Page 249 - Laboratory Manual in Physical Geology
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ACTIVIT Y 8.3 Use Index Fossils to Date Rocks and Events
Name: ______________________________________ Course/Section: ______________________ Date: ___________
A. Analyze this fossiliferous rock from New York.
1. What index fossils from FIGURE 8.10 are present?
2. Based on the overlap of range zones for these index fossils what is the
relative age of the rock (expressed as the early, middle, or late part of one or
more periods of time)?
A
3. Using FIGURE 8.10 , what is the absolute age of the rock in Ma (millions of
years old/ago), as a range from oldest to youngest?
B. Analyze this fossiliferous sand from Delaware.
1. What index fossils from FIGURE 8.10 are present? 1
2. Based on the overlap of range zones for these index fossils what is the
relative age of the rock (expressed as the early, middle, or late part of one or
more periods of time)?
B
3. Using FIGURE 8.10 , what is the absolute age of the rock in Ma (millions of
years old/ago), as a range from oldest to youngest?
C. Analyze this fossiliferous rock from Ohio.
1. What index fossils from FIGURE 8.10 are present? 1 /3
2. Based on the overlap of range zones for these index fossils, what is the
relative age of the rock (expressed as the early, middle, or late part of one or
more periods of time)?
3. Using FIGURE 8.10 , what is the absolute age of the rock in Ma (millions of
years old/ago), as a range from oldest to youngest?
C
D. Using FIGURE 8.10 , re-evaluate the geologic cross section in FIGURE 8.2 based
on its fossils.
1. Which one of the contacts (surfaces)
between lettered layers is a disconformity?____________ 1
2. A system is the rock/sediment deposited during a period of time. What
system of rock is completely missing at the disconformity?
3. What amount of absolute time in m.y. (millions of years) is missing at the disconformity? ____________ m.y.
E. REFLECT & DISCUSS What geologic event occurred during the Mesozoic Era in the region where FIGURE 8.4
is located? Explain.
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