B-Lab Report 04 Ohio - All Versions
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School
University of South Florida *
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Course
2000
Subject
Geology
Date
Apr 3, 2024
Type
Pages
8
Uploaded by BaronArtGrouse30
Report 4-1 Activity 4.1, Topography of Ohio (9 Minutes) O
BJECTIVES
: (a) To learn about Ohio’s landscape by examining topographic maps; (b) To understand the relationship between Quaternary glaciation and landscape. 1.
First look at the Ohio State Topographic Map, which provides an overview of the landscape of the entire state. The land can be divided into two main regions. One of the principal regions is characterized by bumpy topography
–
hills, valleys, many streams. The other principal region is very flat. On the base map of Ohio below, shade in the bumpier region. (2 points, ☆
) 2.
The green areas signify woods. Why do you think there are more green areas in the southeast portion of the map? (1 point,
☆☆
) 3.
The boundary between the two regions is seen in more detail on the Columbus 1:250,000 scale quadrangle topographic map. What geologic process is responsible for forming the hilly terrain seen on the southeastern part of this map? Be as specific as you can. What is your evidence? (3 points, ☆☆
) 4.
Now compare the Ohio topographic map with the map
of
the Quaternary Geology of Ohio. What geologic difference seen on the Quaternary Geology map explains the different topographic regions? (3 points, ☆☆
)
EXTRA CREDIT: How does glaciation affect the landscape? Describe the physical processes that occur when an area is glaciated and the effect on the shape of the land. (5 points, ☆☆☆
) Activity 4.2, Terrigenous Clastic Rocks (13 Minutes) O
BJECTIVE
: To learn how to recognize the main terrigenous clastic rocks: conglomerate, sandstone, siltstone, shale, and mudstone.
Although limestones were the dominant rock formed in Ohio at the beginning of the Paleozoic era, terrigenous clastic rocks
were also formed. This activity contains five rocks labeled OA-1 through OA-6, representing the important terrigenous clastic sedimentary rocks conglomerate
, sandstone
, siltstone
, mudstone
, and shale
. 1.
For each rock, write a simple description in your own words that will aid you in identifying it in the future. Do not simply emphasize color! Make sure you use a sediment card. (2 points each, all ☆
) Laboratory Number Four: Ancient Rocks and Critters of Ohio
Name: Partners:
Report 4-2 Rock Description OA-1: Sandstone OA-2, OA-5: Shale OA-3: Siltstone OA-4: Conglomerate OA-6: Mudstone 2. Look carefully the conglomerate, OA-4. Use the chart on the inside cover of your laboratory manual to determine the roundness of the clasts. What do you think explains this shape? (3 points, ☆☆☆
) Activity 4.3, Sandstones (17 Minutes) O
BJECTIVE
: To learn how to determine sorting and roundness of clasts in sandstones, through examination of both hand samples and thin sections. Rocks OX-1 through OX-4 are late Paleozoic sandstones collected from northeastern Ohio. 1. Determine the predominant clast size in samples OX-1 and OX-2 by comparing them with your sediment card. (1 point each, ☆
) Clast Size OX-1 OX-2 2. Using a hand lens, determine the sorting and roundness of the sand grains
–if you can! If you can’t, explain why. Use the charts on the inside cover of your lab manual; do not just guess. (2 points each, ☆
) Sorting Roundness OX-1 OX-2 3. Examine the thin sections of OX-3 and OX-4 under the microscope and determine the sorting and roundness of the sand grains. Again, use the charts on the inside cover of your lab manual. (3 points each, ☆
) Sorting Roundness OX-3 OX-4 4. Examine thin section CC-S-1. This thin section was made by embedding loose sand grains in epoxy and shaving a piece of the solidified aggregate into a thin section. a. Notice that the sand grains are surrounded by epoxy. Is the epoxy opaque, isotropic, or anisotropic? HINT: the same epoxy holds the rock slice to the glass slide. (2 points, ☆
). b. Describe the rounding and sorting of the sand grains in CC-S-1. (3 points, ☆
) Sorting Roundness CC-S-1 Activity 4.4, Ordovician Rocks of Ohio (13 Minutes) O
BJECTIVE
: To learn how to recognize limestones and silty limestones, which were formed during the Ordovician Period in Ohio.
Report 4-3 Rock OO-1B was collected from an area fifty miles southeast of Cincinnati and is Ordovician in age. 1.
First examine the hand sample of OO-1B. Does the rock contain either calcite or aragonite? How can you tell? (2 points, ☆☆
) 2.
Now examine the thin section of OO-1B. What two minerals can you identify in the thin section? HINT: One of them is easy
–you’ve just identified it!
(4 points, ☆
) 1. 2. 4.
What percentage of this rock consists of terrigenous clasts? Do not just guess. Use the charts on the inside cover of your lab manual. You should be able to estimate percentages within one picture on the chart. (2 points, ☆
) EXTRA CREDIT: What name would you give this rock? (i.e., sandstone, conglomerate, etc.) Justify your answer! (4 points, ☆☆☆
) Rock OO-12B was collected from the same locality as OO-1B, approximately fifty miles southeast of Cincinnati, Ohio. 5.
First examine the hand-sample of OO-12B. What name would you give this rock? (1 point, ☆
) 6. Was this rock formed in a marine or terrestrial (land-based) geologic environment? Justify your answer! (2 points, ☆☆
) Marine or terrestrial? 7.
Without using acid, do you think this rock has been
extensively dolomitized? Why or why not? (2 points, ☆☆☆
) EXTRA CREDIT: Examine the thin section of OO-12B. Notice that many different fossils can be recognized in thin section. Some of them are corrugated and undulating like this: ⌣⌢⌣⌢⌣⌢
, while others are straight and dark like this: ====. The squiggly, undulating fossil shells are brachiopod shells and are composed of calcite, while the straight, darker shells are mollusk (clam) shells and are made of aragonite. Examine the fine structure of the crystals that make up both shells. In one of them, the crystals are parallel to the walls of the shell, and in the other they are perpendicular. Sketch both arrangements below and indicate which one is a brachiopod shell. (4 points, ☆☆
) Brachiopod shell: Clam shell: Activity 4.5, Silurian Rocks of Ohio (9 Minutes) O
BJECTIVE
: To learn how to recognize and interpret Silurian rocks from Ohio.
Rocks of Silurian age are relatively rare world-wide because they are infrequently preserved. In this activity, you will be examining a Silurian rock from near Dayton, Ohio, rock
OS-6.
1.
First examine the hand-sample of rock OS-6. What is the
major mineral in this rock? (3 points, ☆
)
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Report 4-4 2.
Is this mineral original or is it a replacement mineral, i.e., was the rock composed of something else that has since been altered? (2 points, ☆
) 3.
What name would you give this rock? (i.e., sandstone, limestone, etc.) (1 point, ☆
) 4.
Now examine the thin section of rock OS-6. Estimate the percentage of porosity of this sample. Do not simply guess. Use the charts on the inside cover of your lab manual. (3 points, ☆
) Activity 4.6, Later Paleozoic Rocks of Ohio (10 Minutes) Note: Complete Activity 4.4 before beginning this activity O
BJECTIVE
: To learn how to identify terrigenous clastic rocks, which were formed in the late Paleozoic in Ohio.
1. This activity contains five rocks from the Mississippian through Permian (late Paleozoic) periods, collected in northeastern Ohio. Identify them. (2 points each, all ☆
) Name of Rock OZ-1 OZ-2 OZ-3 OZ-4 OZ-5 Activity 4.7, Paleozoic Ohio Fossils (17 Minutes) O
BJECTIVE
: To learn how to identify the common Paleozoic invertebrate marine fossils: brachiopods, bryozoans, rugose corals, nautiloid cephalopods, and crinoids. Note: Please put the fossils back in the correct boxes. 1.
Locate the box containing many examples of Ordovician brachiopods. These were all collected from limestones in the Cincinnati area, and all represent brachiopods that lived in the late Ordovician period. Examine these brachiopods carefully and separate them into different groups based on morphology. Now make a little sketch of the three most common forms. Make sure to include a scale bar for your sketch. (6 points, ☆☆
) Brachiopod 1: Brachiopod 2: Brachiopod 3:
Report 4-5 2.
Bryozoans were very common animals in the Ordovician and assumed many different forms. Some grew upright like plants, while others formed encrusting patches on other animals. Look very carefully at the outer surface of the Bryozoan twigs using a hand lens and sketch what you see. (3 points, ☆☆
) 3. Most of the time, crinoids are preserved as pieces, as seen in Box P-1355. What part of the whole crinoid animal do these “cheerios” represent? (2 points, ☆
) 4. Pick out a specimen of rugose coral from its box and sketch it in the next box. Make sure to include a scale bar. (3 points, ☆☆
)
5. Nautiloid cephalopods fared much better than some of its friends at the end of the Paleozoic, surviving the great extinction event that spelled the demise of the trilobites, most brachiopods, and nearly 90% of marine invertebrate species. Examine P-1785, Treptoceras
sp., a nautiloid cephalopod from Cincinnati. How can it be distinguished from a rugose coral? Be as specific as you can. (3 points, ☆☆
)
Report 4-6 Activity 4.8, Fossils in Ohio Rocks (15 Minutes)
O
BJECTIVE
: To learn how to identify the common Paleozoic invertebrate marine fossils in rocks.
NOTE: You must complete Activity 4.7 before you begin this activity. For each of the following rocks, identify all the major fossils. (3 points each, all ☆
) Rock Fossils OH-2 OH-3 OH-7 OH-20 OH-21 O-13 ▼ EXTRA CREDIT ▼
OO-10 OO-11 Activity 4.9, Identifying Specific Fossils (8 Minutes) O
BJECTIVE
: To learn how to identify specific genera of fossils using a guidebook.
1. All the specific fossils in these rocks were collected from Caesar Creek State Park in Ohio and are described in Guidebook No. 12, Excursion to Caesar Creek State Park in Warren County, Ohio, Plates 1-4, published by the Ohio Geologic Survey. Use this guidebook to identify the genus
of the following fossils. a. Bryozoans in OH-6: (4 points, ☆
) b. Brachiopods in A-715: (4 points, ☆
) Activity 4.10, Glaciers and the Landscape of Ohio (14 Minutes)
O
BJECTIVES
: (a) To learn how read a Quaternary geologic map; (b) to learn how Pleistocene glaciations affected the landscape of the northern United States.
This activity uses the map Quaternary Geology of Ohio. 1.
The terms “Wisconsinan”, “Illinoisan”, and “pre
-
Illinoisan” (or “Kansan”) refer to different advances of the continental glaciers over North America. Each advance ended with a substantial retreat of the glaciers. We are presently in a period of glacial
retreat. During which geologic epoch
did these glacial advances occur?
NOTE:
the symbol kA means “thousands of years”; also, look at your geologic time scale. (2 points, ☆
) 2.
Locate the dark grayish-green units with symbols M5, M4, and M3, and notice that they occur in large drooping pendants or “necklaces”. What kind of glacial deposit do these units represent? Describe how they form in as much detail as possible. (3 points, ☆☆☆
) 3.
You can use the necklaces to determine the direction from which the ice advanced. Use this technique to determine the direction from which the ice advanced to produce the dark green arcuate necklaces with symbol M2, in the area of Greene, Fayette, and Clinton counties. (2 points, ☆
)
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Report 4-7 4.
Locate the Wisconsinan lacustrine deposits with symbol LC. a. What does “lacustrine” mean? (1
point, ☆☆
) b. These lakes only existed during the height of glacial advance. They consisted of water trapped between two barriers, one to the north and one to the south. What was the origin of these barriers? HINT: They were formed during the ice-age! (4 points, ☆
) Northern: Southern: 5. Geologists estimate that the ice covering Ohio during the last ice age was about 1 mile thick! Estimate the pressure at the base of this ice sheet using the formula: 𝑃 = 𝜌𝑔𝐷
where 𝜌
is the density, g is the gravitational acceleration at the surface of the earth (
g
= 9.81 m/s
2
≈ 10 m/s
2
), and D is the depth. Remember that this equation produces pressure in Pa when 𝜌
, g
, and D
are in their standard MKS units (
𝜌
in kg/m
3
; g
in m/s
2
; and D
in m). The density of ice is approximately 931 kg/m
3
. Express pressure in MPa (megapascals) and make sure you show all your work in the box to get full credit. (5 points, ☆
) 6. Convert this pressure in MPa to atmospheres of pressure. The conversion factor is: 1 MPa = 9.87 atmospheres.
Report 4-8