DINOSAUR-BEARING HYPERCONCENTRATED FLOWS OF CRETACEOUS ARCTIC ALASKA: RECURRING CATASTROPHIC EVENT BEDS ON A DISTAL PALEOPOLAR COASTAL PLAIN

Abstract

ABSTRACT The Cretaceous coastal plain of Arctic Alaska contains the richest concentration of high-latitude dinosaurs on Earth. Three bonebeds (Liscomb, Byers, Sling Point) are found in paleopolar (82°–85° N) coastal-plain deposits of the Prince Creek Formation on Alaska's North Slope. 40Ar/39Ar analysis of a tuff below the oldest bonebed (Sling Point) returned an age of 69.2 ± 0.5 Ma indicating a maximum early Maastrichtian age for these bonebeds. Bonebeds are overwhelmingly dominated by partially articulated to associated late-stage juvenile Edmontosaurus sp. Bone is rarely found in channels; instead high-density accumulations are preserved on floodplains in laterally extensive, muddy alluvium. Bone size grading is vertically nonuniform and most bones are in hydraulic disequilibrium with the surrounding clay-rich matrix. Bones exhibit little evidence of rounding, weathering, predation, or trampling, suggesting short-distance transport and rapid burial. Because these bonebeds are unlike typical debris-flo...