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The geology of Ukhaa Tolgod (Djadokhta Formation, Upper Cretaceous, Nemegt Basin, Mongolia) ; American Museum novitates, no. 3616

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dc.contributor.author Dingus, Lowell. en_US
dc.contributor.author Loope, David B. en_US
dc.contributor.author Dashzeveg, Demberelyin. en_US
dc.contributor.author Swisher, Carl Celso. en_US
dc.contributor.author Minjin, Chuluun. en_US
dc.contributor.author Novacek, Michael J. en_US
dc.contributor.author Norell, Mark. en_US
dc.date.accessioned 2008-06-23T15:02:31Z
dc.date.available 2008-06-23T15:02:31Z
dc.date.issued 2008 en_US
dc.identifier.uri http://hdl.handle.net/2246/5916
dc.description 40 p. : ill. (some col.), maps ; 26 cm. en_US
dc.description Includes bibliographical references (p. 35-40). en_US
dc.description.abstract The lithostratigrahy and sedimentology of the fossiliferous Upper Cretaceous strata exposed in the Gobi Desert of Mongolia at Ukhaa Tolgod are described and mapped on aerial photos. Topographic features are also mapped by plane table and alidade. Five lithologic and sedimentologic facies are described: E-1, distinctly cross-stratified sandstone with fine structure, interpreted to represent eolian dune deposits; E-2, vaguely bedded sandstone with cross-stratified concretionary sheets, interpreted to represent eolian dune deposits modified by diagenetic formation of slope-parallel concretionary sheets of pedogenic calcite; S, structureless sandstone lacking concretions or cross-strata, interpreted to represent sandslide deposits generated by mass wasting along the lee slopes; C, conglomerate interpreted to represent basin-margin conglomerates washed into the dune field from adjacent topographic highs; and M, mudstone and siltstone interpreted to represent interdune deposition in ephemeral ponds and lakes. Facies E-2 and S have not been reported previously. Eleven stratigraphic sections at various localities within the Ukhaa Tolgod drainage basin are documented. The exposed composite section consists of about 75 m of pale orange sandstones, greenish-brown conglomerates, and brown siltstones that are products of an arid environment. Four schematic cross sections are documented to illustrate the lateral relationships among the five facies. In the Ukhaa Tolgod area, the beds dip about 2.5° to the south, away from the nearby Gilbent Range. This structural attitude is interpreted to be related to the uplift of the Gilbent block along normal faults exposed at the base of the range. The strata at Ukhaa Tolgod are referred to the Djadokhta Formation. Similar to the classic Djadokhta exposures at Bayn Dzak, the sequence of strata reflects a mixture of facies E-1, E-2, S, and M in the lower part of the section, with prominent beds of Facies C near the top. The dune-derived sandslides of Facies S contain a rich skeletal fauna of Late Cretaceous dinosaurs, mammals, and lizards. Essentially, all the skeletal remains collected at Ukhaa Tolgod come from Facies S. Facies E-1 does contain numerous, concave-up depressions in the cross-strata interpreted as vertebrate tracks. Facies E-2 contains abundant cylindrical structures interpreted as burrows. As seen in the Bayn Dzak Member at Bayn Dzak, facies E-1, E-2, S, and M dominate the lower part of the section at Ukhaa Tolgod, with prominent beds of Facies C exposed near the top. Accordingly, the exposures at Ukhaa Tolgod are referred to the Bayn Dzak Member of the Djadokhta Formation. Classic exposures of the Barun Goyot Formation at Khulsan differ in having units of flat-bedded sandstone intercalated with beds of Facies S near the top of the section. To date, over 1,000 vertebrate skulls and skeletons have been collected from Facies S. Most are preserved as float contained in small calcareous nodules; however, some were found in situ. Many specimens represent either fairly complete skulls or skulls with articulated or associated postcranial skeletons. Based on faunal similarities between Bayn Dzak and Ukhaa Tolgod, the fauna at Ukhaa Tolgod is interpreted to reflect a Campanian age. The rich assemblage of fossils makes Ukhaa Tolgod one of the richest Late Cretaceous vertebrate fossil localities in the world, and the fossils provide unique insights into evolutionary developments of mammals, lizards, and dinosaurs, including birds, less than 10 my before the terminal Cretaceous extinction event. en_US
dc.format.extent 29186498 bytes
dc.format.mimetype application/pdf
dc.language eng en_US
dc.language.iso en_US
dc.publisher New York, NY : American Museum of Natural History en_US
dc.relation.ispartofseries American Museum novitates, no. 3616 en_US
dc.subject.lcc QL1 .A436 no.3616 2008 en_US
dc.subject.lcsh Geology, Stratigraphic -- Cretaceous -- Mongolia -- Ukhaa Tolgod. en_US
dc.subject.lcsh Geology -- Mongolia -- Ukhaa Tolgod. en_US
dc.subject.lcsh Paleontology -- Cretaceous -- Mongolia -- Ukhaa Tolgod. en_US
dc.subject.lcsh Vertebrates, Fossil -- Mongolia -- Ukhaa Tolgod. en_US
dc.subject.lcsh Paleontology -- Mongolia -- Ukhaa Tolgod. en_US
dc.title The geology of Ukhaa Tolgod (Djadokhta Formation, Upper Cretaceous, Nemegt Basin, Mongolia) ; American Museum novitates, no. 3616 en_US
dc.type text en_US


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  • American Museum Novitates
    Novitates (Latin for "new acquaintances"), published continuously and numbered consecutively since 1921, are short papers that contain descriptions of new forms and reports in zoology, paleontology, and geology. New numbers are published at irregular intervals.

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