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62.14: Wind River Canyon, Wyoming

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    22464
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    ROCK TYPES

    Here are three samples of rock collected at Wind River Canyon, Wyoming. Examine each sample in detail by zooming in and exploring its composition and texture.

    Sample A:

    Sample B:

    Sample C:

    Now answer these interpretive questions:

    Exercise \(\PageIndex{1}\)

    Identify the rock type that makes up each sample:

    A) _________________________________

    B) _________________________________

    C) _________________________________

    Exercise \(\PageIndex{2}\)

    Which of these three rock samples is sedimentary? (answer A, B, or C) _________________________________

    Exercise \(\PageIndex{3}\)

    Which of these three rock samples is metamorphic? (answer A, B, or C) _________________________________

    Exercise \(\PageIndex{4}\)

    Which of these three rock samples is igneous? (answer A, B, or C) _________________________________

    Exercise \(\PageIndex{5}\)

    Is the igneous sample plutonic or volcanic? __________________________________

    Explain how you know: ______________________________

    OUTCROPS

    Now, let’s explore the larger context in which these rocks were collected. We will do this by exploring some outcrops.

    The samples were collected at Wind River Canyon, Wyoming, at these sites:

    Site 1:

    Site 2:

    Now answer these interpretive questions:

    Exercise \(\PageIndex{6}\)

    Site 2 shows all three rock types, but Site 1 only shows two. Which two are present at Site 1? (answer ‘A and B,’ ‘B and C,’ or ‘C and A’) _________________________________

    Exercise \(\PageIndex{7}\)

    Based on the principles of relative dating, which of these three rocks is the oldest? _________________________________

    Cite your rationale (which principle of relative dating you used for your previous answer): _________________________________

    Exercise \(\PageIndex{8}\)

    Based on the principles of relative dating, which of these three rocks is the youngest? _________________________________

    Cite your rationale (which principle of relative dating you used for your previous answer): _________________________________

    Exercise \(\PageIndex{9}\)

    Therefore, what sort of surface divides samples B and C from sample A? ________________________________

    Exercise \(\PageIndex{10}\)

    Sample B includes zircon crystals. Imagine you collected some of these zircons and ran them through a mass spectrometer. The analysis produced a ratio of \(\ce{^{238}U}\) to \(\ce{^{206}Pb}\) of 3:1. How many half-lives have elapsed since the formation of the rock? ____________________________

    Exercise \(\PageIndex{11}\)

    Considering that the half-life of \(\ce{^{238}U}\) is 4.468 billion years, calculate the crystallization age of sample B: _________________________________

    Photograph showing small, disc-like shells of the inarticulate brachiopod Lingulepis. About 12 shells are shown, in various states of preservation. The host rock is a siltstone, and the photo is labeled "Lingulepis sp."

    Exercise \(\PageIndex{12}\)

    Sample A is found to include these fossil specimens: Lingulepis is an inarticulate brachiopod. According to the Paleobiology Database, it has a geologic range from 516.0 to 449.5 Ma. What period(s) is/are included in that range? _______________________________ (Feel free to consult a geologic timescale.)

    Exercise \(\PageIndex{13}\)

    Which of the major North American cratonic sequences was Sample A deposited as part of? _____________________________________

    Exercise \(\PageIndex{14}\)

    Constrain the amount of time missing along the surface you noted in your answer to question #8 above. Record your answer as a minimum and a maximum number of millions of years missing:

    "Between _________________________________ minimum and _____________________________ maximum are missing."

    Please submit your answers to the instructor.


    This page titled 62.14: Wind River Canyon, Wyoming is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Callan Bentley, Karen Layou, Russ Kohrs, Shelley Jaye, Matt Affolter, and Brian Ricketts (VIVA, the Virginia Library Consortium) via source content that was edited to the style and standards of the LibreTexts platform.