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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.

AAPG Search and Discovery Article #90058©2006 AAPG Pacific Section Meeting, Anchorage, Alaska