1. What type of contact is between the Ridpath Sandstone and the Kavalier Shale?
ID: 293302 • Letter: 1
Question
1. What type of contact is between the Ridpath Sandstone and the Kavalier Shale? How did you determine this? (Refer to the Geologic Time Scale, which is Figure 1 in the Geologic Dating lab, to help you.)
2. The Gem Fault dips 45 degrees southeast. What kind of fault is this? Explain your reasoning. (Refer to the Geologic Time Scale, which is Figure 1 in the Geologic Dating lab, to help you.)
3. The Stohr Fault is vertical (90° dip). What kind of fault is it? Explain your reasoning.
4. Which fault is older: the Stohr Fault or the Gem fault? How can you tell? (Refer to the Geologic Time Scale, which is Figure 1 in the Geologic Dating lab, to help you.)
5. Describe the geologic history of this area (list from youngest to oldest). Include all depositional events (the deposition of the rock formations), development of unconformities, and faulting.
10. (youngest):
9.
8.
7.
6.
5.
4.
3.
2.
1. (oldest):
Map 2 (Figure 12)
1. What is the oldest geologic unit present on the map? (Refer to the Geologic Time Scale, which is Figure 1 in the Geologic Dating lab, to help you.) What type of rock is it? When was it deposited?
2. What does the dashed line in the northwest corner of the map represent? Refer to Figure 10 in this lab to help you.
3. What does the pink line in the southeast corner of the map represent? How do you know?
4. Are there any unconformities on this map? If so, what geologic units border them, and what time span(s) do they cover?
5. The topography of almost every region reflects an adjustment between the dominant surficial processes and the underlying lithology. Knowing this, describe the outcrop pattern of the Morrison Formation compared to the Plainview sandstone Member (Hint: look at the spacing of the contour lines). What do you think controls the way these two rock bodies appear in outcrop?
Explanation / Answer
The contact between Ridpath Sandstone and Kavalier Shale is an unconformity as it indicates a gap in the deposition, i.e from Cambrian to Devonian.
The Gem is a normal fault as it allowed younger sediments during Jurassic, Triassic, and Permian to deposit in a valley-type setting.
The Stohr fault is a vertical dip-slip fault as the beds on either side of the fault don't show any displacement on the map.
The Gem fault is older than Stohr fault as the latter vertically displaced the Jurassic Adams Sandstone. Since faults are always younger than the rock they cut, the Stohr fault is younger.
Geological History:
10. Tertiary Duncan Basalt
9. Stohr Fault
8. Jurassic Adams Sandstone
7. Jurassic Yamoto Sandstone
6. Permian Austen Siltstone
5. Gem Fault
4. Carboniferous Erving Limestone
3. Devonian Kavalier Shale
2. Unconformity
1. Cambrian Ridpath Sandstone
Map2
1. Oldest geological unit us Lyons Sandstone belonging to Lower Permian.
2. In the northwest corner of the map, the dashed line represents a stream as evident by the V-shape of contours.
3. The pink line in the southeast corner of the map represents a syncline as there is a repetition of beds on either side of the Plainview Sandstone.
4. There is an unconformity which is bordered by Qc, PII, PIf, Piu and Pfy units, indicating that there was a gap in sedimentation from Quartenary to Lower Permian, covering a time span of about 298 million years.
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