Prince Creek Formation

Habitat

During the time when the fossiliferous beds were deposited, Earth was going through a global cooling phase. The depositional environment included tidally influenced meandering rivers, anastomosed distributary channels, crevasse splays, levees, lakes, ponds, and mires. Large amounts of plants material are represented by peridonoid dinocysts, algae, fungal hyphae, fern and moss spores, projectates, Wodehouseia edmontonicola, bisaccate pollen, taxodiaceous pollen, and pollen from trees, shrubs, and herbs. False rings observed in the dendrochronology of the stumps were likely to have been caused by sudden drops below 10 °C (50 °F) due to fluctuating summer temperatures, but other explanations are possible such as insect damage, flood and drought. Methodologies using oxygen-18 isotope values from fossil vertebrate to estimate average meteoric water temperature have estimated a mean air temperature of around 5 °C (41 °F) for the north slope of Alaska. However there is a growing controversy about temperature estimates from stable isotope tracers during greenhouse conditions, their distributions do not align with the modern global meteoric water line making these results questionable. High but variable mean annual precipitation with low values of 350 to 1200mm/yr and high values of 1000 and 3900mm/yr suggests the presence of an intensified hydrological cycle which enhanced heat transport to the poles. This data supports the interpretation of greenhouse conditions in the Maastrichtian paleo-Arctic.

North of Oceans Point, a section of non-marine deposits represent moderately to poorly consolidated conglomerate, sand, gravelly-sand as well as pebbly shale with thin coal beds and lignitised logs. Many gravel clasts are composed of rock types which do not occur in the nearby parts of the Brooks Range, arguing against the source of local bedrock fragmentation. These clasts are as large as 1.2 meters in diameter with some bearing faceted surfaces characteristic of glacial transportation, though not by iceberg transport, as indicated by the non-marine deposition. These deposits are later assigned a Maastrichtian to lowermost Tertiary age, though recent radiometric revisions in age of older strata could suggest a slightly older age. Palynological assemblages here are characterised by a depauperate assemblage of Betulaceae, Myricaceae, Ulmaceae, Ericales, Pinaceae, Taxodiaceae, various Tracheophytes and Sphagnum. The paleolatitude of the formation at the time of deposition was around 80°N, high in the Arctic Circle, and would have likely experienced 120 days of winter darkness.

Vertebrate paleofauna

Dinosaurs

Theropods

Indeterminate tyrannosaurid remains are present, mostly in the form of teeth. The teeth are from the Kikak-Tegoseak Quarry, Liscomb Quarry, and Byers Bed, totaling 8 teeth. Fossils of crown or near-crown birds as well as members of Hesperornithes and Ichthyornithes have been reported in 2025, providing the oldest evidence of birds nesting at polar latitudes reported to date.

Ornithischians

Mammals

Cartilaginous fish

Ray-finned fish

Plants

A Reinvestigation of the Parataxodium-type flora has revealed the assemblage was far more diverse than previously thought. However, this sedimentary block's stratigraphic origins are uncertain. No other in situ limestone blocks comparable to the Parataxodium-type flora have been located along the Colville River. Rivers upstream from the point of discovery cut through Upper Cretaceous deposits that range in age from Late Albian to Cenomanian. The diversity of flora present is more consistent with the Tuluvak Formation, which is dated to the Turonian-Coniacian.