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Everything you know about the Iren Dabasu age is wrong...
...or so it seems, from a forthcoming paper in Cretaceous Research.
van Itterbeecka, J., D.J. Horne, P. Bultynck, and N. Vandenbergh. 2005.
Stratigraphy and palaeoenvironment of the dinosaur-bearing
Upper Cretaceous Iren Dabasu Formation, Inner Mongolia, People's Republic of
China. Cretaceous Research, in press.
New field observations and sedimentological analyses of the dinosaur-bearing
Upper Cretaceous Iren Dabasu Formation in the Iren Nor
region of Inner Mongolia (People's Republic of China) have led to a better
understanding of its palaeoenvironment. The fluvial
deposits represent a braided river that, due to the large amount of fines, does
not fit the classical model for braided rivers. The
study area is divided into two parts: in the northern part, sediments of the
main channel belt of the ancient braided river system
are exposed along a dry river valley on the northern edge of the Iren Nor salt
lake, while in the southern part, comprising all
other studied exposures, different facies of the ancient floodplain are
represented, including minor channels, temporary ponds, and
palaeosols. The difference between the northern and southern parts is also
reflected in the fossil content; only the southern
exposures have yielded dinosaur remains. The ancient braided river had a broad,
vegetated floodplain populated by a diverse dinosaur
fauna. Four species of charophytes are described and illustrated from the Iren
Nor site, together with eight species of ostracods,
one of which (Cypridea irennorensis sp. nov.) is new. Contrary to the
vertebrate data, both groups of microfossils indicate a latest
Cretaceous age (Campanian?Maastrichtian) for the Iren Dabasu Formation, and
suggest a possible correlation with the Nemegt
Formation, which would allow the age estimation to be refined to latest
Possible correlation with the Nemegt?!? Yeah, I knew the stratigraphy there was
poorly understood, but the Iren Dabasu and Nemegt
were traditionally considered as opposite ends of the stack of dinosaur bearing
Late K sediments.
Thomas R. Holtz, Jr.
Senior Lecturer, Vertebrate Paleontology
Department of Geology Director, Earth, Life & Time Program
University of Maryland College Park Scholars
Building 237, Room 1117
College Park, MD 20742
Phone: 301-405-4084 Email: firstname.lastname@example.org
Fax (Geol): 301-314-9661 Fax (CPS-ELT): 301-405-0796