Tag Archives: fossil

05-14-21 – Jurassic National Monument


Jurassic National Monument, at the site of the Cleveland-Lloyd Dinosaur Quarry, well known for containing the densest concentration of Jurassic dinosaur fossils ever found, is a paleontological site located near Cleveland, Utah, in the San Rafael Swell, a part of the geological layers known as the Morrison Formation.

Well over 15,000 bones have been excavated from this Jurassic excavation site and there are many thousands more awaiting excavation and study. It was designated a National Natural Landmark in October 1965. The John D. Dingell, Jr. Conservation, Management, and Recreation Act, signed into law March 12, 2019, named it as a national monument.

All of these bones, belonging to different species, are found disarticulated and indistinctly mixed together. It has been hypothesised that this strong concentration of mixed fossilised bones is due to a “predator trap”, but any kind of definitive scientific consensus hasn’t been reached yet and debates still continue to the present day.

Source: Wikipedia
https://en.wikipedia.org/wiki/Jurassic_National_Monument

08-08/09-20, 09-12-20 – Rainbow Basin Natural Area

Rainbow Basin is a geological formation in the Calico Peaks range, located approximately 8 miles (13 km) north of Barstow in the Mojave Desert in San Bernardino County, California.

The Rainbow Basin has been designated a National Natural Landmark and is in the Bureau of Land Management managed Rainbow Basin Natural Area. Rainbow Basin is a mixture of private and public land, but it is managed by the Bureau of Land Management. It is accessible to the public via Irwin Road from Barstow to an unpaved loop road through the colorful basin.

The basin is notable for: the fantastic and beautiful shapes of its rock formations: its fossil beds, which have provided scientists with valuable information about life during the middle Miocene epoch, between 12 and 16 million years ago; and to the northeast the Calico Early Man Site.

Underneath Rainbow Basin is the massive batholith that lies below much of the western Mojave. Made from a type of rock called quartz monzonite, this batholith dates to either the Cretaceous, or possibly the late Jurassic period. Early in the Cenozoic Era this batholith was exposed in the area surrounding Rainbow Basin and bent downward as it underwent compression, to form a basin. Sediments deposited in this basin became the sedimentary rocks that are most visible in Rainbow Basin today. Further compression, uplift, and finally extension left these sedimentary formations deeply folded, the most prominent fold being the Barstow Syncline. These same stresses also produced several faults in the Rainbow Basin area.

The thick sedimentary layers can be divided into three distinct formations. The lowest is called the Jackhammer Formation, and it is composed of layers of sandstone, siltstone, limestone, and conglomerate, all probably dating to the early Miocene Epoch.

Above this is the Pickhandle Formation. The sediments making up this formation are mostly of volcanic origin – tuff, rhyolite and andesite, indicating that they were laid down during a period of active volcanism. That time was probably during the early Miocene.

The highest of the three formations is the Barstow Formation, which is made up of layers of conglomerate, limestone, sandstone, and shale. This formation dates to the middle to late Miocene and it contains one of the largest Cenozoic fossil assemblages in North America. Most of the sediment that makes up the layers in this formation was stream-laid, but there is a white layer of rhyolitic tuff (sometimes called marker tuff) near the top.

Finally, on top of everything else, is a relatively thin layer of fanglomerate (alluvial fan deposits) laid down during the late Pleistocene. Differential erosion of rocks of different hardness finished the job of sculpting the formations into the fantastic shapes that can be seen in Rainbow Basin today.

Source: Wikipedia
https://en.wikipedia.org/wiki/Rainbow_Basin

09-18-19 – Jurassic National Monument


Jurassic National Monument, at the site of the Cleveland-Lloyd Dinosaur Quarry, well known for containing the densest concentration of Jurassic dinosaur fossils ever found, is a paleontological site located near Cleveland, Utah, in the San Rafael Swell, a part of the geological layers known as the Morrison Formation.

Well over 15,000 bones have been excavated from this Jurassic excavation site and there are many thousands more awaiting excavation and study. It was designated a National Natural Landmark in October 1965. The John D. Dingell, Jr. Conservation, Management, and Recreation Act, signed into law March 12, 2019, named it as a national monument.

All of these bones, belonging to different species, are found disarticulated and indistinctly mixed together. It has been hypothesised that this strong concentration of mixed fossilised bones is due to a “predator trap”, but any kind of definitive scientific consensus hasn’t been reached yet and debates still continue to the present day.

Unfortunately I arrived only to learn that it was closed for the season, so I explored the surrounding area. I’ll return next year to see the visitor center.

09-16-19 – Dinosaur National Monument


Dinosaur National Monument is a United States National Monument located on the southeast flank of the Uinta Mountains on the border between Colorado and Utah at the confluence of the Green and Yampa Rivers. Although most of the monument area is in Moffat County, Colorado, the Dinosaur Quarry is located in Utah just to the north of the town of Jensen, Utah.

The nearest communities are Jensen, Utah, and Dinosaur, Colorado. The park contains over 800 paleontological sites and has fossils of dinosaurs including Allosaurus, Deinonychus, Abydosaurus (a nearly complete skull, lower jaws and first four neck vertebrae of the specimen DINO 16488 found here at the base of the Mussentuchit Member of the Cedar Mountain Formation is the holotype for the description) and various long-neck, long-tail sauropods. It was declared a National Monument on October 4, 1915. In April 2019, the International Dark-Sky Association designated Dinosaur National Monument an International Dark Sky Park.

The rock layer enclosing the fossils is a sandstone and conglomerate bed of alluvial or river bed origin known as the Morrison Formation from the Jurassic Period some 150 million years old. The dinosaurs and other ancient animals were carried by the river system which eventually entombed their remains in Utah. The pile of sediments were later buried and lithified into solid rock. The layers of rock were later uplifted and tilted to their present angle by the mountain building forces that formed the Uintas during the Laramide orogeny. The relentless forces of erosion exposed the layers at the surface to be found by paleontologists.

The dinosaur fossil beds (bone beds) were discovered in 1909 by Earl Douglass, a paleontologist working and collecting for the Carnegie Museum of Natural History. He and his crews excavated thousands of fossils and shipped them back to the museum in Pittsburgh, Pennsylvania for study and display. President Woodrow Wilson proclaimed the dinosaur beds as Dinosaur National Monument in 1915. The monument boundaries were expanded in 1938 from the original 80-acre (320,000 m2) tract surrounding the dinosaur quarry in Utah, to its present extent of over 200,000 acres (800 km²) in Utah and Colorado, encompassing the spectacular river canyons of the Green and Yampa.

The plans made by the U.S. Bureau of Reclamation on a ten-dam, billion dollar Colorado River Storage Project began to arouse opposition in the early 1950s when it was announced that one of the proposed dams would be at Echo Park, in the middle of Dinosaur National Monument. The controversy assumed major proportions, dominating conservation politics for years. David Brower, executive director of the Sierra Club, and Howard Zahniser of The Wilderness Society led an unprecedented nationwide campaign to preserve the free-flowing rivers and scenic canyons of the Green and Yampa Rivers. They argued that if a national monument was not safe from development, how could any wildland be kept intact? On the other side of the argument were powerful members of Congress from western states, who were committed to the project in order to secure water rights, obtain cheap hydroelectric power and develop reservoirs as tourist destinations. After much debate, Congress settled on a compromise that eliminated Echo Park Dam and authorized the rest of the project. The Colorado River Storage Project Act became law on April 11, 1956. It stated, “that no dam or reservoir constructed under the authorization of the Act shall be within any National Park or Monument.” Historians view the Echo Park Dam controversy as signaling the start of an era that includes major conservationist political successes such as the Wilderness Act and the Wild and Scenic Rivers Act.