question 42

What does poorly-sorted sediment have?

A) no sharp edges
B) restricted size range
C) only particles larger than sand
D) great size variation
E) only particles smaller than sand

Question 43

A vertical sequence of transgressive facies shows an offshore facies,superposed on nearshore facies.

Question 44

In a marine environment,the largest sediments are found ____.

A) just offshore because the largest sediments come from the continents
B) in the deep sea because the largest sediments fall down from the sea surface
C) in the deep sea because the largest sediments come out from continents
D) in the deep sea because the largest sediments are brought out by glaciers
E) nowhere; there are no large sediments in the ocean basins

Question 45

A rock composed almost entirely of fragmented seashells is called

A) coquina.
B) ooid.
C) limestone.
D) carbonate.

Question 46

If all of the grains in a sedimentary rock are about the same size,shape,and composition,what can the rock can be characterized as?

A) cemented
B) compacted
C) cross bedded
D) graded
E) well-sorted

Question 47

Graded bedding forms when ____.

A) erosion planes off a portion of the sea bottom
B) sediment is deposited on a steep slope or grade
C) turbidity currents deposit first coarse sediment then fine sediment
D) cross-bedding is truncated
E) turbidity currents deposit first fine sediment followed by coarse sediment

Question 48

If all the grains in a sedimentary rock are about the same size,the rock can be characterized as ____.

A) poorly sorted
B) well-sorted
C) compacted
D) poorly graded
E) cemented

Question 49

Wind blown deposits tend to be very well sorted.

Question 50

Sedimentary rocks can undergo lithification by

A) compaction
B) cementation
C) dissolution
D) compaction and cementation

Question 51

Any mass of material that can be easily separated from the enclosing rock is a

A) primary sedimentary structure.
B) septaria.
C) geode.
D) concretion.

Question 52

Chemical sedimentary rocks generally have an interlocking grain texture called what?

A) clastic
B) porphyritic
C) particulate
D) crystalline
E) detrital

Question 53

A detrital rock that is made mostly made of quartz sand is called arkose.

Question 54

Chert is hard rock consisting of microscopic crystals of silica that was shaped into sharp cutting tools by early humans.

Question 55

A vertical sequence of transgressive and regressive facies records the rise and fall of sea level.

Question 56

Sediments are classified as ____.

A) detrital, clastic, and chemical
B) detrital and clastic
C) detrital and chemical
D) particulate and crystalline
E) organic, particulate, and crystalline

Question 57

Hydrocarbons are formed largely from what?

A) the remains of dinosaurs
B) any type of fossil
C) microorganisms like algae
D) the same types of plants which form coal deposits
E) marine invertebrate animals

Question 58

Sedimentary structures refer to what?

A) sedimentary rock folded and faulted after lithification
B) features that form as a result of physical or biological processes operating in the depositional environment
C) only layering in sedimentary rocks
D) only grain size and textural features in sedimentary rocks
E) none of these

Question 59

Which coal contains the most carbon and is the hottest burning?

A) lignite
B) anthracite
C) bituminous
D) peat
E) subbituminous

Question 60

What is the most common and effective agent for transporting sediment?

A) wind
B) waves and currents
C) glaciers
D) storms
E) running water

Question 61

Cross-beds indicate that current flow changed direction and that the new direction flows across the old direction at an angle.

Question 62

Current flow direction can be determined by cross-beds and ripple marks.

Question 63

Sedimentary layers in which grain size decreases from bottom to top are called graded beds.

Question 64

Glacial deposits tend to be well sorted.

Question 65

The United States is the world's largest producer and exporter of uranium.

Question 66

Fossil "shoe prints" are evidence that humans and dinosaurs coexisted.

Question 67

Graded beds refer to sedimentary beds that show an increase in grain size from bottom to top.

Question 68

The uranium used in nuclear reactors comes largely from precipitated deposits in rocks such as black shale containing abundant organic matter.