Lecture 8

Question 1

As the distance from source rock increases, so does the degree of what three things (siliciclastic rocks)?

Answer 1

• rounding
• sorting
• maturity

Question 2

Match the following with the types of siliciclastic rocks provided:
gravel, conglomerate, breccia, sand, silt, clay/mud, mudstone

• > 2mm diameter; granules, pebbles, cobbles, boulders
• rounded grains
• angular grains
• 1/16-2 mm diameter; often quartz, sandstone
• 1/256-1/16 mm
• smaller than 1/256 mm
• shale (fissile mudstone)

Answer 2

Gravel: >2 mm diameter, granules, pebbles, cobbles, boulders

Conglomerate: rounded grains
Breccia: angular grains

Sand: 1/16-2 mmd diameter, often quarts, sandstone

Clay/mud: smaller than 1/256 mm

Mudstones: shale (fissile mudstone)

Question 3

What do evaporites form from?

Answer 3

evaporation of seawater

Question 4

What are Anhydrite, Gypsum, and Halite examples of?

Answer 4

Evaporites

Question 5

What are readily formed and readily dissolved?

Answer 5

evaporites

Question 6

What is chert an example of?

Answer 6

chemical sedimentary rock

Question 7

Describe chert.

Answer 7

• extremely small quartz crystals precipitated from watery solutions
• brown, gray, or black (impurities)
• flint

Question 8

What is a biological sedimentary rock?

Answer 8

Any sedimentary rock that is made from biological material (either transported or in place)

Question 9

What are coal and limestones examples of?

Answer 9

biological sedimentary rocks

Question 10

What are carbonates? Ex?

Answer 10

• biological sedimentary rocks

- ex. limestone

Question 11

What is limestone formed from? Where is limestone typically formed?

Answer 11

• often formed from skeletal particles of organisms that secrete calcium carbonate
• typically forms in warm, shallow sea water

Question 12

Where does limestone dissolve easily?

Answer 12

In water and in the presence of acid.

Question 13

What is limestone commonly deposited as?

Answer 13

• fossil reef communities made of corals, sponges, and calcareous algae (fossiliferous limestone0
• accumulations of shelled mollusks (bioclastic limestone)
• accumulations of microscopic organisms with calcareous shells (chalks)

Question 14

What are distinctive arrangements of grains in sedimentary rocks?

Answer 14

sedimentary structures

Question 15

What do sedimentary structures reflect?

Answer 15

modes of deposition

Question 16

Why are sedimentary structures important?

Answer 16

useful tools for interpreting ancient environment of deposition

Question 17

What are ripples formed by?

Answer 17

• structures formed by water or wind

- sediments accumulate downslope (lee)

Question 18

What are the two types of ripples? What distinguishes them?

Answer 18

1) symmetrical –> bidirectional current

2) asymmetrical –> unidirectional current