HISTORICAL GEOLOGY
SEMESTER PROJECT
Introduction
The purpose of the project is for you to produce a poster presentation of the historical geology of a county of your choice. The county must be in Texas and must have at least five different rock-units
(rock types e.g. limestone, sandstone, etc. – can include multiple layers of one rock type e.g. different layers of limestone) outcropping at the surface. The objective is to provide the reader with an image of what the county was like at various times in the past (e.g. shallow tropical ocean with abundant coral reefs... hot, dry desert with blowing sand dunes... wet coastal plain with sandy rivers and lush forests, etc.) and explain how these different environmental conditions are recorded by the different layers of rock. The poster design is up to you, but it must include a map and legend of the county’s geology and the following information (in a single table – see attached example for format):
1. Time period (from the youngest to the oldest in your county)
2. Age range in millions of years
3. Outcrop name
4. Lithologic description and approximate thickness
5. Fossils
6. Environment of deposition* (detailed description**)
7. Modern-day analog (should be a well-known place e.g. Padre Island beaches, Texas; Louisiana coastal marshes; Mojave Desert; Brazos River floodplain; Bahamas sea floor)*
You must also include about 1 page of text (on the poster) summarizing the geologic history of the county (starting with the oldest outcrop and ending with the youngest).
Sources of Information
The map library (Willis, government documents) has 1:250,000 scale geology maps covering all of Texas. These are part of the Geologic Atlas of Texas series produced by the Bureau of Economic
Geology, UT Austin. Each map covers about 6 counties. These maps show the rock outcrops in each county and have descriptive notes on the age, lithology, fossils and thickness of each rock type. The maps are available on 2-hour reserve-loan for in-library use – however, you should be able to take the map to a color copier outside the library (you may use a color copy on your poster (map and legend)).
The class textbook contains paleogeographic maps of North America for each time period; these provide an approximate guide to environmental conditions in different parts of Texas at these times. The textbook also describes environmental conditions in different parts of the U.S. (including
Texas) during these time periods. If desired, library and internet searches may yield additional information. Visiting the county to view and photograph rock outcrops, collect rock samples, fossils, etc., may also provide more insight, although this is not a requirement of the project.
The Poster
The poster should be approximately 2 feet by 3 feet in size. Quality of presentation WILL be taken into consideration during grading. All text must be typed. The exact style of the poster is left to your judgement. Include a bibliography somewhere near the bottom - all internet material must be fully referenced. You can find examples of posters around the EESAT building – these may give you ideas for a format.
ALL work must be completely INDEPENDENT.
Due date: May 4th, late penalty 10%/day up to a maximum of 4 days.
* consider these sections the most important part of the project. ** in your OWN words; text copied word for word will not receive high marks.

WILLIAMS COUNTY
TIME PERIOD
NEOGENE/
HOLOCENE
NEOGENE/
PLEISTOCENE
NEOGENE/
MIOCENE
PALEOGENE
CRETACEOUS
PENNSYLVANIAN
AGE
<10,000
OUTCROP
NAME
ALLUVIUM
LITHOLOGY
CLAY, SILT,
SAND, GRAVEL,
ORGANICS
SAND, GRAVEL 10,000 – 1.8
MIL
FLUVIATILE
TERRACE
DEPOSITS
5-23 MIL
23-65 MIL
~65-75 MIL
~299-318
MIL
CATAHOULA
FORMATION
CLAYS, SHALES
WHITSETT
FORMATION
MANNING
FORMATION
CLAYS,
SANDSTONES,
SHALES
CARBONATES
WELLBORN
FORMATION
CARBONATES,
REEFS, MARLS
FOSSILS
PETRIFIED WOOD
PETRIFIED WOOD
RUSHES, SNAILS,
REEDS, GRASSES.
OPHIOMORPHA
(SHRIMP
BURROWS)
BIVALVES, CORALS
ENVIR. OF
DEPOSITION
RIVER
FLOODPLAINS
RIVER
FLOODPLAINS
COASTAL PLAIN,
SWAMPS
SHALLOW
MARINE,
NEARSHORE
EPEIRIC SEA,
TROPICAL
BIVLAVES, CORALS EPEIRIC SEA,
TROPICAL, NEAR
RIVER
MOUTH(S) AT
TIMES
MODERN
ANALOGY
COLORADO
RIVER; OTHER
SIMILAR
RIVERS
TRINITY RIVER;
OTHER
SIMILAR
RIVERS
GULF COAST
COASTAL
PLAIN
GULF COAST
(NEAR -OFF
SHORE)
BAHAMAS
DEEPER
OFFSHORE
CARIBBEAN
DEEPER
OFFSHORE