Week 5 (7/3-7/9)
Monday-Wednesday: Our last field trip consisted of traveling to Snake Range in Nevada to study a metamorphic core complex on Monday and Tuesday, and going to Great Basin National Park on Wednesday. On Monday we went to Old Man’s Canyon of Snake Range to study both intrusive plutonic rock as well as metamorphosed mylonitic rock which were both a part of the ductile deformation of the metamorphic core complex. We made our way up to the decollement, which separates the ductile and the brittle deformation, while studying the different lithologies and different grades of metamorphism within the rocks as we went. Shear sense indicators were found by studying porphyroclasts, which gave us a better understanding of the stresses that caused the metamorphic core complex to form.
On Tuesday we continued our study of Snake Range by measuring lineations, foliations, joint sets, and faults in order to understand the direction of both ductile and brittle maximum compression and maximum extension. Physically being on a metamorphic core complex is something many professional geologists never get to do. It was an amazing opportunity and learning experience.
On Wednesday we spent time exploring in Great Basin National Park. We first went on a tour of the Lehman Cave in the morning, then had the opportunity to hike various trails before heading back to Ephraim.
The decollement at Snake Range.
Ptygmatic folding seen in metamorphosed rock below the decollement.
Joint fault sets used to understand the direction of stress.
Studying the foliations and lineations of Staurolite Garnet Quartz Mica Schist at Snake Range.
Lehman Cave at Great Basin National Park
3,000-5,000 year old bristlecone pine tree at Great Basin National Park
Rock Glacier at Great Basin National Park.
Thursday (7/6): This was an office day used to work on our structural analysis of Snake Range. We went to the computer lab and entered the data that we collected from lineations, foliations, joint sets, and faults from Snake Range into a stereonet software which helped us to better understand the types of stresses that caused the metamorphic core complex. We found that both the ductile deformation (linations and foliations) and brittle deformation (joint sets and faults) were a result of the same orientation of stress. This meant that both the brittle and ductile deformation were caused by the same event!
Friday-Saturday (7/7-7/8): We started the North Cross Section on Friday morning, and finished our field work on Saturday evening. We had 24 stops total during the two days in the field, so we had to move quickly and efficiently. A lot of ground was covered, with a lot of formations, contacts, and attitudes.
Looking at a formation during a stop of the North Cross Section.
Taking strikes and dips of a formation.
Petroglyph found during North Cross Section.
Sunday (7/9): This was an office day to work on the North Cross Section. With all of the data from the field, plus three well data points, we were given the task of creating a very large and complex cross section. Just like South Cross Section, we had to interpret the data and create a cross section that not only made geologic sense, but also matched the data we were given. Even though this project was very difficult, I found myself enjoying the challenge. I had to try many wrong options before I figured out the correct geology, and I learned that it’s okay to make mistakes because the mistakes were needed for me to figure out the right answer.