A wacke is a poorly sorted sandstone with a high content of matrix, which is typically made up of clay minerals, but can also contain other materials such as volcanic ash or calcite. The sand grains are usually angular and immature, meaning they have not been transported very far from their source. Choice B describes such a rock.

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What Is a Wacke

Question 47

Multiple Choice

What is a wacke?

A) a limestone with abundant, sand-sized, quartz grains
B) a sandstone with immature lithic sand grains embedded in a clay-rich matrix
C) a dark-grey, calcite-rich mudstone or shale containing pyrite
D) a dark, organic-rich, chemical sedimentary rock containing small crystals of halite

Correct Answer: