Eolian Environments, Paleo-Wind-Direction and Dinosaur Habitats of the Upper Cretaceous Djadokhta Formation, Central Gobi Desert, Mongolia

The Djadokhta Formation (Mid-Campanian) is widely distributed in the central Gobi Desert, Mongolia, known as dinosaur fossiliferous beds. We reports the relationships among paleoenvironments, paleo-wind-direction and dinosaur habitats from the formation based on the data from the fossil localities such as: Tugrikin-Shireh, Bayn Dzak, Udyn Sayr and Alag Teg.

The Djadokhta Formation consists of eolian deposits with minor fluvio-lacustrine deposits. In the Tugrikin-Shireh, the formation is comprised of a large number of eolian dune deposits which exhibit large-scale cross bedding. These eolian deposits are divided, from base to top, into Unit1, Unit2 and Unit3. These units are separated by 1st order boundary. These eolian deposits contain diverse trace fossils from 5.0 to 100 cm in length. The formation in the Bayn Dzak and Udyn Sayr is characterized by red colored eolian sandstone containing caliche beds and fluvio-lacsustrine deposits that are only minor components of the sites. In the Alag Teg, the formation consists of fluvio-lacustrine deposits that have been covered by eolian sand dune deposits. Many eolian deposits in these sites suggest that paleoenvironments in Djadokhta age are interpreted to sand sea conditions with transverse dune fields which are indicated by the large-scale cross bedding, in spite of rare co-existence of small-scaled fluvio-lacustrine. Paleo-wind-direction, that were obtained by dip data of large-scale cross bedding in eolian deposits, show a strongly unimodal flow to a sector from the north to the east.

Many dinosaur remains, such as, Protoceratops, Velociraptor, Oviraptor, Pinacosaurus, eggs and egg nests are discovered form this formation. In the Tugrikin-Shireh, each boundary zone of those eolian deposits is characterized by rich findings of dinosaur eggs and egg nests. This fossil occurrence suggests that eolian environment, especially interdune fields, had been utilized as a constant habitat by dinosaurs.