Geo 101 Midterm Practical Information
The Midterm will be a
practical exam consisting of five parts:
Part I - Will consist of identifying ten unknown minerals in hand
sample:
1.
Determine the unknown specimen’s major physical characteristics
2.
Determine the mineral name for each sample.
The necessary knowledge and skills for identifying a mineral include:
a) Know the proper steps for mineral
sample determination.
b) Know how to ascertain each type of
physical characteristic
c)
Know the major minerals and their associated characteristics
Part
II - Will consist
of identifying twenty unknown rocks in hand sample:
1.
Determine the unknown specimen’s major physical characteristics
a) Texture
b) Mineral composition
2.
Determine the rock name for each sample.
The necessary knowledge and skills for identifying a mineral include:
a) Know the proper steps for rock sample
determination.
b) Be able to recognize all the major
types of texture and mineralogy.
c) Know the major rock
types and their associated characteristics that are
unique
to each rock type, such as those for granite, basalt, schist, marble,
sandstone,
shale, etc. In essence, when you pick
up a rock sample and
examine it, you
should be able to recognize what type of rock it is, and know its name.
Part III - Will consist of determining the relative age sequence for
a hypothetical geologic cross section
consisting of a stratigraphic column of rock
layers, using the basic stratigraphic principles like superposition
and crosscutting. This exercise will be much
like the cross sections you analyzed in the geology dating lab.
Part IV- Will consist of determining the absolute ages sequence
for three igneous rock units in a hypothetical geologic
cross section consisting of a stratigraphic
column of rock layers. This exercise
will be much like the geology dating
lab.
Part V- Will consist of determining the resolved ages of
sedimentary units from a hypothetical geologic cross section using relative
and
absolute age data gathered in Parts III and IV. This exercise will be much like your geology dating lab.
The Midterm will look
like this:
Directions: Test and identify each of the ten unknown
mineral samples. 1) Circle the correct
physical
properties you observed and tested. 2) Name the mineral.
Mineral Sample A
a) Luster - Circle one: Metallic Nonmetallic
b) Mineral Hardness – Circle
one: Soft (1 to 3) Medium (3 ½ to 5 ½ )
Hard (6 and up)
c) Cleavage
- How many sets? - Circle
one: None
1 2 3
4
d) Other Tests: Streak: NA Yes No Acid Test: NA
Yes No Magnetic:
NA Yes
No
e) Name of the Mineral ______________________________
Directions:
Observe, test, analyze, and identify the 20 unknown rock samples.
1) Circle one of the six possible italicized types
of rock textures/fabrics.
2) Circle ALL mineral and other component
choices identifiable in the rock.
Note: you must circle at least
one composition item
3) Write down the petrological name of the rock
sample.
Rock Sample #1
a) Textural/Fabric
Igneous =
Plutonic Volcanic
Sedimentary =
Detrital (Bio)chemical
Metamorphic =
Foliated Nonfoliated
b) Composition
Amphibole Biotite Calcite Carbon Clay Feldspar Fossils Garnet
Glass Gypsum Muscovite Olivine Pyroxene Quartz Rock fragments
Salt Serpentine Tourmaline Vesicles None Observed
c) Name
of the rock sample = _______________________________
Directions: Analyze the stratigraphic
block diagram handout. Do the following:
1) List the correct relative order of the labeled geologic events (letters A
to T);
and 2) List the
appropriate stratigraphic principle applied for each lettered event.
Relative Order of Events Principle(s) Applied Principle Abbreviations
_____ (youngest) ______________ Superposition = SP
_____
______________ Cross-Cutting
= CC
_____
______________ Inclusion
= IN
_____
______________ Lateral
Continuity = LC
_____
______________ Original
Horizontality = OH
_____
______________
_____
______________
_____
______________
_____
______________
_____ ______________
_____
______________
_____
______________
_____
______________
_____ ______________
_____
______________
_____
______________
_____
______________
_____
______________
_____
______________
_____ (oldest) ______________
Questions:
1) Which type of unconformity
does “I” represent?
__________________________
2) Which type of unconformity
does “N” represent?
__________________________
3) Which type of unconformity
does “T” represent?
__________________________
4) What type of metamorphism has
Pluton “B” and Dike “R” imposed on the surrounding
sedimentary
country rock layers? Answer:
___________________________
5) Platystrophia
fossils were found in Sandstone Unit “A”. Elrathia fossils were found in
Conglomerate Unit “L”. Based on the geologic time scale, what is
the possible age range of
the tilting, uplift, and erosional
event recorded in the Unconformity
“I” event as constrained
by the above
fossil ages? Use Figure 8.13 to answer this question.
Directions: Calculate the correct
absolute dates for the igneous rock units using the appropriate
isotopic
analyses and the radiometric dating method. Use the info in your lab
book’s Figure 8.16
for finding the
proper half-life and decay rate for the specific parent-daughter isotopic
pair. Note:
you must show your
calculations to earn full credit.
Isotopic Analyses of Granite Pluton
Unit “B”: The granite intrusion “B” in the
geologic block
diagram contains pristine zircon
crystals that were processed and analyzed for Uranium-235 and
Lead-207
content. The laboratory analyses of the samples
yielded the following U-235 / Pb-207
ratio:
Parent
U-235 = 50.0% Daughter Pb-207 =
50.0%
1) Number of half lives
elapsed: _______
2) Calculated age of Granite
Intrusion “B” =
_______________ million years old
Do
Your Calculations Here:
Part V. Stratigraphic Analysis with
the Absolute Dating Information:
Directions: Using the numeric dates of the igneous units that you determined in
Section IV above,
answer the following questions
concerning the timing of geologic events in the geologic column
diagram.
Questions:
1)
Based on your calculated radiometric age results above, what is the tightest
possible age
range for the uplift and erosional surface event
recorded in unconformity
“N-T-N” ?
Answer: ____________to___________ million years old
2)
Based on your calculated radiometric age results above, what is the tightest
possible age
range for Limestone
Unit G?
Answer: ___________to____________ million years old
3) Which of the
absolute dated igneous rock units, Granite Pluton “B”, Basalt
Dike Unit “R”,
or Andesite Lava
Flow Unit “O” does the BEST job at constraining the minimum possible
age of Sandstone
Unit “K”? Explain why you chose your answer.
Circle one: Pluton “B” Dike “R” Lava Flow “O”
WHY? Explain Below
4) Phacops trillobite fossil were found in Rock Unit
“K”. Using BOTH the
fossil
ages
(found in Figure 8.13 in your lab manual) combined with the absolute
ages of the
igneous rocks
(calculated in Part IV), what is the BEST possible resolved age range for the
uplift and
erosional surface event recorded in unconformity “N-T-N”? Explain why you
chose your answer.
WHY? Explain Below: