Tidally Influenced, High Latitude, Alluvial-Deltaic Deposits of the Dinosaur-Bearing Late Cretaceous Prince Creek Formation: North Slope, Alaska

The Campanian-Maastrichtian Prince Creek Formation is a dinosaur-bearing, alluvial succession exposed semi-continuously in 30-50 m bluffs along a 50 km stretch of the Colville, Kogosukruk, and Kikiakrorak rivers on the North Slope of Alaska. All accessible bluffs were photographed and 75 stratigraphic sections were measured to document alluvial architecture and stratigraphy. Facies analysis indicates that the Prince Creek Formation is composed of four main associations: (1) rare, 13-20 m thick fining upward successions composed primarily of medium-grained, multistory, laterally/downstream accreting, massive to trough-crossbedded sandbodies with basal lags, (2) common, 2-6 m thick, finer-grained and ubiquitously rooted sheet sandbodies containing prominent lateral accretion surfaces, inclined heterolithic stratification (IHS), and mud-filled abandoned channels, (3) 1-3 m thick laterally stable ribbon sandbodies, and (4) fine-grained floodplain facies.

Very-fine to fine-grained sandstone, organic siltstone, carbonaceous shale, and rooted mudstone are the most common facies in these alluvial deposits while medium-to coarse-grained material is extremely rare. Ripples are the most common bedform and root-traces are nearly ubiquitous within sands, silts, and muds.

Thick fining upward successions are interpreted as meandering trunk channels. Rooted, erosionally based heterolithic sheet sandbodies composed of inclined couplets of fine-grained sand/mud and including mud-filled abandoned channels are interpreted as highly sinuous, ephemeral, tidally influenced meandering streams. Laterally stable ribbon sandbodies incised into either IHS or fine-grained floodplain deposits are interpreted as anastomosing channels, possibly on associated splay complexes. Non-channelized, fine-grained facies are interpreted as levees, crevasse splays, lakes, swamps, and paleosols.

Low-energy, highly-sinuous meandering and laterally-stable anastomosing channels appear to coexist in the Prince Creek Formation. Heterolithic sheet sandstones and ribbon sandbodies are often found stratigraphically at the same level, with multiple ribbons occasionally occupying the same horizontal plane. This architecture suggests evolving splay complexes adjacent to meandering channels or contemporaneous existence of meandering and anastomosing channels in this alluvial-deltaic system.