Fossil Correlation Project
Purpose:
The purpose of this exercise is to provide a means of integrating the concepts you have learned over the
semester by simulating some of the actual work of historical geologists. Both lecture material and laboratory
exercises serve as the foundation for this project. The lectures on Fossilization, Evolution, Relative Time, and
Absolute Time (lectures 3-6) provide the background for the specific depositional settings we have examined
through the semester, as well as their specific maturities. Your knowledge of sea level and climate changes
over time should also be of use. The study area is part of the Table Top Mountains in south-central Arizona.
Therefore, your knowledge of the geographic position and orientation of this part of Laurentia-Laurussia-North
America may prove useful.
You are given three sections containing several formations. The formations have all been described and
measured for you, and a certain fossil assemblage collected from each by your trusty graduate assistant. Your
task is to use faunal assemblages, superposition, and lithologic characteristics to:
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1) determine the age of each formation within a section;
2) arrange the formations stratigraphically;
3) correlate the formations from one section to another, and
4) answer some interpretive questions concerning the geologic history of the study area.
After reading over the entire exercise, follow the steps below. You will need some graph paper, colored
pencils, paper, ruler, your lecture slides and notes, text, and lab manual though you may find some sections
of your product easily convertible to digital composition. Several resources that you may find useful can be
found in the appendices. Step 1 (Fossil Identification) may be done as a group. ALL OTHER SECTIONS,
however, should be done alone and pledged.
Step 1 • Fossil Identification
1.Identify the fossils in each formation of each section. Use your lab manuals, the figures in Appendix A, and
any other supplementary resources you may have. You may work together on this part though each of you
will be compiling your own “field book” to turn in. This should consist of a sketch of the fossil (with scale),
as well as a description of its condition, fossilization process, and any other descriptive characteristic we
have learned this semester. If there are similar genera, I should be able to tell from your descriptions and
drawing(s) of the sample why you chose the classification you did.
2.Make a list of the identified fossils and their ranges for each formation. For example:
Section: Balsam Canyon
Formation: Barstow Shale
Fossil Name
Geologic Periods of Existence
#1 Genus Name
Cambrian - Silurian
#2 Genus Name
Ordovician - Devonian
#3 Genus Name
Silurian - Permian
#4 Genus Name
Silurian
3.Check your results with the lab instructor before going to Step 2.
Step 2 - Construct range charts.
1.Plot the ranges of the fossils you identified in Step 1. Do each formation separately. The one period that all
fossil ranges have in common will define the geologic age of the formation. The figure below shows an
example of what your range charts might look like. A blank copy of the chart used to create the example
can be found in Appendix E, but you are not required to use it.
2.When doing the range chart, make sure you write the genus name of the fossil and clearly indicate the
intersection of their ranges. When you finish this section, you will have a total of 14 range charts.
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Step 3 - Construct a time correlation chart.
1.Construct a time correlation chart based on the geologic period for each formation that you determined in
step 2.
2.Correlate the formations from one section to the other using the method shown in the example below.
Remember, it is an EXAMPLE ONLY. It is not the actual correlation chart, although yours should resemble
it. A blank copy of this chart may also be found in Appendix E, though, again, you are not required to use
it. Only the method is important.
3.Put each formation into the chart corresponding to its age (geologic period). Don't worry about representing
thickness or rock type: you are correlating based on time units only. Unconformities will appear as
darkened or slashed spaces.
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Step 4 – Construct a stratigraphic column
Draw a stratigraphic column for each section using the lithologic descriptions given in Appendix B and the ages
you have established for all the formations in each section. Remember that the information in a stratigraphic
section is always arranged with the youngest rock unit at the top and the oldest rock unit at the bottom
regardless of how deformed the actual rocks really are. The section should be first plotted in pencil, finalized,
and then inked with a fine-tipped pen.
1.Choose a suitable scale depending on the total thickness of the described units. A scale of 1mm to 1m
should suffice in this exercise
2.In pencil, draw a vertical column with scale bar next to which you will plot your data.
3.Draw the cross section on graph paper.
i.Mark off the thickness of each bed or formation using the scale you established.
ii.Draw in the contacts between . Mark unconformities with a bold wavy line.
iii.Once you have drawn in contacts, refer to each sediment description to determine the grain-size
profile for each bed and draw it in the appropriate space. The left side of column should be straight
while the right side of column conforms to texture (grain size). As you can see in the example below, in
which f sand, m sand, c sand, and vc sand stand for “fine sand”, “medium sand”, “coarse sand”, and
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“very coarse sand” respectively, coarser grained beds will extend further to the right than will the finer
sands and shales.
Not all beds have an homogenous texture though. Some beds are described as “fining upward” or
“coarsening upward”. In the next example notice how the right line of the bed to which the red arrow
points trends to the left as you move up the column. It starts out near the “c sand” line and finishes
between the “m sand” and “f sand” lines. This means that, while the layer is still a cohesive unit, there
is a greater percentage of coarse grains near the bottom. This bed is said to “fine upward”.
.
Remember that formations are composed of members, that can be further subdivided. If a formation is
described as “thinly-bedded” you can show this by drawing several rectangles for the formation instead
of just one, as was done here:
You should now have a have a stratigraphic column with plain beds, some of which are simple
rectangles, others of which may show a coarsening or fining upward
iv.Fill the rectangles for each unit with the lithologic pattern appropriate for the description using the
standard key provided for you in Appendix C.
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v.Information on fossils may be placed within the unit, or beside it using a special symbol or small
sketch. This aspect will be up to you. You must determine which way is best in order to clearly show all
of the features
vi.You should place a brief description of the formation at the far right. Your stratigraphic column
should now look similar to:
vii.Ink your stratigraphic section and color the units according the description. Though a pain, this will
immensely increase the level of readability and ease with which you will correlate this section with other
stratigraphic sections from the same area.
4.Repeat the process for the other two sections.
Step 5 - Interpretive questions
The area of the Table Top Mountains is in the southwestern part of the U.S., which today is an arid
plateau region. But in the geologic past, climates and depositional environments were quite different. The first
question relates to the modem topography shown on the locality map. Write each answer so that the question
is rephrased in your answer. Your instructor does not have the questions memorized and may be too lazy to
keep referring to them. The rest of the questions deal with the depositional environments which existed in past
geologic periods. Use the fossils you found in each formation as well as the lithologic descriptions and the time
correlation chart to answer these questions. Write your answers in complete sentences and indicate the
question number and letter (e.g. 1a, 1b) at the beginning of each question. Highest grades will be given for
complete thoughtful answers that show just how much you have learned from your instructor. Keep it neat
(typed reports are neat), logical and concise (typing helps to keep reports logical and concise), etc. Also
remember good grammar and spelling.
Be sure to do your own work. You may discuss your answers with your instructor but your answers to
these questions are intended to be a measure of your effort and learning over the past one or two semesters in
geology.
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INTERPRETIVE QUESTIONS
1)a)
Calculate the total relief of the area shown or, the locality map. Explain how you calculated it.
b)Calculate the gradient of the stream in Oak Creek from the 6800 contour line to the 6400 contour line.
Show your work for this problem.
c)Does the stream in Balsam Canyon flow continuously'? How can you tell? Where is the sediment carried
by this stream deposited?
2)a)
During the Ordovician period, in which direction (N, S, E, W) did the land (sediment source) lie? Explain
the evidence behind your answer.
b)Determine possible depositional environments for all three Ordovician formations. (We did a lab on
depositional environments that may prove useful.) Consider each formation separately and explain
your evidence for each depositional environment that you describe.
c)In the Arapahoe Cliffs section, the Barstow Shale is becoming calcareous at the top. What can you infer
about the contact of the Barstow Shale with the overlying formation?
d)The Old Phoenix Shale in the Table Butte section contains glauconite which has been radiometrically
dated at 550 ± 5 million years. Determine whether or not this date corresponds with the age of the Old
Phoenix Shale from your range chart. Explain your answer and why there is or is not a discrepancy.
3)a)
Taking into account the fossils you found in the Granger Siltstone and its lithologic description, describe
in some detail a possible depositional environment for this formation.
b)On your time correlation chart there are two other formations from the same geologic period as the
Granger Siltstone. By examining the fossil content, lithologic descriptions, and map locations of these
three formations, determine in which direction the land lay during this period of geologic time, and in
which direction offshore marine environments lay. Describe the evidence that led you to your
conclusions.
4)a)
Examine the fossil content and lithologic descriptions of the Austin Sandstone in the Balsam Canyon
section. Propose a possible depositional environment for this formation and cite the evidence for your
conclusion.
b)Compare the grain size and sorting of the Austin Sandstone and the formation which directly overlies it
in the Balsam Canyon section. What conclusion can you draw about sea level changes occurring over
time in this part of the section? Explain your answer
c)Examine the Sacramento Shale and the formation directly above it in the Table Butte section, as well
as the Livingston Limestone and the formation directly above it in the Arapahoe Cliffs section. Do these
formations show a change in sea level over time which is similar to that in the Balsam Canyon section?
Explain why you answered as you did.
5)a)
By examining the fossil content, lithologic descriptions and map localities of the Austin Sandstone,
Sacramento Shale and Livingston Limestone, determine the direction in which the sediment source
(land) lay during this geologic period Explain your reasoning.
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b)Examine the fossil content, lithologic descriptions and map localities of the formation directly above each
of the formations in question 5(a). Has the direction of the sediment source changed over time?
Explain your answer.
6)a)
Explain a possible cause for the minor shale lenses in the basal portion of the Winslow Sandstone.
b)Could the same cause explain the calcareous nature of the lower part of the Fremont Shale? Explain
your reasoning.
7)List the formations between which unconformities occur in the Table Butte section and calculate the amount
of geologic time missing in each unconformity.
8)For the Arapahoe Cliffs section only, write a description of the geologic history. Refer to specific formations
and specific geologic periods. Show the instructor what you know.
Step 6 - Completion and Turn-In
Pledge your work and turn in your project to your instructor only. The finished product should include:
1) your field work
2) 14 range charts
3) a time correlation chart
4) 3 stratigraphic columns
5) answers to interpretive questions
Your grade will be based on the following weights:
Field Work:
14 points
Range Charts:
14 points
Time Correlation Chart:
10 points
Stratigraphic Columns:
30 points
Interpretive Questions:
24 points
Presentation:
8 pointsAppendix A
Fossil Identification
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Appendix A
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Appendix A
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Appendix A
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Appendix A
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Appendix A
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Appendix A
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Appendix A
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Appendix A
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Appendix A
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Appendix A
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Appendix A
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Appendix A
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Appendix A
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Appendix B
LITHOLOGIC DESCRIPTION OF FORMATIONS
(Formations are not given in stratigraphic order on this page)
Balsam Canyon Section contains 4 formations:
Missoula Sandstone: Sandstone, medium-grained, yellow-brown, well-sorted, cross-bedded grains
with high roundness and sphericity, fossiliferous. 42.0 m
San Pedro Sandstone: Sandstone, coarse-grained, brownish-gray, well-sorted, massive bedded,
fossiliferous. 36.6 m
San Diego Shale: Shale, gray, massive-bedded, calcareous, fossiliferous, 24.4 m
Austin Sandstone: Sandstone, fine-grained, yellow-brown, moderately sorted, fossiliferous, 36.6 m
Table Butte Section contains 5 formations:
Sacramento Shale: Shale, dark gray, grading to sandy shale, thin-bedded, fossiliferous, 27.0 m
Winslow Sandstone: Sandstone, thin-bedded, tan, fossiliterous. moderately sorted, 24.4 m
Old Phoenix Shale: Shale, dark-gray green, glauconitic, thinly-bedded, calcareous, fossiliferous,
42.0 m
Minneapolis Sandstone: Sandstone, light yellow-brown, medium-coarse grained, well –sorted, crossbedded, grains with high roundness and sphericity, fossiliferous, 39.7 m
Wheeler Limestone: Limestone, light gray, thinly bedded, grading to sandy limestone at the top,
20.6 m
Arapahoe Cliffs Section contains 5 formations:
Livingston Limestone: Limestone, gray, massive-bedded, shaley in upper portion, fossiliferous,
33.5 m
Granger Siltstone: Siltstone, medium-brown, fine-grained, thin-bedded, micaceous, carbonaceous,
interbedded layers of bituminous coal. 27.0 m
North Teton Limestone: Limestone, dark gray, thinly bedded at bottom, grading to sandy limestone
at top, fossiliferous, 21.9 m
Fremont Shale: Shale, dark gray, fissile, limey at bottom, fossiliferous. 45.7 m
Barstow Shale: Shale, gray, thin-bedded, calcareous at top, fossiliferous, 39.7 mAppendix C
LITHOLOGIC PATTERNS FOR SEDIMENTARY ROCKS
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Appendix D
FOSSIL TYPE SYMBOLS FOR STRATIGRAPHIC COLUMNS
Appendix E
USEFUL TEMPLATES
Individual Formation Fossil Ranges
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Section Correlation Chart
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