Discover the USA and Explore the Fossils and Geodiversity of the North Slope in Alaska
- Wayne Munday
- Oct 4
- 4 min read
Sip back and discover the USA and explore the fossils, dinosaurs and geodiversity of the Prince Creek Formation in North Slope high in Alaska’s Arctic that preserves one of Earth's most northerly polar dinosaur ecosystems from the Late Cretaceous. Located along the Colville River and its tributaries in one of North America’s most remote fossil regions. Deposited between the Brooks Range and the Arctic Ocean on a tidally influenced alluvial–deltaic coastal plain these sediments of sandstone, siltstone, coal, organic-rich mudstone, and bentonites capture an environment of rivers, floodplains, swamps and crevasse splays that once supported a thriving polar ecosystem that experienced prolonged winter darkness and cool seasonal climates. Fossil evidence from key sites such as the Liscomb Bonebed and the Kikak-Tegoseak Quarry reveals dense accumulations of hadrosaurid dinosaurs including the Arctic species Ugrunaaluk kuukpikensis as well as lambeosaurines, horned dinosaurs like Pachyrhinosaurus, theropods, birds, fish and small mammals demonstrating year-round Arctic living rather than seasonal migration. The fossil record here highlights unique evolutionary adaptations including the earliest salmonids (Sivulliusalmo alaskensis), pike-like esocids, sturgeon, paddlefish and the shark Squatina while ectothermic vertebrates common at lower latitudes are absent. Collectively, these discoveries define a high-latitude Paanaqtat Province or distinct polar faunal community shaped by isolation, extreme seasonal light, and environmental pressures. Ongoing erosion along the Colville River continues to expose new fossils, providing critical insight into Arctic dinosaur ecology and the resilience of polar ecosystems during the Late Cretaceous.
Outcrops of the Prince Creek Formation are exposed from east to west along sections of the Colville River and tributaries of the Kogosukruk and Kikiakrorak rivers flowing into the Arctic Ocean. This fossil location is one of the most remotest in North America and lies hundreds of kilometers from the nearest town of Prudhoe Bay to the east and the City of Utqiaġvik (formerly Barrow) to the west.
High in the remote Arctic reaches of northern Alaska lies the Prince Creek Formation an expansive foreland basin bounded to the south by the rugged Brooks Range and to the north by the icy margin of the Arctic Ocean. The Prince Creek Formation is a Late Cretaceous alluvial–deltaic coastal plain succession deposited in the Colville Basin north of the Brooks Range and dated to between the late Campanian – late Maastrichtian around 70 – 66 million years ago. Preserved along the Colville River and its tributaries the Prince Creek Formation is not only one of the most northerly dinosaur-bearing formations in the world but also tells a story of a high-latitude polar ecosystem.
Deposited between the Brooks Range and the Arctic Ocean on a tidally influenced coastal and alluvial plain. Over time, compaction and cementation altered the sedimentary rocks, while iron mineralisation has stained many fossils with reddish-brown hues. Unlike more tectonically active mountain belts the Prince Creek Formation is not heavily folded or thrust-faulted.
The dinosaur and mammal fossils of the Prince Creek Formation support the existence of a distinct polar faunal region called the Paanaqtat Province where vertebrate communities were unique to this Arctic area, shaped by isolation, extreme seasonal conditions, and environmental pressures in contrast to those farther south in Laramidia.
For example, species such as the hadrosaur Ugrunaaluk kuukpikensis and the tyrannosaurid Nanuqsaurus hoglundi are found only in this Arctic region while terrestrial ectotherms like crocodilians, turtles and amphibians are absent. The fossil record of the Prince Creek Formation also reveals unique evolutionary adaptations among teleost fishes and birds including the earliest salmonid (Sivulliusalmo alaskensis), Esocidae of pike like fish including Archaeosiilik gilmulli and Nunikuluk gracilis, the earliest cypriniform, sturgeon, paddlefish and the shark Squatina. Notably several fish that were common at lower latitudes including Myledaphus, lepisosteids and amiids are also absent highlighting the distinctiveness of this Arctic faunal ecosystem.
One of the most intriguing carnivores is Nanuqsaurus hoglundi a small relative of Tyrannosaurus rex. With proportionally larger olfactory bulbs this reflect the predator's olfactory acuity was highly developed and crucial for detecting prey and may have been adapted to hunting in low-light conditions an essential skill in an environment that spent months in winter darkness. Evidence suggests that these dinosaurs were not seasonal migrants but permanent residents of the polar floodplain. They endured long periods of darkness and cold.
Within the Prince Creek Formation a key fossil-bearing locality is the Liscomb bonebed known for its dense concentration of hadrosaur remains. The bonebed is part of a nearly 200 meter sequence overwhelmingly dominated by thousands of disarticulated bones from herds of late juveniles hadrosaurids called Edmontosaurus sp. an Arctic hadrosaur called Ugrunaaluk kuukpikensis and the presence of a lambeosaurine hadrosaurid that indicates links between Arctic and lower-latitude regions of North America suggesting broader dispersal of crested hadrosaurids. This bonebed indicates to be rapid burial from mass mortality events driven by a series of floods creating floodplain mires and ponds that trapped and preserved a dense accumulation of bones.
Another fossil site is the Kikak-Tegoseak Quarry discovered in the late 1990s and excavated with the collaboration of local Inupiat communities. The quarry has yielded a rich assemblage of non-marine vertebrates fossils including horned dinosaurs (Pachyrhinosaurus), hadrosaurs, dromaeosaurs, tyrannosaurids, birds, fish and small mammals that reflect a biodiverse coastal plain ecosystem. Many dinosaurs were again juveniles that appear to live year-round in the Arctic Circle rather than migrating meaning they had adapted to living in the polar extremes.
The plant fossil record includes pollen, spores, and macrofossils that reconstruct a low-canopy forest of small trees, shrubs, and ferns. Fossil wood often shows growth rings including “false rings” that mark periods of seasonal stress suggesting that even during greenhouse phases high-latitude environments experienced cold snaps and extended darkness.
The discovery of dinosaurs, birds and freshwater fish indicates that Arctic ecosystems supported year-round life at these extreme latitudes. Ongoing erosion along the Colville River continues to reveal new fossils from the Prince Creek Formation steadily expanding our knowledge of polar dinosaurs and their environments. This was a world where dinosaurs thrived despite months of winter darkness, they navigated seasonal extremes and flourished at the northernmost edge of a cold Late Cretaceous Earth.
