annotated-GEOL%201302%20-%20Lab%2004%20-%20Strat%26Corr.docx
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Geology
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Jan 9, 2024
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5
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GEOL 1302
Lab 04
Stratigraphy and Correlation
In this lab, you are going to review the different stratigraphic approaches and the concept of
correlation, while studying a North Texas stratigraphic section. Please submit your
worksheets to your instructor.
Supplies needed:
1 sheet of graph paper, ruler
Helpful Websites:
http://en.wikipedia.org/wiki/Lithostratigraphy
http://en.wikipedia.org/wiki/Biostratigraphy
http://en.wikipedia.org/wiki/Chronostratigraphy
http://en.wikipedia.org/wiki/Facies
You also find very useful information in your textbook.
Standard lithologic symbols used in stratigraphic sections:
1
Stratigraphy of North Texas
Displayed in the lab is the lithostratigraphy (left and middle) and chronostratigraphy (right)
of the sedimentary units in North Texas in NE-SW direction from Paris (point A) through
Sherman (point B), McKinney (point C), Dallas (point D), to Waxahachie (E). Black layers
illustrate unconformities.
How many unconformities extend all the way from Paris to Waxahachie between the Antlers
(L) rock at the bottom and the Wolfe City rock at the top?
7
The unconformity that occurs at the top of the lithostratigraphic rock unit called the Britton
formation occurred during which chronostratigraphic stage?
Upper Cenomanian
What is the absolute age at the top of the unconformity between the Britton and Acadia Park
lithostratigraphic units?
93.4 mya
Name all the different limestone units (gray brick pattern) in the North Texas stratigraphic
section.
Glenrose, Goodland, Duck Creek, Fort Worth, Waco, Mainstreet, Ector, Atco,
Hutchins, Gober, Roxton, Pecan Gap, Kamp Ranch, Six Flags
2
In the North Texas stratigraphic section, sandstones are shown in olive, limestones in a gray
brick pattern, shales in dark gray, and marlstones (=calcareous mudstones) in lighter gray.
Name the chronostratigraphic stages during which no lateral facies changes occurred in
North Texas.
Walnut, Goodland, Kiamichi, Duck Creek, Fort Worth, Waco, Mainstreet,
Grayson, Britton, Kamp Ranch, Wolfe City
Remember that a typical facies succession from land to sea is sandstone - siltstone or shale –
limestone. During a transgression, these facies shift landward, during a regression they shift
towards the sea. Now study the facies changes for the Middle Albian in the North Texas
section. Based on the succession of rock types, what happened in the area? Explain your
answer.
Goodland remained the same through A-E, Walnut also had no change from A-E.
Antlers was the only one that changed and transitioned into Paluxy.
Now study the Austin Group of the North Texas section. Where and when did the lowest sea
level occur in this section?
Lower Coniacian, 87.3 mya
3
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Lithostratigraphic Correlation in North Texas
In the diagram shown below, section A is located near Del Rio, TX, and section B near
Arlington, TX.
Describe the lithologies in the two sections. What could have caused these successions of
rocks?
Section A
: Dolomite, Limestone, Sandstone, Sandy Shale
Section B
: Dolomite, Sandy Shale, and Sandstone
Draw the best lithostratigraphic correlation between the two sections and explain your
choice.
Dolomite, Sandy Shale, and Sandstone
4
Drawing a Stratigraphic Section
Using the data from the table below and the lithologic symbols from the front page, draw a
stratigraphic section on the sheet of graph paper that you brought to the lab. Don’t forget to
put your name on it, and attach it to this worksheet. Make sure to use an appropriate scale
and plot the correct thickness for each lithologic unit. The units in the table are listed in their
order from the surface down.
Thickness (m)
Rock type
5
Shale
2
Volcanic ash
1
Evaporites
3
Conglomerate
6
Sandstone
3
Dolostone
4
Limestone
1
Marlstone
3
Breccia
4
Sandstone
1
Siltstone
2
Limestone
Where in this section can you identify a marine regression?
From Siltstone to Limestone
5