Name
Date
Biostratigraphy and Sea Level Change
The objectives of this lab are to:
o Use the fossil guide book and lab manual to look up information about fossils.
o Gain a better understanding of ways in which geologists use fossils to determine the age of sedimentary
rocks.
o Use geologic range and absolute age data to determine the age of rocks.
o Create a chronostratigraphy (label the rock units with their absolute ages) for last week’s Folly Beach
correlation.
Exercise 1: Geologic Range
Materials:
o
o
o
o
Geologic range / dated age table – Table 1
Geologic range / dated age graph – Figure 1
Lab manual – chapters 2, 6, and 7
Fossil guide book
Instructions:
Using the geologic ranges and/or absolute ages of the fossils shown in Table 1, plot the age “range”* of the
fossils on Figure 1. Refer to your fossil book and lab manual to become more familiar with these fossils, as
they are the same ones that will appear in the core data (Exercise 2). Some geologic ranges in Table 1 may
not be identical to those listed in the field book or the lab manual.
Background:
The fossils listed in Table 1 have been found in the sediment beneath Folly Beach, for which you created a
cross section in lab last week. The fossils have either:
o A Radiometrically Dated Absolute Age (columns 3 and 4 in Table 1):
o
When a fossil is dated using radiometric dating techniques, there is an age range within which
the fossil falls. We are assuming that our fossils have been radiometrically dated in a laboratory
and these are the results.
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OR
o A known geologic range (columns 5 and 6 in Table 1):
o
The span of time in which the species first evolved (First Appearance) to when it went extinct
(Disappearance), obtained by a compilation of fossil record data.
Plot the age data for these fossils on Figure 1. Plot them from oldest to youngest going left to right
across the chart. This figure will then give you a visual image of concurrent fauna, index species, and fossil
assemblages that you can use to date the sediment in the Folly Beach cross section.
Table 1. Specimens and their geologic ranges or absolute age.
Geologic Range
Specimen
(Informal Name)
Specimen
Symbol
Radiometrically Dated
Geologic Range
Absolute Age
First Appearance
Disappearance
Ghost crab
ACDO
Recent (0)
N/A
N/A
Sand dollar
EECM
5,000 - 0 YBP
N/A
N/A
Olive shell
MGNO
10,000 - 0 YBP
N/A
N/A
Mastodon
CMPM
N/A
2.4 MYA
10,000 YBP
Mammoth
CMPE
N/A
5.2 MYA
10,000 YBP
Dire Wolf
CMCC
N/A
1.0 MYA
10,000 YBP
Big Cat
CMCF
N/A
2.5 MYA
10,000 YBP
Giant Beaver
CMRC
N/A
70,000 YBP
10,000 YBP
Horse
CMPEE
N/A
4.0 MYA
0
Scallop
MBOP
50,000 -25,000 YBP
N/A
N/A
Oyster
MBPO
65,000 - 45,000 YBP
N/A
N/A
Shark Tooth
CCCC
45,000 -40,000 YBP
N/A
N/A
Sea Urchin
EECE
75,000 - 55,000 YBP
N/A
N/A
Moon snail
MGMN
100,000 -55,000 - YBP
N/A
N/A
Fan Mussel
MBMP
30,000 -25,000 YBP
N/A
N/A
Homo sapiens
CMPH
30,000 -25,000 YBP
N/A
N/A
Incongruous ark
MBAA
55,000 -25,000 YBP
N/A
N/A
2
0 (today)
Geologic age range in years
CMPE
100,000
Figure 1. Graph of specimens and their geologic ranges or absolute age. Complete the labeling of the Y-axis (years) and
then darken a bar representing each specimen’s geologic range (label them!). Start with the oldest specimen and work
toward the present. The first one is completed for you. Note: Y-axis goes from 100,000 years ago (bottom) to today (top).
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Exercise 2: Biostratigraphy
Materials:
o
o
o
o
o
Pencil
Folly Beach correlation – Figure 2
Geologic range / dated age table – Table 1
Lab manual – chapters 2, 6, and 7, Appendix A
Fossil guide book
Instructions:
Using the fossil samples provided at stations around the room, record in which cores and what depth each
fossil occurs. Use the key for the fossils in Table 1 so that you can write CMPE (for example) in the cross
section at the proper location.
Exercise 3: Chronostratigraphy
Materials:
o
o
o
o
Pencil
Geologic range / dated age table – Table 1
Folly Beach correlation – Figure 2
Lab manual – chapters 2, 6, and 7, Appendix A
Instructions:
Now assign ages to the sediment beneath Folly Beach using your completed fossil data (Figure 2) and age
graph (Figure 1). Using the concepts of index fossils, fossil assemblages, and concurrent fauna, determine
how old the sediment is throughout the depth of the cross section. Then mark the age of the sediment on
the Y-axis of the cross section (on the right hand side). This is one of the main purposes of biostratigraphy
and it will take some time and thought, so be patient.
Use the Biostratigraphy worksheet to help you determine the age range for each layer!
Finally, answer the following questions.
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1. If you find a fossilized ghost crab, what does this tell you about the depositional environment? Hint: think
about where ghost crabs dig their burrows.
2. Sand dollars and sea urchins both belong to which phylum? What are two distinctive characteristics of this
phylum? Note: your fossil guide refers to a “phylum” as a group.
3. The oyster, which lives in the marsh, and the moon shell belong to Phylum Mollusca. Classify them down to
class (include Phylum, Class in your answer). Describe the habitat and life habits of each. Why wouldn’t
you expect to find an oyster and a moon shell in the same rock type?
4. As you are exploring the beach, you find some darkened oyster shells in what appears to be mud with
plants in it. What is mud doing on the beach – isn’t the beach supposed to be sandy? Do oysters live in the
surf zone or nearby? Does this finding give you any clues as to sea level changes? If so, what does it tell
you? Consider Walther’s law in your answer.
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5. What are the criteria that make a good index fossil? Which of the Pleistocene mega fauna is the best index
fossil?
6. Did Homo sapiens and the mammoth coexist? What is your evidence? What implications would this have
for early humans’ diets?
7. If Core A is to the west and Core E is to the east, describe what happens to the cross-bedded sandstone
facies through time using these directions.
8. For Core D, identify the interval(s) where you find a fining-upward sequence (see pg. 102 in lab manual for
explanation of fining-upward). What does this fining-upward sequence indicate?
_
9. For Core D, identify the interval(s) where you find a coarsening-upward sequence (see pg. 102 in lab
manual for explanation of coarsening-upward). What does this coarsening-upward sequence indicate?
10. Given the history of sea level change through time, would you want to invest in ocean front property on Folly
Beach? Why or why not?
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