Bedrock type and age

One Geology Bedrock Data

Name – Mesozoic sedimentary rocks  (83 Ma – 66 Ma)

Details – Maastrichtian – Campanian sedimentary rocks

Age (max – min) – Campanian – Maastrichtian

Description – Sedimentary rocks

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Data Assessment

Age Assessment

My sample was collected in my parents flower bed, but it was originally found in a rock pile at the edge of one of the fields we farm. Since it was found in a collection of loose sediment far from bedrock, there is no way to know for sure my sample is from the Campanian-Maastrichtian era.

Rock Type Assessment

I saw many different types of rocks in our flower bed while looking for my sample, but OneGeology only shows sedimentary rocks by the areas around rivercourse. Because of this information, I can not say for certain that my sample is a sedimentary rock.

Plate Tectonic Setting

My sample was collected from the North American Plate. The sample site is not near a plate boundary. It is part of a shield. The sample location is marked with red circles in the maps in figure 2-1 below.

Figure 2-1. Location of Rivercourse-MA1520-1 on maps showing the tectonic setting. The sample is from a shield, and not near a plate boundary. Plotted by Brynn Gabrielson on maps provided in course materials.

Assessment of Plate Tectonic Setting

I could not find information on Rivercourse because it is so small, so I chose a few places nearby.

Source one

“In the Lloydminster area the lower and middle Mannville strata are dominantly quartzose whereas the upper Mannville contains both quartzose and lithic feldspathic sandstones. To the north of the study area all rocks above the quartzose lower Mannville are lithic feldspathic. Lloydminster area sandstones were derived from sedimentary, metamorphic and igneous terrains located to the south, east and west, whereas post – lower Mannville sandstones found to the north originated from dominantly metamorphic and igneous terrains located to the west.”

https://pubs.geoscienceworld.org/cspg/bcpg/article-abstract/30/2/81/57311/ASPECTS-OF-THE-PETROLEUM-GEOLOGY-OF-THE?redirectedFrom=PDF

Source two

“Rocks in Alberta are part of what is known as the Western Canadian Sedimentary Basin, a massive package of sedimentary rocks nestled to the west of the Canadian Shield. Generally, both shallow marine and low-land terrestrial deposits have the best rock records, as eroded rock material tends to get swept easily into these environments, creating the perfect conditions for fossil formation. For example, during the time of the dinosaurs (Mesozoic), the Rocky Mountains were forming, meaning all of the rocks on the western side of Alberta were getting pushed up, while at the same time experiencing erosion that carried all of that sedimentary material down and towards the east, where there was a shallow seaway called the Western Interior Seaway that acted as a giant catch basin for all of that material.”

https://timescavengers.blog/2020/04/22/fossils-of-alberta/

Source three

The Precambrian Canadian Shield consists of very old, resistant rocks that range in age from 570 million to more than 3 billion years old. The rocks of the Canadian Shield consist of crystalline igneous, sedimentary and metamorphic rocks that have had a complex history of volcanic eruptions, mountain building, faulting, deformation, burial, uplift, weathering and erosion.

These rocks were deposited in large sedimentary basins during long periods of sedimentation that also saw the development of life forms from simple algae through primitive marine invertebrates to dinosaurs and mammals.

https://www.mndm.gov.on.ca/en/mines-and-minerals/geoscience/bedrock-geology

Summary

Rivercourse is far from any plate boundaries, and is part of a shield. Sedimentary rocks are not the only rocks found near Rivercourse.

Deformations

Observations

My sample is showing patterns of breaking as shown in figure 2-2. This can be caused by pressure release or physical weathering. The breakage suggests that pressure was applied slowly instead of rapidly. I believe that it was likely brittle deformation that took place on my rock.

Figure 2-2. Rivercourse-MA1520-1 shows breakage on the whole top of the sample. Photo by Brynn Gabrielson.

Figure 2-3. Rivercourse-MA1520-1 shows a pair of lines that look like they are parallel to each other. (In green) Half of my sample also shows a different view of the breakage. Photo taken by Brynn Gabrielson

 

Conclusions

Based on the discoveries I have found while looking at my sample for any flaws, I have come to the conclusion that my sample has been deformed. The deformation was caused by slow pressure applied to my rock, which made the breakage. The deformation I found on my sample is consistent in the location of its plate tectonic settings.

Part 2 – Peer Review Results

“I would suggest also putting the age in numerical years for Campanian-Maastrichtian (Max – Min.)” (Updated the OneGeology Bedrock Data.)

“I would like to see a bit more description about the features of the sample.” (Updated the description of features).

“The conclusion needs to elaborate on what caused the deformation.” (Updated the conclusion).