Description and interpretation of
structural hand specimens.
In addition to developing a toolkit of skills (reasoning, mathematical,
writing, etc.) and a base of technical knowledge (e.g. the geologic
time scale, the definition of strike and slip, etc.), experience
looking at and working with rocks and in the field is crucial
to becoming a geoscientist. It is a fundamental reality check.
This lab intends to give you some experience with describing and
thinking about structures seen in hand specimen. You can get feedback
from your fellow students but when it come time to write up your
results, work on your own.
For each of the 10 specimens do the following.
- Identify the rock type.
- Where appropriate, identify the protolith.
- Describe any primary textures that are preserved.
- Do at least one sketch of the structures evident. The sketch
should be fully labeled as to what structures you are seeing
and have an indication of scale. They do not need to be detailed,
realistic artistic rendition, but can be more schematic (abstracting
out the crucial elements). However, your peers should be able
to connect the sketch with the specimen. Using different colors
can work well, as well as using different thickness or types
of lines, and shading.
- Interpret the structural history and conditions of formation
of the structures. This could include, but would not be limited
to, noting evidence for multiple deformation episodes, noting
evidence for the depth and approximate temperatures of deformation,
and noting evidence for the role of fluids.