A Paleontological Paradise
NPS/Big Bend National Park
The Ruling Reptiles
The fossil record here spans a rich history of 35 million years within the Cretaceous Period. Beginning about 100 million years ago, when a huge sea covered what is today most of the midwestern U.S., the of the ruling reptiles appeared in Big Bend's fossil record. The sea layers of limestone known as the Boquillas Formation (100-95 million years ago) preserve numerous marine fossils, including a 30-foot long sea-dwelling reptile known as Mosasaurus.
The most exciting finds have occured in strata that chronicle Big Bend's emergence from this sea. Nearly 70 dinosaur species have been discovered in the Aguja Formation (80-75 million years ago) where we find evidence of a humid and swampy land. At this time, Big Bend was closer to the equator, and this tropical coastal swamp had palms, ferns, and diverse dinosaur life, including duck-billed Hadrosaurs.
By 75-60 million years ago, plant fossils suggest that the sea had retreated and Big Bend had become a drier floodplain environment. The sediments from these times, the Javelina Formation, have yielded over 80 species of plants, including cypress, laurel, conifers, and mangroves. While these plant finds are remarkable in their own right, they are usually overshadowed by several unique and spectacular dinosaur finds. Over 20 dinosaur species have been found in the Javelina Formation, giving us a rich glimpse into the last days of the ruling reptiles. These were the giants who ruled the earth at the time of the great extinction. These finds, and the possibility of future discoveries, make these sediments worth their weight in gold for paleontologists.
Did You Know?
Many people have searched for the lost mine and other metallic deposits in the Chisos Mountains of Big Bend National Park. One of these was Homer Wilson, a geologist, who divided his time between ranching and mining from 1929-1942. More...