Field Assignment
At the Bighorn Mountains
Wyoming

Stephanie WrennGeo. 103Prof. Lawler26 July, 2012

Table of Contents

Map of area traveled

Shell Falls: Big Horn Mountains, Wyoming. Visited July 7th, 2012

Amsden Formation, Dayton, Wyoming. Visited July 14th, 2012

Syncline Fault, Dayton, Wyoming. Visited July 14th, 2012

Goose Egg Formation, Dayton, Wyoming. Visited July 14th, 2012

Leopardite Rock, Big Horn Mountains, Wyoming. Visited July 21st, 2012

Pink Flower, Big Horn Mountains, Wyoming. Visited July 21st, 2012

Elk, Big Horn Mountains, Wyoming. Seen July 22nd, 2012

How the area changed over time

Works cited

Map of area traveled

Shell Falls

The rock shown is a 2.9 Billion year old Mesoarchean granite (James, 479).

It has been cut out over the years to form a natural water fall.

The Shell Falls are an example of a very rare pre-cambrian crust that has not been overlayed by other sediment. Most rocks this old have been covered deep below the rising marine layer. With these rocks still uncovered, it shows that either the mountain range could have started to rise before many others, or that their was an early cut that diverted the water away from them (Wyckoff, 113).

Amsden Formation

This formation was discovered after a road cut was made.

The exposed rock is from the Pennsylvanian Period, 280-325 Million years old

The formation originated from carbonate-shale-sandstone that was carried over when the sea encroached through Northeastern Wyoming during that period. (Sandro, A1, A2)

Syncline Fault

The Syncline Fault is apart of the Amsden Formation, it resides at the tail end of the road cut.

The fault is shown as a Syncline Fault by the way it curves down in a U shape. (James, 237)

The fold on this Syncline Fault was from a compression where two plate boundaries met. (James, 238)

Goose Egg Formation

This formation was formed in the Triassic- Permian Period, 205- 290 Million years ago.

The primary rock type is red sandstone and siltstone, and it also has: white gypsum, halite, dolmite and limestone. (Schweitzer, no page number)

The formation came into the area from a large evaporite basin when a thin marine layer came in through Idaho and Utah during that period. (Miller, 11)

The Goose Egg Formation's age was easily distinguished because of the abundance of fauna. Also, it is a very noticeable and uncommon occurrence in the area. Basically, the area did not see much water during that period when the marine layer rose. (Miller, 4)

Leopard Rock

The Leopard Rock was found in an old quarry that used them for decorative fireplaces. They are a very remote rock. Many other rocks are nicknamed Leopard rocks for their spots. However this is an actually Leopardite rock which is rare in these mountain ranges. They are Diabase, porphyritic, or porphyritic dolerite with a white subhedral plagioclase phenocrysts. This means they have quartz dolerite inside an igneous rock or landmass ( Leopardite, no page number).

Pink Flower

This Western Germander with beautiful purplish rose petals is caught in bloom at 9000 feet elevation. The genus it belongs to is Teucrium candense and the species is Lupinus argenteus. (Jensen, 142)

This high elevation plant can not simply choose where to grow, the strict habitat is primarily made up of debris and rocks, and have to contend with other species for their spot. (Huxley, 14)

These plants can be described as very strong in order to have germenated so high up and to have been able to survive underneath heavy snow loads. (Huxley, 15)

Elk

Elk Continued

While camping at the Tie Flume campground I overheard a low growl which sounded like a moose. As I started up towards the sound with my party the woods became thick so we retreated back and I almost gave up on the task of finding an animal for my project. However, as luck would have it, a elk cow with her calf walked right behind our campsite. I also saw the beautiful six point bull in the distant laying down, but was unable to gather enough nerve to venture for a photo.

This majestic creature is of the Cervidae family, and one of the largest in the deer family, just under the moose. Their fossil records indicate they have survived since the Miocene period, 25 million years ago. They first originated on the continent Eurasia, but were able to cross into North America when the Baltic was frozen over. (Lapinski, 123)

They have survived for so long by keeping a yearly rutting season in the same area where bulls compete to breed with the cows. They also are very adaptable, but prefer to be away from humans. (Clark, 250)

How the area changed over time

Sedimentary rocks have been making their way into the folded mountains of the Big Horns by marine intrusions as previously mentioned in the first few formations. That is how the Big Horns have gained an exciting array of rocks. These mountain ranges are proven to have rock formations from the Archean period, like Shell Falls, which constitutes them as being from the Laurasia super continent (Monroe, 236). The Big Horns are a folded Mountain range which means a part of the crust folded down which plunged the Lithosphere deep into the Asthenosphere causing steep mountain ranges (Wyckoff, 197). Also, they have contained a water gap which allowed water to come in through a cut (Wyckoff, 113). When the marine layer hightened it would settle on what used to be a foothill, but what was soon folding to become a mountain range. It is interesting to see that during different periods, a different sedimentary rock would settle making a unique formation. This settling came during the time when the mountain range was beginning to grow, so you can see that the older formations, 500 million years old, are now at the top of the mountain, and the younger formations, 200 million years old, are at the base.

Works Cited

Clark, Tim W., and Mark R. Stromberg. Mammals in Wyoming. Lawrence,Ks: University Press of Kansas, 1987. 250. Print.

Huxley, Anthony. Mountain Flowers in color. New York: The Macmillian Co, 1968. 14-15. Print.

Lane, Donald W. The Phosphora and Goose Egg Formations in Wyoming. Laramie, Wy: State of Wyoming Geological Survey, 1973. 4-11. WYGS. Web. 21 July 2012. .

Lapinski, Mike. The Elk Mystique. Stevensville, Mo: Stoneydale Press, 1998. 123. Print.

Leopardite and Leopard Rock. Ed. R V. Dietrich. Central Michigan University, 24 June 2005. Web. 18 July 2012. .

Jensen, Earl R. Flowers of Wyoming's Big Horn Mountains. First ed. Basin, Wy: Basin Republican Rustler Printing, 1987. 147. Print.

Monroe, James S., and Reed Wicander. Historical Geology: Evolution of the Earth and Life through time. San Francisco: West Publishing, 1989. 236. Print.

Monroe, James S., and Reed Wicander. The Changing Earth: Exploring Geology and Evolution. sixth ed. Belmont, Ca: Brooks/Cole, 2012, 2009. 237, 238, 479, Print.

Sandro, William J., Mackenzie Gordon, and Thomas J. Dutro. Stratigraphy and geologic history of the Amsden Formation (Mississippian and Pennsylvanian) of Wyoming. N.p.: U.S. Department of the interior, 1975. A1-A2. Geological Survey Professional Paper. Web. 19 July 2012. http://books.google.com/books?id=VVNCAAAAIAAJ&printsec=frontcover#v=onepage&q&f=false.

Schweitzer, Peter. Mineral Resources, Chugwater and Goose Egg Formations. USGS, 2012, 2009. Web. 19 July 2012. .

Wyckoff, Jerome. Reading the Earth: Landforms in the Making. New Jersey: World Color Press, 1999. 113-97. Print.

Column 1Column 2Column 3

Row 19.13.24.54

Row 22.48.89.65

Row 33.11.53.7

Row 44.39.026.2