GEOL 1302 - Extra Credit Lab JA.docx
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University of Texas, San Antonio *
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1302
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Geology
Date
Jan 9, 2024
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Uploaded by ElderHawkPerson1000
GEOL 1302
Extra Credit
Geology of Texas
In this lab, you are going to research “milestones” of Texas’ geologic history. Please submit
your completed lab on Canvas under Extra Credit.
Please study the following websites on the geologic history of Texas in order to answer the
questions:
https://texasalmanac.com/topics/environment/geology-texas-0
https://tshaonline.org/handbook/online/articles/swgqz
https://www.dallaspaleo.org/Surfac
https://txpub.usgs.gov/txgeology/
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Questions about the Geologic History of Texas
1. When did the geologic story of Texas begin, and where are the oldest rocks found?
The
geologic story of Texas began over a billion years ago. The oldest rocks are found in the
Llano Uplift in central Texas, dating back to the Precambrian period, around 1.3 to 1.0 billion
years ago.
2. Where are the Ouachita Mountains located, and when and how did they form?
The
Ouachita Mountains are located in the southeastern United States, primarily in Arkansas and
Oklahoma. They formed around 300 to 250 million years ago during the Late Paleozoic Era
through the collision of tectonic plates, a process known as the Ouachita orogeny.
3. What was the landscape like in West Texas during the Late Paleozoic Era (in the Permian
Period)?
During the Late Paleozoic Era (Permian Period) in West Texas, the landscape
featured a shallow sea that periodically advanced and retreated, depositing marine sediments
like limestone and shale. Over time, the sea retreated, leading to the development of coastal
plains and terrestrial environments with sandstones and mudstones. The region experienced a
transition from marine to terrestrial conditions.
4. Describe the Texas landscape during the Late Mesozoic Era (during the Cretaceous
Period).
During the Late Mesozoic Era, the Texas landscape featured a shallow sea covering
parts of the state. The Western Interior Seaway extended into what is now Texas, depositing
marine sediments. The land also had coastal plains with river systems, and there were forests
and diverse plant and animal life. Fossils from this time include marine reptiles, ammonites,
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and dinosaurs. The Cretaceous landscape in Texas was a mix of marine and terrestrial
environments.
5. Now go to the United States Geological Survey website for Texas and look at the rock
units present in the State of Texas:
https://txpub.usgs.gov/txgeology/.
Under "Search for a place", enter the following locations: Abilene, Mineral Wells, Arlington,
Huntsville, Houston (always choose the “City”). For each location, choose “Zoom to”, click
on “Rock Units”, click on the city name, then note the period, the epoch or series, and the
major rock type(s).
Abilene:
Permian, Leonard, Mudstone Limestone, dolomite, siltstone
Mineral Wells:
Pennsylvanian, Des Moines, Shale, Sandstone, limestone, and conglomerate
Arlington:
Cretaceous, gulfian, sandstone, clay, and shale
Huntsville:
Tertiary, Miocene, clay, silt, and sand
Houston:
Quaternary, holocene, pleistocene, clay, and mud
Overall, as you get closer to the Gulf Coast, which trend do you notice when looking at the
ages of the rocks exposed at the various locations?
As you move closer to the Gulf Coast in
Texas, the rocks exposed at various locations become progressively younger.
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