Vertebrate ichnology and palaeoenvironmental associations of Alaska’s largest known dinosaur tracksite in the Cretaceous Cantwell Formation (Maastrichtian) of Denali National Park and Preserve

ABSTRACT

The Upper Cretaceous Cantwell Formation in Denali National Park and Preserve (DENA) preserves an abundant and diverse ichnofossil record of high latitude dinosaurs. Field-based investigations of the formation remain limited due to its wide areal extent and remoteness, leaving questions concerning its temporal and faunistic relationships to other units unaddressed. Here we describe the largest tracksite known in DENA and all of Alaska – a 7500 square metre outcrop of steeply dipping beds known as the Coliseum. The site exposes 66.3 metres of vertical section consisting of laterally extensive fine- to medium-grained sandstone, mudstone, calcareous shale, and bentonite. Vertebrate trace fossils include true tracks, transmitted tracks, natural casts, and trackways documented via handheld and UAV-assisted photogrammetry, enabling three-dimensional mapping of the site. Facies analysis reveals a depositional environment of crevasse splay and overbank deposits within a fluvial floodplain. U-Pb dating of bentonite collected from the site returned an age of 69.3 ± 0.9 Ma, improving the limited temporal constraints of the formation. We document several ichnotaxa, some new to the formation, representing ornithopods, ceratopsids, and large and small-bodied avian and non-avian theropods. The Coliseum provides a rare window into a high latitude, Late Cretaceous forested ecosystem deposited in a Greenhouse World.

KEYWORDS:

• Palaeontology
• ichnology
• Palaeoenvironment
• dinosaur tracks
• Denali National Park and Preserve
• Alaska

Acknowledgments

We thank UAMN staff and volunteers, including R. Missler, T. Wensaas, H. Mirczak, M. Sterling, H. MacFarlane, J. Rynasko, N. Freymueller, T. Hunt, N. Boone, C. Heninger, E. Metz, and K. Anderson. We recognize the initial discovery at the site by T. Jacobus, S. Fowell. S. Tomsich assisted with palaeofloristic identifications. The Alaska Center for Unmanned Aircraft Systems Integration provided UAV support for aerial photogrammetry. We thank D. Schirokauer and the National Park Service for administrative and logistical support. This work was supported by Cynthia and David Schraer, the Geist Fund, NPS grant P15AC01027, and National Science Foundation grants EAR 1226730 (to P. Druckenmiller and G. Erickson) and EAR 1736515 (to P. Druckenmiller, G. Erickson, and J. Eberle).

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/08912963.2023.2221267.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Park Service [P15AC01027] and the National Science Foundation [EAR 1226730] and [EAR 1736515].