33 GSA: Accreted Terranes of Western North America: An Update on Current Research on the Construction of the Cordillera II

Wednesday, 10 May 2006
8:20 AM - 11:20 AM

THE FIRST RECORD OF DINOSAURIA AND FOSSIL AVES FROM THE LOWER CANTWELL FORMATION (LATEST CRETACEOUS), DENALI NATIONAL PARK

Paper number: 33-4
Program: THEME SESSIONS
Time: 9:20 AM – 9:40 AM

Authors

Abstract

The Cantwell Formation (Late Cretaceous to Early Tertiary) is a thick rock unit that crops out in much of the central part of Denali National Park. The lower part of this succession is dominantly comprised of fine-grained channel and floodplain sedimentary facies, including crevasse splay, crevasse delta, levee, and minor lacustrine and palustrine components. Floodplain deposits contain abundant evidence of weak pedogenesis, including root traces, blocky structure, iron oxide mottles and nodules, suggesting widespread poorly drained conditions in a highly aggradational setting. The upper Cantwell succession is largely volcanic. The lower Cantwell Formation correlates in age with the famous dinosaur-bearing rocks of the Prince Creek Formation of the North Slope of Alaska, as well as the dinosaur-bearing Chignik Formation of Aniakchak National Park in southwestern Alaska.

Three new vertebrate fossil sites have been discovered in Denali National Park. The first locality, along Igloo Creek yielded the impression of an isolated right pes of a medium-sized theropod. The track measures approximately 22 cm in length and 15 cm in width, which provides an estimated hip height of approximately 90 cm and a body length of approximately 3 m.

The remaining two localities were found on Double Mountain. One site produced an additional partial impression of a theropod approximately the same size as the one from the Igloo Creek locality. The remaining locality is in a lacustrine facies and has yielded dozens of tracks attributable to a medium-sized wading bird. The morphology of the tracks indicates the substrate was still very wet when these birds walked on the surface.

These footprints demonstrate that the Cantwell Formation has great potential as a fossil vertebrate-bearing rock unit. And lastly, the assembling of Beringia through accretion began in the Cretaceous and these discoveries highlight the biological diversity of Beringia.