51 Utah

Elizabeth Johnson

Geologic map of the Pine Grove-Blawn Mountain area, Beaver County, Utah.

Figure 10. Geologic map of the Pine Grove-Blawn Mountain area, Beaver County, Utah: U.S. Geological Survey, Miscellaneous Investigations Series Map I-1479, scale 1:24,000.

Use this link to zoom in and pan around the map: https://ngmdb.usgs.gov/ngm-bin/pdp/zui_viewer.pl?id=426

Figure 11. Geologic cross sections of the Pine Grove-Blawn Mountain area, Beaver County, Utah: U.S. Geological Survey, Miscellaneous Investigations Series Map I-1479, scale 1:24,000.

Use this link to zoom in and pan around the cross-sections, which also includes detailed descriptions of the rock units: https://ngmdb.usgs.gov/ngm-bin/pdp/zui_viewer.pl?id=427

This is the link to the page for the Geologic map of the Pine Grove-Blawn Mountain area, Beaver County, Utah: https://ngmdb.usgs.gov/Prodesc/proddesc_9255.htm

Questions

There is a lot going on in this map!  But we will focus on specific parts for each question.

8. Locate the Wah Wah syncline (left / west side of map) and the Wah Wah thrust fault (center of map).
The Wah Wah syncline and thrust fault are indications that this area experienced which type of plate tectonic force in the past?

  • Compression
  • Tension
  • Shear

 

Now locate this fault on the map and cross-section (tan arrows point to the fault – we will call it the “tan arrow fault”):

Figure 12. Close-up of fault on map and in cross-sections A-A’ and B-B’.

 

9. Rock unit Pc is _______ than rock unit Tel. Hint: use the map key.

  • younger than
  • older than

 

10. Cross-section B-B’ shows that the Tel side of the “tan arrow” fault is the hanging wall.  Given your answer above, and the information in B-B’, what type of fault is this? (Hints: look at the cross-section and Faults)

  • Normal
  • Thrust (reverse)
  • Strike-slip

 

11. Cross-section A-A’ shows the intersection of the Wah Wah thrust fault (below the brown Zcc unit) and the “tan arrow” fault.  Based upon Principles of Relative Dating, which fault happened last?

  • Wah Wah Thrust
  • Tan Arrow Fault

 

12. The Tan Arrow Fault (and many other faults in the area of the same type) indicate that this area experienced which type of plate tectonic force?

  • Compression
  • Tension
  • Shear

 

Want to know more? This area of Utah is part of the Basin and Range Province.

The connection between the San Andreas and the Basin and Range is illustrated in this video: (watch from the beginning to 4:07 minutes): https://youtu.be/2TSTVCIZ-dg 

The connection between the San Andreas fault system and the Basin and Range is described in detail in this page: https://opengeology.org/historicalgeology/san-andreas-fault-and-basin-and-range/ 

 

 

 

 

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Physical Geology Laboratory by Elizabeth Johnson is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License, except where otherwise noted.

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