Question

The cross section below represents large boulders made of granite, gneiss, and quartzite that are found lying on limestone bedrock near Oswego, New York.



If no overturning of bedrock has occurred, which statement correctly explains the source of boulders?

A)The limestone was changed by contact metamorphism caused by a lava flow

B)The limestone bedrock formed under conditions of heat and pressure

C)Older igneous and metamorphic bedrock that once covered the limestone eroded away, forming the boulders

D)The boulders were transported and deposited on the limestone bedrock by a glacier

Answer 1

Answer:

D)The boulders were transported and deposited on the limestone bedrock by a glacier

Explanation:

Most rock boulders especially of this type can be interpreted to have been transported and deposited in this location.

It is the most geologic explanation for the occurrence of the boulders here.

• Boulders according to the udden-wentworth's scale have the largest particle size of all sediments known.
• The term boulder is used relatively for sedimentary rocks as well as for large chunks of any rock type.

Now that we know what a boulder is, let us delve into the nature of rock type it is.

The boulders here metamorphic and igneous rock types

• If contact metamorphism had occurred, the rock on top would have been marble.
• Limestone is a sedimentary rock that is metamorphosed to marble.
• The boulders are extraneous to the underlining lithology.
• There is no relationship between them.
• Therefore, only glaciers are capable of moving such random materials of that size from one place to another.