UPPER CRETACEOUS BUGEEN TSAV, DJADOKHTA FORMATIONS OF MONGOLIA

Abstract

Upper Cretaceous Bugeen tsav and Djadokhta formations of Mongolia including remarks on previous understandings are discussed and their diagnosis refined. Stratigraphical collumnar sections of type and references localizes and lists of fossils are given. It is shown that two upper cretaceous formations represent different lithological and faunistic units.The only dinosaur and other reptiles genera known to be common to upper cretaceous deposits of Asia and North America are Tyrannosauridae (Tyrannosaurus and Tarbosaurus). Ornithomimidae (Ornithomimus, Gallimimus), Camarosauridae (Sauropods) and Turtles (Trionichidae) several dinosaur and other reptiles families are endemic to Asia and North America.

The stratigraphy of upper Cretaceous rocks of the south Eastern parts of Mongolia was first discussed in Geological and Palaeontological literature in a note by Charles P.Berkey (Granger & Gregory,1923) more detailed results of stratigraphic studies accomplished by members of the Polish-Mongolian Paleontological Expeditions (Lefeld, R.Gradzinsky, Jerzikevicz 1971-1977). The most important excavations were made South Mongolia and important papers on the stratigraphy of the upper cretaceous beds resulted ((I.A.Efremov. 19154.1955, Rozhdestvensky 1975, 1965, 1971, 1974;) Maleev 1952, 1955, 1956).

             Members of the Polish-Mongolian Paleontological Expedition between 1963­-1965 and 1970-1971 also explored parts of southern Mongolia. Geological results of expedition were discussed mainly by Gradzinsky et, al 1969, 1970, Gradzinsky Jerzykiewicz 1972, 1974, kielan Jaworowskal974a. 1975a. 1975c.Lefeld 1965, 1971 and Maryanska & Osmolska 1974, 1975.

The Soviet-Mongolian Paleontological expedition has began to work in Mongolia from south to North, and east to west completely explored by intervals on stratigraphy for cambrian-to Neogenian periods as whole Kramarenko, 1974,Beliaeva1974,Rozhdestven sky1979, Barsbold (1972,1983), Perle (1979,
1931,1982,1993,2005).general essys of the stra tigraphy of Mongolian upper cretaceous deposits were have been provided by Mannov 1957, Vasiliev 1959, Martinson 1975, Barsbo!d(1981,1983).Still now some problems we have discussed about stratigraphical units and formation of the upper cretaceous deposits and refined the diagnoses of two important rock units Bugeen tsav formation and of Djadochta formation presented lists of life assemblages (faunal characteristics) Bugeen tsav formation lithology. Dominant lithology is poorly cemented, fine grained arkosic sandstone of reddish - orange to brick orange fossil - bearing layer 15-20 cm. thin clay strata in the uppermost section of profile we have usually search.