1. What are the minimum and maximum sizes of sand grains?
Answer: Sand grains range in size from 1/16 mm to 2 mm.
2. The material that makes up a rock such as conglomerate cannot be deposited by a slow-flowing river. Why?
Answer: Conglomerate cannot be deposited by a slow-flowing river because clasts larger than 2 mm are not
transported by slow-moving water.
3. Describe the two main processes of lithification.
Answer: Sediments are buried beneath other sediments where, because of the increased pressure, they
become compacted and water is forced out from between the grains. With additional burial they
are warmed to the point where cementing minerals can form between the grains (less than 200˚C).
4. What is the difference between a lithic arenite and a lithic wacke?
Answer: Lithic arenite has less than 15% silt- and clay-sized particles, while a lithic wacke has more than
15%. Both have more than 10% rock fragments and more rock fragments than feldspar.
5. How does a feldspathic arenite differ from a quartz arenite?
Answer: Feldspathic arenite has more than 10% feldspar and more feldspar than rock fragments. Quartz
arenite has less than 10% feldspar and less than 10% rock fragments. Both have less than 15% silt
and clay.
6. What can we say about the source area lithology, and the weathering and transportation history of a sandstone that is primarily composed of rounded quartz grains?
Answer: Source area lithology: rock that contains quartz (such as granite or sandstone). Strong weathering
is required to remove feldspar, and long fluvial transportation to round the grains.
7. What is the original source of the carbon that is present within carbonate deposits such as limestone?
Answer: The carbon within carbonate deposits such as limestone ultimately comes from the atmosphere.
8. What long-term environmental change on Earth led to the deposition of banded iron formations?
Answer: Most of Earth’s banded iron formations formed during the initial oxygenation of the atmosphere
between 2.4 and 1.8 Ga because iron that had been soluble in the anoxic oceans became insoluble
in the oxidized oceans.
9. Name two important terrestrial depositional environments and two important marine ones.
Answer: Terrestrial depositional environments: rivers, lakes, deltas, deserts, glaciers. Marine depositional
environments: continental shelves, continental slopes, deep ocean.
10. What is the origin of a foreland basin, and how does it differ from a forearc basin?
Answer: A foreland basin forms in the vicinity of a large range of mountains where the weight of the
mountains depresses the crust on either side. A forearc basin lies between a subduction zone and
the related volcanic arc.
11. Explain the origins of (a) bedding, (b) cross-bedding, (c) graded bedding, and (d) mud cracks.
Answer: (a) Bedding forms where there is an interruption or change in the depositional process, or a change
in the composition of the material being deposited. (b) Cross-bedding forms in fluvial or aeolian
environments where sand-sized sediments are being moved and ripples or dunes are present. (c)
Graded bedding forms when transport energy decreases, depositing finer and finer particles. (d)
Mud cracks form where fine-grained sediments (silt or clay) are allowed to dry.
12. Under what conditions will reverse-graded bedding form?
Answer: Reverse-graded bedding forms during gravity flows, such as debris flows.
13. What are the criteria for the application of a formation name to a series of sedimentary rocks?
Answer: A formation is a series of beds that is distinct from other beds above and below it, and is thick
enough to be shown on the geological maps that are widely used within the area in question.
14. Explain why some of the Nanaimo Group formations have been divided into members, while others have not.
Answer: The Nanaimo Group was actively mined for coal for many decades. During that time the names
were given to members and individual beds that were important to the coal miners.
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