B-Lab Report 03 Florida 2 - All Versions
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University of South Florida *
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Course
2000
Subject
Geology
Date
Apr 3, 2024
Type
Pages
8
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Report 3-1 Note: Activities 3.1 & 3.2 must be completed at the beginning of class and before you begin any other activity. Activity 3.1, Geologic Time and Florida O
BJECTIVE
:
To become familiar with the periods of the Mesozoic and epochs of the Tertiary, the time when Florida’s sedimentary rocks were formed. Fill in the blanks in the first three columns
of the following table, Table III-1, which summarizes the geologic periods and epochs that are important in Florida’s geologic history. Use the Geologic Time Scale on the inside front cover as a reference (5 points, ☆
). Activity 3.2, Florida Rock Summary
(2 Minutes)
O
BJECTIVE
:
To summarize the lithology of Florida rocks you determined in the last laboratory. Table III-2 is identical to Table II-1 you completed last laboratory, expanded to include several sediment samples. Transfer your answers from last week (from the graded
lab report) into the last column of Table III-1 for every row corresponding to a rock
. (2 points, ☆
) Activity 3.3, Introduction to Drilling Logs (5 Minutes)
O
BJECTIVE
:
To learn how to extract information from IC-103, the Summary of Stratigraphic Information derived from drilling logs.
Because Florida has so few outcrops, almost everything about the geology of the state is known from drilling. As the agency in charge of s
tudying and managing Florida’s geologic resources, the Florida Geologic Survey has compiled a summary of drilling logs titled Information Circular No. 103,
Shallow Stratigraphic Core Test on File at the Florida Geologic Survey. You will be using an abridged version of this book (the full book contains over 400 pages of core descriptions!) to learn about the rocks and sediments hidden from view beneath the surface. 1.
What material was recovered from a depth of 50 feet in well W-12942 in Hardee County? (2 points, ☆
) 2.
Would you characterize this material as rock or sediment? (1 point, ☆
) 3.
What minerals become increasingly abundant beneath 1000 feet at Polk County well W-10254? (In fact, it is the presence of this mineral that defines the base of the Floridan Aquifer
–
file this away for future use!) (2 points, ☆
) 4.
EXTRA CREDIT: The well-fields that supply Pinellas County with drinking water are located in Polk County. The water is supplied from big, 12-inch wells that draw water from a depth of 500-1000 feet. Does this groundwater reside in loose, unconsolidated sediment or in hard rock? How can you tell? (The aquifer in which the water is stored is called the Floridan Aquifer and is one of the most important aquifers in the United States.) Use Well W-10254 as representative of Polk County. (Answer box is on the next page.) (4 points, ☆☆☆
) Laboratory Number Three: Florida, The Land Beneath Our Feet II Name: Partners: Table III-
1, Florida’s Geologic History
Years ago Period Epoch Event, Rocks Formed Oldest Youngest 12,000 Quaternary Pleistocene Last ice age
1.6 m.y. - 10,000 Quaternary Pleistocene 5 - 1.6 m.y. Tertiary Tertiary Tertiary Oligocene Tertiary Eocene 66-58 m.y. Tertiary Paleocene 144 - 66 m.y. Cretaceous 208 - 144 m.y. Jurassic Anhydrite
Report 3-2 Where does groundwater reside? How can you tell? Activity 3.4, Miocene Sediments of Florida (12 Minutes)
O
BJECTIVE
:
To summarize the type of Miocene sediments found in Florida.
You might have noticed that Table III-2 contains many rocks of Eocene and Oligocene age but very few of Miocene and Pliocene age. The reason has to do with the difficulty in collecting core samples from poorly indurated sediment, which characterizes much of the Miocene and Pliocene material
beneath Florida. Although Miocene and Pliocene sediments are thick beneath Florida, they are not usually indurated, and they are therefore under-represented in a compilation of rock core data. To compensate for this bias, you will supplement your observations of rocks in Table III-2 with inferences drawn from IC-103 for Miocene- and Pliocene-aged sediments. Information Circular No. 103 organizes the kinds of rocks or sediment encountered when drilling in terms of formations and groups. In Florida, the most important Miocene/Pliocene units are the Hawthorn Group, and Peace River Formation. The Peace River Formation is the most important subdivision of the Hawthorn Group. 1.
Notice that some of the entries in Table III-2 are for sediments (“Sed.”) recovered from specific wells (“Well #”). Use IC
-103 to characterize the depth and lithology of these sediments. Enter the midpoint
of the depth at which the sediment occurs, and quickly summarize the kind of sediments found in the last column. Use the Hawthorn Group (Undifferentiated) or the Peace River Formation as representative of the Miocene or Pliocene sediments. Note: the midpoint is just the average of the high and low depths. (3 points each, all ☆
) Table III-2, Representative Rocks and Sediments of Florida Sample Rock or Sediment? County Depth (feet) Age Group or Formation Name of Rock or Sediment? Youngest
. FLA-6 Rock Dade 40 Pliocene Miami Fm. W-15511 Sed
Calhoun Miocene Hawthorn Grp. W-11907 Sed
Charlotte Miocene Peace River Fm. W-15509 Sed
Jackson Miocene Hawthorn Grp. FLA-7 Rock Manatee 343 Miocene Arcadia Fm. FLA-5 Rock Clay? ≈ 250
Miocene Hawthorn Grp. Siltstone
FLA-8 Rock Hardee? ≈ 100
Miocene Hawthorn Grp. FLA-9 Rock Manatee 920 Eocene Ocala Grp. FLA-10 Rock Lafayette 300 Eocene Avon Park Fm. FLA-11 Rock Citrus 35 Eocene Ocala Grp. FLA-2 Rock Citrus 280 Eocene Avon Park Fm. Dolostone
FLA-1 Rock Charlotte 1180 Eocene Avon Park Fm. Limestone
FLA-12 Rock Escambia 15847 K/J Unknown Oldest FLA-13 Rock Charlotte >10,000 K/J Unknown FLA-3 Rock Charlotte? >15,000 Jurassic Unknown Nodular Anhydrite
Report 3-3 2.
Do you think the Miocene sediments comprise an aquifer or confining unit? Defend your answer. (3 points, ☆☆
) Activity 3.5, Paleogeography of Florida (15 Minutes)
O
BJECTIVE
:
To learn how sediments and sedimentary rocks can be used to infer paleogeography, particular in Florida. 1.
Go back to Table III-1 and, for each row, enter into the last column the name of the predominant rock formed during that period. For example, careful study of Table III-2 indicates that nodular evaporite rocks were formed during the Jurassic period, so “Anhydrite” has been entered into the row for Jurassic on Table III-1. Fill in all the entries in the last column of Table III-1. (3 points, ☆
) 2.
Take a yellow colored pencil and lightly cross hatch those rows in Table III-1 that correspond to times when terrigenous clastic
sediment
was being deposited in Florida. (2 points, ☆
) 3.
What mountain range was the source of the terrigenous clastic sediments deposited on Florida? (1 point, ☆
) 4.
The Bahamas is a classic modern example of pure carbonate deposition (i.e., aragonite and calcite). Examine a map of the United States that includes the Bahamas Islands. Why aren’t the carbonate sediments in the Bahamas contaminated with terrigenous clastic sediment shed off the eastern United States? Why doesn’t this sediment reach the Bahamas? (3 points, ☆☆
) 5.
Now speculate why pure limestones, devoid of terrigenous clasts, were able to accumulate during parts of Florida’s geologic history. HINT: think about your explanation for the Bahamas, above. (3 points, ☆☆☆
) ? 6.
How can you explain the sudden influx of terrigenous clastic sediments in Florida indicated by the rows you just colored yellow in Table III-1? (3 points, ☆☆☆
) Activity 3.6, Temperatures beneath Florida (
10 Minutes
)
O
BJECTIVE
:
To learn how to calculate temperatures as a function of depth using the geothermal gradient.
While coring rock FLA-1 (Table III-2), the temperature in the boring was measured at 25.75°C. This is higher than the average temperature on the surface (20°C) because temperature increases toward the center of the Earth. The rate at which temperature increases with depth is called the geothermal gradient
. 1.
Calculate the geothermal gradient in °C/km based on the measurement of 25.75°C for FLA-1. NOTE: there are 3.28 feet /meter, and 1,000 meters in a kilometer. Show your work for full credit! (5 points, ☆☆
)
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