DEPOSITIONAL ENVIRONMENTS OF THE UPPER CRETACEOUS PRINCE CREEK FORMATION, KIKAK-TEGOSEAK DINOSAUR SITE, NORTH SLOPE, ALASKA

BRANDLEN, Erik, D.¹, MCCARTHY, Paul J.¹, FLAIG, Peter P.¹, and FIORILLO, Anthony R.², (1) Dept. of Geology and Geophysics, and Geophysical Institute, University of Alaska Fairbanks, P.O. Box 755780, Fairbanks, AK 99775-5780, [email protected], (2) Dallas Museum of Natural History, P.O. Box 150349, Dallas, TX 75315

The Prince Creek Formation is the most dinosaur-rich high latitude formation in the world but there remains relatively little detailed work that integrates the well known paleontological sites with the local sedimentology. A preliminary facies analysis of the Upper Cretaceous Prince Creek Formation near the Kikak-Tegoseak dinosaur site, North Slope, Alaska, indicates that, overall, the depositional environment was a swampy wetland delta plain. Palynological data suggest the dinosaur site is near the Campanian-Maastrichtian boundary. Typical facies include sandy trough cross-laminated and rippled channel deposits, unconsolidated silt deposits, and organic-rich siltstones and shales. Small, shallow, ribbon-like channels with sharp margins are surrounded by overbank mudstones. Channelized facies at the Kikak-Tegoseak site are dominated by small, non-migrating (probably anastomosed) predominantly fine-grained sandstone channel fills, although larger, coarser-grained sandstone channel fills with well-developed lateral accretion surfaces (meandering channels) have been observed elsewhere within the Prince Creek Formation. Non-channelized facies represent lake, lake margin, levee and crevasse splay environments and primarily poorly drained and weakly developed paleosols. Organic-rich siltstones and coaly shales indicate abundant plant material and hydromorphic environments. Root traces, organic debris and siderite are ubiquitous elements of overbank facies. Bentonites are locally present. The Kikak-Tegoseak bonebed is dominated by the associated skeletal remains of the horned dinosaur, Pachyrhinosaurus. The quarry also contains the cranial and post-cranial remains of several taxa of both large and small theropods, and hadrosaurs. No other bone material has been collected from fine-grained sediments present in the area, and preserved evidence of dinoturbation is extremely rare.