GEO1115_2021_Activity9.4S
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University of Ottawa *
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1115
Subject
Geology
Date
Dec 6, 2023
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docx
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THEME 9 – SEDIMENTARY ROCKS
[ 54.25/60 : A+ ]
A
CTIVITY
9.4S – V
ISUAL
IDENTIFICATION
AND
ASSOCIATED
QUESTIONS
(
/60)
Reference material:
-
Lecture of associated theme (Brightspace)
-
Glossary (
https://mysite.science.uottawa.ca/dumas/
)
-
Reference document “Section of the lab manual” in Brightspace
Activity:
Answer the questions associated to each of the following pictures.
N.B. The rocks shown in the pictures
below can be any of the rocks highlighted in yellow, with the addition of breccia, in the reference
material “Section of the lab manual” (see Tables 1 and 2).
Sedimentary rock 1 (
/8)
a)
Name this rock. (
/1)
Breccia
b)
Name the dominant grain size (i.e. the coarser particles) forming this rock, and qualify the energy
level (low or high) associated with the deposition of the sediments forming this rock. (
/2)
Gravel, high energy
c)
Qualify the roundness (or angularity) of the particles forming this rock, and relate it to the
distance/time of transport these particles likely experienced from their parent rock. (
/2)
Angular, sediment has travelled only a short distance from their parent rock
d)
Specify under which of the three categories/groups of sedimentary rocks this rock would be
classified. (
/1)
Clastic
e)
Give the name of another rock of the same type which has the same grain size. What textural
feature distinguishes the two rocks you have just named? (
/2)
Conglomerate, the roundness distinguishes them best. Breccia has angular grains whereas
conglomerate has rounded grains.
Sedimentary rock 2 (
/8)
a)
Knowing that the mineral forming this rock has a cubic cleavage, give the name of this mineral.
(
/1)
Halite
b)
Name this rock. (
/1)
Rock Salt
c)
Specify under which of the three categories/groups of sedimentary rocks it would be classified,
and briefly explain what that means in terms of the origin of the particles forming this rock. (
/2)
Chemical, this means the particles precipitated inorganically, generally as evaporites from a
supersaturated solution
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d)
In what climate would you expect this rock to have formed: (cold or warm), and (dry or humid)?
Justify your answer.
Hint: look at the “comments” column for this rock in the appropriate table in
the reference material “Section of the lab manual”.
(
/3)
This rock would have formed in a warm and dry environment as they are produced from an
evaporite which requires these conditions to form.
e)
What is the general term given to such sedimentary rocks (i.e. formed by the process and in the
conditions explained in “d)”)? (
/1)
Chemical sedimentary rock
Sedimentary rock 3 (
/10)
a)
Name the grain size of the particles forming this rock, and qualify the energy level (low or high)
associated with the deposition of the sediments forming this rock. (
/2)
Mud(<0.062mm), low energy
b)
Would you expect trace fossils in this rock to be vertical, or horizontal? Justify your answer. (
/3)
Horizontal as it was a low energy environment in which it was formed which allowed for various
marine life to settle along the bottom without being swept away by currents and then others would
have to comb along the sea floor in order to find their food. If it were a high energy environment
these particles would be scattered withing the water and then we would see vertical trace fossils.
c)
Name the characteristic of this rock that causes it to break along defined, sheet-like planes (as
seen on the picture).
Hint: see Table 1 in the reference material “Section of the lab manual”.
(
/1)
Fissile
d)
Name this rock. (
/1)
Shale
e)
Would you expect the sediment forming this rock to have deposited in a rather shallow or deep
setting (i.e. near the shoreline, or offshore)? Justify your answer.
Hint: think of the energy level
required for the deposition of the sediment of this size, and of where you would expect this level of
energy to occur with respect to the shoreline based on the waves dynamic (i.e. how the waves
energy changes with depth).
(
/3)
It would have deposited in a deep environment as shallow water, such as a shoreline, has much
higher energy and movement within it. We can see with the grain size that this sediment required
low energy to be deposited which is found in deeper settings. This deeper setting with lower energy
levels would also allow for the horizontal trace fossils as discussed in b.
Sedimentary rock 4 (
/8)
a)
Name the dominant grain size forming this rock. (
/1)
cL
b)
Is the energy level associated with the deposition of this sediment lower or higher than the one
associated with the deposition of a shale? (
/1)
Higher
c)
Would you expect trace fossils in this rock to be vertical, or horizontal? Justify your answer. (
/3)
Vertical as the higher energy environment in which it was formed would have caused the various
marine life to be scattered within the water and to capture this in order to eat, other lifeforms such
as marine worms would rise out of the bottom in order to capture these particles out of the free
flowing water above.
d)
Name this rock. (
/1)
Sandstone
e)
What do you think is the mineral forming the vast majority of the grains in this rock? Based on this
mineral, give a more precise name for this rock by adding a qualifier to the name given in “d)”.
Hint: look at the note below Table 1 in the reference material “Section of the lab manual”.
(
/2)
Quartz, quartz sandstone
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Sedimentary rock 5 (
/5)
a)
What are the majority of particles forming this sedimentary rock, as seen on this picture? (
/1)
Fossils
b)
Knowing that most of these particles strongly react with HCl, what is the name of the mineral
forming these particles? (
/1)
Calcite(CaCO
3
)
c)
Name this rock. (
/1)
Limestone
d)
Specify under which of the three categories/groups of sedimentary rocks it would be classified,
and justify your answer (make sure to base your answer on the particles seen on this picture).
(
/2)
Fossiliferous limestone, as it is composed mainly of bioclastic sediments which we can see clearly
from the rock being thoroughly covered with fossils.
Sedimentary rock 6 (
/5)
a)
Name the dominant grain size (i.e. the coarser particles) forming this rock. (
/1)
Gravel
b)
Qualify the roundness (or angularity) of the particles forming this rock. (
/1)
Rounded
c)
Name this rock. (
/1)
Conglomerate
d)
Specify under which of the three categories/groups of sedimentary rocks this rock would be
classified, and explain what that means in terms of the origin of the particles forming this rock.
(
/2)
Clastic, this means the sediment comes mainly from continental erosion.
Sedimentary rock 7 (
/4)
a)
Knowing that this rock is soft and very lightweight, give the name of this rock. (
/1)
Coal
b)
What materials are at the origin of this rock? (
/1)
Plant fragments
c)
What is the chemical composition of this rock? (
/1)
Mainly organic debris
d)
On the first field trip (the campus walk), we mentioned that this rock was used in the manufacture
of a certain building material. What building material is it? (
/1)
Steel
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Sedimentary rock 8 (
/5)
a)
Knowing that this rock does not taste salty, does not react with HCl, and can be scratched with the
fingernail, what is the dominant mineral forming this rock? (
/1)
CaSO
4
• 2H
2
O
b)
Name this rock. (
/1)
Gypsum
c)
Specify under which of the three categories/groups of sedimentary rocks it would be classified,
and justify your answer. (
/2)
Chemical as it is formed by precipitation of evaporite from a supersaturated solution.
d)
Give the name of another rock (from Table 2 in the reference material “Section of the lab manual”)
formed by the same process and in the same climatic conditions as this one. (
/1)
Rock salt
Sedimentary rock 9 (
/4)
a)
Name the dominant grain size forming this rock. (
/1)
mU
b)
Name this rock. (
/1)
Sandstone
c)
Based on the colour, what do you think is the mineral forming the vast majority of the grains in
this rock? Based on this mineral, give a more precise name for this rock by adding a qualifier to the
name given in “b)”.
Hint: look at the note below Table 1 in the reference material “Section of the
lab manual”.
(
/2)
Feldspar, Arkosic Sandstone(arkose)
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Sedimentary rock 10 (
/3)
a)
Knowing that the dominant mineral forming this rock has no cleavage and is harder than glass,
what is the dominant mineral forming this rock? (
/1)
Quartz
b)
Name this rock. (
/1)
Chert
c)
Give a prehistoric use of this rock. (
/1)
If necessary, do a quick little research on the Internet...
In prehistoric times, chert was used as a raw material in the fabrication of stone tools.