Bronze Pleurocoelus, courtesy Karen Carr
The sound of prehistoric giants slurping water fills the air. Hundreds of dinosaurs are crowded around a muddy lake, an occasional animal being pushed in by the crowd. Ocean waves lap at a beach just a mile away, but the animals can’t drink saltwater. Although the climate isn’t that arid, there are few lakes in the porous ground, which is largely made of limestone and fossilized reefs.
The lake is thirstily shared by a small herd of horned Chasmosaurus and a couple armored Panoplosaurus. An Alamosaurus stretches its long neck out over an area the other dinosaurs can’t reach.
But most of the slurping dinosaurs are duck-billed hadrosaurs. Cows protect their young from the larger, more aggressive bulls, which drink first.
“Splash!” Another hadrosaur has fallen in. Frantically, it scrambles to its feet and tries to penetrate the thick wall of bodies lining the shore.
“SPLASH!!!” The entire herd falls back in alarm as an enormous creature lunges out of the water. It’s a crocodile some fifty feet long! Just as the sea is ruled by Carcharodon, a great white shark that grows to lengths of fifty feet, so is the land ruled by Deinosuchus.
The thick-skinned monster doesn’t really patrol the land. It lies in lakes waiting for land animals to come to it. Not even Tyrannosaurus is safe from this fearsome creature.
The hadrosaur that fell in the water is the luckiest dinosaur on Earth; the Deinosuchus has clamped its awesome jaws on another hadrosaur.
Suddenly, the shadow of another fifty-foot creature falls over the water. Overhead flies a Quetzalcoatlus, a pterosaur with a fifty-foot wingspan.
A human who could travel back in time to this prehistoric scene would feel like a mouse cowering at the feet of the giants that ruled the land, water and sky. But it’s just another day in prehistoric Texas.
Texas boasts fossils of the biggest known pterosaur and crocodile, along with ancient trilobites, “sailfin reptiles,” dinosaurs, Ice Age mammals and lots of stuff in between!
The Great Plains
The Jurassic and Cretaceous rocks found in Texas’ portion of the Great Plains are largely covered by sediments eroded from the Rocky Mountains and deposited by the wind. Mammal remains have been found in several places.
The Edwards Plateau is an area of extensive Cretaceous outcrops, with abundant fossils in places.
Central Lowlands
Many fossils of both land and marine animals from the Permian and Triassic periods have been collected in north-central Texas. Fossils from the older Pennsylvanian Period are also common.
During the Permian, marine invertebrates built great reefs around basins covered by shallow seas. These limestone reefs and banks later acted as giant sponges, soaking up oil from the bodies of dead marine organisms.
Today, much of Texas’ oil comes from a great Permian basin here. Eastern portions of this basin are exposed, while it is covered by younger formations in the west.
Coastal Plain
Looking at a geologic map, you can see that the rock formations underneath pecan trees and orchards seem to parallel the Gulf Coast. That is because they once were coasts themselves. Since the Cretaceous Period, the Gulf Coast has moved farther and farther south.
Standing on a Gulf Coast beach with your back to the sea, you can walk into the past. Waves slap your feet as you stand in the present. Walking inland, you cross over rocks representing the Pliocene Epoch, the Miocene, Oligocene, Eocene...
Finally, you have exited the Cenozoic Era. Dig here and you may discover fossils of creatures that lived over 65 million years ago during the Cretaceous Period of the Mesozoic Era.
Most rocks in the Coastal Plain have few fossils. However, the retreating Gulf of Mexico left behind plentiful fossil shells in the Lower Cretaceous limestones of Central Texas, bones of mosasaurs and plesiosaurs in the Upper Cretaceous limestones of North Texas, and perfectly preserved fossil shells in East Texas’ Eocene deposits. It is along the coastal plain that one would look for Texas’ official state stone, petrified palmwood.
Texas’ official state dinosaur also hails from the Cretaceous. It’s a sauropod (related to the long-necked Brontosaurus) called Pleuroceolus. Far more famous than Pleuroceolus are the fossilized tracks it left along the Paluxy River (a tributary of the Brazos) near Glen Rose now protected in Dinosaur Valley State Park.
Texas’ Gulf Coastal Plain is also important for what lies deep underground. As the Gulf of Mexico widened millions of years ago, evaporating sea water left great salt deposits. Rivers and streams then deposited organic-rich sediments along the coast — or coasts — and on top of the salt deposits.
When the weight of the sediments became too much, the salt formations were fractured and pushed upward as salt domes. Oil then collected around these domes.
Texas’ Favorite Balcony
Within Texas’ Cretaceous beaches zone, there is a very special boundary. An early Spanish explorer named the region Los Balcones — “The Balconies” to describe the land rising like stair-steps above the plains. They are not steps, but a series of faults which represent the ancient edge of Texas when it was joined to South America between 100 and 80 million years ago.
As the continents separated, Cretaceous rocks on the Gulf or ocean side of the faults slipped down thousands of feet. This left the older Cretaceous rocks on the west side of the fault zone standing higher than the surrounding land. Because of this elevated position, underground water forms many springs and caverns along the fault zone. These caverns sheltered such Pleistocene animals as mammoths and saber-tooths, which have left many important fossils.
People have long liked to live near the Balcones escarpment, also. Springs gush forth water, timber grows on the hills, and nearby fertile prairies support agriculture. The escarpment even provides building stone. The Alamo is built of limestone from the Balcones escarpment.
Some of Texas’ most important cities, including Dallas, Waco, Austin, and San Antonio are built along the Balcones Fault Zone. Unlike the area around California’s San Andreas Fault, which is subject to earthquakes, the Balcones Fault Zone is a very stable region.
Basin & Range: The Trans-Pecos
Separated from Mexico by the Rio Grande River and from the rest of Texas by the Pecos River, western Texas, known as the Trans-Pecos, is Pecos Bill country. Among its mountains, lava flows, deserts and cacti are bigger-than-life fossils, including prehistoric reefs. You can see these wonders along the New Mexico border in Guadalupe Mountains National Park or in Big Bend National Park, tucked in a bend in the Rio Grande River near the Mexican border.
During much of the Paleozoic Era, the Trans-Pecos region was under shallow seas. But most Trans-Pecos rocks date to the Permian Period (which ended the Paleozoic), the Cretaceous Period (which ended the Mesozoic Era), and the Eocene and Oligocene epochs of the Cenozoic Era.
The most southerly dinosaurs in the United States have been found in the Trans-Pecos’ Cretaceous rocks. (Dinosaur fossils are found south into South America, however.) While Cretaceous seas covered much of South and East Texas, Big Bend was becoming more rugged, for the Rocky Mountains were rising.
About fifty million years ago, during the Eocene and Oligocene epochs, volcanoes flooded much of the Trans-Pecos with lava. Much of the Trans-Pecos is covered by even more recent sediments.
Desert Reefs
You may know that the largest coral reef is Australia’s Great Barrier Reef. But the largest known fossil reef is in Texas and New Mexico. A portion of this horseshoe-shaped reef, which is nearly 400 miles long, is protected in Guadalupe Mountains National Park along the Texas-New Mexico border.
The principal reef-builders here were lime-secreting algae, not corals. Sponges, bryozoans, and brachiopods also contributed to the reef about 250 million years ago during the Permian period. Their limey skeletons piled up over millions of years. The reef built upwards to 1,300 feet and migrated seaward for miles. Just as modern tidewater glaciers calve chunks of ice, so did chunks of reef fall off to litter the sea floor.
Later, the land was uplifted, and the reef became the Guadalupe Mountains. If you want to see the inside of this fabulous fossil reef, just cross the New Mexico border and visit Carlsbad Caverns National Park.
Trans-Pecos Dinosaurs
Dinosaurs that lived in what is now the Trans-Pecos included at least one long-necked sauropod. Pecos Bill might have appreciated Alamosaurus, which was discovered near the Alamo. There was armored Panoplosaurus, the horned Chasmosaurus, and others. But the most abundant large herbivores appear to have been hadrosaurs.
The largest known flying creature of all time was a pterosaur whose remains have been found in the Trans-Pecos. Quetzalcoatlus boasted a wingspan of about forty feet — as wide as a small airplane!
What preyed on these prehistoric Texans? A few bones suggest the presence of a smaller relative of the northern Tyrannosaurus. But another Cretaceous critter may have preyed on tyrannosaurs...
A Texas Mousetrap
The baddest animal in Trans-Pecos Texas probably wasn’t a dinosaur or a Texas-sized cockroach. It was probably Deinosuchus, a crocodile that may have grown to a length of fifty feet, equal to Quetzalcoatlus ’ wingspan.
Modern crocodiles twenty feet long are considered monsters that can tackle just about every but elephants and hippopotamuses. Ranging north into Montana, Deinosuchus probably ate tyrannosaurs from time to time. Who knows — maybe Quetzalcoatlus was a giant vulture that lived on the scraps Deinosuchus left behind!
Texas’ Uplifts
The town of Llano is surrounded by one of Texas’ most remarkable geologic formations. The earth here has been pushed up into a dome. As higher areas erode faster than lower areas, the oldest rocks are exposed at the center of the dome.
Rocks at the center of the Llano Uplift are dated at 1.35 billion years, probably Texas’ oldest. Rock rings become younger as one walks away from the center of the uplift. Other Texas uplifts include the Van Horn and Solitario.
Straight west of the Llano Uplift in the Big Bend area is the Marathon Basin, where the earth was pushed down. Here the rock rings get younger as you toward the center.
Fossils in Our Lives
The great Spindletop oil field near Beaumont was discovered in 1901 and was followed by other fields in almost every area. Finally, the opening of the giant East Texas field in the early 1930’s produced such a flood of oil that the legislature adopted a policy of limiting production to protect the market and to conserve Texas’ most valuable natural resources.
Today, over ninety percent of Texas’ mineral industry is based on fossil fuels. Texas produces one third of the nation’s domestic crude oil and an even larger percentage of natural gas. Natural gas liquids are also valuable.
The Shock Doctrine: The Rise of Disaster Capitalism - 
