Name __________________________________________ Chapter 7 Investigation Worksheet To complete this worksheet, see the instructions in the textbook (Chapter 7 Investigation). You can print this out in black and white. Table 1. Observations and Characteristics of Sedimentary Layers The two photographs below show the upper and lower parts of a sequence of layers. Try to identify boundaries between different sedimentary rock units, and draw a dashed line on the photograph along any main boundary. Write some observations of the scenery and some possible interpretations about how resistant each main rock unit is to erosion. Observations and interpretations: Observations and interpretations: Chapter 7 Investigation Worksheet; page 2 Table 2: Interpreting the Sedimentary History from a Stratigraphic Section Using both the stratigraphic section and the cross section located in the textbook (Chapter 7 Investigation), determine the environment of deposition and list supporting evidence for that environment. Then, answer the questions below this table. Rock Unit Upper sandstone and mudstone unit Environment of Deposition and Observations to Support Your Chosen Environment Dark gray shale Yellowish-tan sandstone Lower basal conglomerate Question 1: What is the oldest environment represented by this rock sequence? ___________________________________________ Question 2: Does the change of environment from the base of the section up to the thick gray shale indicate an advance (transgression) or retreat (regression) of the sea? Explain the reasons for your answer. ______________________________________ ___________________________________________________________________________________________________________ ___________________________________________________________________________________________________________ Question 3: Does the change from the thick gray shale to the overlying sandstone indicate a transgression or a regression? Explain your answer. ________________________________________________________________________________________________ ___________________________________________________________________________________________________________ Question 4: Which of the following phrases summarizes the history of the entire sequence: (a) a transgression, (b) a regression, (c) a transgression following by a regression, or (d) a regression followed by a transgression? (circle your answer) Question 5: Compare this sedimentary sequence to the one exposed west of Denver (in the previous two-page spread). What names from the Denver area would you apply to the lowest unit and to the overlying yellowish-tan sandstone in this plateau? Lowest unit: _____________________________________________ Yellowish-tan sandstone: ___________________________________