The Nemegt Formation is a geological formation located in the Gobi Desert of Mongolia. It dates back to the Late Cretaceous period and contains a variety of fossils of fish, turtles, crocodilians, and a diverse fauna of dinosaurs, including birds. The formation consists of river channel sediments, and its lowest section includes grey-to-brown lenticular paleochannel sandstones, alluvial sheet sandstones, and planar laminated red-brown to grey-green mudstones and fine-grained sandstones of paludal and lacustrine origin.
One of the most significant discoveries in the Nemegt Formation was the Deinocheirus, a large ornithomimosaur that lived during the Late Cretaceous around 70 million years ago. In 1965, a pair of large arms, shoulder girdles, and a few other bones of a new dinosaur were first discovered in the Nemegt Formation of Mongolia. This specimen later became the holotype of the only species within the genus Deinocheirus.
The Nemegt Formation is an essential site for paleontologists and geologists because of its rich history of fossils and its unique geological features. The formation’s fossils provide valuable information about the diverse fauna that lived during the Late Cretaceous period, while its geological features offer insight into the environmental conditions that existed during that time.
Geological Background
The Nemegt Formation is a Late Cretaceous geological formation located in the Gobi Desert of Mongolia. It consists of river channel sediments and is known for its diverse fauna of dinosaurs, including birds, as well as fish, turtles, and crocodilians.
Stratigraphy
The Nemegt Formation is part of the Nemegt Basin, which is situated in south-central Mongolia. It is composed of several different layers, including the Baruungoyot Formation and the Djadochta Formation. The Nemegt Formation is the uppermost layer and is estimated to be around 70-71 million years old.
Sedimentology
The Nemegt Formation is made up of river channel sediments, which were deposited by a series of braided rivers that flowed through the area during the Late Cretaceous period. The sediments are composed of sandstones, mudstones, and conglomerates, which were transported and deposited by the rivers.
Paleoenvironment
The Nemegt Formation is known for its diverse fauna of dinosaurs, which provides important insights into the paleoenvironment of the Late Cretaceous period. The area was once a floodplain, with a warm and humid climate that supported a variety of plant and animal life. The presence of river channels in the formation suggests that the area was also prone to flooding, which would have created a dynamic and ever-changing environment for the dinosaurs and other animals that lived there.
Location and Discovery
Geographic Setting
The Nemegt Formation is a geological formation in the Gobi Desert of Mongolia, dating to the Late Cretaceous. The formation consists of river channel sediments and contains fossils of fish, turtles, crocodilians, and a diverse fauna of dinosaurs, including birds. The Nemegt Basin is located in the southern part of Mongolia and is approximately 200 kilometers long and 40 kilometers wide.
History of Research
The Nemegt Formation was first discovered in the 1920s by the Polish-Mongolian expeditions led by Roy Chapman Andrews. However, the formation was not fully explored until the 1990s when the Japanese-Mongolian expeditions led by Rinchen Barsbold and Yoshitsugu Kobayashi began their research. The expeditions uncovered a vast array of fossils, including some of the most spectacular dinosaur specimens ever found. Since then, many other expeditions have explored the Nemegt Formation, leading to the discovery of new species and a better understanding of the Late Cretaceous ecosystem.
In recent years, the Nemegt Formation has become a popular destination for paleontologists and tourists alike. The area has been designated a UNESCO World Heritage Site and is now protected by the Mongolian government. Despite this protection, however, the Nemegt Formation is still threatened by illegal fossil hunting and mining activities.
Paleontology
The Nemegt Formation is well-known for its diverse and rich fossil record. The formation contains fossils of various vertebrates and invertebrates such as dinosaurs, fish, turtles, crocodilians, and plants.
Dinosaur Fauna
The Nemegt Formation is particularly famous for its dinosaur fauna. The formation has yielded fossils of several species of dinosaurs, including the theropod Tarbosaurus bataar, the ankylosaurid Tarchia teresae, the ornithomimid Anserimimus planinychus, and the oviraptorosaur Nemegtomaia barsboldi. The formation has also yielded fossils of various other dinosaur species, including hadrosaurs, ceratopsians, and sauropods.
Other Vertebrates
Apart from dinosaurs, the Nemegt Formation also contains fossils of various other vertebrates such as fish, turtles, and crocodilians. The formation has yielded fossils of several species of fish, including the ray-finned fish Hiodon sp., the lungfish Ceratodus sp., and the coelacanth Latimeria sp. The formation has also yielded fossils of turtles and crocodilians, including the turtle Mongolochelys efremovi and the crocodilian Gobiosuchus sp.
Invertebrates and Plants
The Nemegt Formation also contains fossils of various invertebrates such as bivalves, gastropods, and ammonites. The formation has yielded fossils of several species of bivalves and gastropods, including the bivalve Unio sp. and the gastropod Viviparus sp. The formation has also yielded fossils of several species of ammonites, including the ammonite Baculites sp. The formation also contains fossils of various plants such as ferns, cycads, and conifers. The formation has yielded fossils of several species of ferns, including the fern Osmunda sp., the cycad Cycadeoidea sp., and the conifer Pinus sp.
Taphonomy and Preservation
The Nemegt Formation is an important geological formation in the Gobi Desert of Mongolia, dating to the Late Cretaceous period. It contains a diverse fauna of dinosaurs, including birds, fish, turtles, and crocodilians. Preservation of these fossils is crucial for understanding the evolution and behavior of these extinct animals.
Taphonomy is the subdiscipline of paleontology related to the processes of fossilization. It includes all things that happen to the remains of an organism after it dies until it is observed or collected by a geoscientist. This might include the decay of soft tissues, the separation of skeletal hard parts, and chemical changes to the organism.
The famous “Dragon’s Tomb” Saurolophus bonebed at Altan Uul II preserves multiple complete skeletons with skin impressions and is exceptional among Nemegt Formation dinosaur localities as the only mass accumulation of articulated individuals. Sedimentological and taphonomic observations on the bonebed have revealed that the skeletons were buried rapidly after death in a fluvial environment, which helped to preserve the soft tissues and skin impressions. The preservation of such delicate features can provide valuable insights into the anatomy and behavior of these animals.
Research and Significance
Paleobiological Studies
The Nemegt Formation has been a subject of extensive paleobiological research due to its rich fossil record. The formation contains fossils of various species of dinosaurs, including birds, crocodilians, turtles, and fish. The fossils of these animals have provided valuable insights into the evolution and ecology of these ancient creatures. Paleobiologists have been able to study the morphology, behavior, and physiology of these animals by examining their fossils. The Nemegt Formation has contributed significantly to our understanding of the Late Cretaceous ecosystem in the Gobi Desert.
Comparative Analysis
Comparative analysis of the fossils found in the Nemegt Formation with other Late Cretaceous fossil records from around the world has revealed interesting patterns of biogeography and evolution. The similarities and differences between the Nemegt Formation fauna and those of other regions have helped scientists understand the dispersal and migration patterns of these animals. The Nemegt Formation fossils have also helped in resolving taxonomic uncertainties and in revising the evolutionary relationships of various dinosaur groups. Comparative analysis of the Nemegt Formation fossils has also revealed the presence of unique dinosaur species that were not previously known to science.
In conclusion, the Nemegt Formation has played a crucial role in advancing our knowledge of Late Cretaceous ecosystems and the evolution of dinosaurs. The rich fossil record of the formation has provided a wealth of information to paleobiologists and has helped in resolving many taxonomic and evolutionary uncertainties. The comparative analysis of the Nemegt Formation fossils with those of other regions has also revealed interesting patterns of biogeography and evolution.