Rocks Lab 3 - Student Handout
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School
Colorado State University, Fort Collins *
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Course
101C
Subject
Geology
Date
Jan 9, 2024
Type
docx
Pages
6
Uploaded by SargentWillpowerMagpie42
GEOL 121
Name _________________________________
Lab Section ____________
Rocks Lab 3 – Rocks of Colorado and Geologic Maps
Learning Objectives
:
1.
Describe, Identify, and Interpret Rocks from Colorado
2.
Find information about the geology of a region from a geologic map
In this week’s lab, you will continue to practice your skills at describing and identifying rocks, this
time using rock samples from the Colorado Front Range. All of the rocks that you will see in lab
this week are rocks that you can see when you are out exploring around Fort Collins and in the
foothills. You will also use a geologic map to gain more detailed information about the rocks of
the Front Range
.
Part 1: Rocks of the Colorado Front Range
For each unknown rock sample, you should provide
:
1)
A detailed description. Your description should be detailed enough that someone
reading your description could easily pick out which rock you are talking about.
Your description should include information such as the rock
’
s color, texture, grain
size, minerals present, layering, fossils present, variability, abnormalities, etc.
2)
Whether the rock is igneous, sedimentary or metamorphic, and how you know.
3)
An identification of the rock.
4)
A hypothesis of how the rock formed and the evidence supporting your hypothesis.
Rubric for rock descriptions:
0.5
pt
.
0.25
pt
.
0
pt
.
Descriptions contain enough detail that
someone reading the description could
picture the rock in their mind. Features
such as color, shape, texture, irregularities,
patterns, layering, grain size and shape,
minerals present, etc. are described when
appropriate
.
Descriptions are given but
lack adequate detail to
fully under- stand what is
being seen
.
No response given
.
Rock Description
Rock Type (ign, sed, or
meta
(
How do you know?
Rock ID
Formation Hypothesis
And Reasoning
-Black and white
-Pink spots
Igneous b/c of the differ
-
ences in minerals
Granite
Intrusive due to the big
crystals and different min
-
erals
-Smooth texture
- Black grey color
Chemically sedimentary due
to the reaction to acid
Shale
Chemical sedimentary
-
larger grains together
-
Different sizes
Sedimentary detrital due to
the differences in grain size
Sandstone
Cemented together w/ dif
-
ferent rocks
Sampl
e
#
Rock Description
Rock Type (ign,
sed, or meta
(
How do you
know?
Rock ID
Formation
Hypothesis and
Reasoning
Sample
4
-
dark in color
-
Has foliation
-
Fine grains
-
Has a shine
Metamorphic due to
foliation
Granite geniss
Foliated meta
-
morphic rock
2
Sample
5
-dark grey in color
-
Smooth surface
-
Brittle
Sedimentary detrital
due to the fine
grains cemented to
-
gether
Claystone or
sandstone
Fine grains sand
or silt cemented
together through
pressure
3
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Part 2: Geologic Maps
Take a few minutes and examine the map that has been provided
.
1
(
What is this map showing you? What spatial area is this map showing? What do the colors
represent
?
Different geological makeups of horse tooth including different time periods as to when it was
formed
.
2
(
In what area of the map do you generally find igneous and metamorphic rocks? In what area
of the map do you generally find sedimentary rocks
?
Igneous and metamorphic were found west and sedimentary in the east
3
(
Find the rock formation labeled Xbc on the map and in the legend.
What is the name, age, and
composition of the formation? Which of the rocks that you previously described best matches the
description for
Xbc
?
Boulder creek granite. Dark in color and is fine grained w/ large crystals. Intrusive
igneous. It’s around 1.7 billion years old. Rock #4
4
(
Find the rock formation labeled Xqs on the map and in the legend.
What is the name, age,
4
and composition of the formation? Which of the rocks that you previously described best
matches the description for
Xqs
?
It is Quartzfeldspathic Mica Schist which is a metamorphic rock made of different foliated rocks.
It is most likely rock number 1 with no foliation
.
5
(
Find the rock formation labeled PPf on the map and in the legend.
What is the name, age, and
composition of the formation? Which of the rocks that you previously described best matches the
description for
PPf
?
Rock #3: Redish conglomerate sedimentary rock. Fountain formation
6
(
Find the rock formation labeled Kn/Kns on the map and in the legend.
What is the name, age,
and composition of the formation? Which of the rocks that you previously described best
matches the description for
Kns
?
Rock #2: Smokey hill Shale
has a smokey color w/ gradient from grey to a shade of brown.
Sedimentary chemical
7
(
Find the rock formation labeled Kpl on the map and in the legend.
What is the name, age, and
composition of the formation? Which of the rocks that you previously described best matches the
description for
Kpl
?
Rock #2: Pierre Shale which is very similar to regular shale and is sedimentary chemical due to
acid reaction
.
5
8
(
Find Horsetooth Reservoir on the map
.
a. Which formations form the east and west edges of Horsetooth Reservoir? What is their
composition
?
The East side is mostly shale and limestone which are sedimentary chemical rocks. To the west
we have a more igneous and metamorphic like Boulder creek Granite
b. Which formations are underneath Horsetooth Reservoir? What is their composition
?
Lykins Formation b/c is shows up on the north and south sides
9
(
Why do you think the reservoir was placed where it was
?
It was placed there b/c the rock underneath is dense and not pours so its good for water storage.
It is deep and within close proximity to the Poudre River
.
10
(
What are one or two other potential ways that geologic maps such as this one could be used
by non-geologists to inform their decisions or planning
?
1
.
It could help construction plans b/c people need to know if land is stable underneath
2
.
Also farmers can know if land is fertile for agriculture
6
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