Exercise_12_Paleoecology_II_2023
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Texas A&M University *
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Geology
Date
Dec 6, 2023
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Paleoecology II – Assemblages and Depositional History
Part 1. Fossil Slabs and Assemblages (Complete by end of lab period)
In the previous lab, you identified the ages and environments of deposition for three
fossil slabs. The TAs have given you feedback on your determinations.
Find a partner that did a
different set of slabs.
Revisit the
slabs
together, correcting any errors and exchanging
information.
Repeat until you have seen and recorded ages and depositional environments for
all
8 slabs
in the list. Fill out the table below.
Slab #
Important Taxa
Age
Depositional Environment
Set #1
(Z and Y)
#4
#5
#8
#9
#10
#11
(Cream
Limestone)
#12
Last time, you also looked at loose a fossil assemblage as well. For your assemblage fill out the
table after making any corrections necessary. Look at and fill out the table for an assemblage
another student completed.
Assemblag
e
Important Taxa
Age
Depositional Environment
Terrestrial Assemblages
(New to this lab)
Sample
Important Taxa
Age
Depositional Environment
#6
#13
#14
Slabs without visible fossils
(New to this lab)
For each of these, use the sedimentology and sedimentary structures to reconstruct the
depositional environment.
Slab
Sedimentology
Sedimentary Structures
Depositional Environment
#3
Age:
Paleocene
#2
Age: Early
Triassic
#7
Age:
Silurian
Part 2: Stratigraphic Interpretation (Due Week of April 24)
Imagine that we have taken the slabs from an outcrop. We have recorded the
stratigraphic location of each slab. Using this information and the determinations you made in
the Paleoecology II lab, you will draw a stratigraphic column.
Each slab has a number and a
level from which it came in the outcrop – which is 300 m of section (below left). Slabs came only
from the uncovered intervals. Fossil assemblages were collected from covered intervals. Using
your corrected lab, reconstruct the outcrop using the template included on a later page. Use the
symbols below to indicate the lithology and the fossil occurrences in the graphical column. Next
to the graphical column, include a descriptive column and construct a relative sea level curve
based on your interpretations of the depositional environments.
300 m total section
Unit containing Slab
Slab #14 – 290-300 m
Slab #3 – 267-269 m
Slab #10 – 258-267 m
Slab #11 – 230-253 m
Slab #9 – 218-230 m
Slab #2 – 198-218 m
Slab #4 –
174-198m
Slab #13 – 136-174 m
Slab #6 – 102-136 m
Slab #8 – 65-87 m
Slab #5 – 40-60 m
Slab #7 – 28-40 m
Slab #12 – 8-28 m
Slab #1 – 5-8 m
Covered section 269-290 m
Covered section 253-258 m
Covered section 87-102 m
Covered section 60-65 m
Covered section 0-5 m
On your stratigraphic column, note which covered intervals that the assemblages in your table
above would fall within. Include those assemblages information in your environmental
interpretations.
Note, some slabs from the previous lab may not be present in this exercise.
Lithological patterns – If you add a new
one, you must add it to this legend.
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Suggested Fossil Symbols – If you make something different, add it to this legend.
Example stratigraphic column. You do not need to do a weathering profile.
On the template on the next page:
300 m
Meters/Age
Litho. Fossils
Description
Sea Level
Create a scale in the leftmost column to accommodate your 300 m of section. Use a
ruler.
Mark out the stratigraphic thickness of each unit across the template making horizontal
lines with a straight edge.
Write in the Period for each stratigraphic unit in the
Geologic Age
column.
Add lithological symbols to the
Graphic Column
for the rock type for each unit. Indicate
covered intervals with an X through the rectangle.
Add fossil symbols to the
Fossil Column
for each unit.
In the
Description Column
, add a brief description such as:
o
“Coarse Sandstone with crossbedding”
Label the relative sea level column with environments at the bottom:
o
Terrestrial (highlands and lowlands)
o
Lagoon to Reef
o
Continental Shelf
o
Continental Slope
o
Deep Sea
Draw a sea level curve based on your environmental interpretations.
Meters
above
base
Geologic
Age
Graphic
Column
Fossils
Description
Relative Sea
Level
Summary Questions:
1.
In words, describe the geological history of the outcrop. Include the history of sea level
during the geologic time intervals represented in this outcrop in your answer.
Describe
from oldest to youngest.
Note any unconformities.
2.
Pose hypotheses for the cause of TWO instances of faunal turnover you observe in your
stratigraphic column. Be specific about which events you are discussing (give age and a
description of the faunal turnover).
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