Question

base your answer to questions 20 through 22 on the cross section below, which shows rock units a through e that have not been overturned.

1. state the diameter of a particle normally found in rock unit b.
2. identify one metamorphic rock that may be found along the boundary between rock units c and e.
3. identify two processes that formed rock unit a from sediment.

Explanation:

1. Rock unit B is a fine-grained sedimentary rock (like shale or siltstone), so its typical particle diameter is very small, in the range of clay or fine silt sizes.
2. Along the contact between igneous rock C and sedimentary rock E, contact metamorphism forms a common metamorphic rock.
3. Rock unit A is a clastic sedimentary rock, formed from sediments through compaction (pressing grains together) and cementation (binding grains with minerals).

Answer:

1. The diameter of a particle in rock unit B is typically between 0.0004 cm and 0.006 cm (or less than 0.006 cm, consistent with fine silt/clay-sized particles).
2. Hornfels (a common contact metamorphic rock formed in this setting)
3. 1. Compaction
4. Cementation