Episode 35

To close out another wonderful season, Season 3, we here at Geology on the Rocks decided to dive deep into all things about the geology of our home state, Texas. While we planned on talking about the specifics of North Texas, it evolved into a broader historical approach. Discussed is the evolution of the Lone Star State from the Precambrian times all the way through to the Cenozoic. The Texas we know and think of today, began as thick sequences of coarse sediment dumped into an ancient sea bordering Laurasia that was eventually buried, squeezed, and heated. Collisions with subsequent mobile belts eventually led to mountains forming, producing metamorphic schists and gneisses along with generating molten magma. The plutons cooled to form the granitic Llano Province around 1.3 to 1.1 billion years ago during the Mesoproterozoic. These Precambrian rocks are seen today in the Llano Uplift in central Texas and in the Franklin Mountains in west Texas. 

Throughout the Phanerozoic Eon, Texas saw a multitude of marine transgressions and regressions that led to most of Texas' history being submerged by shallow, epeiric seas. This undoubtedly led to the vast expanse of limestones and fossil assemblages we see throughout the state. We also see that during the Carboniferous Period Ouchita Mobile Belt is responsible for the distinctive S-shaped feature seen in geologic maps that spans across Texas. The Permian is responsible for a lot of the red bed formations we see up in the panhandle in the Quartermaster formation and the Dockum Group at Caprock Canyon State Park in Palo Duro Canyon. Near-shore evaporation flats produced deposits of bright red shales along with salt and gypsum deposits. As the supercontinent Pangaea began rifting apart, the Gulf of Mexico began opening allowing for sediment accommodation of the weathering of the uplifted Ouchita Mountains to the southeast. Early restriction of the gulf allowed for multiple evaporative phases that is represented by the famous Louann Salt deposits. 

During the Cretaceous, sandy shorelines and mudflats record the majestic presence of dinosaurs, most famously seen in the Paluxy River in Glen Rose. You name it, Texas probably has it, geologically speaking. Between the bars of our main discussion we bring to you another Mineral Minute and close things out with Leaves, Driving Slow Motion’s latest single from their upcoming album. Sit back and enjoy the Geology of Texas in this final episode of the season! We look forward to starting anew sometime in late August.

Until next time, be cool, stay tuned, and keep it on the rocks!

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