Module 4 Stratigraphy and Geologic Time Assignment
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University of Texas, Permian Basin *
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Course
1102
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Geology
Date
Jan 9, 2024
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5
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GEOL 1102: Historical Geology Online University of Texas Permian Basin
MAH (2019) modified from Activity by Roger Steinberg, Del Mar College 1 Module 4 Stratigraphy and Geologic Time Using Geologic Maps: A Texas Example Introduction: A geologic map is a map on which geologic information of rocks by rock types and other physical features (geologic formations) at or near the Earth’s surface directly beneath the soil cover is recorded. Rocks at the surface without any soil cover are called exposures or outcrops. Information typically portrayed on geologic maps includes: •
Distribution of rocks by age (Periods or Epochs) •
Distribution of rocks by rock type and other physical features (Geologic Formations). Formations and the age of rocks are both generally shown by different colors and symbols on the map. •
Occurrence of structural features like folds and faults. A good geologic map (with cross sections) is essential to any additional work, such as petroleum and mineral exploration, groundwater studies, or the interpretation of the geologic history of an area. Module Objective:
After successfully completing the following module lab activity, and discussion, you should be able to: •
Identify the age of bedrock using a geologic map •
Interpret the geologic history of an area using a geologic map •
Utilize the surface expression of geologic formations to visualize geologic history and time Purpose: This module explores how geologists use geologic maps to understand the environmental history of an area. You are welcome to collaborate with others in the class, but all work must be completed in your own words. Please use proper spelling on the Canvas quiz or it will count your answers wrong. Supplies: You will use the information provided in the Module Introduction PowerPoint, knowledge from your readings, colored pencils, the 8 ½ x 11” Geologic Map of Texas, the cross section, and the stratigraphic section for South Texas provided in the course module.
GEOL 1102: Historical Geology Online University of Texas Permian Basin
MAH (2019) modified from Activity by Roger Steinberg, Del Mar College 2 Exercise 1: (1) What Formation (by name) is found around Corpus Christi and, in fact, around most of the Texas Coastal Zone? Beaumont Formation (2) What is the age of the formation identified in Question 1? (Give the geologic Epoch). Color in this formation in yellow on Figure 1. Pleistocene In the Mathis, TX area (northwest of Corpus) the flat, clay-rich Pleistocene coastal plain ends, and older, Tertiary aged, Goliad Formation Sandstones can be seen forming hills and in sand quarries. The white sand of the Goliad is very distinctive here and contains abundant fossil horse teeth. (3) What is the age of the Goliad Formation as shown on the geologic map? (Give the Epoch) Miocene
Color in the Goliad Formation orange on Figure 1. The Catahoula Formation is a tuffaceous sandstone. The abundant tuff fragments were blown in from extensive volcanic eruptions hundreds of miles to the west and northwest, in the Trans-
Pecos region. The Catahoula can be seen in outcrops along I-37 (west side of the highway in particular) about 60 miles from Corpus Christi. (4) What is the age of the Catahoula Formation as shown on the geologic map? (Give the Epoch) Oligocene Color in the Catahoula Formation Red on Figure 1. Near Pleasanton, south of San Antonio, snail and clam fossils can be found in the Cook Mountain Formation of the Claiborne Group. (5) What is the age of the Cook Mountain Formation as shown on the geologic map? (Give the Epoch)
GEOL 1102: Historical Geology Online University of Texas Permian Basin
MAH (2019) modified from Activity by Roger Steinberg, Del Mar College 3 Eocene
Color in the Claiborne Group containing the Cook Mountain Formation in red-orange on Figure 1. (6) What is the age (Period) of the rocks portrayed in green on the geologic map, and with a ‘K’ symbol? Mesozoic Rocks of this age are shown in green on most geologic maps made in the United States. Colors are standardized for rocks of each of the Geologic Periods. The southeast edge of the area of outcrop of these rocks passes more or less through San Antonio and Austin and marks the position of both the Late Cretaceous Gulf of Mexico shoreline and the buried, tightly folded Paleozoic rocks of the Ouachita Mountains. The Balcones Fault zone, activated about 10 million years ago follows this same trend. (7) Using the cross section (Figure 2) are the Balcones faults normal or reverse?
Normal (8) If you drilled a well on the border between Guadalupe and Gonzales County, approximately how deep would you have to go to hit the rocks of the Ouachita Fold Belt? About 6000 feet under sea level The Edwards Limestone is the main Hill County aquifer. It is part of the Fredericksburg Group. Color the Edwards Limestone (Fredericksburg Group) rocks yellow and green on Figure 1. All of the dinosaur footprints preserved in Texas rocks are found in the Glen Rose Formation of the Trinity Group.
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GEOL 1102: Historical Geology Online University of Texas Permian Basin
MAH (2019) modified from Activity by Roger Steinberg, Del Mar College 4 (9) What is the age (Period) of the Glen Rose? Mesozoic (10) Was the Glen Rose deposited in the early or late part of the Period identified in (9) above? Early Color the Glen Rose (Trinity Group) rocks green on Figure 1. The best place in the world to find Early Permian vertebrate fossils is in Texas. Color Permian-aged rocks sky (light) blue on Figure 1. Color all of the Pennsylvanian-age rock dark blue on Figure 1. Find the largest area of Precambrian-aged rocks exposed at the surface in Texas. Color this area brown on Figure 1. (11) What two geologic processes have occurred to expose these Precambrian-aged rocks at the Earth’s surface in this area? Weathering and erosion
(12) What kinds of rocks are these Precambrian rocks? Intrusive igneous, volcanic, metamorphic The largest area of Cambrian-aged rocks exposed at the surface in Texas is found next to the Precambrian rocks. Color in the Cambrian rocks purple on Figure 1.
GEOL 1102: Historical Geology Online University of Texas Permian Basin
MAH (2019) modified from Activity by Roger Steinberg, Del Mar College 5 (13) As you drive from Corpus Christi to San Antonio or Austin, the rocks get progressively (older or younger) in age? Older (14) Using your knowledge of environmental change and rock types from the lecture explain this age progression? (15) Upload your completed geologic map (Figure 1) to Canvas.